Note on some rare and aberrant Australian crabs

13 Pages·1991·4.2 MB·

by  Zdravko Števčić

The Beaffle, Records of the Northern Territory Museum of Arts and Sciences. 1991 8(1): 121-134
NOTE ON SOME RARE AND ABERRANT AUSTRALIAN CRABS.
ZDRAVKO STEVCIC
Rudjcr Boskovic Institute,
Center for Marine Research 52210 Rovinj, Croatia, Yugoslavia.
ABSTRACT
Four rare and aberrant species of brachyuran crabs (Crustacea: Decapoda:
Brachyura) are studied from Australian waters including the majid Plaiiotergum
niirahile, the pilumnid Calmania prima, the eumedonid Rhahdonotus picttis and
the portunid Brusinia hrucei. The systematic status and position of these species
are reconsidered, their geographical distributions are completed, a new genus and
species (Brusinia hrucei) is described, new subfamily Planoterginae and new
tribes Calmaniini and Brusiniini are erected.
Keywords; Australian waters, brachyuran crabs, Brusinia gen.nov., Calmania,
Plaiiotergum, Rhahdonotus.
INTRODUCTION figs 1-4, pis 1-2; Griffin and Tranter 1986:92.
Anomalopisa incongruens Johnson, 1965:174-
During the course of a benthic survey of the 180, fig. 1.
North-West Shelf of Western Australia Com¬ Material. NTM Cr.0007873: 1 female, CL
monwealth Scientific and Industrial Research 11.4 mm. CW 9.0 mm. Soda cruise ASO 283,
Organization (CSIRO) R V Soda, under the Op. 46, stn. (NWS 46), I9°06..5'S, 118°00.15’ E,
leadership of Dr Trevor Ward, produced a 86.9m; 26.2° C. 16 April 1983. coll. P. Blyth.
number of unusual brachyuran crabs. I re¬ I female, CL 12.0 mm. Soda cruise ASO 383,
ceived a small collection of these crabs for ,stn. B7 BT, I male, CL 7.0,, CW 5.2, Soda stn.
taxonomic study, which were found to be very B7 BT. (Second female specimen with cara¬
interesting from both systematic and biogeo- pace encrusted, preventing measurement of
graphical points of view. The species identi¬ width).
fied are either extremely rare or new to the Historical background. On 12 June 1906, a
Australian fauna, or their systematic positions pair of crabs were collected from a depth of 3m
are very obscure and need further elucidation. northwest of Denham, Shark Bay, Western
The collection includes the following species: Australia. BaIss (1935) described these speci¬
Planoterguin niirahile BaIss, Calmania prima mens under the name Planotergum mirahile.
Laurie. Rhahdonotus pictus A. Milne Edwards No further examples of this species were col¬
and Brusinia hrucei gen. et sp.nov., which is lected until 1953. when two females of this
described in this paper. The material is depos¬ species were sampled from Pulau Sikijang
ited in the Northern Territory Mu.seum of Arts Pelepah, Singapore, and described by Johnson
and Sciences. Abbreviations used in the text: (1965) under the name of Anomalopisa incon-
BMNH, Natural History Museum, London; gruens. Thereafter Romimohtarto sampled a
CL, carapace length; CW, carapace width; female specimen in the Java Sea on April 1963,
NSMT. National Science Museum, Tokyo; during the “Jalanidhi” cruises and reported by
NTM, Northern Territory Museum, Darwin. Serene (1965a). Recently Griffin and Tranter
(1986) reported two female specimens pre¬
SYSTEMATICS served in the Australian Museum, Sydney, one
from Roebuck Bay. Western Australia and
Family Majidae Samouelle
another from KeppcI Islands, Queensland.
Planotergum mirahile BaIss, 1935
Description. Balss’s original description
(Fig. 1)
was very short, but the subsequent reports of
Planotergum mirahile BaIss, 1935:36-38, Johnson and Serene are detailed and well illus¬
figs 1-3; 1957: 1628; Serene 1965a:457-488, trated so that a further general description of
121
Z. Stevcic
this species is not necessary. I would only like obscured. In the second female, the telson is
to add the description of the male first pleopod. readily visible and the entire abdomen sparsely
Male first pleopod (Fig. 1) is elongated and setose. The abdomen of the first female shows
slender, only slightly curved in the middle distinct callosities, but these are not present in
portion, proximally bulbous, distally swollen, the second female specimen.
ending in a blunt ape.x extending little beyond The male specimen is almost completely
the aperture. On the subterminal swelling, non-setose. The denticulate ridge on the ven¬
several tubercles in a longitudinal row and a tral side of the crest on the first ambulatory leg
longitudinal row of 6 bristles. The present is not very distinct, in contrast to the Java Sea
specimens agree closely with the previous and Singapore specimens, in which it is mark¬
description except for some small differences edly turned out.
in length and density of setae in the callosities Distribution. The species ranges from In¬
of the female abdomen. In the first female donesian to northern and Western Australian
there are many long plumose setae on the waters. Probably extremely rare.
frontal ridge of the pseudorostrum, ambula¬ Keinarks. Mode of life: The highly specific
tory legs and ridges of the carapace, especially shape and structure of the appendages in Ph-
posteriorly; sparse long silky setae are present notergiim relate to an unknown, but undoubt¬
on the surface of the carapace; the anterior edly peculiar, mode of life. Without direct
ridge of the abdomen is covered by short dense field or laboratory observations, it is only
setae, so that the tekson is almost completely possible to speculate upon its habits and mi¬
cro-habitat. The position of the ambulatory
legs precludes "normal” walking or swimming
behaviour and climbing would be only possi¬
ble with difficulty. It seems probable that most
of the time it is attached to the substrate with
its subchelate ambulatory legs. Serene (1963n)
and Johnson (1965) have noted a superficial
resemblance to parasitic isopods (Bopyridae),
and Johnson (1965:180) stated: “their general
build and appearance suggest parasitic or
endocommensal relations, but this is contra¬
dicted by the hardness of the exoskeleton and
the well developed eyes”. 1 also consider that
it probably lives as an ectoparasite or at least
on the surface of some animal. It would proba¬
bly be able to attach itself very strongly to the
skin of the host by means of subchelate pereio-
pods. It would completely cover the site of
attachment with its body situated in a pit on the
host’s outer surface, so that the dorsal surface
of the carapace lies in the same plane as the
host’s body surface. Beneath the anterior part
of the carapace, in the “external pseudo-buccal
cavity”, noted by Serene (1965a), the small
chelipeds, with their .sharp tips, could tear off
morsels of the host tissues. These chelipeds
cannot reach the dorsal surface of the cara¬
pace, as they do in majid crabs, which enables
encrusting organisms such as bryozoans, bi¬
valve mollusks and .serpulids, to attach and
grow (Serene 1965a; Johnson 1965). Other
morphological features support this assump¬
tion. The sensory organs are peculiar. The
Fig. 1. Plaiwrevf’um mirahile. male, first pleopod. antennulae lie in the previously mentioned
122
Some aberrant Australian crabs
"external pseudo-buccal cavity”, but the an¬ those taxa mentioned by Balss. also incorpo¬
tennae have the terminal segment oriented rating a number of other possible relatives, but
dorsally so that the flagellum would be over he concluded that the genus shared most of its
the pseudorostrum. Auxiliary orbital cavities features with the genus Hemus. The shared
are also present on the median side of the characters are the following: antennules. an¬
merus of the second pereiopod (first ambula¬ tennae, third maxillipcds, chelipeds. christiform
tory leg) into which the eye can fit when not ambulatory legs and auxiliary "external pseudo-
lodged in the true orbit. In this situation the eye buccal cavity". However, there are a number
can see all dorsal aspects of the body. of differences peculiar to Plauotergiim, differ¬
Sy.stematic .status and position: The place entiating it from all other brachyuran crabs
of the genus Planotergiini in the brachyuran (i.e. form of carapace and ambulatory legs,
system has been subject to different interpre¬ small telson), so that the classification into an
tations by carcinologists. The main reason for extant single higher taxon is very question¬
this disagreement lies in the fact that this genus able.
is very aberrant. Its mode of life and larval A third author also independently consid¬
stages are not known so that it is impossible to ered the problems of the systematic status and
confidently place it into an existing structure position of the genus Plaiiotergum. Johnson
of the brachyuran crabs. Accordingly, a com¬ (1965:174), in his title of the paper wrote "a
plete re-evaluation of all known related data is highly aberrant .spider-crab” (i.e. majid crab),
needed. concluded that "They are sufficiently unlike
In his description of the genus. Balss (193.5) all known members of that alliance to make
pointed out that Planoterf>um is “an extremely their systematic position doubtful, but they
aberrant oxyrhynchous crab”, the exact posi¬ appear to belong to the subfamily Pisinae of
tion of which is very difficult to establish. the family Majidae”. Nevertheless, he was
Balss did not say precisely in which oxyrhyn¬ faced with some dilemmas in his final decision
chous family or subfamily it should be classi¬ on the systematic status and position of Pla-
fied. although, from the context it is probable notergum when he stated that "There seem to
that he intended the family Majidac Samouelle. be only two reasonable solutions. Either
As a potential near relative he noted first the Anomalopisa should be made the type of a new
subfamily Acanthonychinae (present valid name sub-family, or it should be treated as an aber¬
Epialtinae MacLeay). and after that the genera rant member of the Pisinae” (Johnson 1965:180).
Eucynctops A. Milne Edwards (from the sub¬ Finally, Griffin and Tranter (1986) classified
family Inachinae Alcock). Laphoniicippa this genus with the Epialtinae, although in the
Rathbun (present valid name Micippa Leach), final discussion (p.297) they remarked: “not
and Hemus A. Milne Edwards. Both last noted majid".
genera at present are classified into the sub¬ As evident from this short historical survey
family Mithracinae MacLeay (.sec Garth 19.58; of elucidation of the systematic status and
Griffin and Tranter 1986) with which Plcmot- position of Planotergum. no solution is tidly
erfpim shares some unusual characters, but satisfactory. All these authors mostly only
differs in all others, suggesting no close rela¬ agree on the majid nature of the crab, and from
tionship to any of taxa mentioned above. Fur¬ the discussions above it can be seen that Pla¬
thermore. Balss (1935) also noted that Plaiiot- notergum is very distinct from any other known
crgitm shared some features with the genus brachyuran. The organization of the genus is
Crassotonotus from a non-oxyrhynchous fam¬ unique and extremely aberrant from other majid
ily Palicidae Rathbun. particularly in some of subfamilies: the general shape {planus - lergum,
its mouth parts, although in his monograph. i.e. plane back; specific frontal region: pecu¬
Balss (1957) classified Planoicrgum at the last liar antennae; size and position of chelipeds;
position of the subfamily Majinae. with a peculiar structure of ambulatory' legs; form of
remark that the systematic position of the dactyls: auxiliar ocular cavity, i.e. small hol¬
genus was uncertain. low on the merus of the first pair of ambulatory
Thirty years later Serene (1965a) mentioned legs for eye protection; minute telson). In
"Oxyrhynque ... aberrant” in comments re¬ these characters Planotergum differs from all
lated to the family Majidae. Serene (I965a:466) other crabs and occupies, as an over-special¬
re-examined the possible relationships with ized crab, an isolated position within the majid
123
Z. Stevcic
crabs. Accordingly, I conclude that it cannot BT, 19°30.6’S, 118°49.4’E, 38 m. 28 June
be referred to any extant majid subfamily, and 1983. coll. T. Ward.
consequently I erect a new taxon for it. Historical background. Calmania prima
was described by Laurie (1906) from the Gulf
Planoterginae subfam. nov. of Manaar, Ceylon (Sri Lanka), and classified
into the family Xanthidae MacLeay. Another
Diagnosis. Carapace irregularly subrectan- similar crab, Ralumia cialili, was described by
gular, dorsal surface smooth, almost flat, only Balss (1933a) and also placed into the Xanthi-
with very small gastric and cardiac tubercles. dae. Balss (1933b) expressed the opinion that
Front lamellar, projecting, rectangular in form, Litocheira sculptimana Tesch, 1918, should
anteriorly straight. Lateral and posterior mar¬ be classified into the genus Calmania, and
gins slightly cristiform. Anterolateral margin shortly thereafter some new and related spe¬
with four unequal lobes. Posterior margin broadly cies were described: Ralumia baissi Sakai.
convex. Antennulae slightly oblique. Anten¬ 1935 and Calmania simodaensis Sakai, 1939.
nae with short, broad, immovable basal (2-t-3) In their revision of these two genera Serene
segment. Fourth article lamellar, long, quad¬ and Umali (1972) concluded that the genus
rangular, fifth article lamellar, but very small. Ralumia consisted of only a single species i.e.
Flagellum short. Eyestalks short, stout, cornea R. dahli, whereas all the other species previ¬
well developed and visible in dorsal view. ously included belong to the genus Calmania,
Orbits incomplete. Supraorbital eave of mod¬ so that this genus comprises the following
erate size, preorbital tubercle inconspicuous, species: C. prima, C. simodaensis, C. halssi
postorbital tubercles small, separated from and C. sculptimana (the latter previously re¬
supraorbital eave and anteriorly cupped for ferred 10 Litocheira). In their conclusions Serene
eye protection. Subocular margin reduced. and Umali (1972:73) claimed that “it must also
Epistome reduced. Third maxillipeds slender, be noted that Calmania is very close, if not
covering the buccal cavern incompletely. synonymous (?) to Ralumia". In his revision of
Chelipeds minute, asymmetric, smooth, not the genus Litocheira, Tiirkay (1975) concluded
visible in dorsal view. Ambulatory legs short, that L. .sculptimana {sensu Tesch 1918) must
with only basal part covered by carapace, be included into the genus Ralumia. Later
distal parts in the same plane as the carapace, Sakai (1976) reclassified this species in the
cristiform, carpus and propodus tightly pressed following manner: Calmania prima and C.
against merus. dactyls short, slender trans¬ simodaensis, and Ralumia dahli and R. halssi.
formed in corneous claw. Merus of the first As mentioned above, Ralumia sculptimana
pair of ambulatory legs with a small hollow for must also be classified with these species.
ocular protection. Abdomen in female very Thus, the number of species to be included in
wide, narrow in males, telson very reduced in Ralumia is still open, and this can only be
both sexes. solved after a male of R. dahli becomes avail¬
able for study.
Family Pilumnidae .Samouelle Description. Refer to the most recent rede¬
Calmania prima Laurie, 1906 scription of this species (e.g. Ng 1983:143.
figs 25 a-d).
Calmania prima Laurie, 1906:407, pi. 1, Distribution. Calmania prima ranges from
figs lOa-b; Balss 1922:137; Gordon 1934:63, Japan to Australia (Great Barrier Reef) and
fig. 32d; Sakai 1935: 80, text fig. 14, pi. 52, fig. Ceylon. It is rarely reported but probably not
3; 1939:538, pi. 65, fig. 3; Bouvier 1942:38; very rare.
Stephensen 1945;222; Balss. 1957; 1631; Sakai Remarks. Systematic status and position:
1965; 126. pl.80. fie.3; Serene 1968:77; Serene The majority of carcinologists followed the
and Umali 1972;7l; Sakai 1976;439, text-fig. classification of Laurie (1906) in placing Cal¬
232, pi. 176. fig. 2; Takeda 1978a; 40; Yamaguchi mania in the Xanthidae, although not specify¬
et al. 1978;26; Ng 1983:143, figs 25 a-d. ing a subfamily. Several other authors such as
Kraiissia laevis Yokoya, 1933:170, text- Balss (1922. 1957). Gordon (1934) and Serene
fig. 62. (1965b) placed Calmania prima in the subfam¬
Material. NTM Cr.0007874: 1 female, CL ily Eumedoninae Dana of the family Partheno-
7.1 mm, CW 7.2 mm, Soela ASO 383, stn. B7 pidae MacLeay. Only Stephensen (1945:222).
Some aberrant Australian crabs
although including the species in the Xanthidae, cal; chelae are depressed, with fingers bearing
was not sure in which subfamily it should be pointed tips, distal part of fingers is toothed
included. Therefore he assigned it to a group of and proximal, with a large hiatus covered with
species designated as “subfamily not certain” rigid setae, and fingers close in an oblique
and remarked; “probably subfamily Pilumninae”. plane in relation to the axis of palm; the dactyls
The closely related genus Ralitmia was also of ambulatory legs are very long, compressed
initially placed by Balss (1933a) and Sakai and styliform; the last pair of ambulatory legs
(1935) in the family Xanthidae, but without a is in the same plane as the carapace; and the
precise declaration as to the subfamily, al¬ male pleopods are of the pilumnid type, al¬
though later Balss (1957) included this genus though the first pleopod is relatively more
with the Pilumninae Alcock. Thereafter, Serene stout than usual pilumnids. The atypical
(1965b) placed it in the alliance Heteropan- pereiopods found in this species are related to
opeoidea Alcock of the subfamily Pilumninae. an enigmatic mode of life, and the function of
Serene (1968) included both genera Calmania these structures cannot be interpreted further
and Raluniia together in the alliance Xan- without field and/or laboratory observations.
thoida Alcock (Xanthinae), and in this he was The second reason for doubts in the affini¬
followed by Sakai (1965). Recently Ng ties of these genera is related to the presently
(1983:127) cla.ssified these both genera in a confused state of the family Pilumnidae. This
particular Calmania-group, and included, as family is very rich in species and genera, but
he .said, the “pilumnien” lineage of the Pilum- the affinities between these lower taxa have
nidae. He did not state the categorial rank of not been precisely established, and thus the
the group (e.g. subfamily or tribe) and only status of the two genera under investigation
claimed that “their status is uncertain” (Ng remains ob.scure. The pilumnid male pleopods
1983:143). and free-articulated male abdomen also occur
The fact that these two genera have previ¬ in various groups such as the Pilumninae Alcock,
ously been assigned to various alliances (i.e. Eumedonidae Dana, Rhizopinae Stimpson and
tribes), subfamilies and families, indicates the genera Dentoxanihus Stephensen, Galene
obvious uncertainties with their classification. de Haan, Halimede de Haan, Parapanope de
However, according to the present state of Man, Heteropanope Stimpson. Bathypiliimmis
knowledge of the brachyuran classification the Ng, Ilampolus Serene and Peyrot-CTlausade,
genera Calmania and Ralumia have to be clas¬ and Peleianus Serene and Umali. A complete
sified in the family Pilumnidae Samouelle. revision (re-description and reclassification)
The reason for such a classification is evident of the whole family Pilumnidae (in fact all
from the following list of shared characters: brachyuran crabs !) is a prerequisite for precise
male pleopods of the pilumnid type - first classification of these two genera. Accord¬
pleopod is long, sinuous, distally hooked with ingly, their placement at the present time can
simple apex, second is short; and the male only be made provisionally, and their true
abdomen has 7 free-articulated segments. status and position within the family Pilumnidae
Moreover, the similarities between the taxa can only be ascertained following such a gen¬
include a wide bilobed front; sternal sutures 4/ eral revision. For the time being the two genera
5 and 5/6 are interrupted, whereas 6/7 and 7/8 can be included within the family Pilumnidae
continuous; and a relatively narrow abdomen in a new tribe, with the following definition.
in females. Accordingly, the position of these
two genera is undoubtedly with the family Calmaniini trib. nov.
Pilumnidae. On the other hand, their position
within the family is not clear. The first reason Diagnosis. Carapace hairy, length and width
for doubts in their affinities lies in the fact that more or less equal. Front projecting, widely
these two genera differ from the typical pilum- bilobed, not deflexed. Antennulae oblique.
nids in several characters: the carapace length Basal antennal article filling orbital hiatus,
and width are nearly equal; the antennulae are next two segments enter orbital hiatus. Third
oblique; the front projects and is not deflexed; maxillipeds do not completely cover the buc¬
there is no antennal groove; the third maxilli- cal cavern. Chelipeds large, symmetric and
peds do not completely cover the buccal cav¬ depressed; distal part of fingers toothed and
ern; chelipeds are symmetrical, large and atypi¬ proximal with large hiatus covered with setae;
125
Z. Stevcic
fingers closing in an oblique plane in relation Romimohtarto (1963) concluded that Caphyra
to the axis of palm. Dactyls of ambulatory legs archeri was a junior synonym of Rhabdonotus
compressed, long and styliform; last pair in the pictus and that it should be placed in the
same plane as the carapace. Male pleopods of Eumedoninae. After general revision of the
pilumnid type, but first pleopod relatively Eumedonidae Stevcic et al. (1988) concluded
stouter. that the genus Rhabdonotus should be referred
to the subfamily Eumedoninae Dana.
Family Eumedonidae Dana The principal reason for the confusion of the
Rhabdonotus pictus A. Milne Edwards, status of this species is due to the somewhat
1879 aberrant form of its carapace. SpeciTically. in
this genus the distinct spine at the junction of
Rhabdonotus pictus A. Milne Edwards, the anterolateral and posterolateral margins is
1879:6, pi. 2, figs 2,2a; de Man 1888:325; absent, so that the lateral margin is rounded.
Balss 1957:1650; Serene and Romimohtarto However, in all other characters it agrees with
1963:9. fig. 5. pi. 2, figs, F.G; Lundoer 1974:5; the Eumedonidae, as follows: prominent front,
Shen etal. 1982:147, fig. 15, pi. 2. fig. 14; Ng oblique folding of antennulae in well devel¬
1983:142; Stevcic el al. 1988:1317. oped fossae; the shape and position of the basal
Caphyra archeri Walker, 1887:116, pi. 9, antennal segment which fills up the inner
figs 4-5; Balss 1934:506. orbital hiatus and does not reach the frontal
Material. NTM Cr.0007875: 1 male, CL 5.2 margin; the disproportionally voluminous
mm, CW 4.7 mm; Soela cruise 0483, stn. B7 chelipeds; the “pulley’’-like propodus/dactylus
BT, 19° 30.8’S, 118° 49.3'E; 30 August 1983, articulation (locking mechanism), permitting
coll. T. Ward. better attachment to the host; the structure of
Description. Refer to the most recent rede¬ the sternum (sutures 4/5 and 5/6 are inter¬
scription of this species (e.g. Shen el al. 1982:147, rupted, whereas 6/7 and 7/8 are continuous); j
fig. 15, pi. 2, fig. 14). the form of the male first pleopod (slender and
Distribution. Rhabdonotus pictus has a wide sinuous); and all 7 abdominal .segments are
Indo-Pacific distribution, having been recorded freely articulated.
from the Indo-west Pacific region (southern
India, Andaman Sea, Singapore, Indonesia, Family Portunidae Rafinesque
Vietnam) and Chinese waters, and it is now Brusinia gen. nov.
reported for the first time from tropical Aus¬ (Tables 1-2)
tralian waters.
Remarks. Mode of life; The details of the Type species. Brusinia brucei sp.nov.
mode of life of Rhabdonotus pictus are insuf¬
ficiently known. It is known to occur as a Etymology. The generic name Brusinia is
commensal on the arms of comatulid crinoids derived from the name of the Croatian zoolo¬
(de Man 1888), and also on Virgularia sp. gist (carcinologist). Spiridion Brusina (1845-
(Anthozoa) (Sankarankutty. in Serene and 1908) (pronunciation: broosseena). Gender:
Romimohtarto 1963). feminine.
Systematic position: A Milne Edwards in¬ Diagnosis. Carapace subelliptical, about 1-
cluded Rhabdonotus in a position near the 2 times longer than wide, surface smooth and
Trapeziinae Miers and Cymo de Haan in the glabrous, finely granular, regions indistinct.
family Xanthidae MacLeay. Caphyra archeri Front lamellar, trilobate and projecting. An¬
was classified by Walker (1887) in the Por- terolateral margin shorter than posterolateral,
tunidae Rafinesque since the Caphyrinae Al- with three teeth (postorbital tooth or angle
cock arc a subfamily of the Portunidae. Balss excluded), no marked transition between an¬
(1934:506) suggested that the genus should be terolateral and posterolateral margins. Anten¬
excluded from the Portunidae and included in nulae transversely folded. Urinal article dis¬
“formes aberrantes des Oxyrhynches”. Later, tinct. Basal antennal article cylindrical, fla¬
Balss (1957:1650) classified Rhabdonotus in gellum recurved. Eyes normally developed.
the Xanthidae, or more precisely in Xanthinae, Sub- and supraorbital borders entire, without
noting that its sy.stematic position was uncer¬ incisions or fissures, postocular angle well
tain. Following a detailed analysis. Serene and developed. Buccal cavern quadrangular, in-
126
Some aberrant Australian crabs
Table 1. Differences between Benthochascon hemingi and B. elongaliim sensu Sakai (1969).
CHARACTERS B. hemingi B. elongatum
Carapace
Form subquadrilaleral subelliptical
Surface regions faintly indicated indistinct
Maximal width posterior tooth (3) penultimate tooth (2)
Hindmost tooth longest, spiniform smaller than other teeth
Transition between anterolat¬
eral and posterolateral borders distinct, pointed indistinct, absent
Frontal lobes
Size nearly equal median lobe smaller
Median lobe bifid (notched) triangular
Antennae
Basal article with small spinule at outer angle cylindrical, no spinules
Flagellum usual position transverse
Antennulae
Folding nearly transverse transverse
Maxillipeds
Merus of third pair long as wide broader than long
Chelipeds
Fingers long as palm or longer shorter than palm
Chelae opening longitudinal oblique
Dentition of occlusive margin teeth fairly long, stout low, triangular
Walking legs (pair 1-3)
Distal upper end of merus with notch and tooth rounded
Dactyl of third pair as preceding 2 upper ridge with backward oriented setae
Dactyls stiliform, proximally depressed leaf-like, laterally compressed
Swimming legs (pair 5)
Dactyl end (tip) pointed (mucronate) rounded
Upper margin fringe with short setae directed laterally with short setae directed backwards
Lower margin fringe with short setae directed laterally with long plumose setae
Male abdomen
Form widely triangular elongated and narrow
Male first pleopod
Form rather stout slender
Position slightly distally diverging straight, nearly parallel
Terminal part simple distorted
completely covered by the third maxillipeds. the male, 3-5 segments more or less fused,
Cheliped.s large, with fingers opening in ob¬ immovable, but articulations very distinct. Third
lique plane, fingers shorter than palm, smooth, abdominal .segment in the male not noticeably
glabrous and finely granular (as carapace). wider than the fourth one. Male first pleopod
Walking legs stout, shorter than chelipeds, basally stout, distally straight. Second pleopod
three anterior pairs with daclylus elongated, longer than first and distally recurved.
compressed, leaf-like fringed dorsally by short Remarks on the genu.s. Historical back¬
setae; last pair fringed by setae, dactyl lamel¬ ground: Sakai (1969) described an aberrant
late and leaf-like, with rounded tip. Thoracic portunid crab and classified it in the genus
sternum elongated, with 4/5-7/8 sutures inter¬ Benthochascon Alcock and Anderson, 1899,
rupted. Abdomen elongated and narrow in under the name B. elongatum. Subsequently
both sexes, first two and a part of the third Takeda (1978b) reported 10 specimens from
abdominal segment visible in dorsal view. In the same locality as the holotype. Later, during
127
Z. Slevcic
Table 2. Differences between Japanese and Australian specimens of Brusinia gen.nov.
CHARACTERS Japanese specimens Australian specimens
(B. etongata (Sakai, 1969)) (= B. hrucei sp. nov.)
Sternum
Sparse long setae on sternite 3-4 present absent
Sternum in male
Sutures 6/7. 7/8 grooved not grooved
Anterior end of sternite 8 sunken, invisible at same level as sternite 7
Abdomen
Setae on 1-3 segments long (Fig.2a) short (Fig.2b)
Setae on segment 3 reaching those on 2 not reaching those on 2
Glabrous median part on segment 3 narrower than 2 same length as 2
Telson of male fringed by setae (Fig.3a) glabrous (Fig.3b)
Male pleopod 1
Apical part distorted asymmetrical, almost straight
Conical spinules on distorted part, numerous only on apical part, sparse
Short setae subapically present (4) absent
cruises of the R.V. Soela, two similar speci¬ Similarly, in order to establish the identity
mens were collected and the evaluation of and determine differences between the Japa¬
these specimens provides the subject of the nese and Australian crabs, specimens from
present contribution. both areas were compared. The results of this
During examination of this material it was comparison are presented in Table 2. Although
questioned whether B. elongatum actually be¬ only two Australian specimens were available,
longed to the genus Benthochascon, and whether they were both adults, male and female
in fact the Australian specimens belong to B. (ovigerous), and as such were eminently suit¬
elongatum at all. In order to answer these able for further study. The Australian and
questions detailed re-examination of material Japanese specimens show a number of differ¬
and comparisons with others have been made. ences, although initially appearing superfi¬
Homogeneity of the genus Benthochas¬ cially very similar. However, significant dif¬
con: The following comparison is based on the ferences were found in the sternal and abdomi¬
description and illustrations of the genus nal structures, and in particular in the male
Benthochascon, namely B. hemingi (Alcock first pleopods. Because of these differences it
and Anderson 1899; Alcock 1899a,b; Doflein seems justifiable to separate the Australian
1904; Stephen.son 1972; Sakai 1976), a BMNH forms as a distinct new species, although it
specimen of 6. schmitti Rathbun. and with the would be preferrable that a greater number of
three NSMT specimens of B. elongatum ob¬ specimens were available to document the
tained by Dr. M. Takeda; i.e. (1 male NSMT species’ variation. For instance, one male speci¬
Cr.6934, CL 7.9, CW 6.5 mm; 1 female ovig., men from the Japanese waters had an indistinct
NSMT Cr. 5591 (damaged); 1 male NSMT 2/3 sternal suture, similar to that of the unique
Cr.5598, CL 9.5, CW 7.5 mm). The differ¬ male specimen of the Australian crabs, but in
ences in the major taxonomic characters are another male specimen from Japanese waters
presented in Table 1. this suture was very prominent.
As evident from this table, the differences
are not only just “variation on a theme”, as Brusinia briicei sp. nov.
normally shown by members of a genus, but (Figs. 2b, 3b, 5, 6a,b)
they actually represent two different “themes”:
or in other words, 1 consider that they belong Material. HOLOTYPE - NTM Cr.()007871:
to two separate genera. The differences refer to I male, CL 7.5 mm, CW 6.6 mm. PARATYPE
the form of the carapace, in particular the - NTM Cr.0007872: 1 female ovig., CL 7.6
frontal region, chelipeds, pereiopods and male mm, CW 6.3 mm; Soela crui.se ASO 283, stn.
pleopods. Consequently, B. elongatum requires B-12 (NSW20), 28 April 1983, beam trawl, 80
the creation of a new genus. m. 19° 03.5’S, 119° 03.6’E.
128
Some aberrant Australian crabs
Description. Carapace subelliptical (Figs. ered by third maxillipeds. Ischium of third
6a-b). longer than wide, with maximal width at maxilliped longer than merus, merus broader
second (penultimate) lateral tooth, longitudi¬ than long. Endostome with obliquely directed
nally moderately convex, transversely very endostomial ridge, less marked on anterior
slightly convex, but concavity a little more border of endostome.
expressed on posterior pair of the carapace. Chelipeds rather large, subequal, smooth,
Dorsal surface smooth,glabrous and very finely glabrous and finely granular (similarly to the
granular, without distinct furrow or regions. carapace). Merus short, prismatic. Carpus sub¬
Front forming lamellar trilobate projection, quadrate with short spine on inner angle, sur¬
lateral lobes bluntly rounded apically, median rounded by long plumose .setae, chela distally
lobe smaller and triangular in outline. Preorbital flattened, palm high, convex on outer surface
tooth absent. Front separated from upper or¬ and slightly concave at inner surface, slightly
bital margin, which is entire (no traces of fis¬ dellected downward distally, fingers notice¬
sures) and slightly elevated anteriorly, form¬ ably shorter than palm; fixed finger short,
ing a short eavc over the basal part of eyestalk. proximally broad, triangular in outline; mov¬
External orbital tooth large and pointed apically, able finger slender, strongly curved inward in
suborbital margin entire, inner suborbital an¬ the distal half. Tips of fingers crossed in re¬
gle wide, orbital hiatus wide. Anterolateral pose, cutting edge sharp, composed of irregu¬
border shorter than posterolateral one and cut lar low, broad, triangular molariform teeth
into three procurved teeth, first two subequal, (superficially similar to molars of the Carnivora)
last tooth smaller. Posterior margin narrow, less di.stinct and somewhat reduced on mov¬
straight. Antennulac folding transversely into able finger.
their fossae. First (urinal) antennal segment Ambulatory legs stout, shorter than cheli¬
di.stinct, basal (2+3) segment slender, cylin¬ peds, laterally compressed, particularly dac¬
drical, longitudinally directed, not filling com¬ tyls; more or less setose on the dorsal margin,
pletely the orbital hiatus, fourth segment nearly in particular mcri; dactyls on three anterior
as thin as ba.sal. slightly shorter, entering or¬ pairs of ambulatory legs (2-4 perciopods) elon¬
bital hiatus, fifth antennal segment shortest gate, leaf-like, i.e. enlarged (but not lamel¬
entering orbit, upwardly directed: nagellum late), upper margins straight, ventral margins
moderately short, recurved backward, reach¬ irregularly semielliptical, tips of dactyls bluntly
ing or slightly overlapping upper orbital mar¬ pointed, and slightly recurved forward, par¬
gin. Orbits deep, eye large, eye.stalk short and ticularly in anterior two ambulatory legs, third
more or less straight. Upper margin of each
thick, cornea rounded.
Epistome well developed, provided with dactylus fringed with short setae, oriented
median anterior projection. Proepistome and forsvard on first two pairs, backward on third
epistome not distinctly separated by a trans¬ pair, last pair of legs paddle-like, and con¬
versal suture. Buccal cavern quadrangular, spicuously setose, dactyl subelliptical, apically
rather broader than long, not completely cov¬ rounded, distal part fringed with long setae;
A B
Fig. 2. Proximal abdominal segments. a, Brusiuia clonj’uta: b, li. hrucei.
129
Z. Stevcic
spinules, apex bluntly rounded. Male second
A B pleopod longer than first, slender, straight
distally (near apex of the first pleopod), regu¬
larly recurved inward so that apex orientates
backward and recurved parts of one supcrim-
po.se on the other.
Etymology. The specific name “hnicei" is
dedicated to the noted Australian carcinologist
A.J. Bruce (NTM, Darwin), who provided me
with the present material.
Ecology and distribution. No information
is available for the species beyond the collec¬
tion data given above. Since the collection was
made by beam trawl at a depth of 80 m, the
Fig. 3. Telson. a. Brusinia eloiinula: b. B. hrucei. crabs presumably occur on sedimentary bot¬
toms in which they can bury themselves.
dorsal margin of carpus and propodus bearing Remarks. The above analysis shows that
sparse long setae; very dense short setae di¬ two species of the genus Brusinia c)iisl:Bnisinia
rected posteriorly backward, ventral margin e/w/go/a (Sakai. 1969) comb. nov. and Brusinio
bearing long dense setae from carpus to end of hrucei sp. nov.
dactylus. Systematic position: The systematic posi¬
Abdomen relatively narrow, elongated in tion of the genus Brusinia is not clear. It is an
both sexes. First segment very short, with atypical portunid crab, which differs from all
sparse setae (Fig. 2b). particularly on both other portunids in many characters, particu¬
sides, .second and third segments with lateral larly in the form of the carapace, pereiopods
areas with setae on distal part, proximal and abdomen. It resembles in its general body
two and part of the third abdominal segments shape the genera Poriuninus Leach and Xaiva
visible in dorsal view, all articulations be¬ MacLeay, whereas the enlarged dactyls of the
tween segments distinct, in male 3-5 segments ambulatory legs resemble those of Tliia Leach.
more or le.ss coalescent. and immovable. Telson Kraussia Dana, and partially Polybius Leach.
triangular with rounded apex (Fig. 3b). Because of these atypical portunid characters
Thoracic sternum relatively elongated. The Brusinia has an isolated position in the sys-
sternal sutures 4/5 to 7/8 interrupted. Median tematics of the family Portunidae, with impre¬
furrow on 7th and 8th sternites, sternal sutures cise subfamily placement. Brusinia shares some
6/7 and particularly 7/8 with inner ends near common characters with both Carcininae
the median furrow, sternites 5 and 6 trans¬ MacLeay and Polybiinac Ortmann (carapace
versely. 7th and in particular 8th, obliquely relatively narrow, anterolateral margin with 3
posed. Episternitcs present. Locking mecha¬ teeth, antennae lying in longitudinal axis of
nism of abdomen present and functional. Sterno- body, basal antennal segment longer than broad,
abdominal cavity of moderate depth. antennal flagellum enters orbit). Moreover, it
Male first pleopod (Fig.5) hasally stout, shares some characters with members of these
slightly tapering distally, distal part slender subfamilies in its similar form and 2-4 pereiopods
and both pleopods parallel, reaching to sixth (Carcininae), and endostomial ridge, oblong
sternite. Distal part provided with scattered and 7-articulated abdomen (Polybiinae). Ac-
130