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Org. Divers. Evol. 6, Electr. Suppl. 6: 1 - 104 (2006)
© Gesellschaft für Biologische Systematik
URL: http://www.senckenberg.de/odes/06-06.htm
URN: urn:nbn:de:0028-odes0606-0
Halacaroidea (Acari): a guide to marine genera
Ilse Bartsch
Forschungsinstitut Senckenberg, Deutsches Zentrum für Marine Biodiversitätsforschung, Notkestr. 85,
22607 Hamburg, Germany
Corresponding author, e-mail: [email protected]
Received 13 December 2004 • Accepted 8 July 2005
Abstract
Halacarid mites (Halacaroidea: Halacaridae) are meiobenthic organisms. The majority of species and genera are marine, only few are
restricted to freshwater. Halacarid mites are present from the tidal area to the deep sea. It is the only mite family completely adapted to permanent life in the sea. The first record was published more than 200 years ago.
At present, 51 marine and brackish water genera of halacarid mites are known, including more than 1000 species. The genera are Acanthohalacarus, Acanthopalpus, Acarochelopodia, Acaromantis, Acarothrix, Actacarus, Agaue, Agauides, Agauopsis, Anomalohalacarus, Arenihalacarus, Arhodeoporus, Atelopsalis, Australacarus, Bathyhalacarus, Bradyagaue, Camactognathus, Caspihalacarus, Coloboceras, Colobocerasides, Copidognathides, Copidognathus, Corallihalacarus, Enterohalacarus, Halacarus, Halacarellus, Halacaroides, Halacaropsis,
Halixodes, Isobactrus, Lohmannella, Metarhombognathus, Mictognathus, Parhalixodes, Pelacarus, Peregrinacarus, Phacacarus, Rhombognathides, Rhombognathus, Scaptognathides, Scaptognathus, Simognathus, Spongihalacarus, Thalassacarus, Thalassarachna, Thalassophthirius, Tropihalacarus, Werthella, Werthelloides, Winlundia, and Xenohalacarus.
The guide, which includes marine and brackish water genera, starts with an introduction to methods of collection, extraction and examination
of halacarid mites, an outline of the external morphology and life history, and an overview of the commonly used terminology. Both a dichotomous key and tabular keys to the genera are presented. The keys have been prepared on the basis of adults. In general, in adults and nymphs
the outline of idiosoma, gnathosoma and legs is similar, whereas the outline of plates, the sculpturing and number of setae on idiosoma and
legs differ. In the tabular keys idiosoma, gnathosoma, palps, legs, tarsi and shape of claws are treated separately.
The major part of the guide deals with descriptions of the 51 genera. Each genus is diagnosed and illustrated, namely a dorsal and ventral
aspect of the idiosoma, the gnathosoma, leg I and tarsi I, II and IV. The diagnoses mention both, characters expected to be relevant in a
phylogenetic sense and those thought to be mainly correlated with environment and mode of life. Rare character variants are included in the
diagnoses; more variants are expected to be found in the future. In addition to the diagnoses, short notes are given on biology and geographical distribution, on similar-looking genera, and distinguishing characters. At the end of the presentation of a genus, relevant and most recent
descriptive or phylogenetic references are listed.
Keywords: Halacaroidea; Acari, General introduction; Marine genera; Keys; Diagnoses
Introduction
The first record of a marine mite (‘insecta marina’)
from coralline algae of a seashore was published
more than 200 years ago (Baster 1758: pl. 10, fig. 7).
A century later, Gosse (1855) introduced the generic
name Halacarus for marine mites, and Murray (1877)
established the family Halacaridae for mites ‘living
habitually under the sea’. Since those days, more than
1000 species in 51 marine and 13 freshwater genera
have been described, and the family Halacaridae is
given the rank of a superfamily Halacaroidea.
Halacarid mites are meiobenthic organisms within a
length range from 150 µm to about 2000 µm. Halacarids
can be found at altitudes of 5000 m (freshwater
halacarids in lakes and springs) as well as at depths
of 7000 m (marine mites in deep-sea trenches). They
generally live in submerged habitats, but a few species
Org. Divers. Evol. 6, Electr. Suppl. 6 (2006)
Bartsch: Halacaroidea (Acari): a guide to marine genera
are adapted to survive in the splash zone. Halacarids are
present at all latitudes, from polar to tropical regions.
Halacarid mites live in a variety of substrata: within
tufts of algae, on large fronds, in and on colonies of
sponges, hydrozoans, bryozoans, barnacles, mussels,
polychaetes, in interstices of coarse sediment or
flocculent ooze, amongst surface structures and gill
filaments of crustaceans and molluscs, and between
spines and in the gut of echinoderms. Some few species
are known or suspected to be parasites. Halacarids
are rare or absent in silty sediments, oxygen-free
habitats, and biotopes regularly defaunated due to
heavy pollution, destruction of the substratum, extreme
temperatures or desiccation. Several species of marine
halacarids inhabit brackish waters, with rare records
even from freshwater habitats.
The keys below deal with genera described from
marine and brackish water habitats. Genera widespread
in fresh water (salinity less than 0.5 ‰) are not included.
The drawings of the genera are generalized; rare
exceptions in external characters are excluded. Both
a tabular and dichotomous key are given, as each has
advantages and disadvantages. The references given at
the end of each chapter or genus are only recent and
major ones.
Collection, extraction and examination
In intertidal and shallow subtidal zones, collecting by
hand at low tide is recommended. Colonies of mussels,
polychaetes, barnacles, bryozoans and hydrozoans are
scraped off; algal tufts, holdfasts and fronds, shells or
pebbles covered with unicellular algae, fine and coarse
deposits from a beach surface as well as from deeper
layers, or rooted saltmarsh sediments are gathered;
50–500 ccm of the substratum may yield hundreds of
halacarid mites. From the sublittoral, collections can
be made with trawl, dredge and grab. Halacarids inhabiting the flocculent ooze are collected with epibenthic
sleds.
The mites are extracted from the substratum by washing. Large algal fronds, stones, decapods, or echinoids
are washed in a bucket with a strong jet of water;
subsequently the washing water is poured through a
60–100 µm sieve. Algal tufts and colonial organisms
are placed in a series of sieves, a 1–2 mm mesh sieve
over a 60–100 µm sieve, and washed with a jet of water.
Sediment samples are either stirred vigorously in water,
and the supernatant water decanted through a 60–100
µm mesh sieve, or placed in a separatory funnel where
lighter particles (such as halacarids) are elutriated by
a water stream and retained in a sieve at the outflow.
As intertidally living species are resistent to extreme
conditions, shock techniques with fresh water, ice water
or anaesthetizing media may prove to be inefficient.
For sediment samples from exposed shores, subsequent
2
stirring with hot water is recommended. A minority
of species has a hydrophobic cuticle; these mites are
trapped at the water surface film when the sample is
treated with air bubbles. Techniques using density
gradient separation can also be used when extracting
mites, with a flotation medium prepared from cooking
salt, sugar or colloidal silica polymers.
The material held back in the fine-mesh sieve is
placed in a petri dish or narrow-channel sorting dish and
scanned for halacarids under a dissecting microscope
(magnification: 12–25x). If possible, sorting should be
done whilst the mites are alive, crawling around in the
dish and thus more conspicuous. Halacarids may be
badly fouled with debris attached to idiosoma and legs.
The mites can be cleaned somewhat by allowing them
to run around in sand. In preserved sediment samples,
staining with rose bengal will facilitate sorting.
Ethanol (70%) should be used for fixation and storing. Formalin hardens the mites and the necessary
clearing will be difficult.
For detailed examination, the mites have to be cleared
and mounted on slides. The halacarids are placed into a
clearing medium, pepsin or lactic acid; gentle warming
(40–50 °C) may facilitate the clearing. The gnathosoma
is torn off using a sharp needle, and body contents are
squeezed out by applying gentle pressure with a blunt
needle. Material stored in formalin for several years
should be transferred into glycerine-acetic acid (with
2% acetic acid); after 1–3 months, the contents of the
idiosoma can be dissolved with lactic acid. Animals
with very delicate plates should not be left in acetic
acid or lactic acid for more than a few hours.
Permanent mounting media are glycerine jelly, glycerine or Hyrax. Careful sealing of the coverslips with
a standard microscopical sealing agent, marine epoxy
paint or nail varnish is necessary. Berlese, modified
Hoyer's fluid or polyvinyl lactophenol can be used
for temporary mounts but are not recommended for
permanent slides. Specimens cleared in lactic acid
have to be rinsed (in glycerine) to prevent subsequent
crystallization in the permanent mount. Over-cleared
specimen can be stained with chlor-azol black. To allow
a microscopic examination of both sides, mounting between coverslips is recommended. The coverslips can
be stored in a metal slide frame or attached to a glass
slide with a drop of glycerine.
References. Newell (1947, 1984), Green and
MacQuitty (1987), Bartsch (1988a, 1993a).
External morphology (Figs 1A, B, 2A–F, 5E)
The body of an adult halacarid is divided into idiosoma,
with four pairs of legs, and gnathosoma, with palps and
chelicerae.
The idiosoma is typically covered with sclerotized
plates, the dorsal plates are: the anterior dorsal plate
(AD), pair of ocular plates (OC), and posterior dorsal
plate (PD) (Fig. 1A). The ventral plates are: the anterior
epimeral plate (AE, by fusion of epimera I and II, EI,
EII), pair of posterior epimeral plate (PE, by fusion of
epimera III and IV), and genitoanal plate (GA, by fusion of the genital and anal plate, GP and AP) (Fig.
1B). The plates are separated by areas of striated (membraneous) integument. Occasionally plates are divided,
reduced or enlarged and fused to a dorsal or ventral
shield. Measurement of length and width generally
presented in species description are outlined in Fig. 2E
and F.
The idiosomal plates may be smooth, uniformly
porose, panelled, or bear porose areolae. The dorsal
plates often have raised areas or longitudinal costae
(Fig. 2A) with a sculpturing different from that of
the remainder. Often these areas include rosette
pores which typically consist of numerous canaliculi
arranged around a blindly ending central pore (ostium
and alveolus) (Fig. 2B). The AD sometimes bears
a frontal spine, the OC often two corneae. On the
dorsum there are six (rarely fewer or up to 10) pairs of
idiosomatic setae (ds), up to five pairs of gland pores
and a pair of pore canaliculi (lyrifissures, slit-organs,
ring apodemes). The posteriormost pair of dorsal setae,
called adanal setae, is mostly situated on the anal plate.
The number of setae and gland pores may be reduced.
The AE typically has three pairs of ventral setae, the
PE one dorsal (or lateral) seta and two or three ventral
setae. In some genera the AE bears a pair of epimeral
pores (external, Fig. 1B), epimeral vesicles (internal,
Fig. 5E), or merely tubes (internal). The genital opening
(GO), situated on the GP, is covered by a pair of genital
sclerites and surrounded by perigenital setae (pgs).
Small setae, the subgenital setae (sgs), are inserted on
the genital sclerites. The number of sgs and pgs of males
usually surpasses that of females. Internal structures
are the female ovipositor, the male spermatopositor
(spematophorotype), and in both sexes of most genera
1–3 pairs of genital acetabula. The idiosoma generally
ends in the anal cone with its anal sclerites.
The gnathosoma consists of a gnathosomal base,
rostrum, palps and chelicerae. On the ventral side of
the gnathosomal base there is a more or less distinct
pharyngeal plate with its internal panels and markings
from muscle attachments. On the dorsal side a
tectum (epistome) bridges the trough of the rostrum.
Commonly there are two pairs of maxillary setae
(trito- and basirostrals), and two pairs of rostral setae
(proto- and deutorostrals). The maxillary setae are on
the gnathosomal base or rostrum, the rostral setae at
the apex of the rostrum. The palps are attached either
lateral or dorsal to the gnathosomal base. The majority
of genera have four-segmented palps; the first and
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third palpal segments (P-1, P-3) are short, the second
and fourth segments (P-2, P-4) often long. Fusion and
reduction of palpal segments occur. The chelicerae are
elongate, in some genera stylet-shaped. They end with
a movable, generally claw-like ventral digit and a fixed
dorsal flap.
Adult halacarids have four pairs of legs. The two
anterior pairs, legs I and II, are directed forward, legs III
and IV backward. The six segments of the legs of adults
are trochanter, basifemur, telofemur, genu, tibia, and
tarsus. Leg segments, particulary the telofemora, may
have elaborate ridges or lamellae. The tarsi often have a
dorsal cavity, the claw fossa, with its fossa membranes.
The setae of the legs may be smooth, branched or
pectinate, long and delicate or short and spiniform. The
ventral setae of the tibiae often are bristles or spines,
which are smooth or pectinate. The tarsi bear at least
three dorsal setae, viz. one basal and two distal (often
paired) fossary setae (Fig. 2C). At the tip of tarsus I, as
well as in most tarsi II, there is a pair of parambulacral
setae (pas), short hollow (eupathid) setae which are
single, doubled or multiplied. The pas on the posterior
tarsi may be fili- or spiniform singlets, or even lacking.
Tarsus I has a dorsolateral solenidion and a famulus.
The former is hollow, setiform, bacilliform or clavate,
small or almost as long as the dorsal fossary setae. The
famulus, adjacent to the solenidion, is short, digitiform
or papilliform, but often reduced to a tiny cap at the end
of an afferent canal. The solenidion of tarsus II is in
dorsolateral, dorsal or dorsomedial position.
The tarsi terminate in a central sclerite and paired
claws. The flexible portion between the end of tarsus
and the central sclerite may include a rod-like sclerite
or carpite (Fig. 2D). The central sclerite often ends
with a minute uni- or bidentate process, called median
claw. Rarely the median claw is as long as, or even
longer than, the adjoining paired claws. The latter may
be smooth or armed with an accessory process and/or
claw pecten. In two genera the paired claws are absent
from tarsus I.
References. Newell (1947, 1984), Green and
MacQuitty (1987), Bartsch (1993a), Abé (1998).
Life history
Halacarids generally are oviparous. The mites run
through one larval and one to three nymphal stages
(proto-, deuto-, tritonymph) before they moult to
the adult. Most species have separate sexes; females
often slightly outnumber males in a given population.
Parthenogenetic reproduction is documented in just
one species. Most species have a univoltine life cycle,
with either short or prolonged periods of reproduction.
In general the fecundity is low. Temperature and day
length influence the cycle of reproduction.
The larvae have six legs, each with five segments. The
outline and size of the plates greatly differ from those
of adults; a genital plate is lacking. The setation of the
ventral idiosomal plates and the legs is incomplete.
Protonymphs have eight legs; legs I to III are sixsegmented, leg IV is five-segmented. A genital plate,
with one pair of genital acetabula, is present but is
smaller than in adults. The chaetotaxy is incomplete.
Deuto- and tritonymphs have eight six-segmented
legs. In the majority of species, the dorsal and ventral
plates are smaller than in adults; the genital plate may
be fused with the anal plate forming a genitoanal plate;
the genital opening is primordial. The number of setae
on the idiosoma and legs often resembles that of the
adults.
Larvae have a life span of a few days, nymphal stages
live a few weeks or several months, adults five to nine
months. Quiescent periods, when the mite develops
into the next stage, are called pupal stages.
Males produce elaborate spermatophores which
are attached to the substratum or to other mites. The
females stick the eggs firmly to or into the substratum
inhabited. In species with a short period of reproduction,
a female normally contains 10–20 eggs at the same
time, and the eggs are deposited in groups. Females of
psammophilous genera bear a single large egg, and one
or two additional small ones; the large egg often has an
elaborately textured membrane.
References. Lohmann (1889), Straarup (1968),
Kirchner (1969), Bartsch (1972), Siemer (1996).
Food and feeding
The chelicerae of halacarids can move to and fro
within the rostral trough, they are made for cutting
and piercing cells rather than for grinding. Halacarids
apparently feed by sucking up their food material
which presumably has been subjected to pre-oral
digestion. The pair of first legs, enlarged and provided
with spines, are well suited to capture and hold prey
organisms. Highly modified legs probably signify a
strong prey specificity. Species with their guts intensely
filled with green material certainly are phytophagous.
In most halacarids the gut contents are pale or slightly
brown; these mites are thought to be predators and
scavengers, feeding on tissue of macrofaunal species,
on meiofauna, protozoans, or on fungi and bacteria. A
few species are known or suspected to be parasites.
Halacarid populations are reduced by predators,
carnivorous invertebrates, amongst others also by other
halacarids, and small fishes, by destruction of their
substratum and physical and chemical environmental
disturbance. Halacarids may be infested by epizoa
(suctorians, peritrich ciliates) and epiphyta (unicellular
green algae, diatoms). Endoparasites are not known.
4
Fungi found in halacarid carcasses apparently colonized the mites after their death.
References. Lohmann (1889, 1893), Krantz (1970),
Bartsch (1974), MacQuitty (1984).
Terminology, abbreviations and methods
accessory process = tiny process at arc of paired
claws.
adanal setae (ads) = posteriormost pair of dorsal idiosomatic setae inserted on anal cone (mostly in dorsal
position) or adjacent on posterodorsal plate.
adjunct setae = marginal setae on AE and PE in addition to the general setation.
anal cone = end of idiosoma with anal sclerites.
anal plate (AP) = plate with anus which is guarded by
pair of anal sclerites.
anal sclerites = pair of cusps flanking the anus.
anterior dorsal plate (AD) = one of the dorsal plates.
anterior epimeral plate (AE) = ventral plate, by fusion
of epimera I and II.
areola = area on dorsal and ventral plates with an ornamentation different from remainder of plates.
Areolae porose or panelled, often raised.
basifemur = second leg segment.
basirostral setae = basalmost pair of maxillary setae.
bipartite genitoanal plate = plate with anterior transverse portion coarsely striated, ornamentation of
remainder of plate resembling that of AE and PE.
camerostome = opening receiving the gnathosoma.
carpite = rodlike sclerite between tip of tarsus and central sclerite.
central sclerite = sclerite articulating with paired claws
and tip of tarsus (or carpite); central sclerite often
bearing a claw-like process or median claw.
cerotegument = superficial layer.
chelicerae = first pair of appendages on gnathosoma.
claw = claw-like structure at the end of tarsi. Tarsi II
to IV always with a pair of claws and often with a
more or less distinct median claw (claw-like process of central sclerite).
claw fossa = dorsal cavity at end of the tarsi in which
the claws can be retracted.
deutonymph = second nymphal stage.
deutorostral setae = pair of setae near tip of rostrum.
dorsal setae (ds) = idiosomatic setae on dorsum of idiosoma, inserted on the dorsal plates or within the
striated integument.
epicuticula = surficial layer on the procuticula.
epimera or epimeral plates (E) = ventral plates with coxae included.
epimeral pore = circular, oblong or slit-like structure
between epimera I and II; with internal tube.
epimeral vesicle = large internal follicle with a slit-like
opening between epimera I and II.
eupathidia = small, ‘hollow’ sensory setae at the tip of
legs.
famulus = sensory seta on tarsus I, often reduced to
small pore and afferent canal.
femur = leg segment, in adults divided into basi- and
telofemur.
fossa membrane = membrane on one or both flanks of
the claw fossa.
genital acetabula (genital acetabulum) = tube- or sucker-like structures, usually inside the genital opening.
genital foramen = genital opening.
genital opening = oval area on the venter, in general
surrounded by a genital plate. Present only in
adults.
genital plate (GP) = ventral plate with genital opening,
often fused with anal plate.
genital sclerites = a pair of sclerites guarding the genital opening.
genitoanal plate (GA) = plate by fusion of genital and
anal plate.
genu = fourth leg segment.
gland pores = dorsal (marginal) pores; majority of genera possess four or five pairs of such pores; internal glands, opening to the exterior through these
pores, in a few genera conspicuously enlarged.
gnathosoma = anterior part of the body, resembling a
head.
idiosoma = posterior portion of the body with legs.
lyrifissure = pore canaliculus.
maxillary setae = generally two pairs of setae, inserted
either on base of gnathosoma or on rostrum (tritoand basirostral setae).
median claw = claw-like process of central sclerite.
ocular plates (OC) = paired dorsal plates, often with
corneae and eye spots.
outlying setae = perigenital setae which lie outside the
arrangement of the other setae.
ovipositor = inverted tubular structure often extending
beyond GO; everted when depositing eggs.
paired claws = present on tarsi II to IV, may be absent
from tarsus I.
palps (P) = pair of appendage on gnathosoma, four- to
two-segmented or even absent.
parambulacral setae = small setae at tip of tarsus; majority of genera with these setae paired; on tarsi I
and II parambulacral setae usually eupathid and
doubled.
perigenital setae (pgs) = setae surrounding the GO.
pore canaliculus = present on ocular plates and on anal
plate (lyrifissure, slit organ, ring apodeme).
posterior dorsal plate (PD) = one of the dorsal plates.
5
posterior epimeral plate (PE) = plate by fusion of
epimera III and IV, generally with large ventral
and marginal but small dorsal portion.
protonymph = first nymphal stage.
protorostral setae = pair of setae near tip of rostrum.
rosette pore = type of porosity consisting of a central
pore (ostium) surrounded by small canaliculi.
rostral setae = two pairs of small setae at tip of rostrum
(proto- and deutorostrals); may be transformed to
barbs.
rostrum = a trough in which chelicerae slide forward
and back; rarely rostrum spatula-shaped or lamellar.
solenidion = minute sensory seta at tip of tarsus; always present on tarsus I and II.
spermatophore = stalked capsule with sperm sac.
spermatophorotype = spermatopositor.
spermatopositor = spermatophorotype; internal cuticular structure, mould for spermatophore.
subgenital setae (sgs) = small setae inserted on the genital sclerites.
tarsus = sixth leg segment.
tectum = dorsal roof of gnathosoma bridging the rostral
trough.
telofemur = third leg segment.
tibia = fifth leg segment.
tripartite genitoanal plate = plate divided into three
transverse portions; middle portion coarsely striated.
tritonymph = third nymphal stage.
tritorostral setae = pair of maxillary setae.
trochanter = first leg segment.
ventral setae (vs-1, vs-2, etc.) = ventral setae on idiosoma.
Abbreviations: AD = anterior dorsal plate; ads = adanal
setae; AE = anterior epimeral plate; AP = anal plate;
ds = dorsal setae on idiosoma, numbered ds-1 to ds-6
from anterior backward; E = epimeron or epimeral
plate, EI to EIV; GA = genitoanal plate; GO = genital
opening; GP = genital plate; OC = ocular plate(s); P =
palp, P-2 to P-4, second to fourth palpal segment; pas =
parambulacral setae; PD = posterior dorsal plate; PE =
posterior epimeral plate; pgs = perigenital setae; sgs =
subgenital setae; vs-1, vs-2 = ventral setae on idiosoma,
numbering from anterior backward. Leg segments and
epimera are numbered I to IV, leg segments 1 to 6; e.g.
I-6 = tarsus of leg I.
In the tabular keys idiosoma, gnathosoma, legs, tarsi,
and shape of claws are treated separately. The keys
have been prepared on the basis of adults. In general, in
adults and nymphs the outline of idiosoma, gnathosoma
and legs is similar, whereas the outlines of plates, the
sculpturing and number of setae on idiosoma and legs
differ. Each given option includes a combination of
characters, and this combination should be represented
in the given specimen.
The diagnoses present a combination of characters
(a) expected to be relevant in a phylogenetic sense,
though they might be difficult to discern, and (b) easily
recognized but thought to be mainly correlated with
environment and mode of life. The number of dorsal
idiosomatic setae will include the adanal setae (ads or
ds-6); their position is given separately. The numbers of
setae of a given leg segment, from I to IV, are separated
by a comma, the number of dorsal/ventral setae of a
leg segment by a slash. Unless stated otherwise, the
tarsal formula includes the solenidia but excludes the
famulus. The solenidia may be almost as long as the
dorsal fossary setae, or be very small and hence easily
escape notice. The famulus is always small.
Broken lines in the figures indicate characters (setae,
spines, segmentation) not present in all given genera or
species. In the diagnoses and in Table 1, rare variants
are enclosed in parentheses, square brackets [] enclose
possible misinterpretations, and a question mark (?)
means the character state is in need of confirmation.
6
Tabular keys (Table 1)
Idiosoma and gnathosoma, dorsal aspect (Fig. 3)
A. Idiosoma slender (length more than 2.3 times width);
2 anterior and posterior pairs of legs inserted near
ends of idiosoma, and interval between insertions
of legs II and III more than 1.3 times width of
idiosoma. Insertion of leg III towards posterior
third of idiosoma. Gnathosoma directly attached
to idiosoma; seen in dorsal aspect (Fig. 3A).
B. Interval between insertions of legs II and III almost
equal to, or less than, 1.3 times width of idiosoma.
Insertion of leg III about halfway between ends of
idiosoma. Gnathosoma directly attached to idiosoma and distinct in dorsal aspect (Fig. 3B).
C. Interval between insertions of legs II and III equal
to, or less than, 1.3 times width of idiosoma. Insertion of leg III about halfway between ends of
idiosoma. Gnathosoma attached to idiosoma via
flexible neck (Fig. 3C).
D. Interval between insertions of legs II and III less
than width of idiosoma. Gnathosoma short, directly attached to idiosoma, directed to ventral and in
dorsal aspect completely or mostly concealed by
anterior portion of idiosoma (Fig. 3D).
Idiosoma, dorsal aspect (Fig. 4)
A. Idiosoma slender, 2 anterior and posterior pairs of
legs inserted near ends of idiosoma; interval between insertions of legs II and III at least 1.3 times
width of idiosoma. AD and PD present, PD may
be divided into right and left half or reduced to
small plate. OC small (less than 50 µm in length
and in general less than half length of AD), may
be divided or absent (Fig. 4A).
B. Interval between insertions of legs II and III equal
to, or less than, width of idiosoma. Dorsum with
4–5 pairs of gland pores, one pair in marginal
(ventromarginal) position (Fig. 4B), situated
within striated integument (rarely on PE). AD, PD
and OC present. Dorsal plates lack raised porose
areolae or costae. PE with dorsal (marginal) seta
anterior to leg III but none anterior to leg IV.
C. Interval between insertions of legs II and III equal
to, or less than, width of idiosoma. Dorsum with 5
pairs of gland pores, one pair in marginal position.
AD present, though margins may be obscured by
epicuticula. PD absent (Fig. 4C). OC absent or
present.
D. Interval between insertions of legs II and III equal
to, or less than, width of idiosoma. Dorsum with 4
or fewer pairs of gland pores. AD, PD and OC present; OC more than 35 µm in length, plate may be
divided. Two or more dorsal plates may be fused.
7
Table 1: Halacarid genera and their character states. Parentheses () enclose rare variants; character states in square brackets [] may be misinterpretations; a question mark (?) means that the character state is in need of confirmation.
Idiosoma
Idiosoma,
Iidiosoma,
Gnatho-
Gnatho-
Palps,
Legs,
Legs,
Tarsus I,
Tarsus IV,
and
dorsum
venter
soma,
soma,
shape
shape
setae
setae
setae
dorsal
ventral
9
10
11
12
gnathosoma
Figure
Claws
and
setae
3
4
5
6
7
8
13
Acanthohalacarus
B
D
C
D
A
E
A
C
E
E
A
Acanthopalpus
B
D
C
D
A
A
A
A
C
A
B
F
Genus
Acarochelopodia
B
D
A
D
A
A
D
A
C
A
Acaromantis
B
F
E
B
J
N
E
H
B
D
F
Acarothrix
B
D
D
D
A
H
A
F
C
A
A
Actacarus
B
E
C
D
A
E
A
G
C
AB
A
Agaue
B
DGH
C
D
C (D)
E (H)
AB
D
E
A
A
Agauides
B
E
C
D
D
I
A
D
H
CF
A
A
Agauopsis
B
D
(C) D
D
A
EFG
A (C)
A (D)
CE
AD
Anomalohalacarus
A
A
AD
D
A
BD
H
DG
C (D)
A
A
Arenihalacarus
A
A
A
D
A
B
H
G
C
A
A
Arhodeoporus
B
D
D
D
A (C)
H (I?)
A
DG
C
AD
A
Atelopsalis
B
D
E
D
J
L
A
BD
C
A
A
Australacarus
A
A
C
D
G
HJ
A
DE
C
A (F)
A
Bathyhalacarus
B
D
C
D
A
E
A
D
E
ADE
A
D
Bradyagaue
B
G
(C) H
D
C
EH
(A) B
D
(C) E
A
Camactognathus
B
D
C
D
A
H
AF
DG
B
A
A
Caspihalacarus
B
D
C
D
A
E
A
D
E
A
A
Coloboceras
B
D
C
D
J
L
A
D
E
D (G)
A
Colobocerasides
B
D
C
D
G
HJ
A
DE
C
A
A
Copidognathides
B
D
D
D
AJ
IJ
A
E
B
A
A
Copidognathus
B
D
D
D
AB
H
AC
(A) E (G)
C
A B (D)
A
Corallihalacarus
C
D
C
D
A
I
C
F
H
A
D
Enterohalacarus
B
D
C
C
K
O
A
C
H
A
A
Halacarellus
B
D
C
D
A
E
A
ADF
CDE
ADE
A
Halacaroides
A
A
B
D
A
E
A
G
C
A
A
Halacaropsis
B
D
D
D
A
E
H
A
E
D
A
Halacarus
B
BCEH
CG
D
A
A
H
A
F (K)
ADE
AC
Halixodes
B
H
C
D
E
E
B
D
E
A
A
Isobactrus
D
D
AC
D
A
H
A (H)
FG
IJ
AB
I
Lohmannella
B
BD
C
A (D)
A
C
A (C)
D
CFI
ADEG
I
Metarhombognathus
B
D
A
B
J
E
A
F
A
A
K
Mictognathus
B
D
C
D
A
G [I]
C
F
BH
A
A
Parhalixodes
A
A
A
D
F
I
A
G
B
A
D
Pelacarus
B
D
D
D
D
I
A
F
B
A
A
Peregrinacarus
B
D
C
D
A
E
A
AD
H
A
A
Phacacarus
B
D
D
D
A
H
AC
E
C
A
A
Rhombognathides
B
D
C
D
J
J
A
F
A
A
IJ
Rhombognathus
B (D)
D
(A) C
D
A
H
A
F
I
A
I
Scaptognathides
B
D (E)
D
D
H
M
G
F
I
A
G
A (C)
Scaptognathus
B
D (E)
DF
A
I
M
A
DEG
CB
A
Simognathus
B
F
E
B
J
K
(E) F
H
B
D
E
Spongihalacarus
B
D
D
C
L
P
A
A
B
A
D
Thalassacarus
B
D
C
D
A
E
A
F
E
A
A
Thalassarachna
B
BE
C
D
AB
E
A
AD
K
ADG
A
Thalassophthirius
B
D
C
D
A
H
F
F
H
A
A
Tropihalacarus
B
D
C
D
A
E [H]
A
D
E
AD
A
Werthella
B
D
D
D
D
I
AC
EF
BC
A
A
Werthelloides
B
D
C
D
F
I
A
D
H
A
A
Winlundia
B
D
C
D
A
H
A
D
C
A
A
Xenohalacarus
B
E
D
D
A
B
A
D
G
F
H
E.
F.
G.
H.
PE with 0–8 dorsal (marginal) setae anterior to leg
III, none anterior to leg IV (Fig. 4D).
Interval between insertions of legs II and III equal
to, or less than, width of idiosoma. AD and PD
present, large, surface smooth, delicately porose
or reticulate. OC small (less than 35 µm in length)
(Fig. 4E), fused with PE, or absent. PE with dorsal
(marginal) seta anterior to leg III but none anterior
to leg IV.
to, or less than, width of idiosoma. AD and PD
present, large, surface coarsely foveate. OC short,
triangular or reduced to elongate sclerites (obscured in coarsely striated integument) (Fig. 4F).
4 or fewer pairs of gland pores. AD, PD and OC
present. PE with dorsal (marginal) seta anterior to
leg III and 1–2 setae anterior to leg IV (Fig. 4G).
(5–)4 or fewer pairs of gland pores. AD, PD and
OC present. PE with dorsal (marginal) seta(e) anterior to leg III but none anterior to leg IV. Dorsal
and epimeral plates with cerotegumental lamellae
(Fig. 4H).
Idiosoma, epimeral plates and genital plate (Fig. 5)
A. EI and EII of right and left side fused but in the
median separated by striated integument. A separate median plate may be present. EIII and EIV of
either side partly or completely fused and forming
a pair of plates (PE). EII and EIII may be contiguous. Epimeral pores present or absent. Genital
plate reduced (Fig. 5A) or large.
B. EI and EII fused, forming an AE. Epimeral pores
lacking. Each of PE with longitudinal fissure (Fig.
5B).
C. EI and EII forming an AE; this plate may be fused
with one or more ventral plates. Neither epimeral
pores nor epimeral vesicles present (Fig. 5C). EIII
and EIV of either side partly or completely fused.
Pair of PE (EIII and EIV fused) less than 1.6 times length of AE; its opposing margins triangular.
Genital plate smooth, punctate or reticulate.
D. EI and EII fused to an AE, which may be fused with
one or more posterior ventral plates (PE, GP). AE
with epimeral pores or small slits. GA smooth,
reticulate, with porose areolae but without raised
cerotegument or markedly differing transverse
sculpturing (Fig. 5D).
E. EI and EII fused, AE with pair of epimeral vesicles
(Fig. 5E).
8
F. EI and EII fused, AE with epimeral pores. GA bi- or
tripartite (Fig. 5F).
G. EI and EII forming an AE. Neither epimeral pores
nor epimeral vesicles present. Female genital plate
with pair of raised, crescent-shaped cerotegumental areas (Fig. 5G).
H. EI and EII fused, forming an AE. Neither epimeral
pores nor epimeral vesicles present. Genital plate
smooth, punctate or reticulate. Length of PE at
least 1.6 times that of AE; medial opposing margins straight (Fig. 5H).
Gnathosoma, dorsal aspect (Fig. 6)
A. Palps attached dorsally (Fig. 6A); interval between
P-1 in general less than 0.8 of width of P-1 (P-1
may be fused). Gnathosomal base longer than
wide, or cubical and as long as wide. Palps longer,
just as long as, or rarely somewhat shorter than,
gnathosomal base.
B. Palps attached dorsally, interval in general less than
width of P-1. Gnathosomal base globular. Palps
as long as or shorter than gnathosomal base (Fig.
6B).
C. Palps inserted dorsally, interval between P-1 greater
than width of P-1. Palps distinctly shorter than
rostrum (Fig. 6C), or absent.
D. Palps attached lateral to rostrum, interval between
P-1 almost equal to, or greater than, width of P-1.
Palps as long as or longer than rostrum (Fig. 6D).
Rostrum long and slender, or reduced to small
cone.
Gnathosoma, ventral aspect (Fig. 7 )
A. Rostrum triangular or parallel-sided. With 2 pairs of
maxillary setae, either both pairs on rostrum or 1
pair on gnathosomal base and 1 pair on rostrum.
In species with long, parallel-sided rostrum the
two pairs of maxillary setae distinctly separated.
No barbs at tip of rostrum. Palps 4-segmented, as
long as or longer than rostrum (Fig. 7A).
B. Rostrum triangular or parallel-sided. With three or
more pairs of maxillary setae, 2 or more pairs of
setae on gnathosomal base, 1 pair on rostrum (Fig.
7B). No barbs at tip of rostrum. Palps 4-segmented, as long as or longer than rostrum.
C. Rostrum slender, parallel-sided, longer than gnathosomal base. One pair of maxillary setae on
gnathosomal base, 1 pair on rostral base, the 4
setae situated almost equidistantly (Fig. 7C). Pair
of setae on rostrum often short, even minute, and
in dorsolateral margin of rostrum. Barbs at tip of
rostrum, if present, seen only at high magnifica-
D.
E.
F.
G.
H.
I.
J.
K.
L.
tion. Palps 4-segmented, as long as or longer than
rostrum.
Rostrum triangular or parallel-sided, about as long
as gnathosomal base. One pair of maxillary setae
on gnathosomal base, 1 pair on rostral base, the
4 setae situated almost equidistantly. No barbs at
tip of rostrum. Palps 4-segmented, as long as or
longer than rostrum (Fig. 7D).
Rostrum parallel-sided. Maxillary setae inserted almost equidistantly. Rostral tip with 2 pairs of distinct barbs (Fig. 7E). Palps 4-segmented, as long
as or longer than rostrum.
Rostrum parallel-sided. Rostral tip with 1 pair of
barbs (Fig. 7F). Palps 4-segmented, about as long
as rostrum.
Rostrum stylet-shaped. Palps 3- or 4-segmented
(Fig. 7G).
Rostrum slender, parallel-sided. Palps 2-segmented
(Fig. 7H).
Rostrum spatula-shaped or lamellar. Palps in general 2-segmented, rarely with 3 segments (Fig.
7I).
Gnathosoma short, conical, gnathosomal base globular, wider than long. Rostrum hardly longer than
wide, shorter than gnathosomal base. Palps short,
2- or 3-segmented (Fig. 7J) (rarely with a wedgelike 4th segment).
Rostrum triangular. Palps less than 1/5 of gnathosomal length (Fig. 7K).
Rostrum triangular. Palpal segments reduced (Fig.
7L).
Palps, shape and number of setae (Fig. 8) (numbers given
exclude the small apicalmost spurs and setulae)
A. 4-segmented (P-3 may be very short). P-2 with 2
setae; both setae in posterior half of that segment
(Fig. 8A). P-3 with spine. P-4 with 3 or more setae
in basal whorl (1 may be spiniform).
B. 4-segmented. P-2 with 1 basal and 1 apical seta
(Fig. 8B). P-3 with spine or seta. P-4 with 3 or
more setae.
C. 4-segmented. P-2 with 1 basal and 1 apical seta (rarely with 1 or more spiniform ventral processes).
P-3 with spiniform process (no seta). P-4 with
small spine and 2 or more setae (Fig. 8C).
D. 4-segmented. P-2 with 1 basal seta. P-3 with spine.
P-4 with 3 setae in basal whorl (Fig. 8D).
E. 4-segmented (3rd segment may be reduced to a
wedge). P-2 with 1 seta in posterior half. P-3 with
spine or seta (Fig. 8E). P-4 with 3–4 setae (generally situated in basal half), 1 of which may be
spurlike.
F. 4-segmented. P-2 with 1 seta in distal half. P-3 with
divaricate spine. P-4 with 3 setae in basal whorl
(Fig. 8F).
9
G. 4-segmented. P-2 with 1 seta in distal half. P-3 with
spine or seta. P-4 with 1–2 setae (Fig. 8G).
H. 4-segmented. P-2 with 1 seta in distal half. No spine
or seta (with alveolus) on P-3. P-4 with 3–4 setae
in basal whorl (Fig. 8H) (rarely these setae situated in posterior half).
I. 4-segmented. P-2 with 1 dorsal seta in distal half.
No seta on P-3. P-4 with 0–2 setae in basal half
(Fig. 8I) (rarely seta moved to apex).
J. 3-segmented. Second segment with 1 dorsal seta
but no apophysis. Apical segment with 0–3 basal
setae (Fig. 8J).
K. 3-segmented. Second segment with 1 bristle-like
ventral seta and often an apophysis (may be lacking), 3rd segment with 1 basal seta (Fig. 8K).
L. 3-segmented. No seta on 2nd segment (Fig. 8L).
Apical segment with 1 or more setae.
M. 2-segmented (rarely seemingly 3-segmented), reaching to or beyond end of rostrum. Apical segment
with 2 or more spines (Fig. 8M).
N. 2-segmented. Short. Apical segment with ventral
and dorsal bristle (Fig. 8N).
O. 2-segmented. Short. Apical segment with small setae at its tip (Fig. 8O).
P. Palps absent, represented by setae only.
Shape of legs (Fig. 9)
A. Genu I shorter than both telofemur and tibia I; its
length less than 0.7 times length of telofemur.
Telofemora and tibiae often cylindrical, sometimes wide but not club-shaped; prominent membranes or lamellae lacking. Tarsus I often shorter
than but not distinctly dissimilar from following
tarsi (Fig. 9A).
B. Genu I shorter than both telofemur and tibia I. Leg
segments slender, cylindrical or club-shaped. Telofemur I with cerotegumental lamellae (Fig. 9B).
C. Genu I shorter than both telofemur and tibia I. Telofemora I and II, or III and IV, or all, with large
cuticular ventral lamellae or a combination of
ventral and articular lamellae; lamellae almost
half height of telofemur (Fig. 9C).
D. Genu I shorter than both telofemur and tibia I. Tibia I with narrow base, then widened. Tarsus I cylindrical, slender, at least 6 times longer than high
(Fig. 9D). Tarsus I much more slender than tarsi II
to IV.
E. Genu I distinctly shorter than both telofemur and
tibia I. Tibiae claviform, with narrow base. Tibia
I with short, narrow base then abruptly widening;
height in basal half at least 3 times that of the
base. Tarsus I short, about as long as high, rotated
inward (Fig. 9E).
F. Genu I distinctly shorter than both telofemur and
tibia I. Tibiae claviform, with a cylindrical, nar-
row base. Tibia I with greatest height in distal half
(height about 2.5–3 times that of the base) (Fig.
9F). Tarsus I at least twice as long as high.
G. Genu I distinctly shorter than both telofemur and tibia I. Telofemur I very large, its length and height
almost twice that of tibia I (Fig. 9G).
H. Genu I approximately as long (0.7-1.1 times) as telofemur I and tibia I (Fig. 9H). Leg I often longer or
wider than leg II.
Legs, shape and chaetotaxy (Fig. 10)
A. Leg I generally wider and longer than leg II. Telofemur I with 1–5 spines; spines blunt or tapering,
smooth, pectinate or divaricate. Tibia I with 3–8
bristle-like setae or spines (Fig. 10A).
B. Leg I markedly wider than leg II. Telofemur I
longer and wider than telofemur II, spines lacking
though spiniform lamellae may be present. Tibia I
with pair of ventral spines (Fig. 10B).
C. Both telofemur and tibia I with numerous (15 or
more) dorsal plus ventral setae (Fig. 10C).
D. Telofemur I with ventral seta(e) but without large
spine(s). Tibia I with 4–9 ventral setae, which may
be spiniform, pectinate or slender (Fig. 10D).
E. Telofemur I with 1–5 ventral setae but no large
spines. Tibia I with 3 ventral setae (Fig. 10E), tibia II with 2–3 ventral setae.
F. Telofemur I with 1–3 ventral setae but no large spines. Tibiae I and II each with 2 ventral setae (in
ventral and ventromedial position) (Fig. 10F).
G. Telofemur I with 2–5 dorsal but no ventral setae.
Tibia I with 1–5 ventral setae (Fig. 10G).
H. Telofemur I with 1–2 dorsal but no ventral setae.
Tibia I with 1 ventral spine (Fig. 10H). Tibia II
with 2 ventral setae.
Chaetotaxy of tarsus I (Fig. 11) (parambulacral setae excluded)
A. With 3 dorsal setae, a seti- or claviform solenidion,
a similar-sized famulus, and 1 apical spiniform
ventral seta (Fig. 11A).
B. With 3 dorsal setae, a small seti- or claviform solenidion and a single ventral seta or tapering spine,
often at about mid-segment (Fig. 11B). Shape of
famulus different from that of solenidion.
C. With 3 dorsal setae, a seti- or claviform solenidion,
1 ventral or ventromedial spine or spur in basal
half, and a single or pair of eupathidia near the
tip (Fig. 11C). Famulus lamelliform or inconspicuous.
D. With 3 dorsal setae, a seti- or claviform solenidion,
2 short ventral setae or spurs in basal half of segment, and a pair of eupathidia apically (Fig. 11D).
Famulus lamelliform or inconspicuous, shorter
than solenidion.
10
E. With 3 dorsal setae, a seti- or claviform solenidion,
and 1 ventral or ventromedial spine or seta, mostly
in basal half or middle of segment, separated from
the following 3–20 short ventral setae (eupathidia) (Fig. 11E). Famulus shorter than solenidion,
lamelliform or inconspicuous.
F. With 3 dorsal setae, a seti- or claviform solenidion,
2 or more bristle-like ventral setae in middle of
segment, and apical eupathidia (Fig. 11F). Famulus small.
G. With 3 dorsal setae and a setiform solenidion. Pair
of strong ventral setae in middle of segment;
small apical eupathidia lacking (Fig. 11G). Famulus small.
H. With 3 dorsal setae, a seti- or claviform solenidion,
and no ventral seta(e) in basal half but 2–20 setae
or eupathidia in apical half of tarsus (Fig. 11H).
Famulus shorter than solenidion.
I. With 3 dorsal setae and a setiform or claviform
solenidion, but no ventral setae. Famulus much
smaller than solenidion (Fig. 11I).
J. With 4 dorsal setae and claviform solenidion; no
ventral setae. Famulus much smaller than solenidion. (Fig. 11J).
K. With 4 or more dorsal setae, a setiform solenidion,
1–2 spiniform ventral setae, and 2 or more eupathidia (Fig. 11K).
Chaetotaxy of tarsus IV (Fig. 12)
A. With 3 dorsal setae, no ventral setae. Tip of tarsus
with pair of pas, rarely with single, unilateral pas;
pas spini-, seti-, filiform or plumose (Fig. 12A).
B. With 4 dorsal setae, no ventral setae. Tip of tarsus
with pair of seti- or spiniform pas (Fig. 12B).
C. With 3 dorsal setae, no ventral setae. Tip of tarsus
without pas (Fig. 12C).
D. With 3 dorsal setae, 1–2 ventral setae. Tip of tarsus
with unilateral or pair of pas (Fig. 12D).
E. With 3 dorsal setae and 3 or more bristle-like ventral
setae. Tip of tarsus with pair of pas (Fig. 12E).
F. With 3 dorsal setae, one or more ventral setae. No
pas at tip of tarsus (Fig. 12F).
G. With 4 or more dorsal setae and 1–5 ventral setae.
Tip of tarsus with pair of pas (Fig. 12G).
Claws (Fig. 13)
A. All tarsi with paired claws. These claws either simlar-sized on all legs, or claws of tarsus I shorter
and often slightly wider than those of following
tarsi. Paired claws smooth, with accessory process
and/or pecten; pectines of tarsus I may be less developed than on posterior tarsi. Median claw, if
present, less stout than paired claws and less than
half their length (Fig. 13 A). Central sclerite of
tarsus I articulating with end of tarsus.
B. All tarsi with paired claws. Paired claws of tarsus
I shorter, median claw longer than claws of following tarsi. Paired claws and median claw of
tarsus I almost similar-sized (Fig. 13B). Central
sclerite of tarsus I articulating with end of tarsus.
C. All tarsi with paired claws. Median claws of tarsi
III and IV more than half length of paired claws
(Fig. 13C) and longer than median claw of tarsus
I. Median claw of tarsus I less than half length of
paired claws.
D. All tarsi with paired claws. On all tarsi median claw
large, as wide or wider (Fig. 13D) than paired
claws and at least half length of paired claws.
Central sclerite articulating with end of tarsus.
E. All tarsi with paired claws. Size of claws of tarsus
I dissimilar from that of following tarsi. Paired
claws of tarsus I much more slender than median
claw (Fig. 13E). Paired claws of tarsi II to IV wider than those of tarsus I; their median claw minute.
F. Tarsus I with median claw, paired claws absent (Fig.
13F). Tarsi II to IV with large paired claws; median claw from minute to almost as long as paired
claws.
G. Paired claws of tarsus I large, umbrella-shaped (Fig.
13G). Claws of tarsi II–IV scythe-shaped, single
tooth or tines of pectines on claw shaft.
H. Paired claws of tarsus I with long tines arranged
along claw shaft; length of tines may reach onethird of length of claws (Fig. 13H). Claws of tarsi
II–IV with distinctly shorter tines.
I. All tarsi with paired claws, these smooth, with accessory process and/or with pecten. Central sclerite small, without claw-like process (Fig. 13I).
Tarsi I–IV with carpite between end of tarsus and
central sclerite.
J. All tarsi with paired claws. Median claw of tarsi I
and II half or less than half of length of paired
claws (Fig. 13J), median claw of tarsi III and IV
either smaller than those of tarsi I and II or absent.
Tarsi I–IV with carpite between end of tarsus and
central sclerite.
K. All tarsi with three large claws; median claw more
than half length of paired claws (Fig. 13K). Tarsi
I–IV with carpite between end of tarsus and central sclerite.
Dichotomous key to the genera
1a. Palps reduced, represented by setae only.
.................................................. Spongihalacarus
1b. Palps present, with 2–4 distinct segments. .......... 2
2a. Palps 2-segmented. Segments slender, cylindrical, their length less than half that of rostrum. Idiosoma approximately 2000 µm long
. ................................................ Enterohalacarus
11
2b. Palps 2- to 4-segmented, at least as long as rostrum.
Idiosoma less than 1500 µm long. .................... 3
3a. Size of median and paired claws of tarsus I very different from that of tarsus II. Paired claws of tarsus
I much more slender than median claw, or absent.
Paired claws of tarsus II as long as or longer than
median claw; median claw may be absent. ....... 4
3b. Paired claws of tarsus I at least as long as, generally
longer than, median claw. Paired claws of tarsus
II similar in length or longer than median claw;
median claw may be absent. ............................. 6
4a. Tarsus I slender, 6 times longer than high; ending
with a single small median claw. Tarsus I ventrally with 1 long seta and 2 short eupathidia. Tibiae
with 5–6 strong, bipectinate bristles. Palps 4-segmented; P-2 with 2 setae. ........ Acarochelopodia
4b. Length of tarsus I 1–4 times its height. Tarsus I with
large median claw; paired claws absent or slender.
Tarsus I with 1 wide ventral seta but no eupathidia. Tibia I with one wide ventral seta, tibiae II
to IV with 2 bristle-like ventral setae. Palps 2- or
3-segmented, 2nd segment with 1 ventral and 0–1
dorsal seta. ........................................................ 5
5a. Tarsus I as long as high and ending with single median claw. Tibia I with narrow cylindrical basis;
longer than telofemur I. Rostrum short, conical;
palps 2-segmented, 2nd segment with 1 dorsal and
1 ventral seta. OC reduced to elongate sclerite.
........................................................ Acaromantis
5b. Tarsus I ending with median claw and slender paired
claws (the latter may be difficult to discern). Tarsus I in general longer than high (exceptions do
exist !); palps 3-segmented; 2nd segment with 1
ventral but no dorsal seta. OC subtriangular or reduced to elongate sclerite. .............. Simognathus
6a. Tines of claws I distinctly larger than those of claws
II to IV. Longest tines at least one third of length
of claw. .............................................................. 7
6b. Tines of claws I absent, smaller than, or similar in
size to, those of claws II to IV. .......................... 8
7a. Tines of claws I arranged umbrella-like. Rostrum
slender, parallel-sided, about as long as gnathosomal base. Palps 2-segmented, with 4 apical spurs.
.................................................. Scaptognathides
7b. Tines of claws I arranged J-shaped. Rostrum slender, parallel-sided, 4 times longer than gnathosomal base. Palps 4-segmented. ..... Xenohalacarus
8a. Gnathosoma attached to idiosoma via long flexible
neck. ........................................ Corallihalacarus
8b. Without flexible neck between idiosoma and gnathosoma. Gnathosoma may be concealed by anterior portion of idiosoma. ................................... 9
9a. Idiosoma slender, at least 2.3 times longer than
wide. Two anterior and two posterior pairs of legs
inserted near ends of idiosoma; interval between
insertions of legs II and III at least 1.3 times width
of idiosoma. OC absent or reduced to sclerites
less than 50 µm in diameter. Gnathosoma slender,
at least 2.5 times longer than wide. ................. 10
9b. Length of idiosoma less than 2.3 times its width. Interval between insertions of legs II and III almost
equal to, or less than, width of idiosoma. Gnathosoma slender or wide. ..................................... 14
10a. Genu I about as long (0.8–1) as adjoining telofemur and tibia. Parallel-sided rostrum with blunt
tip; both pairs of maxillary setae in posterior two
thirds of rostrum. ............................................. 11
10b. Genu I shorter (0.6 or less) than adjoining telofemur or tibia. Slender rostrum with blunt, stylet- or
arrow-shaped (barbed) tip. Basal pair of maxillary setae near base of rostrum or on gnathosomal
base. ................................................................ 12
11a. Basifemur IV with 0 setae. Female with 3 pairs
of perigenital setae; anterior pair of setae on
minute platelets or within striated integument.
.............................................. Anomalohalacarus
11a. Basifemur IV with 1 long and delicately plumose
seta. Female with 2 pairs of perigenital setae; anterior pair inserted on a plate. .... Arenihalacarus
12a. Rostrum parallel-sided and with blunt tip. PE with
longitudinal fissure. ....................... Halacaroides
12b. Slender rostrum with stylet- or arrow-shaped (barbed) tip. PE of either side undivided. .............. 13
13a. Rostrum stylet-shaped. Both pairs of maxillary setae on gnathosomal base, one pair in about middle of gnathosomal base, one pair close to rostral
base. ............................................. Australacarus
13b. Rostrum with arrow-shaped (barbed) tip. Gnathosomal base with one pair of maxillary setae.
..................................................... Parhalixodes
14a. All tarsi ending with 3 almost equal-sized claws;
median claw about as large as paired claws, crescent-shaped and smooth. Paired claws with row
of small, or few large, denticles along dorsal margin. .................................... Metarhombognathus
14b. Median claw of tarsi II to IV shorter than paired
claws, or absent. Paired claws smooth, with accessory process or with tines of pecten along ventral flank. ......................................................... 15
15a. Apical fourth of rostrum with two pairs of barbs
extending beyond lateral margin of rostrum. Legs
with cerotegumental lamellae. ............ Halixodes
15b. Apex of rostrum with rostral setae; barbs, if present, minute and not extending beyond lateral
margin. Legs with or without cerotegumental lamellae. ............................................................. 16
16a. Palps inserted dorsally (major part of P-1 obscured in ventral aspect); distance between palps ge-
12
nerally less than half width of P-1 (rarely about
width of P-1). .................................................. 17
16b. Palps lateral to gnathosomal base (major part of
P-1 seen in ventral aspect); distance between P-1
more than half width of that segment. ............ 18
17a. Rostrum slender and parallel-sided. Palps 4-segmented, P-4 with small spur but without large spines. Both pairs of maxillary setae on rostrum. AE
with (3–)4 pairs of setae. ................ Lohmannella
17b. Rostrum spatula-shaped or lamellar, its apex wide
and truncate. Palps 2-segmented (rarely seemingly 3-segmented), with 2 large apical spines. Both
pairs of maxillary setae on rostrum. AE with 3
pairs of setae. .............................. Scaptognathus
18a. P-2 with 2 setae, palps 4-segmented. .............. 19
18b. P-2 with 0 or 1 seta. Palps 2- to 4-segmented . 20
19a. Genua I and II as long as or longer than corresponding tibiae (and generally also longer than
telofemora). Length of genu I more than twice
its height. Telofemur with spiniform, genu and tibia I with spiniform or bristle-like smooth setae.
............................................................ Halacarus
19b. Genua I and II shorter than (less than 0.8) tibiae.
Length of genu I less than 1.5 times its height.
Telofemur, genu and tibia I with short, apically
dentate or divaricate spines ......... Acanthopalpus
20a. Palps slender, 3-segmented, hardly extending beyond rostrum. No seta on second palpal segment.
Apical segment with 1 seta in basal whorl. .... 21
20b. Other combination of characters. Palps 3- or 4segmented. Second palpal segment with 1 dorsal
seta. Apical palpal segment with 0–4 setae in basal whorl. ......................................................... 22
21a. Tarsus I with 3 ventral setae. Tibia I with pair of
spines and pair of slender ventral setae. AE with
epimeral vesicles. .............................. Atelopsalis
21b. Tarsus I with more than 3 ventral setae. Ventral
setae on leg I setiform. AE without epimeral vesicles or epimeral pores. .................. Coloboceras
22a. Ocular plate divided into anterior and posterior
plate. ................................................................ 23
22b. Ocular plate undivided or absent; may be fused
with dorsal or epimeral plates. ........................ 24
23a. Rostrum almost as long as palps, stylet-shaped.
Tarsus I with 3 ventral setae (pas excluded). Anterior ocular plate with small gland pore; posterior
plate with small pore canaliculus but no gland pore.
................................................Colobocerasides
23b. Rostrum shorter than palps, triangular. Tarsus
I with more than 8 ventral setae (pas excluded).
Anterior and posterior ocular plate each with large
gland pore. .................. Bathyhalacarus (in part)
24a. Tarsus I with 5 or more dorsal setae (solenidion and famulus excluded) and 4 or more ven-
tral setae (pas excluded). Solenidion setiform.
................................................... Thalassarachna
24b. Tarsus I either with 4 dorsal setae plus small clavate solenidion but no ventral setae (pair of pas
present), or with 3 dorsal setae plus long setiform
or short solenidion, number of ventral setae from
none to numerous (pas excluded). .................. 25
25a. No ventral seta on tarsus I (though pas present).
......................................................................... 26
25b. Number of ventral setae on tarsus I from one to
numerous. ........................................................ 27
26a. Tarsi I and II with small claviform solenidia. Tibia
I with pair of setae, one of these setae pectinate.
OC with 0, rarely 1 seta. Ventral plates delicate,
often separate. PE with 0–1 dorsal and 2 ventral
setae, the latter may be within striated integument.
Adanal setae lacking. ......................... Isobactrus
26b. Tarsi I and II with short bacilliform solenidion.
Tibia I with pair of setae, both pectinate. OC with
2 setae. Ventral plates often fused. PE generally
with 4 or more (rarely 3) setae. Adanal setae near
anal cone. .................................. Rhombognathus
27a. Idiosoma with more than 7 dorsal idiosomatic setae (pair of adanal setae excluded). Tarsi I and II
with short ventral spine close to apex; solenidion
and famulus of tarsus I similar in length and shape.
............................................. Rhombognathides
27b. Idiosoma with 5 or fewer dorsal setae (pair of
adanal setae excluded). Solenidion and famulus
of tarsus I dissimilar in shape. No short ventral
spine close to apex of tarsus I or II. ................ 28
28a. AE with 5 or more pairs of setae. ................... 29
28b. AE with 2–4 pairs of setae. ............................. 30
29a. Telofemora I to IV with more than 25 setae,
majority of setae arranged in rows. Tarsi IV
with numerous ventral setae and pair of pas.
............................................... Acanthohalacarus
29b. Telofemora I to IV with 10 or fewer setae.
Tarsi IV with 0–1 ventral setae; pas lacking.
........................................................... Agauides
30a. With no more than 2 pairs of dorsal idiosomatic
setae. Adanal setae lacking .............. Phacacarus
30b. With 4–5 pairs of dorsal idiosomatic setae plus
pair of adanal setae. ........................................ 31
31a. Tibia I with 3–5 spines. Spines large and wide
throughout their length; the latter more than half
height of that segment. Blunt tip of spines serrate
or coarsely denticulate. Spines not paired. ..... 32
31b. Tibia I with 2–8 ventral setae or spines, often
arranged in pairs. Setae slender or bipectinate;
spines, if present, short, their length less than half
height of tibia I. ............................................... 33
32a. Basifemur I with 3 setae. P-3 about half length of
P-2. Median claws of tarsi II to IV distinct, though
13
less than half length of paired claws. Tarsi III and
IV with 1–2 ventral setae. ............. Halacaropsis
32b. Basifemur I with 2 setae. P-3 shorter than half
length of P-2. Median claws of tarsi II to IV minute. Tarsi III and IV in general without ventral setae. ...................................................... Agauopsis
33a. Median claws of all tarsi nearly half length of
paired claws. Opposing margins between pair of
PE (at level of insertion of leg III) generally long
and straight. PE with 2 dorsal setae anterior to insertion of leg IV. Tarsi III and IV slightly curved.
......................................................... Bradyagaue
33b. Median claws of tarsi I–IV less than one quarter
length of paired claws. Opposing margins of pair
of PE triangular or plates fused. PE with 0, rarely
1 dorsal seta anterior to insertion of leg IV. Tarsi
III and IV straight. .......................................... 34
34a. Apex of rostrum with single pair of minute
barbs. Legs without cerotegumental lamellae.
.................................................... Werthelloides
34b. Apex of rostrum with pairs of rostral setae, rarely
with minute barbs. If barbs present then legs with
cerotegumental lamellae. ................................ 35
35a. Ocular plates minute (less than 20 µm in length)
or fused with PE. ................................. Actacarus
35b. Ocular plates larger than 25 µm in length; may be
fused with AD or PD. ...................................... 36
36a. AE with pair of epimeral pores. ...................... 37
36b. AE without epimeral pores. ............................ 42
37a. Tibia I with 4 ventral setae. .......... Arhodeoporus
37b. Tibia I with 2 or 3 ventral setae. ..................... 38
38a. Apical palpal segment with 3 setae in basal
whorl. .............................................................. 39
38b. Apical palpal segment with 0–1 setae. ............ 40
39a. Tibiae I and II with 3 and 3 (rarely 2) ventral setae. .............................................. Copidognathus
39b. Tibiae I and II each with a pair of ventral setae.
............................................................ Acarothrix
40a. Gnathosoma about as long as wide, and rostrum shorter than wide. Two of the 3 ventral
setae of tibiae I and II distinctly bipectinate.
................................................. Copidognathides
40b. Gnathosoma and rostrum longer than wide, rostrum triangular. Ventral setae of tibiae I and II
slender, smooth, rarely delicately pectinate. ... 41
41a. Tarsus II with 1 ventral seta; solenidion in dorsomedial position. Female genital sclerites with
3 subgenital setae. Perigenital setae in males scattered around GO. ................................. Pelacarus
41b. Solenidion on tarsus II in dorsolateral position;
ventral seta rarely present. No subgenital setae on
female genital sclerites. Perigenital setae in males
arranged in a ring close to GO. ........... Werthella
42a. Tibia I with 2 ventral setae. ............................. 43
42b. Tibia I with 4 or more ventral setae. ............... 46
43a. P-4 with single seta in basal whorl.
....................................................... Mictognathus
43b. P-4 with 3 setae in basal whorl. ...................... 44
44a. Tibia I club-shaped. Tarsus I with 2 ventral setae
plus pas. .................................. Thalassopthirius
44b. Tibia I cylindrical. Tarsus I with 3 or more ventral
setae plus pas. ................................................. 45
45a. Tarsus I with ventromedial seta, pair of eupathidia
plus pas. ........................... Halacarellus (in part)
45b. Tarsus I with ventromedial seta, numerous eupathidia plus pas. ............................ Thalassacarus
46a. Females and males with external pairs of genital
acetabula; acetabula of males posterior to genital
opening. ..................................... Caspihalacarus
46b. Genital acetabula internal. .............................. 47
47a. Both pairs of maxillary setae situated adjacent
to base of rostrum. Dorsal plates and margins of
idiosoma often with cerotegumental lamellae or
spiniform filaments. .................................. Agaue
47b. Distal pair of maxillary setae in apical half of rostrum, basal pair near base of rostrum. No cerotegumental lamellae present. ............................. 48
48a. Tarsus I with 1 basal seta or spur (rarely spur doubled) separated from 2 or more apical eupathidia.
...................................................................... 49
48b. Other arrangement of setae. ............................ 51
49a. Ocular plate more than 3 times as long as wide; its
posterior portion slender, tail-like. No gland pore
in posterior third of OC. ............. Tropihalacarus
49b. OC 1–2.5 times as long as wide; its posterior portion not conspicuously slender. If OC elongate
then a gland pore present in its posterior corner.
......................................................................... 50
50a. OC elongate, length at least twice width, with
gland pores in anterior and posterior half; plate
sometimes divided. PE with (1–)3–6 dorsal (dorsomarginal) setae. PD in general uniformly reticulate, without gland pores. ..... Bathyhalacarus (in
part)
50b. OC mostly less elongate, with 1 or 2 gland pores.
PE in general with 1 dorsal (dorsomarginal) seta.
If OC long and provided with a gland pore anteriorly and posteriorly, then PD with pair of costae
and gland pores. ............... Halacarellus (in part)
51a. P-3 with readily recognizable seta or spur. Tarsus I with 1–2 pairs of eupathidia and pair of pas.
................................................. Peregrinacarus
51b. P-3 without seta or spur. Tarsus I with 1 seta and
0–1 single eupathidia and pair of pas. ............. 52
52a. Tibiae I and II with 4 and 2 ventral setae, respectively. Tarsi I and II with a single ventral seta.
............................................... Camactognathus
14
52b. Tibiae I and II with 4 and 3 ventral setae, tarsi
I and II with 2 and 0 ventral setae, respectively.
......................................................... Winlundia
Description of marine halacarid genera
Acanthohalacarus Bartsch, 2001 (Fig. 14)
Diagnosis. Idiosoma: Length 450–540 µm. Dorsum
with AD, PD, and pair of OC, 6 pairs of idiosomatic
setae and four pairs of gland pores. Adanal setae on
anal cone. AD and PD each with pair of gland pores,
OC with 2 pores. Venter with AE, pair of PE, and GA.
AE and PE with adjunct setae. Female GA with up to
5 pairs of perigenital setae and 2 pairs of subgenital
setae. Male GA with numerous perigenital setae and 5
pairs of subgenital setae.
Gnathosoma: With 1 pair of maxillary setae
on gnathosomal base, 1 pair on rostrum. Palps 4segmented, attached laterally. P-2 with 1 distodorsal
seta; P-3 with medial spur; P-4 with 3 setae in basal
whorl.
Legs: Genua of legs much shorter than adjoining
segments. Basifemora I–IV with 3–7 setae each. Tibiae
and telofemora with ventromedial and ventrolateral,
dorsomedial and dorsolateral rows of short spiniform
setae, more than 5 setae in each row. Tarsus I with 1
ventromedial seta and numerous eupathidia; tarsi II to
IV with 5–6 ventral setae. Solenidia short, setiform, on
tarsi I and II in dorsolateral and dorsomedial position,
respectively. Famulus inconspicuous. Tarsi I to IV with
3 long dorsal setae each (solenidia excluded).
Apex of tarsi with pair of claws; central sclerite
ending with small claw-like process.
Biology and distribution. With larva and 2 nymphal
stages during ontogenetic development. The genus is
recorded from a seamount (Great Meteor Seamount)
in the northeastern Atlantic. Because of the numerous
spiniform setae on the legs, Acanthohalacarus is
expected to live in a close association with other
organisms.
Remarks. Acanthohalacarus is characterized by its
numerous spiniform setae on the legs and idiosoma.
References. Bartsch (2001a).
Acanthopalpus Makarova, 1978 (Fig. 15)
Diagnosis. Idiosoma: Length 440–550 µm. Dorsal
plates AD, OC and PD large; PD and anal plate fused.
Dorsum with 6 pairs of idiosomatic setae; adanal setae
on anal plate. First pair of gland pores on AD, following gland pores vestigial. OC with pore canaliculus.
Venter with AE, PE and GA. AE with 3 pairs of setae;
epimeral pores lacking. PE with 1 dorsal and 3 ventral
setae. Female GA with 3 pairs of perigenital setae,
genital sclerites with 2 pairs of subgenital setae.
Gnathosoma: Short. Rostrum shorter than
gnathosomal base, triangular in ventral aspect. Both
pairs of maxillary setae on rostrum. Palps 4-segmented,
attached laterally, extending beyond rostrum. P-3 and
P-4 short. P-2 with 2 setae; P-3 with medial spine; P-4
with 3 setae in basal whorl, 1 of these setae spiniform.
Legs: Leg I wider than following legs. Genua of all
legs shorter than telofemora and tibiae. Basifemora I–
IV with 2 setae each. Telofemur I with short, spinose,
divaricate spine; genua I with pair of spines, tibia I
with ventral spines and a seta. Tibiae II–IV with 3,2,2
ventral and 4,3,3 dorsal setae. Ventral spiniform setae
of telofemora, genua and tibiae often divaricate. Tarsi
I to IV with 4,4,3,3 dorsal setae and 3,1,0,0 ventral
setae; each tarsus with pair of parambulacral setae.
Tarsus I with setiform solenidion and lamellar famulus
in dorsolateral position. Solenidion on tarsus II in
dorsomedial position.
Paired claws of tarsus I short, slightly longer than
enlarged median claw. Paired claws of tarsi II to IV
slender, elongate; central sclerite without a claw-like
process. Posterior tarsi with carpite between tip of
tarsus and central sclerite.
Biology and distribution. With three juvenile
stages, larva, protonymph and deutonymph. Males at
present not known. Two species, A. hirsutus Makarova,
1978 and A. spinosus (Bartsch, 1978), are described,
the former is from the northern Pacific, the latter from
the northern Atlantic. The differences between these
species are slight and A. hirsutus may be a junior synonym.
Remarks. Similar to species of the Agauopsis
furcata group and Halacarellus species such as H.
subterraneus, but in contrast to these the P-2 of
Acanthopalpus bears two setae. The presently known
Acanthopalpus species are easily separated from other
halacarid species on the basis of the divaricate and
denticulate spine on telofemur I.
References. Makarova (1978), Bartsch (1978).
Acarochelopodia Angelier 1954 (Fig. 16)
Diagnosis. Idiosoma: Length 140–270 µm. AD, OC
and PD separated by striated integument; plates delicate,
uniformly and finely porose. Dorsum with 6 pairs of
idiosomatic setae; ds-2, ds-3 and ds-4 within striated
integument. AE divided into a right and left half, in
some species prolonged posteriorly. Each of PE may
be divided by longitudinal fissure. AE with 2 ventral
setae; PE with 1 dorsal and 2 ventral setae. Female GA
with 3 pairs of perigenital setae and 0 subgenital setae.
Male GA with ca 7 pairs of perigenital setae and 3 pairs
of subgenital setae.
Gnathosoma: Longer than wide. Rostrum triangular
in ventral aspect. Both pairs of maxillary setae on
rostrum. Palps 4-segmented, lateral to gnathosoma. P-
15
2 with 2 dorsal setae in distal half; these setae generally
bristle-like and pectinate. P-3 with short dorsal bristle.
P-4 with 3 setae basally, 1 setula and 2 spinelets
apically.
Legs: Leg I much longer and stronger than following
legs. Genua I to IV shorter than adjoining leg segments.
Basifemora I to IV with 2,2,1,0 setae. Telofemur I with
short, distinctly pectinate ventral spine. Genu I with 2
long, heavily pectinate spines. Tibia I wide, with 5–6
such spines. Tibiae II, III and IV ventrally with a pair
of short setae. Tarsus I slender, at least 6 times longer
than high. Tarsus I dorsally with 3 setae, ventrally with
1 long bristle and 2 small setae; tip of tarsus with setula
and flagelliform seta. Tarsus II with 3 dorsal setae,
1 tiny dorsomedial solenidion and (0?–)1–2 small
ventral setae. Tarsi III and IV with 4 and 3 dorsal setae,
respectively, and 0 ventral setae. Tarsi II to IV each
with paired parambulacral setae.
Tarsus I with small median claw; paired claws
absent. Tarsi II to IV with ‘normal-sized’ paired claws;
median claw either small or almost as long as paired
claws.
Biology and distribution. One larval and two
nymphal stages during ontogenetic development.
Acarochelopodia is exclusively psammobiont,
inhabiting tidal beaches. Nine species are described.
Records are from the Atlantic Ocean, Mediterranean
and Black Sea, the Indian and Pacific Ocean.
Remarks. Acarochelopodia is identified on the basis
of the enlarged leg I with the very slender tarsus ending
with a single small claw.
References. Angelier (1954), Bartsch (1977, 1988c),
Morselli et al. (1998).
Acaromantis Trouessart & Neumann, 1893 (Fig. 17)
Diagnosis. Idiosoma: Length 230–400 µm. AD and PD
large, often foveate; OC reduced to minute sclerites.
AD generally with pairs of ds-1 and ds-3; ds-2 within
striated integument; ds-4 and ds-5 on PD; adanal setae
usually in dorsal position. Ventral plates large. AE with
a pair of epimeral vesicles and 3 pairs of setae. Epimera
III and IV of either side contiguous or fused, forming
the PE; that latter plate with 1 dorsal and 3 ventral setae.
Female GA with 4 pairs of perigenital setae; subgenital
setae lacking. Male GA with 15–20 perigenital setae
arranged in a ring around GO and 0–3 pairs of outlying
setae; genital sclerites with 3 pairs of minute subgenital
setae. Male perigenital setae often plumose.
Gnathosoma: Globular, broadly attached to
idiosoma. Rostrum small, conical, much shorter than
gnathosomal base. One pair of long maxillary setae on
gnathosomal base, 1 pair of short setae near apex of
rostrum. Palps attached to gnathosomal base dorsally.
Palps short, 2-segmented; second palpal segment with
1 ventral bristle and 1 dorsal seta; palpal tip with tiny
setae.
Legs: Telofemora and tibiae much longer than small
and globular genua. Basifemora I to IV with 1–2,2,1,1
setae. Telofemora with ventrolateral and -medial
carinae. Shape of leg I different from that of following
legs. Tibia I long, its base narrow, cylindrical, then
rapidly expanded; tibia I ending with wide, smooth
spine. Tarsus I hardly longer than high and rotated
inward. Genu I with bipectinate seta. Tibia I with
spine, a medial seta and 3 dorsal setae; tibiae II, III
and IV each with 2 bipectinate ventral spines and 3
dorsal setae. Tarsus I with dorsolateral solenidion and
famulus. Solenidion on tarsus II on inner flank of medial
membrane of claw fossa. Tarsi I to IV with 4,4,3,3
dorsal setae (solenidia included, famulus excluded),
1,1,1,1–2 ventral setae, and each tarsus with pair of
single parambulacral setae.
Tarsus I with median claw; paired claws lacking.
Tarsi II to IV with large paired claws; central sclerite
small, claw-like process, if present, small.
nymphal stages are known. Eleven species are presently
described; all are psammobionts. With the strongly
sclerotized plates, the gnathosoma broadly attached to
the idiosoma, and legs which can be clasped against the
idiosoma, these creatures are protected against lesion
from grinding sediment particles. When walking, leg
I is often raised, the tibiae are held horizontally above
the gnathosoma, the claw of tarsus I is turned inward.
Records of Acaromantis are from the western and
eastern North Atlantic Ocean and the Mediterranean
Sea, and from the western and eastern Pacific Ocean.
The records are from tidal and shallow subtidal
habitats.
Remarks. Acaromantis is related to Simognathus.
In contrast to Simognathus the palps of Acaromantis
are two-segmented and tarsus I bears a single claw. In
general (but not always), the two genera can be separated on the basis of the shape of leg I. In Acaromantis
tibia I is widest in its basal third and tarsus I is very short
and rotated, whereas in the majority of Simognathus
species tibia I is club-shaped (widest in its apical third)
and tarsus I distinctly longer than high and ending with
a large median and two slender lateral claws.
References. Bartsch (1977), Otto (2000a).
Acarothrix Bartsch, 1990 (Fig. 18)
Diagnosis. Idiosoma: Length 280–320 µm. AD, OC
and PD present. OC with 1–2 setae. Dorsum with (3–)4
pairs of gland pores, posteriormost pair situated on
cones, and 5–6 pairs of idiosomatic setae; third pair of
setae on OC; adanal setae on anal plate in either dorsal
or ventral position. AE with pair of epimeral pores. PE
16
with 1 dorsal seta and 3 ventral setae. Female GA with 3
pairs of perigenital setae and 1 pair of subgenital setae.
Male GA with numerous perigenital setae, its genital
sclerites with 4 pairs of subgenital setae and 1 pair of
external genital acetabula.
Gnathosoma: Four-segmented palps attached
laterally. Rostrum triangular. Gnathosomal base and
rostrum each with a pair of maxillary setae. Rostral tip
with 2 pairs of rostral setae. P-2 with 1 dorsal seta. No
seta on P-3. P-4 with 3 setae in basal whorl.
Legs: Genua shorter than telofemora and tibiae.
Basifemora I–IV with 2,3,2,2 setae. Tibiae I to IV with
3–4,3–4,3,3 dorsal setae and 2,2,2,2 ventral setae of
which the ventromedial one is bipectinate on tibiae I
to III (and IV). Solenidion on both tarsus I and II in
dorsolateral position. Tarsi I–IV with 2–3,0,0,0 ventral
and 4,4,4,3 dorsal setae.
All tarsi end with a pair of claws. Central sclerite
with small, bidentate median claw.
Biology and distribution. With larva and
protonymph. Deutonymphal stage not known. At
present four species are described. Records are from
warm-temperate and tropical brackish water areas of
Australia, Asia, Africa and North America.
Remarks. Unique in Acarothrix is the presence of
a pair of acetabula in the posterior portion of the male
genital sclerites.
Acarothrix resembles Copidognathus and Werthella
but bears three setae on basifemur II instead of the most
general number of two. In contrast to Copidognathus,
the tibiae I and II of Acarothrix have two instead of
three ventral setae; and in contrast to Werthella, the
fourth palpal segment of Acarothrix bears three setae,
that of Werthella just one seta.
References. Bartsch (1990a, 1997b, 2004b), Proches
(2002).
Actacarus Schulz, 1937 (Fig. 19)
Diagnosis. Idiosoma: Length 140–360 µm. AD and
PD large, opposing margins often truncate with few
striae of membraneous integument; rarely plates widely
separated or fused. OC minute, sometimes fused with
PE or lacking. Dorsal plates finely porose or foveate,
never coarsely sculptured. Dorsum with 4 pairs of
gland pores, 1 each on AD and OC and 2 on PD, and
6 pairs of idiosomatic setae; adanal setae adjacent to
anal sclerites. AE with 3–4 pairs of setae; PE with 1
dorsal and 2–3 ventral setae. Membraneous integument
between AE and GA with 0–1 setae. Female with 3(–5)
pairs of perigenital setae, though posterior pair may be
minute and concealed by protruding genital sclerites;
subgenital setae lacking. Male with 7–18 pairs of
perigenital setae and 1–3 pairs of subgenital setae.
Gnathosoma: Generally longer than wide. Rostrum
triangular or elongate. Tectum truncate or with a
triangular process. Both pairs of maxillary setae inserted
on rostrum. Palps 4-segmented, attached laterally and
extending beyond rostrum. P-2 with 1 distal seta. P-3
short, with medial spur. P-4 with 3–4 basal setae and
1 spur.
Legs: First two pairs not markedly dissimilar in
outline. No lamellae present. Genua shorter than
adjoining leg segments. Basifemora I to IV with 2,2,1–
2,1–2 setae. Tibia I with 2–4 ventral bristle-like setae,
tibiae II, III and IV each with 2 ventral setae. Tarsus I
with large lateral membrane of claw fossa; setation: 3
dorsal setae, dorsal solenidion, 3 ventral setae. Tarsus II
with 3 dorsal setae, 1 large dorsal solenidion, no ventral
setae. Tarsi III and IV with 3–4 dorsal but no ventral
setae. All tarsi with pair of parambulacral setae.
Paired claws of tarsus I smaller than those of
following tarsi. Median claw small on all tarsi.
Biology and distribution. With one larval and the
two nymphal stages protonymph and deutonymph. Actacarus is psammobiont, inhabiting coarse or fine sand,
common in tidal areas. The deepest record is from
400 m depth. Actacarus is distributed world-wide, 25
species are described.
Remarks. Actacarus is characterized by the
small OC, less than 20 µm in length, and can thus
be distinguished from similar shaped psammobiont
species of the genera Arhodeoporus, Camactognathus,
Copidognathus, and Winlundia.
References. Bartsch (1996a), Abé (1997), Otto
(2000c).
Agaue Lohmann, 1889 (Fig. 20)
Diagnosis. Idiosoma: Length 320–1600 µm. Idiosoma
usually with cerotegumental layers, these may be
delicate membranes, covering plates and striated
integument, or raised and structured like walls of a
honeycomb; other species have hair-like or spur-like
filaments (cerotegumental structures may be lost during
the clearing procedure). Dorsal and ventral plates
large. Dorsum with 3 pairs of gland pores, situated on
or lateral to AD, on OC and PD. Pairs of ds-1 to ds-5
in some species small in others long and erect; adanal
setae on anal plate. AE with 3 pairs of ventral setae.
PE with 1–3 dorsal setae anterior to leg III, 0–1 setae
anterior to leg IV, and 3 ventral setae. Female GA with
3–10 (rarely more) pairs of perigenital setae and 0–2
pairs of subgenital setae. Male GA with more than 80
perigenital setae densely arranged around GO; genital
sclerites with 5 pairs of spur-like subgenital setae.
Gnathosoma: Longer than wide, generally slender.
Tectum with scaliform lamella. Rostrum almost
parallel-sided, rarely as long, often much longer than
gnathosomal base. Maxillary setae inserted close
together, 1 pair on gnathosomal base, 1 pair in basal
portion of rostrum. Distal pair of maxillary setae often
17
shorter than basal pair, sometimes that pair of setae
hardly recognizable. Rostral setae minute, often spurlike or divaricate. Slender 4-segmented palps lateral to
gnathosoma, reaching to or surpassing tip of rostrum.
P-2 with 1 distodorsal seta. P-3 short, usually with 1
distodorsal bristle (absent in some few species). Seta
on P-2 smooth or flattened and bipectinate. P-4 with
3 long setae in basal whorl (rarely situated in apical
half of segment), 1 seta in about middle of segment,
and 1 setula and 2 spurs apically. Chelicerae slender,
cheliceral claw with few but strong teeth.
Legs: Generally slender; often with cerotegumental
lamellae; lamellae of telofemora may even exceed the
segments height. Genua much shorter than telofemora
and tibiae. Basifemora I–IV with 2(–3),2–3,2,2 setae.
Tibiae cylindrical or clavate, with 4–6 slender, usually
smooth and bristle-like ventral setae. The majority of
species with large membranes of claw fossae on all tarsi.
Tarsus I with 3 dorsal setae, dorsolateral solenidion,
1 long ventral seta, and a cluster of 10–30 ventral
eupathidia at tip of tarsus. Tarsus II with 3 dorsal setae,
dorsomedial solenidion, and 0–4 ventral eupathidia.
Tarsi III and IV with 3 dorsal but no ventral setae.
Paired claws large, smooth, with single or numerous
tines. Median claw minute.
nymphal stages are known. More than 40 species are
described. Most species are recorded from the southern
hemisphere, from both tropical, temperate and polar
waters. Representatives of this genus live in a depth
range from the intertidal to the abyss.
Remarks. Species of the genera Bradyagaue, Halacarellus and Thalassacarus may be mistaken for
Agaue. Agaue species never have curved tarsi and an
enlarged median claw as present in Bradyagaue. The
P-3 of Halacarellus species have a spiniform seta in
medial position, and the posterior pair of maxillary
setae is in general situated in the posterior two-third
of the rostrum. In most of the northern hemisphere Halacarellus species, the tip of tarsus I has no more than
two eupathidia beside the pair of parambulacral setae,
whereas in Agaue species there are numerous setae.
Thalassacarus bears numerous eupathidia on tarsus I
but, in contrast to Agaue, the dorsal and ventral plates
are ornamented with foveae and rosette pores.
References. Newell (1984), Bartsch (1990b, 1999d),
Otto (1999b).
Agauides Bartsch, 1988 (Fig. 21)
and ventral plates separated by wide areas of intensely
striated integument. OC greatly reduced, wider than long,
corneae lacking. Dorsum with 6 pairs of idiosomatic
setae; adanal setae in dorsal position. PD with pair of
gland pores. Ventral setae of AE often multiplied, plate
with 5–8 pairs of setae. PE with 1 dorsal and 2(–3)
ventral setae. Female GA with 4–7 pairs of perigenital
setae; genital sclerites lack subgenital setae.
Gnathosoma: Rostrum triangular, about as long
as gnathosomal base. Maxillary setae short, inserted
adjacent on gnathosomal base and rostrum. Apical
rostral setae minute. Palps 4-segmented, lateral to
gnathosoma and extending to tip of rostrum. P-2 with
1 distal seta. No seta on P-3. P-4 with 2 long setae,
apically with setula and 2 spurs.
Legs: Genua much shorter than tibiae and telofemora.
Basifemora I–IV with 3,3–4,2–3,2 setae. Tibiae I–IV
with 7,6,3–6,5–6 ventral setae which are short, bristlelike, sometimes slightly pectinate. Tarsus I and II with
dorsolateral and dorsomedial solenidion, respectively.
Tarsi I–IV with 4,4,3,3 dorsal setae and 5–8,1,0,0–1
ventral setae; tarsus I with pair of parambulacral setae;
tarsus II with lateral but no medial parambulacral seta.
Tarsi III and IV lack parambulacral setae.
Claws of all tarsi similar-shaped; paired claws large,
median claw small.
Biology and distribution. Agauides may be a
temporary parasite. Two species are recorded, one from
the Atlantic, one from the Pacific Ocean, from bathyal
and abyssal depths.
Remarks. In contrast to the majority of halacarids,
tarsi III and IV lack parambulacral setae. Unusual is the
increased number of setae on the AE.
References. Bartsch (1988b, 1989).
Agauopsis Viets, 1927 (Fig. 22)
usually wide, flattened and heavily armed. In the
majority of species AD and PD with slightly raised
longitudinal costae; costae with canaliculi or rosette
pores. Gland pores small; AD, OC and PD with 1, 1 and
1–2 pairs of pores, respectively. Dorsum with 5–6 pairs
of idiosomatic setae; adanal setae close to anal cone.
AE large; generally extending dorsad, fused to anterior
dorsal plate and thus forming the anterior margin of
idiosoma. AE with 3 pairs of ventral setae and in the
majority of species with a pair of epimeral pores (often
opening with a slit). PE with 1 dorsal and (1–)3 ventral
setae. Female GA with (2–)3 pairs of perigenital setae;
genital sclerites with 0–4 subgenital setae. Male GA
with approximately 30–100 perigenital setae, and often
a pair of outlying perigenital setae; genital sclerites
with 3–5 subgenital setae.
Gnathosoma: Longer than wide. Gnathosomal base
subquadrangular; rostrum almost parallel-sided, from
slightly shorter to longer than gnathosomal base. First
pair of maxillary setae near base of rostrum, either on
gnathosomal base or on rostrum; 2nd pair of maxillary
setae in distal third of rostrum. Palps 4-segmented,
lateral to gnathosoma. P-2 with 1 distodorsal seta. P-3
18
short, with median bristle- or spiniform seta, in some
few species with denticulate divaricate spine. P-4 with
1–3 setae in basal half, rarely these setae in distal half;
Legs: Genua distinctly shorter than adjoining
segments. Leg I much wider and longer than following
legs and armed with conspicuous spines, viz. (0–)1–5
spines on telofemur, 2 spinelets (may be bristle-like) on
genu, 3–5 spines on tibia, and 1 spine on tarsus. Spines
generally blunt and delicately pectinate, in a few
species spines conspicuously denticulate. Basifemora
I–IV with 2,2(–3),(1–)2,(1–)2 setae. Tibiae II–IV with
2–3 ventral spines or bristles. In the majority of species,
tarsus I with 3 dorsal setae, dorsolateral solenidion, 1
ventromedial spine, and 2 (rarely 1) minute ventral
setae; apically with pair of parambulacral setae.
Tarsus II with 3 dorsal setae, dorsomedial solenidion,
0–1 minute ventral setae, 1–2 lateral and 0–2 medial
parambulacral setae. Tarsus III and IV with 3–4 and 3
dorsal setae, respectively, and 0 (rarely 2) ventral setae;
apically with 0–1 parambulacral setae on either side.
Paired claws of posterior legs generally larger than
those of tarsus I, median claw small, often hardly
developed.
nymphal stages present. At present, 80 species are
described. The genus is cosmopolitan, inhabiting the
range from tidal to the abyss. Most records are from
warm and temperate waters. The number of species
known from the southern hemisphere exceeds that
from the north.
Remarks. In contrast to species of Atelopsalis,
which also have enlarged leg I equipped with
spines, the palps of Agauopsis are four-segmented.
Enlarged leg I with conspicuous spines are present
in Acanthohalacarus and a few species of the genus
Halacarellus (e.g. species of the subterraneus group
and H. auzendei). These Halacarellus species have a
triangular rostrum, and their females often no more
than two pairs of perigenital setae. The second palpal
segment of Acanthohalacarus bears two setae.
References. Bartsch (1986b, 1996b), Otto (1999a).
Anomalohalacarus Newell, 1949 (Fig. 23)
Diagnosis. Idiosoma: Length 200–520 µm.
Idiosoma very slender; its width less than interval
between epimera II and III. Dorsal and ventral plates
small, delicate, they lack conspicuous ornamentation.
OC absent or reduced to minute sclerites; corneae
lacking. PD present; in adults of most species divided
longitudinally. One pair of gland pores on AD, 0–1
pairs of pores in striated integument, and 1–2 pairs
on PD. Dorsum with 5–6 pairs of idiosomatic setae;
ds-1, ds-2 and ds-4 generally remarkably long; small
adanal setae on anal cone. AE in the majority of
species divided longitudinally (rarely epimera fused in
the median); each plate with 3 ventral setae and pair
of epimeral pores. PE small, with 1 dorsal and 2–3
ventral setae. Female genital plate divided; with 2 pairs
of perigenital setae on genital plates and 1 pair within
striated integument, on a pair of small sclerites or on
a single median sclerite; genital groove present. Male
GA large; 7–50 pairs of perigenital setae lateral to GO
and genital groove; genital sclerites with 3 pairs of
subgenital setae.
Gnathosoma: Longer than wide. Rostrum slender,
parallel-sided; from half as long to almost as long as
palps. Both pairs of maxillary setae inserted on rostrum.
Four-segmented palps slender, attached laterally and
surpassing rostrum. P-2 with 1–2 setae, either a single
basal seta or 1 basal and 1 distal seta. P-3 short, with
1 spine. P-4 with 3 setae in basal whorl; apically with
setula and 2 spurs.
Legs: All legs slender; anterior 2 pairs of legs widely
separated from posterior ones. Leg I longer than leg II.
Genu of leg I only slightly shorter than telofemur and
tibia; genua II–IV shorter than adjoining leg segments.
Dorsal and lateral setae on legs remarkably long.
Basifemora I to IV with (1–)2,(1–)2(–3),1–2,0 setae,
respectively. Tibia I ventrally with 0–2 short spurs,
0–2 delicately pectinated setae and 3–5 smooth setae;
tibiae II–IV with 2–3,2–3,2 ventral setae, 1–3 of these
setae bipectinate. Tarsus I with enlarged lateral fossa
membrane, 3 dorsal setae, and a solenidion adjacent to
fossa membrane; ventrally with 1 spur, rarely 2 spurs,
and a pair of small, eupathid setae. Tarsus II with 3
dorsal setae, claviform dorsolateral solenidion, and
0–1 ventral setae. Tarsi III and IV each with 3 dorsal
and 0 ventral setae. All tarsi with an apical pair of
parambulacral setae.
Paired claws on tarsus I somewhat smaller than those
on following tarsi. All tarsi with small median claw.
Biology and distribution. A larval and a single
nymphal stage, the protonymph, occur during
development. Juveniles have a fused, quadrangular PD.
Anomalohalacarus exclusively inhabits the interstitium
of sandy deposits. Most records are from intertidal and
subtidal sediments. Anomalohalacarus, with 19 species
described, is recorded from the North Atlantic Ocean,
Mediterranean, Black Sea, Indian, and Pacific Ocean.
Remarks. The general shape of Anomalohalacarus,
Arenihalacarus and Halacaroides is almost identical.
Arenihalacarus has five pairs of gland pores, the
females have two pairs of perigenital setae and a
distinct genital plate anterior to the GO, basifemur
IV bears a seta, and two nymphal stages occur during
development. In contrast to Anomalohalacarus, species
of Halacaroides still have small OC, the female GA
19
is not divided and genu I is distinctly shorter than the
adjoining segments.
References. Bartsch (1981b, 2003c), Abé (1996b).
Arenihalacarus Abé, 1991 (Fig. 24)
spindle-shaped; its width less than interval between
insertions of legs II and III. Dorsal and ventral plates
small; OC vestigial; corneae lacking. Dorsum with 6
pairs of idiosomatic setae, ds-1 to ds-4 slender and
long; ds-2 to ds-5 within striated integument. Short
adanal setae in posterior margin of PD. AE divided into
right and left plate; each plate with epimeral pore and 3
setae. PE with 1 dorsal and 3 ventral setae. Female GA
divided into 4 platelets; male with fused GA. Female
with 2 pairs of perigenital setae; subgenital setae
lacking. Male with about 25 perigenital setae, genital
sclerites with 3 pairs of subgenital setae.
Gnathosoma: Slender. Palps 4-segmented, attached
laterally; surpassing rostrum. P-2 with 1 basal and 1
distal seta. P-3 with medial spur. P-4 with 3 setae in
basal whorl. Rostrum slender. Both pairs of maxillary
setae situated on rostrum.
Legs: Slender. Genu of leg I somewhat shorter than
telofemur and tibia; genua of following legs distinctly
shorter than adjacent leg segments. Lateral membrane
of claw fossa of tarsus I enlarged. Basifemora I to
IV with 2,2,2,1 setae, at least 1 seta of each segment
long and delicately plumose. Genua and tibiae with
bipectinate ventral setae. Solenidion of tarsus I and II
situated dorsolaterally. Tarsi I–IV with 3,0,0,0 ventral
setae and 4,4,3,3 dorsal setae (solenidia included). Each
of tarsi I to IV with pair of parambulacral setae.
Paired claws of tarsus I smaller than those of
following legs. Median claw present but small.
Biology and distribution. With three juvenile
stages, one larva and two nymphs. At present a single
species is described, which was extracted from coarse
sandy deposits in northern Japan.
Remarks. In its shape similar to Anomalohalacarus.
Both genera are psammobionts. Most of the
Anomalohalacarus species bear one seta on P-2, in
contrast, in the single Arenihalacarus species there are
two setae. The female Arenihalacarus bears the anterior
pair of the two pairs of perigenital setae on a platelet
immediately anterior to the genital slit, whereas in
Anomalohalacarus there are three pairs of perigenital
setae, the anterior pair is situated on tiny sclerite(s)
or within the striated integument. Arenihalacarus
has five pairs of gland pores, Anomalohalacarus four
(rarely two) pairs of pores; basifemur IV bears one
seta whereas in Anomalohalacarus there is none. In
Anomalohalacarus a free-living deutonymphal stage is
suppressed.
References. Abé (1991).
Arhodeoporus Newell, 1947 (Fig. 25)
plates large, often reticulate and with porose areas;
OC often tail-like extended. Majority of species with 4
pairs of gland pores; in some few species glands large,
opening on cones. Dorsum with 6 pairs of dorsal setae;
adanal setae at anal cone. Ventral plates large, may
be fused. AE with 3 pairs of ventral setae and pair of
epimeral pores, the latter in some few species enlarged.
PE with 1–2 dorsal and 3 ventral setae. Female GA with
3 pairs of perigenital setae and 1–2 pairs of subgenital
setae. Male GA with 15–40 perigenital setae and 4–5
Gnathosoma: From slightly to distinctly longer
than wide. Rostrum triangular or slender and almost
parallel-sided. One pair of maxillary setae either on
gnathosomal base or in basal part of rostrum, 1 pair
on rostrum. Palps 4-segmented, attached laterally,
extending beyond tip of rostrum. P-2 with 1 distal seta.
No seta on short P-3. P-4 with 3 (rarely 2?) setae in
basal whorl.
Legs: Slender. Genua much shorter than adjoining
segments. Basifemora I to IV with 2,2,1–2,1–2 setae.
Tibia I with 2 pairs of bristle-like ventral setae, the
ventromedial ones either smooth or bipectinate, the
ventrolateral ones smooth. Tibia II with 3–4 ventral
setae, the 2 ventromedial ones bipectinate. Tibiae III
and IV with 2 ventral setae each. Tarsus I with 3 dorsal
setae, 1 dorsolateral solenidion, and 3(–2) ventral setae.
Tarsus II with 3 dorsal setae, 0–1, rarely 2, ventral
setae; solenidion in dorsomedial position, often long,
seta-like. Tarsi III and IV with 4(–3) and 3 dorsal setae,
respectively and 0–1 ventral setae. Tarsi I and II each
with pair of parambulacral setae, tarsi III and IV either
with pair of parambulacral setae and 0 ventral setae or
with single parambulacral seta and 1 long ventral seta.
Tarsi end with pair of claws and small median claw.
Claws often with pectines.
nymphal stages are known. Arhodeoporus lives in
a variety of substrata, in coarse sand and amongst
colonial organisms; it is common in shallow waters
though present also in the bathyal. The genus is spread
in temperate and tropical areas around the globe; there
are no records from polar waters. At present 30 species
are described; several of them can be assigned to
species groups.
Remarks. Arhodeoporus shares several characters
with Winlundia and Camactognathus, namely four
ventral setae on tibia I, no seta on P-3, three basal
setae on P-4. The three genera can be separated on the
basis of the number of setae on tarsus I. Tarsus I of
Camactognathus has a single ventral seta, Winlundia
20
has two setae and Arhodeoporus three ventral setae
(except one species with two setae). Similar shaped
Copidognathus species differ from Arhodeoporus in
the position of the solenidion on tarsus II (in lateral
instead of medial position as in Arhodeoporus) and the
suppression of a free-living deutonymph.
References. Bartsch (1983, 1997c), Otto (2000g).
Atelopsalis Trouessart, 1896 (Fig. 26)
Diagnosis. Idiosoma: Length 180–220 µm. Dorsal and
ventral plates large, in the majority of species almost
adjoining; plates often ornamented, panelled, foveate,
and/or with cup-like pores. Gland pores present
though rather inconspicuous. Dorsum with 6 pairs of
idiosomatic setae; adanal setae on anal plate. AE with
3 pairs of ventral setae and a pair of large epimeral
vesicles. PE with 1 dorsal and 3 ventral setae. Female
GA with 3 pairs of perigenital setae and 1–2 pairs of
subgenital setae. Males with 4–5 pairs of perigenital
setae, their genital sclerites with 4 minute subgenital
setae. Internal genital acetabula may be enlarged.
Gnathosoma: Almost as long as wide; base globular.
Rostrum shorter than gnathosomal base. One pair of
maxillary setae in basal third of rostrum, the other pair
minute, spur-like, situated near tip of rostrum. Palps
3-segmented (P-2 and P-3 fused), slender, lateral to
gnathosoma and hardly surpassing tip of rostrum. No
seta on second segment (corresponding to P-2 + P-3);
third segment (corresponding to P-4) with 1 basal seta,
1 apical setula and 2 apical spurs.
Legs: Leg I distinctly longer and wider than
following legs. All legs with their genua being smaller
than telofemora and tibiae. Basifemora I to IV with
2,2–3,2,2 setae. Telofemur I large, often with cuticular
spiniform lamellae. Tibia I with pair of ventral spines
in middle and pair of ventral setae near distal end of
that segment. Tibia II with 1 dorsomedial spinelet and
2 ventral setae (1 pectinate, 1 smooth). Tibiae III and IV
each with pair of ventral setae, 1 pectinate, 1 smooth.
Tarsus I with 3 dorsal setae, dorsolateral solenidion
and famulus, and 3 ventral setae. Tarsus II with 3
dorsal setae, dorsomedial solenidion, and 1 often long
ventral seta. Tarsi III and IV with 4 and 3 dorsal setae,
respectively, but no ventral setae. All tarsi with pair of
Tarsi I to IV end with paired claws and small median
claw.
Biology and distribution. Two nymphal stages are
present. Seven species are described. Atelopsalis is
recorded from all oceans, it inhabits tidal and subtidal
sediments.
Remarks. The enlarged legs I of Atelopsalis
resemble those of Agauopsis. Distinguishing characters
are: the AE of Atelopsalis bears epimeral vesicles and
the gnathosoma slender, 3-segmented palps, in contrast,
in Agauopsis there is a pair of slit-like epimeral pores
and the palps are 4-segmented.
References. Bartsch (2002).
Australacarus Bartsch, 1987 (Fig. 27)
slender; its width less than interval between insertions
of legs II and III. Dorsal and ventral plates small;
membraneous integument between plates rather thick.
AD and PD each with pair of gland pores. OC divided
into small anterior and posterior platelet; anterior
platelet with gland pore; corneae lacking. Dorsum
with 6 pairs of short idiosomatic setae; adanal setae
on anal plates. Venter with small platelets between
widely separated AE and PE. AE with 3 pairs of setae.
PE with 1 dorsal and 2 ventral setae. Female GA with
2–3 pairs of perigenital setae, no subgenital setae. Male
GA with genital groove posterior to GO and numerous
perigenital setae on either side of GO and genital
groove; each genital sclerite with 4 subgenital setae.
Gnathosoma: Slender. Rostrum attenuate, needleshaped. Palps 3–4-segmented (P-2 and P-3 may be
fused), slender, about as long as rostrum. P-2 with 1
distal seta; none on P-3 (if palps are 4-segmented);
apical segment with 2–3 setae in basal whorl.
Pharyngeal plate large. Both pairs of maxillary setae
on gnathosomal base.
Legs: Genua I–IV shorter than telofemora or tibiae.
Basifemora I to IV with 2,2,1,1 setae. Tibiae I–IV
with 3–4,2,2,2 ventral setae, 1–2 setae of tibia I may
be bipectinate. Dorsal setae of legs slender. Solenidia
slender, on tarsus I in dorsolateral position, on tarsus II
in dorsomedial. Tarsus I–IV with 4,4,4,3 dorsal setae
(solenidia included), 3,1,0,0 ventral setae and apical
pair of parambulacral setae; 1 or 2 of parambulacral
setae may be moved from apical position basalward.
Paired claws large. Median claw present but smaller
than the other claws.
Biology and distribution. Five species are presently
described, all are from the southern hemisphere.
Australacarus is believed to be a temporary parasite.
The palps form a trough, enclosing the needle-like
rostrum and chelicerae.
Remarks. Related to Colobocerasides but
Australacarus has the dorsal and ventral plates more
reduced and the rostrum more attenuate.
References. Bartsch (1987, 1993b), Otto (2000d).
Bathyhalacarus Sokolov & Yankovskaya, 1968 (Fig. 28)
plates often reticulate. AD in several species with small
frontal spine. OC elongate, in some species divided
into anterior and posterior portion; corneae usually
lacking. PD may be reduced. AD with 1 pair of large
21
gland pores; OC with 2 pairs of distinct gland pores,
generally 1 in anterior and 1 in posterior portion of OC
and situated on, sometimes tube-like, cones. No gland
pores on PD. Dorsum with 6 pairs of idiosomatic setae;
adanal setae on anal plate. AE with 3 pairs of setae.
PE with 1–6 dorsal (marginal) and 2–3 ventral setae.
Female GA with 2–4 pairs of perigenital setae and 1–3
pairs of subgenital setae. Male GO surrounded by 50–
100 perigenital setae, genital sclerites with 5 pairs of
subgenital setae.
Gnathosoma: Rostrum almost as long as or
longer than gnathosomal base, its shape triangular to
parallel-sided. One pair of maxillary setae inserted
on gnathosomal base, 1 pair on rostrum. Palps 4segmented, attached laterally, extending beyond
rostrum. P-2 with 1 distal seta, P-3 with 1 median spine
(may be very minute), P-4 with 3 setae in basal whorl,
0–1 lateral setae in middle of segment, 1 setula and 2
spurs apically.
Legs: All legs slender. Genua distinctly shorter than
adjoining segments. Basifemora I to IV with 2,3,2–
4,3–4 setae. Tibia I with 2–4 pairs of ventral bristlelike setae; tibiae II, III and IV with 3–8 ventral bristles.
Tarsus I with 3 dorsal setae, 1 setiform dorsolateral
solenidion, 1 ventral seta and a cluster with up to 30
ventral eupathidia. Tarsus II with 3 dorsal setae, slender
dorsomedial solenidion, 0–10 ventral setae; tarsi III
and IV with 3 dorsal and 0–4 ventral setae. Each tarsus
with pair of parambulacral setae.
Claws large, smooth or with pectines with delicate
tines. Median claw small.
nymphal stages are known. A dozen species are
described. Records are from the Atlantic and Pacific
Ocean. Most of the records are from the deep-sea.
Remarks. Bathyhalacarus resembles Thalassacarus
and a few species of the genus Halacarellus. In contrast
to species of the two latter genera the ocular plates of
Bathyhalacarus are elongate, often divided and bear a
gland pore in their anterior and posterior portions, the
PE in general have three to six dorsal setae, and the PD
lacks gland pores.
References. Sokolov and Yankovskaya (1968),
Newell (1967), Bartsch (1982, 1989).
Bradyagaue Newell, 1971 (Fig. 29)
elongate, length about twice the width. Insertion of
leg III in about middle of length of idiosoma. Dorsal
and ventral plates large. Plates marginally (rarely also
dorsally) with cerotegumental layers. Dorsal plates not
conspicuously sculptured, integument evenly pierced
by very fine canaliculi. AD, OC and PD each with pair
of gland pores. Dorsum with 6 pairs of idiosomatic
setae; adanal setae on anal plate. AE with 3 pairs of
ventral setae. PE with (1–)2–3 dorsal setae anterior to
leg III, 2 dorsal setae anterior to leg IV, and 3 ventral
setae. In most species opposing margins of right and
left PE straight and approaching in the median. Female
GA with 5–12 pairs of perigenital setae; no subgenital
setae. Male GA with more than 100 perigenital setae
arranged in a dense ring around GO; each genital
sclerite with 5 subgenital setae which are spur- or
stump-like.
Gnathosoma: Longer than wide. Rostrum parallelsided, slender, generally longer than gnathosomal
base. One pair of maxillary setae on gnathosomal base,
1 pair in basal part of rostrum; the 4 setae situated
close together. Four-segmented palps slender, slightly
surpassing rostrum. P-2 with 1 distal seta, P-3 with 0–1
seta, P-4 with 3 basal setae, apically with 2 setulae and
2 spurs.
Legs: Slender. Genua shorter than adjoining
segments. Telofemora, genua and tibiae often with
cerotegument. Basifemora with 2,2,2,2 setae. Tibia I
with 2–3 pairs of bristle-like ventral setae; tibiae II–IV
with 4–5,3–4,3–4 ventral setae. Ventral setae of tibiae
short, never spiniform, never bipectinate. Tibiae and
genua III and IV in general with setigerous processes.
Tarsi III and IV slightly curved. Tarsus I with 3 dorsal
setae; short dorsolateral solenidion, 1 ventral seta,
and apically with 4–12 pairs of eupathidia (pair of
parambulacral setae included). Tarsus II with 3 dorsal
setae, short dorsomedial solenidion, 0–1 ventral setae
and pair of parambulacral setae. Tarsi III and IV each
with 3 dorsal and 0 ventral setae, apically with pair of
All tarsi with massive, bidentate median claw. Paired
claws longer but generally more slender than median
claw. These paired claws usually with accessory
process and long pecten.
Biology and distribution. One larval and the two
nymphal stages proto- and deutonymph are present
during development. Bradyagaue is world-wide
distributed, in polar as well as in warm-temperate
regions, in littoral waters as well as in depths of 1500 m.
Almost 20 species are described, twelve of them live in
the southern hemisphere. Bradyagaue supposedly live
on stolons of hydrozoans. One of the males examined
had a spermatophor attached to leg IV.
Remarks. Bradyagaue can be distinguished from
Agaue with help of the tarsi; in Bradyagaue the posterior
tarsi are slightly curved, the median claw of all tarsi is
enlarged, the paired claws are slender, in contrast, the
tarsi of Agaue are straight, the median claw is small or
inconspicuous.
References. Newell (1971), Bartsch (1992c,
2004a).
22
Camactognathus Newell, 1984 (Fig. 30)
ventral plates developed. Dorsum with (5–)6 pairs of
idiosomatic setae; adanal setae in margin of anal plate.
AE with 3 pairs of setae. PE with 1 dorsal seta and 3
ventral setae. Female GA with 3–4 pairs of perigenital
setae and 1 pair of subgenital setae. Male GA with 50–
100 perigenital setae and 2–3 pairs of subgenital setae.
Gnathosoma: Rostrum slender, as long as or longer
than gnathosomal base. Basal pair of maxillary setae
near base of rostrum, apical pair near apex. Palps 4segmented, attached laterally and surpassing rostrum.
P-2 with 1 distal seta. No seta on P-3. P-4 with 3 setae
in basal whorl.
Legs: Genua much shorter than tibiae and
telofemora. Basifemora with 2,2,1–2,1–2 setae. Tibiae
I–IV with 4,2,2,2 ventral setae; ventromedial setae
often bipectinate. Solenidion on both tarsus I and
II positioned dorsolaterally. Tarsi I–IV with 1,1,0,0
ventral setae and 4,4,4,3 dorsal setae.
Paired claws large. Central sclerite with very small
claw-like process.
Biology and distribution. Both proto- and
deutonymph are free-living stages. Three species are
recorded, viz. from the Southern American Pacific
coast, the Mediterranean and the North Sea. The
records are from sandy deposits.
Remarks.
Resembling
Arhodeoporus,
Copidognathus and Winlundia in the shape of idiosoma
and absence of a seta on P-3, but tarsi I and II of
Camactognathus each bear a ventral seta, whereas in
the other three genera there are two or three setae on
tarsus I and one or none on tarsus II.
References. Newell (1984), Morselli and Mari
(1982), Bartsch (1991).
Caspihalacarus Viets, 1928 (Fig. 31)
with AD, OC and PD, and 6 pairs of dorsal idiosomatic
setae. Setae ds-2 to ds-4 on minute sclerites within
striated integument. AD and OC with pair of gland pores.
AE with 3 pairs of ventral setae; PE with 1 dorsal and
2 ventral setae. Female GA with 2 pairs of perigenital
setae; genital sclerites with 2 pairs of subgenital setae
and external genital acetabula. Male GA with almost
100 perigenital setae and 5 pairs of subgenital setae; 2
pairs of large external genital acetabula posterior to GO,
1 pair of small acetabula between genital sclerites.
Gnathosoma: Rostrum triangular, about as long
as gnathosomal base. Palps 4-segmented, lateral to
gnathosoma. Palps extending beyond rostrum. P-2 with
1 distodorsal seta. P-3 with medial spur. P-4 with 3
basal setae and 1 mid-lateral seta. Apically with setula
and spurs.
Legs: Leg I slightly larger than leg II. Basifemora
I–IV with 2,2,2,2 setae. Tibiae I–IV with 6(–7),4,2,2
ventral setae. Tarsus I and II with dorsolateral and
dorsomedial solenidion, respectively. All tarsi with
3 dorsal setae (solenidia excluded). Tarsus I with
spiniform ventromedial seta and 3–4 apical eupathidia
(without parambulacral setae), tarsus II with 1–2 apical
eupathidia; tarsi III and IV without ventral setae. Each
tarsus with pair of parambulacral setae.
Paired claws large, with pecten. Median claw very
small.
Biology and distribution. A free-living larval, protoand deutonymphal stage present during ontogeny. The
single species known was described on the basis of
individuals from the Caspian Sea, collected at salinity
of 12.5 ‰. The species proved to be abundant in
freshwater, in rivers emptying into the Caspian Sea and
Black Sea. Recently, the species was collected in the
river Rhine.
Remarks. In dorsal aspect similar to Halacarellus,
in ventral aspect easily separated from that genus on
the basis of the large genital acetabula.
References. Viets (1928), Bartsch (1998b).
Coloboceras Trouessart, 1889 (Fig. 32)
and ventral plates large; integument evenly and finely
porose, often slightly brown or green. Gland pores
small. Dorsum with 6 pairs of small setae; adanal
setae on anal cone. AE with 3 pairs of setae. PE with
1 dorsal seta and 3 ventral setae. Female GA with 3
pairs of perigenital setae and 0 subgenital setae. Male
GO surrounded by approximately 50 perigenital setae;
genital sclerites with 5 pairs of subgenital setae.
Gnathosoma: Short, slightly longer than wide.
Rostrum conical or triangular. One pair of maxillary
setae on gnathosomal base, 1 pair on rostrum. Palps 3segmented, attached laterally, only slightly extending
beyond rostrum. No seta on 2nd segment. Apical
segment with 1 basal seta and setula and 2 spurs near
its tip. Chelicerae elongate, stylet-like.
Legs: Genua distinctly shorter than telofemora and
tibiae. Genua and tibiae with distal lamellae, tarsi with
large fossa membranes. Basifemora I to IV with 2,2,1,1
setae. Tibiae I, II and III each with 4 bristle-like ventral
setae, tibia IV with 3 wide ventral setae. Tarsus I with
3 dorsal setae, long setiform solenidion on dorsolateral
fossa membrane, 1 ventral seta, apical cluster of
7–8 eupathidia, and parambulacral setae. Tarsus II
with 3 dorsal setae, solenidion on dorsomedial fossa
membrane, 2–3 ventral setae, and pair of parambulacral
setae. Tarsi III and IV each with 3(–4?) dorsal setae, 1
ventral seta and pair of parambulacral setae.
Paired claws large, often with accessory process and
pecten. Median claw present, minute.
23
nymphal stages are known. The three species described
are recorded from the northeastern Atlantic and the
Mediterranean.
Remarks. Coloboceras has a short gnathosoma with
three-segmented palps. Similar short palps are present
in Atelopsalis, but in that genus legs I bear prominent
spiniform processes.
References. Monniot (1962), Bartsch (1973).
Colobocerasides Viets, 1950 (Fig. 33)
and ventral plates distinct. OC divided into anterior
and posterior plate. Dorsum with 6 pairs of idiosomatic
setae; adanal setae on anal plate. Venter with
supplementary sclerites. AE with 3 pairs of ventral
setae. PE with 1 dorsal and 2 ventral setae. Female
with 3 pairs of perigenital setae; genital sclerites lack
subgenital setae.
Gnathosoma: Rostrum long, slender, pointed.
Chelicerae with slender serrate claw. One pair of
maxillary setae inserted on gnathosomal base, 1 pair
on base of rostrum. P-2 and P-3 not distinctly separate.
Second palpal segment with 1 distodorsal seta; P-3
(if present) without seta; apical segment with 3 basal
setae.
Legs: Genua shorter than telofemora and tibiae.
Basifemora I to IV with 2,2,1,1 setae. Tibiae with strong
ventral bristles, from I to IV numbering 3–4,2–5,2–4,3.
Tarsus I with 3 ventral and 3 dorsal setae and setiform
dorsolateral solenidion. Tarsus II with 1 ventral seta, 3
dorsal setae and long dorsomedial solenidion. Tarsi III
and IV without ventral but with 3 dorsal setae. Tarsi
I–IV each with a pair of parambulacral setae.
Paired claws large, slender. Median claw distinct
though smaller than paired claws.
Biology and distribution. Two species are described,
one from the northern, the other from the southern
Atlantic Ocean, from a depth range of 450–1400 m.
Remarks. Colobocerasides is thought to be related
to Australacarus. In the latter genus, the dorsal and
ventral plates are greatly reduced.
Copidognathides Bartsch, 1976 (Fig. 34)
wide. Dorsal and ventral plates large, with porose
panels. Gland pores present but inconspicuous. Dorsum
with 5–6 pairs of setae; adanal setae on anal plate. AE
with 3 pairs of ventral setae and pair of small epimeral
pores. PE with 1 dorsal seta and 3 ventral setae. Female
GA with 3 pairs of perigenital setae and 1 pair of
subgenital setae. Male GA with 12–15 perigenital setae
on either side of GO; genital sclerites with 4 pairs of
subgenital setae.
Gnathosoma: Short, only slightly longer than wide.
Rostrum shorter than gnathosomal base. One pair of
maxillary setae inserted on gnathosomal base, 1 pair
on rostrum. Palps 3–4-segmented, attached laterally;
extending beyond tip of rostrum. P-2 with 1 distal seta,
P-3 (if present) with none. Apical segment with 0–1
basal setae; its tip ending with setula and 2 spurs.
Legs: Short. Genua much shorter than adjoining
segments. Basifemora with 2,2,1–2,1–2 setae.
Tibiae I and II with 3 ventral setae; the ventrolateral
seta slender and smooth, the 2 ventromedial setae
bipectinate. Tibiae III and IV ventrally each with 1
bipectinate and 1 smooth seta. Tarsus I with 3 dorsal
setae, setiform dorsolateral solenidion, 1 ventral seta,
and pair of parambulacral setae. Tarsus II with 3 dorsal
setae, dorsolateral solenidion, no ventral seta, and pair
of parambulacral setae. Tarsi III and IV with 4 and 3
dorsal setae, respectively, pair of parambulacral setae,
but no ventral seta. On tarsus III lateral parambulacral
seta scaliform, medial one setiform. On tarsus IV both
parambulacral setae scaliform.
Paired claws large, with accessory process. Median
claw present but small.
Biology and distribution. A larval and a single
nymphal stage, a protonymph, present. One species
recorded from the eastern Atlantic Ocean, one from
the Mediterranean and one from the Pacific coast
of southern South America. The three species are
inhabitants of the middle and upper shore.
Remarks.
Copidognathides
resembles
Copidognathus and Werthella. Compared with
Copidognathus, the number of setae of both P-4 and
and tarsus I are reduced. In contrast to Werthella, the
epimeral pores on the AE are small.
References. Bartsch (1976, 1999c).
Copidognathus Trouessart, 1888 (Fig. 35)
and ventral plates generally large (or even fused).
Plates smooth or heavily ornamented, panelled and
with raised circular or subquadrangular areolae and
longitudinal costae; areolae and costae with rosette
pores or uniform porosity. With 4 pairs of gland pores
which may be small, almost inconspicuous, or large
and opening on raised cones. Dorsum with 6 pairs of
dorsal setae; adanal setae on anal plate. AE with 3 pairs
of ventral setae and pair of epimeral pores (rarely with
small internal vesicles); PE in general with 1 dorsal
and 3 ventral setae. Female GA with 3(–5) pairs of
perigenital setae and 1 pair of subgenital setae. Male
GA with 4–40 pairs of perigenital setae; genital sclerites
with 3–4 (rarely 2) pairs of subgenital setae.
Gnathosoma: Longer than wide, rarely about as
long as wide. Shape of rostrum varying from short (half
24
length of gnathosomal base) and triangular to long,
slender and parallel-sided (longer than gnathosomal
base). Tectum truncate, with median process or huge
crest. Normally with 2 pairs of maxillary setae, 1
pair inserted on gnathosomal base, 1 pair on rostrum;
a few species with 2–7 pairs of maxillary setae on
gnathosomal base. Palps 4-segmented, attached
laterally and at least slightly surpassing rostrum. P-2
with 1 distal seta. No seta on P-3 (there may be a small
spiniform cuticular process which is no seta because
an alveolus is lacking). P-4 with 3 setae in basal whorl;
Legs: From short and wide to long and slender in
shape; a few species with large lamellae. Genua shorter
than telofemora and tibiae. Basifemora I to IV with
2,2,(1–)2,(1–)2 setae. Genua I–IV with 4(–3),4(–3),3,3–
4(–5) setae. Tibia I with 3 ventral setae, often 1 of these
setae bristle-like and smooth and 2 setae pectinate
or spiniform. Tibia II with 3 ventral setae (1 species
with 2 setae), in general 1 seta slender and smooth, 2
setae bipectinate. Tibia III with 2 ventral setae, often 1
slender and smooth and 1 bipectinate. Tibia IV either
with 1 smooth and 1 bipectinate or with 2 smooth setae.
In general, tibiae I and II with 4 dorsal setae and tibiae
III and IV with 3 such setae. Tarsus I with 3 dorsal
setae, a dorsolateral seti- or baculiform solenidion, a
lamellar, rarely digitiform famulus, 3 ventral setae, and
a pair of parambulacral setae. Tarsus II with 3 dorsal
setae, setiform dorsolateral solenidion, no ventral
seta but a pair of parambulacral setae. Tarsi III and
IV with 3–4 dorsal setae, no ventral setae, and pair of
parambulacral setae (rarely 1 of parambulacral setae
moved to a ventral position or lacking); parambulacral
setae setiform or short and spur-like.
Paired claws large; median claw present, though
small. Claws of leg I may be shorter than those of
following tarsi. Claws smooth or with an accessory
process, with or without pecten.
Biology and distribution. The ontogeny includes
a larval and a single nymphal stage, the protonymph.
More than 300 species are described. The genus is
cosmopolitan; present from the upper shore to deep
sea basins. Copidognathus is found in a wide range
of substrata, in sand, gravel, coral debris, bushy algae,
colonial organisms, and amongst gills and eggs of
decapods. A few species live in fresh water.
Remarks.
Copidognathus
resembles
Copidognathides
and
Arhodeoporus.
In
Copidognathides the number of setae of tarsus I and P-4
is reduced. Arhodeoporus differs from Copidognathus
in having four ventral setae on tibia I, the solenidion
on tarsus II in dorsomedial position, and two nymphal
stages during its development.
The setation of the legs of Copidognathus
demonstrates a great uniformity, normally trochanters
I–IV have 1,1,1,0 setae, basifemora I–IV 2,2,2,2,
telofemora 4–5,4–5,2–3,2–3, genua 4,4,3,3, and tibiae
7,7,5,5 setae. Only few species have a larger or lower
number of setae.
References. Bartsch (1994c, 1998c, 1999b), Otto
(2000h).
Corallihalacarus Otto, 1999 (Fig. 36)
Diagnosis. Idiosoma: Length 580 µm. Dorsal plates
AD, OC, PD contiguous. Dorsal parts of AE and PE
fused, ventral parts contiguous. Dorsum with 4 pairs
of gland pores and 5 pairs of idiosomatic setae; adanal
setae on anal plate. AD with 2 pairs of setae and 1 pair
of gland pores; OC with 2 gland pores. AE with 3 pairs
of setae, PE with 1 dorsal seta and 3 ventral setae.
Female GA with 2 pairs of perigenital setae, genital
sclerites with 1 pair of subgenital setae.
Gnathosoma: Long and slender, fused to idiosoma
via flexible neck. Rostrum parallel-sided. Both pairs
of maxillary setae on rostrum. Palps 4-segmented,
attached laterally. P-2 with apical seta. No seta on P-3.
P-4 with 1 seta in distal half and a setula plus 2 spurs
at the tip.
Legs: Genua shorter than telofemora. Telofemora
III and IV with large lamellae. Basifemora I–IV with
2,2,2,2 setae. Genua I–IV with 4,4,3,3 setae. All
tibiae ventrally with 2 bipectinate setae. Tarsi I–IV
with 4,4,4,3 dorsal setae, setiform solenidia included.
Solenidion on tarsus I in dorsolateral, on tarsus II in
dorsomedial position. Tarsus I with pair of eupathid
ventral setae; tarsus II with single ventral seta; tarsi
III and IV lack ventral setae. All tarsi with pair of
Paired claws slender. Median claw only slightly
shorter than paired claws.
Biology and distribution. The single species
recorded is from sandy deposits off northeastern
Australia.
Remarks. Corallihalacarus resembles Mictognathus
but has, unique within the Halacaridae, a very long,
flexible neck.
References. Otto (1999c).
Enterohalacarus Viets, 1938 (Fig. 37)
Diagnosis. Idiosoma: Length 2000 µm. AD, OC and
PD present, in ovigerous females widely separated
by striated integument. Dorsum with at least 4 pairs
of dorsal setae. AE with 3 pairs of ventral setae, PE
with 2 ventral setae. Female with approximately 160
perigenital setae arranged around GO. Genital sclerites
with 2 pairs of subgenital setae.
Gnathosoma: Longer than wide. Rostrum short,
tapering. Two pairs of maxillary setae close together
25
within an area where rostrum is passing over into
gnathosomal base. Palps attached dorsally but separated
from each other by distinctly more than width of basal
palpal segment. Length of palps less than 1/3rd of that
of rostrum. Palps 2-segmented; apically with 2 spurs.
Legs: Cylindrical, long. Genua shorter than adjoining
segments. Basifemora with 4–7 setae each. Telofemora
I–IV each with 6–9 bristle-like ventral setae and 8–10
dorsal setae; tibiae I–IV each with 8–10 bristle-like
ventral setae and 7–10 dorsal setae. Tarsi with short
fossa membranes. Tarsus I with 3 dorsal setae, tiny
dorsolateral solenidion, 1–2 minute ventral setae, 6
eupathidia and pair of doubled parambulacral setae.
Tarsus II with 3 dorsal setae, bud-like dorsolateral
solenidion, 1 minute ventral seta, 5 eupathidia and a
pair of doubled parambulacral setae. Tarsi III and IV
each with a pair of parambulacral setae, 3 dorsal but no
ventral setae.
Tarsi end with pair of rather small claws. Median
claw well developed.
Biology and distribution. A single species is
described which has been found on and in the sea
urchin Plesiodiadema indicum (Döderlein, 1900), taken
at 430 m depth, at 7°N and 127°E. Enterohalacarus is
believed to be a parasite.
Remarks. Compared with other halacarids,
Enterohalacarus has a very large idiosoma but
extremely small palps. There is only one genus,
Spongihalacarus, in which the palps are more reduced
than in Enterohalacarus.
References. Viets (1938).
Halacarellus Viets, 1927 (Fig. 38)
and ventral plates present; small platelets may be
found within dorsal striated integument. PD of males
sometimes larger than that of females. Surface of
dorsal plates smooth, finely porose or reticulated;
plates often with slightly raised costae. Conspicuous
ornamentation not known. Ventral plates generally
delicately and uniformly punctate. Dorsum with 3–5
pairs of gland pores and 6 pairs of idiosomatic setae;
adanal setae on anal cone. AE with 3 pairs of setae, PE
with 1(–3) dorsal and 2–3 ventral setae. Female GA
with 2–4 (rarely 7) pairs of perigenital setae and 0–5
pairs of subgenital setae. Male GO surrounded by 20–
100 perigenital setae; genital sclerites generally with 5
pairs of subgenital setae, rarely with less setae.
Gnathosoma: Longer than wide. Rostrum triangular
or elongate and parallel-sided, its length may be less,
same or distinctly more than length of gnathosomal base.
Apical pair of maxillary setae in distal half of rostrum,
basal pair of setae either on rostrum or on gnathosomal
base close to rostrum. Palps 4-segmented, lateral to
gnathosoma and extending beyond tip of rostrum. P-2
with 1 distodorsal seta, P-3 short, with 1 medial spine
or spinelet. P-4 with 3 setae in basal whorl, 1 setula and
2 minute spurs at the tip, and often with 1 lateral seta
in middle or posterior half of P-4. Cheliceral claw with
serrate dorsal margin.
Legs: Leg I often longer and wider than following
legs; in a few species provided with stout ventral spines.
Genua shorter than adjoining segments. Basifemora
I–IV with 2,2–4,2(–4),2(–4) setae, respectively. Tibiae
I–IV with (2–)4–8,(2–)3–8,2–8,2–6 ventral setae
which are slender or spiniform, smooth or delicately
pectinate. Tarsus I with 3 dorsal setae, dorsolateral
solenidion, 1 (rarely 2) ventromedial seta (which is
slender, spur-like or spiniform), 2–26 eupathidia,
and pair of doubled parambulacral setae. Tarsus II
with 3 dorsal setae, dorsomedial solenidion, 0–7
ventral setae (often eupathidia), and pair of doubled
parambulacral setae. Tarsi III and IV with 3–4 and 3
dorsal setae, respectively, 0–6 ventral setae, and pair of
Claws large; on tarsus I sometimes slightly smaller
than on posterior tarsi. Claws smooth or with pectines.
Median claw present, small.
nymphal stages are known. Almost 50 species are
described. The genus is cosmopolitan but species
groups have a restricted distribution. Records are both
from shallow waters and deep-sea regions. On cold
water shores, the genus Halacarellus is one of the
numerically important genera in the halacarid fauna.
Records from tropical beaches are rare. Several species
are adapted to brackish water, few to almost fresh
water. Most species are carnivorous, some few may
temporarily be algivorous.
Remarks. For several years, Thalassarachna had
been used as a synonym for Halacarellus, but the genera
are now regarded as separate. Thalassarachna has an
increased number of dorsal setae on the tarsi (more
than three setae on tarsi I and II), and most species have
a pair of gland pores in the marginal membraneous
integument, which is lacking in Halacarellus.
A few species of Halacarellus resemble Agaue;
differences are: P-3 in Halacarellus bears a medial
spine or seta, in Agaue there is a dorsal seta. Other
Halacarellus species are similar to Agauopsis, but
Agauopsis generally has a parallel-sided rostrum, the
arrangement of the spines on its leg I is different, the
number of setae on P-4 generally reduced.
Thalassacarus, which also demonstrates an overall
resemblance with Halacarellus, bears 2 large basal
tines on its cheliceral claws. Such tines are lacking in
Halacarellus.
Bathyhalacarus species have elongate ocular plates
with large gland pores. Halacarellus species with
26
similar elongate plates have a PD with a pair of costae
and gland pores.
Halacaroides Bartsch, 1981 (Fig. 39)
slender, its width less than distance between insertions
of legs II and III. Dorsal and ventral plates delicate. OC
reduced to platelets. PD smaller than AD. Gland pores
inconspicuous. Dorsal idiosomatic setae short, 6 pairs
present; adanal setae on anal plate. Anterior epimera
fused in the median, this AE with 3 pairs of ventral
setae. PE small, with a longitudinal fissure, 1 dorsal
and 3 ventral setae. Female GA small, with 3 pairs of
perigenital setae and 2 pairs of subgenital setae. Male
GA larger, with approximately 20 perigenital setae and
5 pairs of subgenital setae.
parallel-sided, about as long as gnathosomal base. Both
pairs of maxillary setae inserted on rostrum. P-2 with 1
distal seta, P-3 with 1 spur, P-4 with 3 basal setae.
Legs: Slender; leg I longer than leg II. Genua shorter
than telofemora and tibiae. Basifemora I to IV with 2
setae each. Tibia I with 3–4 ventral setae; tibiae II, III
and IV with 3 ventral setae each. Tarsus I with enlarged
lateral fossa membrane, 3 dorsal setae, solenidion and
famulus adjacent to lateral membrane of claw fossa, 3
ventral setae, and pair of doubled parambulacral setae.
Tarsus II with 3 dorsal setae, dorsomedial solenidion, 1
ventral seta, and pair of parambulacral setae. Tarsi III
and IV each with a pair of parambulacral setae, 3 dorsal
but no ventral setae.
Claws on tarsus I somewhat smaller than on
following tarsi. Median claw present though small.
Biology and distribution. Two species are known,
taken on the shores of southern South America. The
genus is supposed to be arenicolous.
Remarks. The shape of Halacaroides is similar
to that of Anomalohalacarus and Arenihalacarus.
Distinguishing characters are: the dorsum of
Halacaroides bears distinct OC, the dorsal setae are
short, the PE longitudinally divided, the female GA
undivided, and genu I distinctly shorter than tibia I.
References. Bartsch (1981b).
Halacaropsis Bartsch, 1996 (Fig. 40)
ventral plates large. Dorsum with 6 pairs of idiosomatic
setae; ds-2, ds-3 and ds-4 generally enlarged; adanal
setae small, on anal plate, often seen only in ventral
aspect. AD and OC with pair of gland pores. AE with
3 pairs of ventral setae. PE with 1 dorsal and 3 ventral
setae. Female GA with 5–6 pairs of perigenital setae
and 4–5 pairs of subgenital setae. Male GA with
approximately 50 perigenital setae around GO, 1 pair
outlying. Genital sclerites with 5–7 spur-like subgenital
setae.
parallel-sided. Rostrum about as long as gnathosomal
base. One pair of maxillary setae on gnathosomal base
near base of rostrum, 1 pair in apical portion of rostrum.
Palps 4-segmented, lateral to gnathosoma; extending
beyond apex of rostrum. P-3 about half length of P2; P-4 about as long as P-3. P-2 and P-3 each with 1
dorsal seta. P-4 basally with 3 long setae, apically with
1 setula and 2 elongate spinelets. Cheliceral claw with
serrate dorsal edge.
Legs: Leg I longer and wider than following legs.
Genua I somewhat shorter than telofemora. Tibiae longer
than genua. Leg I with prominent spines, telofemur to
tarsus I with 3,2,3,1 such spines. Basifemora I to IV
with 3,4,2,2 setae. Tibiae II–IV with 4 ventral setae
each, 1–3 of these setae spiniform and pectinate. Tarsi
slightly bent. Tarsus I with 3 dorsal setae, baculiform
dorsolateral solenidion, 1 medial spine, 3–5 ventral
setae, and apical pair of doubled parambulacral setae.
Tarsus II with 3 dorsal setae, dorsomedial solenidion, 3
ventral setae and pair of doubled parambulacral setae.
Tarsi III and IV with 3 dorsal setae, 1–2 ventral setae
and pair of parambulacral setae.
Each tarsus with paired claws and stout median
claw.
Biology and distribution. Larval, protonymphal and
deutonymphal stage present. Five species are described,
one from the Atlantic Ocean and Mediterranean, one
from South Africa and three from Australia.
Remarks. Halacaropsis and Agauopsis share the
shape of leg I, enlarged and armed with long, apically
truncate spines. Halacaropsis can be separated from
Agauopsis with help of its number of ventral setae on
the tarsi, the length ratio of telofemur I to genu I, that
of P-3 to P-2, and the size of the median claw on the
tarsi.
Halacaropsis has characters in common with
Halacarus. In Halacarus, too, leg I is longer than the
following legs and its telofemur, genu, tibia and tarsus
are armed with spines, and the tarsi bear several ventral
setae. Halacarus has five (rarely four) pairs of gland
pores, whereas in Halacaropsis the posterior gland
pores are vestigial or absent. Halacarus has both pairs
of the maxillary setae on the rostrum and the median
claw of the tarsi is rarely enlarged.
References. Bartsch (1996b), Otto (1999a), Proches
(2001).
Halacarus Gosse, 1855 (Fig. 41)
plates smooth or faintly reticulated; no prominent
costae or conspicuous porose areolae present. Dorsal
plates may be obscured by layers of striated or maze-
27
like ornamented cerotegument. AD often with frontal
process. OC and/or PD in several species lacking. PD
in males often larger than in females. The majority of
species with 5 pairs of distinct gland pores, first pair
arising from or close to AD, second pair marginally,
within striated integument (rarely on PE). Dorsum with
(5–)6 pairs of idiosomatic setae; adanal setae adjacent
to posterior pair of gland pores. PE usually with 1 dorsal
seta, rarely with 2 setae, and 3 ventral setae. Female
GA with 2–15 pairs of perigenital setae; in species with
2 pairs of perigenital setae on GA, a 3rd pair (rarely
a 4th pair) present within striated integument anterior
to GA. Several species with crescent sclerotized areas
on either side of GO. Female genital sclerites with 3–5
pairs of subgenital setae. Male GA rounded or oval
in outline; number of perigenital setae surrounding
GO ranging from about 30 to more than 150; a pair
of outlying perigenital setae may be present within
striated integument. Genital sclerites with 3–5 pairs of
subgenital setae.
Gnathosoma: Longer than wide. Gnathosomal base
subquadrangular in ventral aspect. Rostrum almost
parallel-sided, ending bluntly. Both pairs of maxillary
setae on rostrum. Palps 4-segmented, lateral to
gnathosoma and extending beyond rostrum. P-2 with
2 setae, generally both in apical half. P-3 short, with
a medial spine. P-4 with 3 basal setae, 1 seta in the
middle and 1 minute seta and 2 spurs at the tip.
Legs: Leg I in most species longer and wider than
following legs, with spines on telofemur and spines
or strong, bristle-like setae on genu and tibia. Genu I
about as long as telofemur and tibia I. Genua of the
other legs, too, almost as long as adjoining segments.
Basifemora I to IV with 2(–3),2–5,2,2 setae. Telofemur
I with 1–5 ventral spines; spines tapering or blunt.
Genu I with 1(–2) pair(s) of spiniform or bristle-like
setae. Tibia I with 4–6 often spiniform ventral setae;
tibiae II, III and IV with 2–7 ventral bristle-like setae.
Tarsus I with 3 dorsal setae (1 species with 5 setae),
baculiform dorsolateral solenidion and famulus, 2–4
ventral bristle-shaped setae , and 2–5 pairs of eupathidia
(parambulacral setae included). Tarsus II with 3(–5)
dorsal setae, dorsomedial solenidion, 0–4 ventral setae,
and pair of doubled or tripled parambulacral setae. Tarsi
III and IV with 3–4 and 3 dorsal setae, respectively,
0–6 ventral setae, and pair of parambulacral setae.
Parambulacral setae of male tarsus IV often plumose.
Pair of claws of leg I may be slightly smaller than
those of following legs. Paired claws either smooth
or with accessory process and pecten. Median claw
present, usually small, rarely almost as long as paired
claws.
Biology and distribution. One free-living larval
and two nymphal stages occur during development.
More than 70 species are described. The genus is
cosmopolitan and abundant in polar as well as in tropical
areas. More species have been taken in the southern
than in the northern oceans. Halacarus inhabits depths
from the low water edge to deep-sea basins.
Remarks. Halacarus is distinguished from
Halacarellus, Halacaropsis, and Thalassarachna on
the basis of the 2 setae on the P-2, the length of the
genua being about as long as the adjoining segments,
and the 5 pairs of large gland pores (though Halacarus
species with no more than 4 pairs of pores do exist).
References. Bartsch (1981a, 2001c), Newell (1984),
Otto (2001b).
Halixodes Brucker & Trouessart, 1900 (Fig. 42)
Diagnosis. Idiosoma: Length 1100–1300 µm.
Dorsal and ventral plates large, with cerotegumental
membranes. Dorsum with 6 pairs of setae; adanal
setae on anal plate. AE with 3 ventral setae; PE with
1 dorsal and 3 ventral setae. Female GA with up to 13
pairs of perigenital setae. Male with approximately 200
perigenital setae close around GO.
Gnathosoma: Longer than wide. Rostrum long,
parallel-sided, almost as long as gnathosomal base.
Both pairs of maxillary setae near base of rostrum. Two
large pairs of barbs at end of rostrum. Palps lateral to
gnathosoma; extending just beyond rostrum. Dorsal and
ventral lamellae of P-2 and rostrum forming a trough.
P-2 long, with 1 distal seta. P-3 with 1 small bristle.
P-4 with 3 setae and 2 apical spinelets. Chelicerae with
serrate dorsal margin.
Legs: Slender. Telofemora with cerotegumental
lamellae. Tarsi with large membranes of claw fossae.
Genua shorter than adjoining segments. Basifemora
I to IV with 2 setae each. Tibiae with short bristlelike setae, none of them bipectinate. Tibiae I and
II with 5–6 ventral setae, tibiae III and IV with 4–5
such setae. Tarsus I with 3 dorsal setae, 1 solenidion
on dorsolateral fossa membrane, 1 ventral seta, and
apically approximately 20 eupathidia (parambulacral
setae included). Tarsus II with 3 dorsal setae,
solenidion on inner flank of medial fossa membrane,
and approximately 15 apical eupathidia (parambulacral
setae included). Tarsus III and IV each with 3 dorsal
setae; apically with parambulacral setae.
Tarsi end with pair of claws. Central sclerite lack a
claw-like process.
Biology and distribution. Two nymphal stages are
known. Halixodes has been found in the mantle cavity
of molluscs but also free-living in crevices between
gravel and colonies of barnacles and mussels. All present
records are from the tidal and shallow subtidal zone.
Nymphal stages demonstrate an enormous difference
in length, in just hatched individuals the areas between
28
the plates are small, after feeding the dorsal aspect is
dominated by the wide areas of striated integument
and the plates are apparently small. The three species
described were taken from New Zealand waters.
Remarks. Halixodes resembles species of the
genus Agaue which have similar large cerotegumental
lamellae on idiosoma and legs, but differs in that the
gnathosoma bears large barbs at the tip of rostrum
and the palps are flattened and form a trough, whereas
Agaue species have two minute spurs at the tip of the
rostrum and the palps are almost cylindrical.
Isobactrus Newell, 1947 (Fig. 43)
plates AD, OC and PD present, two or more plates
may be fused. OC with a single cornea. Gland pores in
most species present but small, AD and PD each with
1 pair of such pores; OC with 2 pores. Dorsum with
5, rarely 4 or only 2 pairs of idiosomatic setae; adanal
setae absent. Ventral plates delicate, generally reduced
to small platelets. Epimera I and II rarely fused to an
AE; a median plate separated from marginal epimera
may be present. Epimeral plates III and IV of each
side contiguous or separated by striated integument.
Anterior half of idiosoma with 3 pairs of ventral setae.
Epimeral plate III with 0–1 dorsal and 1 ventral seta
(the latter sometimes within the striated integument),
epimeral region IV with 1 ventral seta. GP in females
often reduced; 3(–4) pairs of perigenital setae positioned
on the plate or within the striated integument; genital
sclerites with 1–2 subgenital setae. Male GP larger than
that of female; with 32–98 perigenital setae and (3–)4
Gnathosoma: Short, its length almost same or even
less than width. Gnathosoma directed ventrad and
often concealed in dorsal aspect. Gnathosomal base
globular. Rostrum conical; both pairs of maxillary
setae on rostrum. Laterally attached 4-segmented palps
slightly surpassing rostrum. P-2 with 1 distal seta, no
seta on P-3 (P-3 may be almost reduced), P-4 with 4
(rarely 3) setae.
Legs: Short. Legs I and II similar in shape. Genua
shorter than adjoining segments. Basifemora I–IV with
2,2,1–2,0–2 setae. Genua I–IV with 2–3,2–3,1–3,1–2
setae. Tibiae I and II with pair of ventral setae; tibiae
III and IV with 1–2 ventral setae; bipectinate setae on
tibiae I–IV numbering 1,0–1,0–1,0–1. Solenidia small,
clavate, on both tarsus I and II in dorsolateral position.
Tarsi I, II, IV with 3 dorsal setae (except for 1 species
which has basidorsal seta doubled) and 0 ventral setae,
tarsus III with 4 dorsal setae (except for 1 species with
5 setae) and 0 ventral setae. Tarsi with apical pair of
All tarsi with a carpite between tip of tarsus and
central sclerite. The 2 claws on tarsi I–IV smooth or
with accessory process, the latter with small or strong
tines. No claw on central sclerite.
Biology and distribution. One larval and three
nymphal stages (proto-, deuto-, tritonymph) present.
Records of the presently described 27 species are
from the intertidal of marine and brackish waters.
Two species are recorded from almost freshwater
areas. Isobactrus is found on algae and barnacles,
shells and pebbles covered with unicellular algae. It is
phytophagous, feeding on unicellular or filamentous
algae. In the boreal Atlantic Ocean, this cosmopolitan
genus is found regularly and in large numbers in the
upper tidal zone.
Remarks. Isobactrus, like Metharhombognathus,
Rhombognathides and Rhombognathus, has a darkgreen body, the legs are transparent. The four genera are
algivorous. Isobactrus has the gnathosoma completely
or almost completely concealed beneath the anterior
idiosoma, whereas in most species of the other genera
the gnathosoma is visible in dorsal aspect.
References. Newell (1947), Abé (1996a, 1998,
2001), Bartsch (2003a, b).
Lohmannella Trouessart, 1901 (Fig. 44, 8C)
Diagnosis. Idiosoma: Length 210–560 µm. Generally
wide and flattened. Dorsal and ventral plates large. AD
subquadrangular to hexagonal. Often with 5 pairs of
gland pores which may be large and prominent, minute
or, rarely, replaced by setae. Second pair of gland pores,
if present, marginally or ventromarginally on platelets
within striated integument. Dorsum with 6(–7) pairs of
idiosomatic setae; adanal setae inserted on anal cone.
AE with 4 pairs of ventral setae. PE with 1–3 dorsal
and 3 ventral setae. Female GA with 12–74 perigenital
setae and 3–4 pairs of subgenital setae. Male GA with
50–80 perigenital setae in a dense ring around GO, plus
1–5 pairs of outlying perigenital setae; genital sclerites
with 4 pairs of tiny subgenital setae.
Gnathosoma: Longer, often much longer than
wide. Length ratio gnathosoma:idiosoma equalling
0.4–1:1. Gnathosomal base cubical, rostrum slender,
parallel-sided. The majority of species with rostrum
distinctly longer than gnathosomal base. Both pairs of
maxillary setae on rostrum, generally in distal half of
rostrum. Palps 4-segmented, inserted dorsally. Pair of
P-1 adjacent or even fused, rarely separated by almost
width of P-1. Palps slightly surpassing rostrum. P-2
with 2 dorsal setae; in many species from the southern
hemisphere 1–5 cuticular ventral spines present (Fig.
8C). P-3 short, with spur-like process (no real spur
because an alveolus is lacking). P-4 with 3 setae and 1
medial spur, apically with eupathid setula and spur.
29
Legs: The majority of species with slender legs.
Genua much shorter than adjoining segments.
Basifemora with (1–)2–3,(1–)2–3,3(–4),(1–)3 setae.
Tibia I with 4–8 bipectinate ventral bristles. Tibia II
with 3–6 ventral setae, bristle-like and bipectinate
or slender and only faintly pectinate. Tibiae III and
IV with 2–7 ventral setae, either bristle-like and
bipectinate or slender, only faintly pectinated. Tarsus
I with 3 dorsal setae, baculiform solenidion, 0–4
bipectinate ventral setae, 0–4 ventral eupathidia, and
pair of parambulacral setae. Tarsus II with 3 dorsal
setae, dorsal or dorsomedial solenidion, 0–4 ventral
setae (basal setae bipectinate, distal setae bipectinate
or smooth), and pair of parambulacral setae. Tarsi III
and IV with 4 and 3(–4) dorsal setae, respectively,
0–6 ventral, usually bipectinate setae, and pair of
Claws smooth or with an accessory process; the
latter may bear tines. Central sclerite small. Tarsi often
with a short carpite between tip of tarsus and central
sclerite.
Biology and distribution. One larval and two freeliving nymphal stages are known. At present about
30 marine species are described. Lohmannella is
cosmopolitan. The majority of the southern hemisphere
species have large gland pores, whereas in those from
the north the pores are small or vestigial. Lohmannella
species are found in shallow tidal waters as well as in
deep sea basins. Lohmannella inhabits marine, brackish
and fresh waters. Five species are recorded from fresh
or diluted brackish water.
Remarks. Lohmannella is related to Scaptognathus
but has a slender rostrum and 4-segmented palps.
References. Newell (1984), Bartsch (1986c, 1993a,
2003d).
Metarhombognathus Newell, 1947 (Fig. 45)
Diagnosis. Idiosoma: Length 320–610 µm. In adults
dorsal plates AD, OC and PD small. OC with 1–2
corneae. Dorsum with 8–10 idiosomatic setae; adanal
setae on anal plate. First pair of gland pores on AD;
following gland pores often replaced by setae. Ventral
plates small. Anterior epimeral plate divided into
right and left half; each plate with 3 setae. PE with 1
dorsal and 2 ventral setae. GP small, in females almost
reduced. Female with 3 pairs of perigenital setae and
0 subgenital setae. Males with 30–40 perigenital setae
and 3 pairs of subgenital setae.
Gnathosoma: About as long as wide. Rostrum
much shorter than gnathosomal base; apically truncate.
Palps 4-segmented; reaching beyond rostrum. P-2 with
1 distal seta, P-3 reduced to minute ventral sclerite with
a setula, P-4 with 3 setae in basal whorl; 1 of setae wide
and flattened.
Legs: Legs with short, globular segments. Leg I not
markedly longer than following legs. Basifemora I–IV
with 2,3,2,2 setae. All tibiae with a pair of spiniform
ventral setae. Tarsus I with 3 dorsal setae, clavate
dorsolateral solenidion, rod-like famulus, and 1 ventral
spiniform seta near tip of tarsus. Tarsus II without
famulus, otherwise identical with tarsus I. Tarsi III
and IV with 4 and 3 dorsal setae, respectively, and 0
ventral setae. Pair of parambulacral setae on tarsi I and
II doubled and eupathid, on tarsus IV spur-like, and
on tarsus III in a combination of 1 lateral spur and 1
medial eupathid seta plus spur.
All tarsi with a rod-like carpite between tip of tarsus
and central sclerite. Median claw almost as large as
paired claws, accordingly all tarsi with 3 stout claws.
Median claw smooth, paired claws serrate or with
apical tines.
Deutonymphs: Dorsal and ventral plates much
larger than in adults. Epimera I and II either separated
in the median or fused to an AE. Genital and anal plate
fused.
nymphal stages are known. The deutonymphs are,
unique within the Halacaridae, much more intensely
armed than the adults are. Only two species are
described. Metarhombognathus inhabits the boreal and
arctic North Atlantic Ocean. The species live, often
in large numbers, in the mid-tide green-algal belts, as
well as amongst intertidal barnacles and brown algae.
Metarhombognathus is algivorous.
Remarks. In Metarhombognathus, as in Isobactrus,
Rhombognathides and Rhombognathus, the body is
dark-green, the legs are pale. Metarhombognathus is
distinguished from the other just mentioned genera on
the basis of the three large claws on the tarsi.
References. Abé (1998), Bartsch (1979, 2003b).
Mictognathus Newell, 1984 (Fig. 46)
ventral plates large, contiguous or fused; plates strongly
sclerotized. Dorsal plates with raised areolae. Dorsum
with 5 (or 6?) pairs of dorsal setae; adanal setae on anal
plate. AE with 3 pairs of ventral setae. PE with 1 dorsal
seta and 3 ventral setae. Female GA with 3 pairs of
perigenital setae; genital sclerites lack subgenital setae.
Male GA with approximately 26–40 perigenital setae
and 3 pairs of subgenital setae.
Gnathosoma: Longer than wide. Rostrum slendertriangular. Both pairs of maxillary setae on rostrum.
Palps 4-segmented; inserted laterally; surpassing the
rostrum. P-2 with 1 distal seta, slender or pectinate.
Medial seta on P-3 minute or absent. P-4 with 1 basal
seta; apically with setula and 2 spurs.
Legs: Leg I slightly larger than following legs.
Telofemora with ventral (and dorsal) lamellae; tarsi
30
without enlarged fossa membranes. Basifemora I–IV
with 2,2,1,1 setae. Tibiae I–IV each with 2 spiniform,
pectinate ventral setae. Tarsus I with 3 dorsal setae,
dorsolateral solenidion, and 1–2 ventral setae (exclusive
of parambulacral setae). Tarsus II with 3 dorsal setae,
dorsomedial solenidion, and 1 ventral seta. Tarsi III and
IV with 4 and 3 dorsal setae, respectively, but no ventral
Paired claws large. Median claw present but
distinctly smaller than paired claws.
Biology and distribution. Two nymphal stages do
occur during the ontogeny. Three species are described,
two have been collected in Antarctic and Subantarctic
waters, one species in the tropical eastern Australia.
The depth range is from low water edge to 155 m. The
species supposedly live in coarse sediments.
Remarks. Mictognathus with its contiguous or
fused plates and large lamellae on the legs resembles
species of Copidognathus. In contrast to the latter, P-4
bears a single basal seta.
References. Newell (1984), Bartsch (1992a), Otto
(2001a).
Parhalixodes Laubier, 1960 (Fig. 47)
Diagnosis. Idiosoma: Length 400 µm. Idiosoma
slender, its width less than distance between epimera
II and III. AD present, not markedly reduced, PD short,
OC lacking. Dorsum with at least 4 pairs of idiosomatic
setae, ds-2, ds-3 and ds-4 very long. Ventral plates small
and delicate; widely separated. Female GA hardly
extending beyond GO.
Gnathosoma: Slender. Rostrum long, parallelsided, apically with pair of barbs. Palps 4-segmented,
lateral to gnathosoma and surpassing rostrum. P-2 with
1 large distal seta. No seta on P-3. Apical half of P-4
with 2 setae and 2 spinelets. Chelicera slender. Large
cheliceral claw with few stout tines.
Legs: Slender. Dorsal and lateral setae long and
slender. Legs III and IV inserted close to posterior
end of idiosoma. Genua shorter than telofemora and
tibiae. All tibiae with 2 ventral bristles. Tarsus I with
3 dorsal setae, setiform solenidion, 1 ventral seta, and
pair of parambulacral setae. Tarsus II with 3 dorsal
setae, dorsomedial solenidion, 0 ventral setae, and pair
of parambulacral setae. Tarsi III and IV each with 3
dorsal but no ventral setae; each tarsus with pair of
Paired claws of ‘normal’ size. Median claw almost
half length of paired claws.
Biology and distribution. Parhalixodes is believed
to be a parasite. Two species are described. Parhalixodes
travei Laubier, 1960 was found in Mediterranean on
the nemertine Cerebratulus hepaticus Hubrecht, 1879.
P. chilensis Newell, 1971 is known from a single
protonymph, found in a sample taken from off South
America.
Remarks. With its slender idiosoma and legs,
Parhalixodes resembles the arenicolous genera
Anomalohalacarus and Arenihalacarus as well as the
presumably temporarily parasitic Australacarus. The
three latter genera have no barbs at the end of rostrum,
their P-2 are much longer relative to P-3, and the P-4
bear three setae in the basal whorl.
References. Laubier (1960), Newell (1971).
Pelacarus Bartsch, 1986 (Fig. 48)
plates AD, OC and PD panelled and with porose raised
areas. With 6 pairs of dorsal setae; adanal setae on anal
plate. Gland pores inconspicuous. Ventral plates with
porose areolae. AE with 3 pairs of setae and enlarged
epimeral pores. PE with 1 dorsal and 3 ventral setae.
Female GA with 3 pairs of perigenital setae and 3 pairs
of subgenital setae. Male GA with 16–22 perigenital
setae scatteredly arranged; genital sclerites with 5 pairs
of subgenital setae.
Gnathosoma. Rostrum triangular, tapering, about
as long as gnathosomal base. Tectum truncate, scalelike. Both pairs of maxillary setae inserted within basal
portion of rostrum. Four-segmented palps about as long
as rostrum and lateral to gnathosomal base. P-2 with 1
distal seta. No seta on P-3. P-4 with 1 long basal seta
and 1 apical setula and 2 spurs.
Legs: Genua much shorter than adjacent leg
segments. Basifemora with 2,(2–)3,2,2 setae. All tibiae
with 2 smooth ventral setae. Solenidion on tarsus I in
dorsolateral position, on tarsus II in dorsomedial. Tarsi
I–IV with 4,4,4,3 dorsal and 1,1,0,0 ventral setae. All
tarsi with pair of parambulacral setae.
Paired claws large; median claw small.
Biology and distribution. The ontogeny includes
a free-living deutonymphal stage. Pelacarus is known
from the sublittoral Mediterranean and the abyss in the
Bay of Biscay.
Remarks. Pelacarus resembles Werthella species.
The ornamentation of the dorsal and ventral plates
is almost the same, the epimeral pores on the AE
are enlarged, the shape of the gnathosoma is almost
identical, on P-4 there is a single seta in the basal
whorl; the setation of the tarsi is almost identical.
Nonetheless, Pelacarus is a separate genus; in Pelacarus
a deutonymphal stage occurs during ontogeny (in
Werthella suppressed), on tarsus II the solenidion is
in a dorsomedial position and there is one ventral seta
(in Werthella solenidion in dorsolateral position and
ventral seta often lacking), the female genital sclerites
each bear three subgenital setae (in Werthella one
pair), and in males the perigenital setae are scatteredly
31
arranged around the GO (in Werthella in a ring close
to the GO).
References. Bartsch (1986d).
Peregrinacarus Bartsch, 1999 (Fig. 49)
with AD, pair of OC and PD, and 6 pairs of idiosomatic
setae; adanal setae on anal plate. Elongate OC with two
gland pores. Venter with AE, pair of PE and GA. AE
with 3 pairs of setae, PE with 1 dorsal seta and 3 ventral
setae. Genital plate and anal plate fused; female GA
with 10–14 perigenital setae, genital sclerites with 0–1
subgenital setae. Male GA with about 40 perigenital
setae. Genital sclerites with 5–6 pairs of subgenital
setae.
Gnathosoma: Longer than wide. Rostrum elongate,
triangular. Basal pair of maxillary setae near base of
rostrum, following pair in distal half of rostrum. Apex
of rostrum with 2 pairs of rostral setae. Four-segmented
palps lateral to gnathosoma. P-2 with 1 dorsal seta. P-3
with medial spine. P-4 with 3 setae in a basal whorl.
Legs: Genua distinctly shorter than both tibiae
and telofemora. Basifemora with 2,3,2–3,2–3 setae.
Telofemur I with ventral seta(e) or spines. Tibia I with
6–8 ventral setae, several of them spiniform. Tibiae II–
IV with 5,2–3,2–3 ventral setae, 3,1–2,1–2 of these setae
bipectinate. Tarsus I with 3 dorsal setae, dorsolateral
solenidion, 2–4 small ventral eupathidia, and pair of
parambulacral setae, but no ventral or ventromedial
seta. Tarsus II with 3 dorsal setae, dorsomedial
solenidion, and pair of parambulacral setae. Tarsi III
and IV each with 3 dorsal setae and apical pair of small
Tarsi I–IV end with pair of claws and minute median
claw. Paired claws of tarsus I slightly smaller than those
of following legs.
Biology and distribution. With one larval and two
nymphal stages. The genital acetabula of nymphs are
somewhat enlarged.
Two species are known, they have been extracted
from slightly brackish freshwater, from the Subantarctic
Marion Island and the Falklands.
Remarks. Peregrinacarus resembles Halacarellus.
The most marked difference is that tarsus I of
Halacarellus has a ventromedial spine or seta distinctly
separated from the apical eupathidia, this seta is absent
in Peregrinacarus.
References. Bartsch (1999a, 2001b).
Phacacarus Bartsch, 1992 (Fig. 50)
Diagnosis. Idiosoma: Length 220–310 µm. Surface
of plates AD, OC and PD almost smooth. In males
dorsal plates very delicate. Dorsum with 2 pairs of
dorsal idiosomatic setae (ds-1 and ds-2). Adanal setae
not seen. AE with 3 pairs of setae and pair of epimeral
pores. PE with 1 dorsal seta and 2 ventral setae. Both
female and male GA with 2 pairs of perigenital setae;
subgenital setae lacking.
Gnathosoma: Short; wider than long. Pharyngeal
plate large. One pair of maxillary setae on gnathosomal
base, 1 pair at base of rostrum. Palps 4-segmented. P-2
with 1 distodorsal seta. No seta on P-3. P-4 with 3 setae
in basal whorl.
Legs: Short. Genua much shorter than both
telofemora and tibiae. Female with large lamellae
on telofemora I–IV; lamellae of legs of male much
smaller. Basifemora with 2,2,2,2 setae. Tibiae I and II
each with 3 ventral setae, tibiae III and IV with 2 setae.
Tarsus I with 3 dorsal setae, dorsolateral solenidion, 3
ventral setae, and pair of apical parambulacral setae.
Tarsus II with 3 dorsal setae, dorsolateral solenidion
and apical pair of parambulacral setae. Tarsi III and IV
with 4 and 3 dorsal setae, respectively, and apical pair
of parambulacral setae. Tarsi II–IV lack ventral setae.
Tarsi with paired claws and small median claw.
Biology and distribution. At present the only
juvenile stage found is the larva. One species is
described which has been collected amongst bushy
corallines growing on rocky shores on the western
coast of Australia.
Remarks. Phacacarus resembles species of
Copidognathus. The most marked differences are: the
reduced number of dorsal idiosomatic setae, the very
short gnathosoma, and the male GA with no more than
2 pairs of perigenital setae and absence of subgenital
setae.
References. Bartsch (1992b, 1994a).
Rhombognathides Viets, 1927 (Fig. 51)
Diagnosis. Idiosoma: Length 280–460 µm. Often
flattened. Dorsal and ventral plates large, contiguous
or fused. Dorsum with 10 pairs of idiosomatic setae;
adanal setae on anal plate. Several of dorsal idiosomatic
setae with a gland pore at their base. OC with 3 setae
and 1–2 corneae. First pair of gland pores on AD. AE
fused medially; with 3 pairs of ventral setae. PE with
1 dorsal and 2 ventral setae. Female GA with 3 pairs
of perigenital setae; genital sclerites without subgenital
setae. Male with 30–83 perigenital setae and 3 pairs of
subgenital setae.
Gnathosoma: Hardly longer than wide. Rostrum
conical, much shorter than gnathosomal base; with 2
pairs of maxillary setae. Palps flattened, 3-segmented,
closely pressed to rostrum. P-2 with 1 distal seta.
Apical palpal segment with 3 wide setae, the dorsal
seta flattened.
Legs: Legs short. Genua shorter than adjoining
segments. Legs I and II similar in shape. Basifemora
32
I–IV with 2,3,2,2 setae, respectively. Tibiae I and II
each with 1 pair of ventral setae, on tibia I both setae
spiniform and bipectinate, on tibia II either 1 or both
of setae stout and bipectinate. Tibia III and IV with
1–2 ventral setae. Tarsi I with 3 dorsal setae, setiform
solenidion and famulus (dorsolateral in position), and
1 ventral spur near the tip. Tarsus II resembling tarsus
I but famulus lacking. Tarsus III with 4 and tarsus IV
with 3 dorsal setae; these tarsi lack ventral setae. Tarsi I
and II with pair of doubled parambulacral setae. Tarsus
III with a spiniform lateral parambulacral seta and a
seti- plus spiniform medial parambulacral seta; tarsus
IV with pair of spiniform parambulacral setae.
All tarsi with rod-like carpite between tarsal tip and
central sclerite. Paired claws large; either smooth or
distally widened and armed with numerous slender
tines. Central sclerite may bear a smooth median claw
which is minute or about two thirds of length of paired
claws.
nymphal stages are known. Six species are described
(exclusive of doubtful species). Rhombognathides is
abundant in intertidal and subtidal areas in the North
Atlantic Ocean, Baltic and Black Sea, on algae and in
unsorted sediment. The species are algivorous.
Remarks. The mites are dark-green due to the
green gut content. Rhombognathides is separated from
Isobactrus and Rhombognathus, which have a similar
dark-green idiosoma, by its flattened, intensely armed
idiosoma and the presence of a ventral spur at the tip
of tarsus I and II. Metarhombognathus, with a darkgreen idiosoma and a ventral spur on tarsus I and II,
has 3 almost equal-sized claws on all legs whereas in
Rhombognathides the median claw, if present, does not
reach the size of the paired claws.
References. Abé (1998), Bartsch (2003b).
Rhombognathus Trouessart, 1888 (Fig. 52)
plates AD, OC and PD present, 2 or more plates may
be fused. Dorsum with 5–6 pairs of idiosomatic setae;
adanal setae on anal plate. OC with 2 dorsal setae, 2
gland pores and often 2 corneae. PD with 1 or 2 dorsal
setae. Ventral plates often fused, rarely separated into
AE, PE and GP. AE (or area of AE) with 3 ventral
plus 0–6 adjunct marginal setae immediately posterior
to insertion of leg II; internal epimeral tubes present
but rather inconspicuous. PE with (0–)1 dorsal and 3
ventral setae, and 0–3 adjunct marginal setae anterior
to insertion of leg III. Female with 1–45 pairs of
perigenital setae and (1–)2 pairs of subgenital setae.
Majority of males with 7–25 pairs of perigenital setae
and 2 pairs of subgenital setae; perigenital setae often
plumose and in trapezoidal arrangement.
Gnathosoma: Generally longer than wide. Rostrum
short and conical or parallel-sided and about as long
as gnathosomal base. Both pairs of maxillary setae on
rostrum. Palps 4-segmented, extending just beyond
rostral tip. P-2 with 1 distal seta; no seta on P-3; 3 setae
in basal whorl of P-4.
Legs: Legs I and II similar in their shape. Basifemora
I and II with 2 and 2–6 setae, respectively; basifemora
III and IV with 1–2 setae each. Tibiae I–IV normally
with 2 ventral bristle-shaped setae, rarely tibiae III
and IV with just 1 such seta. Ventral setae of tibia I
bipectinate. Tarsi I, II and IV with 3 dorsal and 0
ventral setae, tarsus III with (3–)4 dorsal and 0 ventral
setae. Dorsolateral solenidion of tarsi I and II generally
setiform. All tarsi apically with pair of parambulacral
setae which are eupathid on tarsi I and II, eupathid,
setiform or scaliform on tarsi III and IV. Parambulacral
setae on tarsus IV often pectinate or divaricate, in
males medial parambulacral seta normally long and
plumose.
With rod-like carpite between tip of tarsus and
median sclerite. Paired claws either smooth, with a Jshaped pecten or with an accessory process, the latter
may be widened and armed with more than 20 tines.
Central sclerite never with a large claw-like hook.
Biology and distribution. Most of the almost 100
species described have 3 nymphal stages, the proto, deuto- and tritonymph. Rhombognathus inhabits
intertidal and subtidal areas, single records are from
about 100 m depth. Some species are adapted to life in the
upper littoral zone. Beside on algae, Rhombognathus is
found in sandy deposits. Rhombognathus is algivorous.
The genus demonstrates a cosmopolitan distribution.
Most of the species are marine, few, probably endemic
species, live in brackish waters, in the meso- and
oligomixohaline zone.
Remarks. There is an unusual high intraspecific
variability in respect of number of adjunct setae and
setae on telofemora, often also of those on basifemora,
genua and tibiae.
References. Abé (1996a, 1998), Bartsch (2000,
2003b).
Scaptognathides Monniot, 1972 (Fig. 53)
flattened. AD and PD large, OC much smaller. AD
rectangular to hexagonal; first pair of gland pores in
truncate anterior margin. OC with 1 or 2 gland pores,
rarely with a minute seta. PD with 2 pairs of gland
pores. Dorsum with 6 pairs of setae; adanal setae on
anal plate. Ventral plates large, delicate. AE with 3
pairs of setae and minute pair of epimeral tubes. PE
with 1 dorsal and 3 ventral setae. Females with 2 pairs
of perigenital setae and 0–1 pairs of subgenital setae.
Males with 7–16 pairs of perigenital setae, included
33
the pair of outlying setae. Male genital sclerites with 3
subgenital setae.
Gnathosoma: Length equalling 0.4–0.6 of idiosomal
length. Gnathosomal base quadrangular. Rostrum
slender, parallel-sided, as long as or somewhat longer
than gnathosomal base. One pair of maxillary setae
inserted on gnathosomal base near rostral base, 1 pair
near apex of rostrum. Palps 2-segmented, P-2, P-3 and
P-4 fused; palps inserted laterally, separated from each
other by more than width of P-1, and extending to end
of rostrum. Second palpal segment with 1 seta in basal
portion and 3 setae plus 4 spines in apical portion.
Spines level with apex of rostrum.
Legs: Leg I distinctly larger than following legs.
Telofemur I long, tibia I longer than genu but less than
half length of telofemur and often shorter than tarsus I.
All genua shorter than tibiae. Basifemora I–IV with 2
setae each. Tibia I–IV each with pair of short bristle-like
ventral setae. Tarsi I and II each with 3 dorsal setae, 1
dorsolateral solenidion and 0 ventral setae; tarsi III and
IV with 3–4 and 3 dorsal setae, respectively, both tarsi
lack ventral setae. Tarsi I–IV each with pair of small
Tarsus I with pair of large claws; their pecten with
umbrella-like arranged tines. On following legs tines
of claw pecten arranged along ventral flank of claw.
Central sclerite minute, without distinct claw-like
process. A carpite-like sclerite may be recognized
between tip of tarsus and central sclerite.
nymphal stages are known, the proto- and deutonymph.
Scaptognathides is arenicolous. The 10 species
described are from tropical and warm-temperate areas.
Remarks. Unique in Scaptognathides is the shape
of gnathosoma and leg I. The gnathosoma has a slender
rostrum and two-segmented palps with four apical
spines. The telofemur of leg I is long, the tibia short
and the tines on the claws of tarsus I are arranged
umbrella-like.
References. Monniot (1972), Bartsch (1996d), Otto
(2000b).
Scaptognathus Trouessart, 1889 (Fig. 54)
Diagnosis. Idiosoma: Flattened. Length 140–480 µm.
AD and PD large, panelled or porose. OC small, less
than 50 µm in diameter. AD, OC and PD each with pair
of gland pores. Dorsum with 7, rarely 6 pairs of small
dorsal setae; no setae close to anal cone. Ventral plates
large. AE with 3 pairs of setae and often with pair of
distinct epimeral pores. PE with 1 dorsal and 3 ventral
setae. Female GA rarely uniform, generally bipartite
or tripartite, i.e., anterior (bipartite GA) or median
(tripartite GA) transverse portion coarsely striated,
remainder of plate structured as AE and PE. Posterior
portion of female GA with 2–4 pairs of subgenital
setae; majority of species with 2 (rarely 1 or 0) pairs of
subgenital setae. Male GA either uni- or bipartite, rarely
coarsely striated areola separated and situated anterior
to remainder of GA. Male GA with 12–40 perigenital
setae and 3, rarely 2, pairs of subgenital setae.
Gnathosoma: Large; length 0.5–0.9 of idiosomal
length. Rostrum spatula-shaped or wide and lamellar,
apex truncate. Both pairs of maxillary setae inserted
in posterior half of rostrum; two pairs of rostral setae
in lateral and medial margin of apex. Palps inserted
dorsally; interval between P-1 less than their width.
Palps 2-segmented (P-2, P-3 and P-4 fused), rarely
seemingly 3-segmented (P-2 separate, P-3 and P-4
fused), and extending to end of rostrum. Palpal shaft
(corresponding to P-2) with 1 basal and 1 distal seta;
apex of palp (corresponding to P-3 and P-4) with 2
large spines, 2 long setae, its tip with 1 setula and 2
spinelets.
Legs: Slender. Genua shorter than adjoining segment.
Basifemora I–IV with 1–2,1–2,1(–2),1(–2) setae.
Telofemora I–IV with 0–3,0–2,0,0 bipectinate dorsal
or dorsomedial setae. Genua I–IV with 0–2,0–1,0,0
bipectinate ventral setae. Tibia I with 3–6 bristle-like
bipectinate ventral setae. Tibiae II–IV with 2–4 ventral
setae, 1–4 are bipectinate. Tarsus I with 3 dorsal setae,
dorsolateral solenidion and famulus, 0–1 bipectinate
ventral setae plus 0–1 short ventral setae. Tarsus II with
3 dorsal setae, a solenidion in dorsal to dorsomedial
position, and 0–1 bipectinate ventral setae. Tarsi III
and IV with 3–4 and 3 dorsal setae, respectively, and
0 ventral setae. All tarsi with pair of parambulacral
setae.
Paired claws large; usually with minute accessory
process. Central sclerite generally with very minute
process, rarely with large median claw (almost half
length of paired claws).
nymphal stages are known. Almost 30 species are
described as yet; most of them are recorded from warm
and temperate regions, though Scaptognathus is also
found in subpolar waters. The species inhabit sandy
and muddy littoral sediments; the deepest records are
from almost 450–770 m.
Remarks. Easily identified on the base of its spatulashaped or wide and lamellar rostrum and the two large
spines at the end of the palps.
References. Abé (1990), Abé and Green (1994),
Otto (2000b).
Simognathus Trouessart, 1889 (Fig. 55)
ventral plates strongly sclerotized; parts of plates may
have a dark-brown pigmentation. Integument of large
AD and PD generally foveate or porose. OC distinctly
smaller than AD and PD, its shape either distinct,
34
rounded or subtriangular, or largely reduced, elongate.
Gland pores minute or vestigial. With 6 pairs of dorsal
setae; pairs of ds-1 and ds-3 usually on AD, ds-4 and ds5 on PD and adanal setae on anal cone, either in dorsal
or ventral position. AE with 3 pairs of ventral setae and
a pair of generally large epimeral vesicles. PE with 1
dorsal and 3 ventral setae. PE seemingly divided into
EIII and EIV though probably always fused. Female
GA with 4–5 pairs of perigenital setae, no subgenital
setae. Males with approximately 10–25 pairs of
perigenital setae arranged around the GO and 0–3 pairs
of outlying perigenital setae; its genital sclerites with
3 subgenital setae. Perigenital setae generally filiform,
rarely plumose.
Gnathosoma: Broadly attached to idiosoma.
Gnathosomal base almost spherical, rostrum short,
conical. Rostrum shorter than gnathosomal base. One
pair of maxillary setae near base of rostrum, 1 pair
close to tip of rostrum. Palps attached to gnathosoma
dorsally; P-1 almost adjacent. Palps 3-segmented,
extending to end or somewhat beyond rostrum. Second
palpal segment with 1 strong ventral seta and often
with quadrangular ventral apophysis. Apical segment
short, with 1 dorsal seta close to base of segment and 3
setulae at the tip.
Legs: Telofemora and tibiae strong; genua small
and spherical. Telofemora often with ventral carinae.
Tibia I clavate, with narrow base and wide, truncate
end. Tibia of leg I larger than tibiae of following legs.
Short tarsus I with length:height ratio 1.2–3.1; tarsi
II–IV at least 3 times longer than high. Basifemora I
to IV with 2(–3),2,1,1 setae. Tibia I with large ventral
spine; often that spine basally wide, distally tapering.
Ventromedial seta of tibia I slender, rarely spiniform,
always much shorter than ventral spine. Tibiae II, III
and IV with 2 pectinate ventral setae. Tarsus I with 3
dorsal setae, dorsolateral solenidion and famulus, and 1
strong, often spiniform ventral seta; apically with pair
of parambulacral setae. Tarsus II with 3 dorsal setae,
solenidion on medial membrane of claw fossa, (0–)1
ventral seta, and pair of parambulacral setae. Tarsi III
and IV each with 3 dorsal setae, 1–2 ventral setae, and
1–2(–3) parambulacral setae.
Large, smooth median claw of tarsus I flanked by
scythe-shaped or almost setiform paired claws. Tarsi
II–IV with large paired claws; minute central sclerite
without or with small claw-like process. Paired claws
generally with accessory process and pecten. Pecten of
tarsus IV often dissimilar from that of tarsi II and III.
nymphal stages occur during ontogeny. More than
40 species are described. Simognathus is found in
intertidal and subtidal areas, but never in high numbers;
the deepest record is from a depth of about 300 m.
The genus is cosmopolitan but much more species
are recorded from the southern than from the northern
hemisphere.
Remarks. Simognathus is most similar to
Acaromantis. In Acaromantis the very short tarsus
I bears a single claw, the palps are 2-segmented, and
the OC are always reduced to small sclerites which are
hidden beneath the striated integument.
References. Bartsch (1994b, 2003c), Otto (2000a).
Spongihalacarus Otto, 2000 (Fig. 56)
Diagnosis. Idiosoma: Length 340 µm. AD, OC and PD
smooth. OC with 2 pairs of gland pores. Dorsum with 6
pairs of setae; ds-4 and ds-5 within striated integument;
adanal setae on anal plate. AE with 3 pairs of setae and
1 pair of epimeral pores. PE with 1 dorsal and 3 ventral
setae. Female GA short, with 4–5 pairs of perigenital
setae and 2 pairs of subgenital setae.
Gnathosoma: Short; with 2 pairs of maxillary
setae. Rostrum triangular. Palps reduced to 2–3 setae in
dorsolateral position relative to rostrum.
Legs: Genua I and II shorter than telofemora and
tibiae of these legs. Genua III and IV almost as long
as telofemora. Leg segments dorsally with short setae.
Basifemora I–IV with 2 setae each. Genua and tibiae
with pectinate ventral spurs. Tibiae I–IV with 3,3,3,2
such spurs. Tarsi I–IV with 4,4,4,3 dorsal setae (solenidia
included) and 1,1,0,0 ventral setae. Solenidion on
tarsus I in dorsolateral, that on tarsus II in dorsomedial
position. All tarsi with pair of parambulacral setae.
Tarsi end with large median claw and slightly smaller
paired claws.
Biology and distribution. The single species known
was found within an alga-sponge association, collected
in shallow waters in the Great Barrier Reef Marine
Park, northeastern Australia.
Remarks. The most unique character of
Spongihalacarus is the absence of palpal segments.
References. Otto (2000e).
Thalassacarus Newell, 1949 (Fig. 57)
and ventral plates large, dorsal plates foveate, ventral
plates with porose panels, marginal ornamentation
resembling rosette pores. OC elongate. Dorsum with
6 pairs of idiosomatic setae; adanal setae on ventral
side of anal plate. AE with 3 pairs of setae. PE with
1 dorsal and 3 ventral setae. Female GA with 3 pairs
of perigenital setae; subgenital setae absent. Male with
approximately 50 perigenital setae, arranged in a ring
around GO, and 4(–5?) pairs of subgenital setae.
Gnathosoma: Rostrum elongate, about as long
as gnathosomal base. One pair of maxillary setae
on gnathosomal base, 1 pair on rostrum. Palps 4segmented, attached laterally and extending beyond
35
tip of rostrum. P-2 with 1 distodorsal seta, P-3 with
1 dorsomedial seta, P-4 with 3 setae in basal whorl, 1
seta midway. Claws of chelicerae with heavy hooks.
Legs: Shape of leg I similar to that of following
legs. Genua much shorter than adjoining segments.
Basifemora I to IV with 2,3,2,2 setae. Each of tibiae
with a pair of short ventral bristle-like setae. Tarsi
with large membranes of claw fossa. Tarsus I with 3
dorsal setae and dorsolateral solenidion; ventrally
with 1 long seta and 8 eupathidia (parambulacral setae
excluded). Tarsus II with 3 dorsal setae, a solenidion
on dorsomedial membrane of claw fossa and 3 ventral
eupathid setae. Tarsi III and IV each with 3 dorsal and 0
ventral setae. Each tarsus with a pair of parambulacral
setae.
Paired claws large; pectines with conspicuous tines.
Median claw present but small.
Biology and distribution. With a free-living
deutonymph. A single species is described which was
collected on the west coast of North America.
Remarks. Thalassacarus resembles species of the
genus Halacarellus. The most marked difference is the
form of the chelicerae; heavy hooks as in Thalassacarus
are not mentioned in any of the Halacarellus species.
The ventral plates of Thalassacarus bear porose panels,
in contrast, these plates of Halacarellus species are
uniformly and delicately punctate. Agaue demonstrates
a slight overall resemblance but its ventral plates bear
no porose panels.
References. Newell (1949).
Thalassarachna Packard, 1871 (Fig. 58)
Diagnosis. Idiosoma: Generally large, 400–1200 µm
long. AD and PD present; OC rarely lacking. In a few
species PD of male larger than that of female. Dorsal
plates faintly reticulated, not prominently sculptured.
Dorsum with 6 pairs of idiosomatic setae; adanal setae
on anal plate. Idiosoma generally with 4 pairs of gland
pores; 2nd pair of pores, if present, marginally within
striated integument. AE with 3 pairs of ventral setae.
PE with 1 dorsal seta; ventrally either with 3 setae,
or with 2 setae and 1 pair of setae within striated
integument. Female GA with 3–5 pairs of perigenital
setae and 3–5 pairs of subgenital setae. Male GA with
40–160 perigenital setae and 4–6 pairs of subgenital
setae. Internal genital acetabula often large.
Gnathosoma: Longer than wide. Rostrum in ventral
aspect triangular or elongate; generally with 2 (rarely
up to 5) pairs of maxillary setae, 1 pair on gnathosomal
base, 1 pair on rostrum. Palps 4-segmented, lateral to
gnathosoma and extending beyond rostrum. P-2 with
distodorsal seta. P-3 with medial spine. P-4 with 3
setae in basal whorl.
Legs: Genua distinctly shorter than telofemora or
tibiae. Leg I longer than leg II. In a few species leg
I equipped with long spines, namely up to 5 spines
on telofemur, 2 on genu, and 6 on tibia. Basifemora
I to IV with 2,2–3,2–3,2–3 setae. Tarsus I with 5–8
dorsal setae, 1 setiform dorsolateral solenidion, 1
ventromedial seta or spine, and 8–19 eupathidia (pair
of parambulacral setae included). Tarsus II with 4–9
dorsal setae, dorsomedial solenidion, and 5–16 ventral
setae (pair of parambulacral setae included). Tarsi III
and IV with 3–7 and 3–6 dorsal setae, respectively, 0–2
ventral setae and pair of parambulacral setae.
Paired claws large, with accessory process and
pecten. Median claw much smaller, bidentate.
Biology and distribution. With one larval and two
nymphal stages (except for one species which has no
deutonymph). Fourteen species are presently described,
recorded from the North Atlantic and Arctic Ocean.
Thalassarachna species are generally epibiontic and
inhabit subtidal habitats. The two species recorded
from the deep-sea have greatly reduced OC.
Remarks. The Thalassarachna species are separated
from Halacarellus on the basis of the enlarged number
of dorsal setae on the tarsi I and II and the pair of gland
pores in the marginal striated integument.
References. Bartsch (1997a, 2001c).
Thalassophthirius Bartsch, 1988 (Fig. 59)
Diagnosis. Idiosoma: Length 210 µm. Dorsal and
ventral plates large. Dorsum with 5 pairs of setae; ds-3,
ds-4 and ds-5 very long, directed backwards. Adanal
setae on anal plates. Gland pores small, inconspicuous.
AE with 2 pairs of ventral setae, PE with 1 lateral
and 3 ventral setae. Male GA with approximately 75
perigenital setae and 5–6 pairs of subgenital setae.
Gnathosoma: Slender; rostrum about as long as
gnathosomal base. One pair of maxillary setae close to
base of rostrum, 1 pair close to end of rostrum. Palps
lateral to gnathosoma, 4-segmented and extending
beyond tip of rostrum. P-2 with 1 distodorsal seta; no
seta on P-3. P-4 with 3 setae in basal whorl.
Legs: Leg I longer than following legs. Genua shorter
than adjoining segments. Basifemora I to IV with 1 seta
each. Tibiae I–IV with 2 ventral setae each. Tarsus I
with 3 dorsal setae, dorsolateral solenidion, pair of
small ventral setae (exclusive of parambulacral setae).
Tarsus II with 3 dorsal setae, dorsomedial solenidion
and 1 small ventral seta. Tarsi III and IV each with 3
dorsal but no ventral setae. Tip of all tarsi with pair of
Biology and distribution. One species is described,
it has been collected on the shores of southeastern part
of South America.
36
Remarks. A similar combination of setation of palps
and tarsi is known in Camactognathus but species of
the latter genus have three pairs of setae on the AE and
four ventral setae on tibia I.
The only Thalassophthirius species described has
very long and robust dorsal setae directed backwards
and the PD has a large median and two smaller lateral
cavities. Similar enlarged setae and cavities have been
mentioned in the descriptions of a few Copidognathus
species.
References. Bartsch (1988d).
Tropihalacarus Otto & Bartsch, 1999 (Fig. 60)
Diagnosis. Idiosoma: Slender 500–650 µm long.
Dorsum with AD, OC and PD, 6 pairs of dorsal
idiosomatic setae; adanal setae on anal cone. OC with 2
gland pores, AD and PD each with 1 pair of gland pores.
Venter with AE, PE and GA. AE with 3 pairs of setae;
PE with 1 dorsal and 3 ventral setae. Female GA with
3 pairs of perigenital setae, genital sclerites without
subgenital setae. Male GA with 30–100 perigenital
setae, each genital sclerite with 5 subgenital setae.
Gnathosoma: Elongate. Rostrum parallel-sided,
shorter than gnathosomal base. Basal pair of maxillary
setae either on gnathosomal base or on rostrum; second
pair of setae on rostrum. Palps 4-segmented, attached
laterally. P-2 with 1 dorsal seta. P-3 with very minute
medial seta. P-4 with 3 setae in basal whorl.
Legs. Slender. Genua shorter than adjoining
segments. Basifemora I–IV with 2 setae each. Tibiae
with 4,3,3,2 ventral setae; ventromedial setae of
tibiae II and III bipectinate. Tarsus I with 1 ventral
(ventromedial) seta, its apex with numerous eupathidia.
Tarsus II with 1–2 ventral setae, tarsi III and IV with
0–2 ventral setae each. Dorsal setae on tarsi I–IV
numbering 4,4,3,3 (solenidia included). Solenidion of
tarsus I and II on dorsolateral and dorsomedial fossa
membrane, respectively. Tarsi I–IV each with pair of
Paired claws large; median claw inconspicuous.
Biology and distribution. Two species are known,
both have been extracted from Pacific shallow water
sediments.
Remarks. A gnathosoma similar to that of
Tropihalacarus and tarsi I with numerous eupathidia
are present also in species of the genera Agaue,
Bathyhalacarus, Halacarellus, Thalassacarus, and
Thalassarachna, but these species have no bipectinate
setae on tibiae II and III as present in Tropihalacarus.
References. Otto and Bartsch (1999).
Werthella Lohmann, 1907 (Fig. 61)
Diagnosis. Idiosoma: Wide; length 410–560 µm.
Dorsal and ventral plates present. Dorsal plates
panelled, with raised porose areas; AD often with 2
porose areolae in middle of plate, these may be fused.
PD with longitudinal costae. Gland pores small.
Dorsum with 6 pairs of idiosomatic setae. Adanal
setae on either side of anal sclerites. AE with 3 pairs of
ventral setae and pair of generally large epimeral pores;
these pores surrounded by numerous tines. PE with
1 dorsal and 3 ventral setae. Females with 3 pairs of
perigenital setae and 1 pair of subgenital setae. Males
with approximately 30–40 perigenital setae arranged in
a ring close to GO, and 4–5(–6?) pairs of subgenital
setae.
Gnathosoma: Short, somewhat longer than wide.
Rostrum short, triangular, pointed. Tectum often scalelike. One pair of maxillary setae on gnathosomal
base, 1 pair on rostrum. Palps 4-segmented, lateral to
gnathosoma, slightly surpassing rostrum. P-2 with 1
distal seta. P-3 short, without seta. P-4 short; with 1
basal seta, apically with setula and 2 spurs.
Legs: Legs either slender, with elongate telofemora
and tibiae, or with short segments, the telofemora
bearing wide ventral lamellae. Genua much shorter than
adjoining segments. Basifemora I–IV with 2(–3?),2,2,2
setae. Tibiae I and II with 2–3 ventral bristle-like setae,
tibiae III and IV with 2 ventral setae. Tarsus I with 3
dorsal setae, setiform dorsolateral solenidion, 1–3
ventral setae, and pair of parambulacral setae. Tarsus
II with 3 dorsal setae, dorsolateral solenidion, 0 ventral
setae and parambulacral setae. Tarsi III and IV with 4
and 3 dorsal setae, respectively, 0 ventral setae and pair
of parambulacral setae.
Paired claws large, smooth or with accessory process,
rarely with pecten. Median claw present but small.
Biology and distribution. A larva and one nymphal
stage, the protonymph, are present during development.
Ten species are described. Werthella is known from
the southern hemisphere, here the genus inhabits both
intertidal and abyssal areas.
Remarks. Werthella is similar to Copidognathides.
The epimeral pores in Werthella are larger than in
Copidognathides, the rostrum pointed, the perigenital
setae on the male GA are arranged in a ring around
the GO. There is an overall similarity with Pelacarus,
but in the latter genus tarsus II has the solenidion in
dorsomedial position, males have the perigenital setae
not in a ring close to the GO, and females bear three
References. Newell (1971), Bartsch (1996c).
Werthelloides Bartsch, 1986 (Fig. 62)
Diagnosis. Idiosoma: Length 725 µm. Dorsal plates
AD, OC and PD separated by large areas of striated
integument. Dorsum with 6 pairs of idiosomatic setae.
Pair of ds-3 in posterior portion of OC, adanal setae
on PD. Gland pores inconspicuous. AE with 3 pairs
37
of setae. PE with 1 dorsal and 3 ventral setae. Female
GA with almost 10 pairs of perigenital setae and 0–1
subgenital setae. Male GA large; genital opening small
and surrounded by approximately 90 perigenital setae;
genital sclerites with 4–5 pairs of subgenital setae.
Gnathosoma: Rostrum parallel-sided; somewhat
shorter than gnathosomal base. Maxillary setae small,
1 pair on gnathosomal base, 1 pair in basal portion of
rostrum. Tip of rostrum with a pair of barbs. Palps 4segmented; passing beyond rostrum. P-2 with dorsal
seta. No seta on P-3. P-4 with 1 seta, 1 setula and 2
spurs.
Legs: Slender. Genua distinctly shorter than
telofemora and tibiae. Basifemur I to IV with 2,3,3,3
setae. Tibiae I and II with 6–7 ventral bristles each,
tibiae III and IV with 4–5 ventral bristles. Tarsi with
large fossa membranes. Tarsi I and II each with
solenidion on dorsolateral fossa membrane. Tarsus I
with 3 dorsal setae (solenidion excluded) and 7–8 pairs
of ventral eupathidia but no ventromedial seta distanced
from eupathidia. Tarsi II–IV with 3,3,3 dorsal setae
(solenidia excluded) and 1,0,0 ventral setae. Tip of all
tarsi with pair of parambulacral setae.
Biology and distribution. With free-living
deutonymph. One species is described which was taken
in the Indian Ocean, off Réunion, at a depth of 1000
m.
Remarks. A single pair of barbs on the tip of
rostrum, as present in Werthelloides, may be found in
Agaue species. But in contrast to Werthelloides, species
of Agaue have 3 setae in the basal whorl of P-4, the
maxillary setae stand close together, and the ds-3 are
not situated in the posterior half of the OC.
References. Bartsch (1986c).
Winlundia Newell, 1984 (Fig. 63)
ventral plates large. Dorsum with 6 pairs of idiosomatic
setae; adanal setae on anal plate. Anterior gland pores
present though not very conspicuous. AE with 3 pairs
of ventral setae. PE with 1 dorsal and 3 ventral setae.
Female GA with 3 pairs of perigenital setae and 2 pairs
of subgenital setae. Males with 20–40 perigenital setae
and 3–5 pairs of subgenital setae.
Gnathosoma: Rostrum elongate. One pair of
maxillary setae inserted on gnathosomal base, adjacent
to rostrum, 1 pair on rostrum. Palps attached laterally,
4-segmented, extending beyond rostrum. P-2 with 1
distal seta; no seta on P-3; P-4 with 3 setae in basal
whorl.
Legs: Genua shorter than adjoining segments.
Basifemora with 2,2,2,2 setae. Tibiae I–IV with 4,3,2,2
ventral setae. Ventrolateral setae of tibiae II–IV smooth,
ventromedial setae of tibia II and III bipectinate, that
seta of tibia IV either smooth or bipectinate. Tarsus
I with 3 dorsal setae, dorsolateral solenidion and 2
ventral setae (1 slender and 1 eupathid). Tarsus II with
3 dorsal setae, dorsomedial solenidion but no ventral
setae. Tarsi III and IV each with 3 dorsal and 0 ventral
Paired claws large, each with an accessory process.
Median claw present though minute.
Biology and distribution. A free-living deutonymph
present. Two species are described, both collected on
the west coast of South America, in tidal sediment.
Remarks. Winlundia is most similar to Arhodeoporus;
a difference is that in general tarsus I of Arhodeoporus
species bears three ventral setae, namely one slender
and two eupathid ones, whereas in Winlundia one of
the eupathid setae is reduced. Tropihalacarus differs
from Winlundia by its large number of eupathidia on
tarsus I and the very long OC.
References. Newell (1984).
Xenohalacarus Otto, 2000 (Fig. 64)
Diagnosis. Idiosoma: Length 355–360 µm. AD and
PD large. OC small, rounded. Dorsum with 6 pairs of
dorsal setae. OC and PD each with 2 pairs of gland
pores. AE with epimeral pores and 3 pairs of ventral
setae. PE with 1 dorsal and 2 ventral setae; 1 pair of
ventral setae within striated integument. Female GA
with 4 pairs of perigenital setae, no subgenital setae.
Male GA with outlying perigenital setae and about 50
perigenital setae close around GO; genital sclerites
with 5 pairs of subgenital setae.
Gnathosoma: Rostrum slender, parallel-sided,
longer than gnathosomal base. One pair of maxillary
setae on gnathosomal base, 1 pair in apical end of
rostrum. Palps 4-segmented, attached lateral to rostrum.
P-2 with 2 setae. P-3 with short median seta. P-4 with
6 setae.
Legs: Genua of all legs shorter than adjoining
segments. Basifemora I–IV with 2,2,2,1 setae Tibiae
with bristle-like ventral setae, tibiae I and II with
4 such setae. Tarsi I–IV with 4,4,4,3 dorsal setae
(solenidion included), and 2,2,1,2 bristle-like ventral
setae. Solenidion on tarsus I in dorsolateral, on tarsus
II in dorsomedial position. Tarsi I and II each with
pair of parambulacral setae; tarsus III with medial
parambulacral seta only; no parambulacral setae on
tarsus IV.
Paired claws on leg I with long strong tines. Claw
pectines on following tarsi with delicate tines. Median
claw present but small.
Biology and distribution. With a free-living
deutonymphal stage. At present known by a single
species which had been extracted from shallow water
38
coral sand in the Queensland Plateau, off northeastern
Australia.
Remarks. Xenohalacarus and Scaptognathides are
the only marine halacarid genera with enlarged tines on
the claws of tarsi I, tines which are much longer than
on the claws of the following legs.
References. Otto (2000f).
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description of a new species (Acari, Halacaridae). Cah.
Biol. mar. 45, 65-69.
Bartsch, I., 2004b. Acarothrix ampliata (Acari: Halacaridae:
Copidognathinae), a new halacarid mite from Florida,
with notes on external genital acetabula. Species
Diversity 9, 259-267.
40
Baster, J., 1758. Observationes de Corrallinis, iisque
infidentibus polypis, aliisque animalculis marinis. Phil.
Trans. R. Soc., London 50, 258-279.
Crowe, J.H., Camara, C.G., 1973. Studies on acarine
cuticles—I, Cuticular pores in a marine mite. Comp.
Biochem. Physiol. 45A, 757-766.
Gosse, P.H., 1855. Notes on some new or little-known
marine animals (II). Ann. Mag. Nat. Hist. 16 (91), 27–36.
Green, J.M., MacQuitty, M., 1987. Halacarid mites.
Synopses Br. Fauna (N.S.) 36, 178 pp.
Kirchner, W.-P., 1969. Zur Biologie und Ökologie von
Halacarus basteri basteri Johnson 1836 (Acari,
Trombidiformes). Oecologia (Berl.) 3, 56-69.
Krantz, G.W., 1970. Agauopsis vidae, a new species of
Halacaridae (Acari: Prostigmata) from the northern
Adriatic Sea, with notes on its behavior. Arch. Oceanogr.
Limnol. 16, 247-261.
Laubier, L., 1960. Parhalixodes travei n. g., n. sp., un
nouvel Halixodinae (Halacariens) ectoparasite de
nemerte en Méditerranée occidentale. Acarologia 2,
541-551.
Lohmann, H., 1889. Die Unterfamilie der Halacaridae Murr.
und die Meeresmilben der Ostsee. Zool. Jb. (Syst.) 4,
269-408.
Lohmann, H., 1893. Die Halacarinen der PlanktonExpedition. Ergebn. Atlant. Ozean Planktonexped.
Humboldt. Stift. 2, 11-95.
MacQuitty, M., 1984. The feeding behaviour of two species
of Agauopsis (Halacaroidea) from California, in: D.A.
Griffith, C.E. Bowman (Eds.), Acarology VI, John Wiley,
New York, pp. 571-580.
Makarova, N.G., 1978. Marine mites (Acarina, Halacaridae)
from the intertidal zone of the Gulf of Anadyr (Bering
Sea), in: Kussakin, O.G. (Ed.), The intertidal zone of the
Bering Sea and south-eastern Kamchatka. pp. 131-149.
(In Russian, with English Summary)
Monniot, F., 1962. Description d’une nouvelle espèce
d’acariens marins, Halacaridae: Coloboceras drachi,
récoltée en Méditerranée. Bull. Soc. Zool. Fr. 87, 492497.
Monniot, F., 1972. Scaptognathides, un nouveau genre
d’acariens marins (Halacaridae) dans l’Atlantique ouest.
Morselli, I., Mari, M., (1982). Alacaridi (Acari,
Prostigmata) di fondi sabbiosi della costa Ionica del
Salento. Atti Soc. Tosc. Sci. nat., Mem. (B) 88, 229-247.
Morselli, I., Mari, M., Sarto, M., 1998. On three species
of the genus Acarochelopodia Angelier, 1954 (Acari,
Halacaroidea) from the Italian coasts. Ital. J. Zool. 65,
381–384.
Murray, A., 1877. Economic Entomology. Aptera. South
Kensington Museum Handbooks, 433 pp.
Newell, I.M., 1947. A systematic and ecological study
of the Halacaridae of eastern North America. Bull.
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Newell, I.M., 1949. New genera and species of Halacaridae
(Acari). Am. Mus. Novitat. 1411, 1–22.
Newell, I.M., 1967. Abyssal Halacaridae (Acari) from the
southeast Pacific. Pacif. Insects 9, 693-708.
Newell, I.M., 1971. Halacaridae (Acari) collected during
cruise 17 of the R/V Anton Bruun, in the southeastern
Pacific Ocean. Anton Bruun Rep. 8, 3–58.
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Otto, J.C., 1999a. Halacarid fauna of the Great Barrier Reef
and Coral Sea: the genera Agauopsis and Halacaropsis
(Acarina: Halacaridae). Mems Qld. Mus. 43, 797-817.
Otto, J.C., 1999b. Four new species of Agaue (Acarina:
Halacaridae) from the Great Barrier Reef Marine Park.
Cah. Biol. mar. 40, 273-281.
Otto, J.C., 1999c. Corallihalacarus chilcottensis, a new
genus and species of marine mites from the Coral Sea
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and Coral Sea: the genera Lohmannella, Scaptognathides
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Halacaridae) from northern Australia, with remarks on
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Otto, J.C., 2000d. Australacarus (Acari: Halacaridae) from
northern Australia, with description of three new species.
Rec. Aust. Mus. 20, 103-114.
Otto, J.C., 2000e. Spongihalacarus longiscutatus n.gen.,
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associated with an alga-sponge symbiosis from the Great
Barrier Reef Lagoon in Australia. Int. J. Acarol. 26, 279283.
Otto, J.C., 2000f. Xenohalacarus longirostris n.gen., n.sp., a
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Chilcott Islet, Australia. Int. J. Acarol. 26, 285-291.
Otto, J.C., 2000g. Seven new species of Arhodeoporus
(Acarina: Halacaridae) from the Great Barrier Reef and
Coral Sea. Hydrobiologia 436, 1-16.
41
Otto, J., 2000h. Six closely related species of the
Copidognathus gibbus group (Acarina: Halacaridae)
from north-eastern Australia. Cah. Biol. mar. 41, 223232.
Otto, J.C., 2001a. A new species of Mictognathus (Acari:
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42
Fig. 1: Generalized halacarid. A, idiosoma and legs, dorsal aspect. B, idiosoma and gnathosoma, ventral aspect.
43
Fig. 2: A, halacarid mite with porose areolae, dorsal aspect; B, diagram of integument with rosette pores (from Newell
1947, Crowe and Camara 1973); C, tarsus I; D, ambulacrum and claws; E, idiosoma, dorsal aspect showing measurements of length and width; F, idiosoma and gnathosoma, ventral aspect, showing measurements of length and width [L
(length) of AD, AE, GA, gnathosoma, idiosoma, OC, PD, PE; W (width) of AD, GA, gnathosoma, idiosoma, OC, PD].
44
Fig. 3: Shape of idiosoma and gnathosoma, dorsal aspect.
45
Fig. 4: Shape of idiosoma and dorsal plates.
46
Fig. 5: Shape of ventral plates.
47
Fig. 6: Shape of gnathosoma, dorsal aspect.
48
Fig. 7: Shape of gnathosoma, ventral aspect.
49
Fig. 8: Shape of palps and number of setae.
50
Fig. 9: Shape of leg I.
51
Fig. 10: Chaetotaxy and shape of legs.
52
Fig. 11: Chaetotaxy of tarsus I.
53
Fig. 12: Chaetotaxy of tarsus IV.
Fig. 13: Shape of claws.
54
Fig. 14: Acanthohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
55
Fig. 15: Acanthopalpus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect;
D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.
56
Fig. 16: Acarochelopodia. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
57
Fig. 17: Acaromantis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, gnathosoma, ventral aspect; E, palp; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.
58
Fig. 18: Acarothrix. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
59
Fig. 19: Actacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
60
Fig. 20: Agaue. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D,
gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
61
Fig. 21: Agauides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D,
leg I; E, tarsus I; F, tarsus II; G, tarsus IV.
62
Fig. 22: Agauopsis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
63
Fig. 23: Anomalohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral
aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
64
Fig. 24: Arenihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
65
Fig. 25: Arhodeoporus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
66
Fig. 26: Atelopsalis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
67
Fig. 27: Australacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
68
Fig. 28: Bathyhalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
69
Fig. 29: Bradyagaue. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
70
Fig. 30: Camactognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
71
Fig. 31: Caspihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
72
Fig. 32: Coloboceras. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
73
Fig. 33: Colobocerasides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral
aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.
74
Fig. 34: Copidognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, palps; E, gnathosoma, ventral aspect; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.
75
Fig. 35: Copidognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, gnathosoma, ventral aspect; E, leg I; F, leg I, G, tarsus I; H, tarsus II; I, tarsus IV.
76
Fig. 36: Corallihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral
77
Fig. 37: Enterohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral
aspect; D, palp; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
78
Fig. 38: Halacarellus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
79
Fig. 39: Halacaroides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
80
Fig. 40: Halacaropsis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
81
Fig. 41: Halacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
82
Fig. 42: Halixodes. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
83
Fig. 43: Isobactrus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
84
Fig. 44: Lohmannella. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
85
Fig. 45: Metarhombognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral
aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.
86
Fig. 46: Mictognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
87
Fig. 47: Parhalixodes. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect;
D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.
88
Fig. 48: Pelacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
89
Fig. 49: Peregrinacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
90
Fig. 50: Phacacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
91
Fig. 51: Rhombognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
92
Fig. 52: Rhombognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV (male).
93
Fig. 53: Scaptognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
94
Fig. 54: Scaptognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
95
Fig. 55: Simognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
male; D, gnathosoma, ventral aspect; E, palp; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.
96
Fig. 56: Spongihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral
97
Fig. 57: Thalassacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
98
Fig. 58: Thalassarachna. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
99
Fig. 59: Thalassophthirius. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, male; C, gnathosoma, ventral
100
Fig. 60: Tropihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
101
Fig. 61: Werthella. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
102
Fig. 62: Werthelloides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,
103
Fig. 63: Winlundia. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male;
104
Fig. 64: Xenohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect,

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