A new deep-sea crab of the genus Chaceon from India (Crustacea: Decapoda: Geryonidae)

5 Pages·1993·1.9 MB·

by  H C Ghosh

4
PROC. BIOL. SOC. WASH.
106(4), 1993, pp. 714-718
A NEW DEEP-SEA CRAB OF THE
GENUS CHACEON FROM INDIA
(CRUSTACEA: DECAPODA: GERYONIDAE)
H. C. Ghosh and Raymond B. Manning
—
Abstract. Chaceon alcocki, a species with laterally compressed dactyli on
thewalkinglegs, is describedfrom afemale identifiedwiththe European Geryon
&
affinis Milne Edwards Bouvier, 1894 by Alcockin 1899. Itis the sixth species
ofthe genus to be recognized from the western Indian Ocean.
Until recently, several species ofgeryonid 224-284 fm (410-520 m); sand; Investiga-
crabs from different localities had been tor station 248; 17 Oct 1898; Zoological
identified with either Geryon quinquedens Survey of India Registry Number C 2907/
Smith, 1879 or with Geryon affinis Milne 10.
Edwards & Bouvier, 1894; both of these Diagnosis. —A large Chaceon, cl to more
species were transferredbyManning&Hol- than 110 mm, cb to more than 126 mm,
thuis (1989) to the genus Chaceon. Of the with low, obtuse anterolateral teeth on the
24 species of Chaceon now recognized, 1 carapace and laterally compressed dactyli
at one time in the past had been identified on the walking legs. Carapace 1.1 times
C
witheither C. quinquedensorwith affinis, broader than long, moderately inflated at
and six species hadbeen identifiedwith both protogastric regions, convex from front to
C &
C. quinquedens and affinis (Manning back. Frontal teeth short and blunt, median
Holthuis 1988, 1989). In their revision of extendingfurtherforwardthanlaterals. Dis-
the geryonids. Manning & Holthuis (1989: tance from first to second anterolateral tooth
76) pointed out that the status ofa species subequal to distance from third to fourth,
identified with Geryon affinis by Alcock distance from first to third tooth equal to
(1899) needed to be determined. That spe- distancefromthirdto fifth. Carapacelargely
cies, which proved to be new, is described smooth, surface pitted behind front and on
below. branchial regions. Orbits shallow, withdeep
The holotype is in the Zoological Survey incision on posterior margin. Suborbital
of India, Calcutta. Measurements are in tooth low, obtusely pointed, falling short of
millimeters. Abbreviations used in the ac- apices of lateral frontal teeth. Outer angle
count below include: cb, carapace breadth; ofmerus ofthird maxilliped not projecting
cl, carapace length; fm, fathoms; m, meters; laterally. Cheliped merus with sharp sub-
P5, fifth leg (fourth walking leg). distal spine dorsally, distal spine absent;
carpus relatively smooth dorsally, lacking
Chaceon alcocki, new species outer spine orangledprojection, innerspine
Figs. 1-3 well developed; propodus lacking distal
dorsal spine. Meri ofwalking legs unarmed
Geryon affinis.—A\coc\<i, 1899:85 [not Ge-
& dorsally. Dactyli of walking legs laterally
ryon affinis Milne Edwards Bouvier,
compressed, heightatmidlengthgreaterthan
1894].
width, tips of dactyli blunt, worn off. P5:
—
Holotype. \9, cl 110.5, cb 126.5; India, merus 4.5 times longer than high; carpus
Travancorecoast, 8°37'N, 75°37'30"E; depth with at most a line oflowtubercles dorsally;
VOLUME NUMBER
106, 4 715
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Fig. 1. Chaceon alcocki, new species. Female holotype, cl 110.5 mm: a, Dorsal view; b, Carapace; c, Buccal
area.
716 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
b
Fig. 2. Chaceon alcocki, new species. Female holotype, cl 110.5 mm: a, Orbit, ventral view; b, Dactylus of
P5, dorsal view; c, Dactylus ofP5, lateral view.
VOLUME NUMBER
106, 4 717
Fig. 3. Chaceon alcocki, new species. Female holotype, cl 110.5 mm: a, P5; b, Carpus ofP5; c, Dactylus of
P5, dorsal view; d, dactylus ofP5, lateral view.
propodus 5.0 times longer than high; dac- bles C. chuni (Macpherson, 1983) and C.
tylus 0.8 times as long as propodus. crosnieri Manning & Holthuis, 1989, and
Size. —Unique female holotype, cl 1 10.5, differs from C macphersoni (Manning &
cb 126.5. Measurements ofP5: merus length Holthuis, 1988) in having laterally com-
C
60.0, height 13.2; propodus length 50.0, pressed dactyli on the walking legs, but
C C
height 10.0; dactyluslength 40.5, height 4.5, alcocki differs from both chuni and
width 3.2. crosnieri in lacking distal dorsal spines on
Color.—Bro^n. Alcock (1899:85) com- the meri ofthe walking legs.
mented that "The colours in life are ad- Etymology —^divcvQd for Alfred William
.
mirably shown in the figure given by MM. Alcock, 23 June 1859-24 March 1935, En-
Milne Edwards and Bouvier." glish surgeon andnaturalist. Superintendent
Remarks.—Mdinmng (1992) pointed out ofthe Indian Museum from 1893 to 1907,
that five species of Chaceon had been re- one of the pioneers in carcinological re-
corded from localities in the western Indian search in India.
Ocean. Two of these, C. paulensis (Chun, Distribution. —Known only from the type
1903) and C. collettei Manning, 1992, differ locality.
C
from alcockiin havinglong, sharp frontal
and anterolateral spines on the carapace and
Acknowledgments
longer, slenderer walking legs with a distal
dorsal spine on the merus of at least the We thank Prof M. S. Jairajpuri, Director
posteriorthree legs. Chaceon alcockiresem- of the Zoological Survey of India, for his
718 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
—
support ofthis project. Lilly King Manning -, & . 1989. Two new genera and nine
prepared the figures for publication. new species ofgeryonid crabs (Crustacea, De-
capoda, Geryonidae).—Proceedings of the Bi-
ological Society ofWashington 102:50-77.
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ouresetanomoures. Crustacesdecapodes prov-
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1887,1888).Premierepartie. Resultatsdesca-
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Chun, C. 1903. Aus den Tiefen derWeltmeeres, 2nd
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radosenlascostadeNamibia.—ResultadosEx-
Cod.—Transactions ofthe Connecticut Acade-
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