Chasmocarcinops gelasimoides Alcock, 1900

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 46-48

Chasmocarcinops gelasimoides Alcock, 1900

( Figs. 9 ; 23I, J; 30E, F; 40A‒D; 51F; 58F; 70; 86F; 90F)

Chasmocarcinops gelasimoides Alcock, 1900: 334 [type localilty: India].— Alcock & McArdle 1903: pl. 62, figs. 2, 2a, 3, 3a [India].— Rathbun 1910: 340, pl. 1, fig. 10, pl. 2, fig. 12 [Gulf of Thailand].— Tesch 1918: 280.— Suvatti 1938: 58 [in list]; 1950: 161 [in list].— Schmitt et al. 1973: 130 [references].— Dai & Yang 1991: 417, fig 204 (3, 4), pl. 56, fig. 4 [Guandong, China].— Chen 1998: 301 fig. 24 [Nansha Is.].— Serène 1964a: 266, fig. 20, pl. 23, fig. C [Philippines]; 1968: 92 [in list].— Serène & Soh 1976: 22 [Andaman Sea].—Dai et al. 1986: 387 [South China Sea].— Dai & Yang 1991: 417, pl. 56, fig. 4 [South China Sea].— Huang 1994: 592 [in list].—Davie et al. 2002: 331 [Andaman Sea].—Ng & Davie 2002: 378 [in list].— Jiang 2008: 770 [in list] [South China Sea].—Ng et al. 2008: 76 [in list].—Castro et al. 2010: 51 [Singapore].— Komai et al. 2012: 149 [Singapore].

Type material (not examined). 1 male, 1 female syntypes, India, off Madras [= Chennai ], 22 m (depository unknown: probably Zoological Survey of India, Kolkata; see Alcock 1900).

Material examined. Andaman Sea. THAI-DANISH EXPEDITION: 1 male (PMBC 2061), 1 male (8.8 × 9.5 mm) (PMBC 16849), 1 male (PMBC 16840); 1 female (11.5 × 12.4 mm) (PMBC 16894), stn 1035, 06°57’N, 99°11’E, 49 m, 21.01.1966.

Vietnam. 4 males ( ZRC 1970.1.23.10–13) , 3 males ( ZRC 1970.8.4.2‒4), Nhatrang Bay , 1958.

Gulf of Thailand. NAGA EXPEDITION: 3 males, 2 females ( SIO C 4411), stn S9A 60-1049, 11°36’42’N, 102°26’00”E, 33 m, beam trawl, 10.12.1960.

Peninsular Malaysia. 1 male (8.6 × 9.0 mm) ( ZRC 1965.11.24.3), Straits of Malacca, Pisang I., 01.1934. — 2 females ( ZRC 1985.1379–1380 ), Johor, off Tanjong Stapa , 11–31 m, 0 7.04.1955.

Singapore. 1 male ( ZRC 1985.1381 ), off Changi, 9 m, no date. —2 males, 3 females ( ZRC 1985.1370–1374 ), Damar Laut, mud with gorgonians, 9‒14.5 m, Singapore Regional Fisheries Research Station ( SRFRS) coll. —4 males (ZRC 1989.3672–3675), Bedok, 15 m, 27.10.1982.— 1 female (9.5 × 10.4 mm) ( ZRC 1989.3676–3677 ), East Coast, 28.08.1983 .— 2 males, Southern Is. ( ZRC 2000.2612 ), shell-gravel, P.K.L. Ng coll., 01.1984. —4 males, 6 females (ZRC), D. Lane coll., 1992.—1 male (ZRC 2000.1501), Southern Is., D.G.B. Chia & Z.L. Xu coll., 01.1992.—1 male, 1 female ( ZRC 2010.0029 ), Johor Shoal, P.K.L. Ng et al. coll., 18.08.1992 .—3 males, 1 male (9.5 × 10.3 mm) ( ZRC 2000.1341 ), Johor Shoal, 01°20’08.1”N, 104°02’31.1”E, mud, D. Wee et al. coll., 14.07.1993 .—1 female (ZRC 1999.0624), 1 female (ZRC 2013.1412), Angler’s Bank, Tekong-Changi Channel, 20 m, L.W. Loh coll., 01°23.628’N, 104°01’242”E, 05.08.1997; 1 male (ZRC 2013.1422), Changi/Tekong channel, Angler's Bank, 01°23.092’N, 104°01.558”E, 12 m, dredge.—1 male (8.0 × 8.3 mm) (ZRC 2009.0234), Marina East, 01°16.815’N, 103°52'645’E, T.M. Sin & A.C. Lee coll., 19.02.2009.— 1 female (9.3 × 10.6 mm) ( ZRC 2013.1411 ), Royal Singapore Yacht Club, beam trawl, 28.02.2012 .—1 female (ZRC 2013.1412), Tekong-Changi Channel, 01°23.628’N, 104°01.242”E, dredge, L.W. Loh coll., 0 5.08.1987.

Indonesia. 1 male, 1 female ( ZRC 1970.3.13.16), unknown location, R. Serène coll.—CORINDON 2 : 3 males, 5 females (MNHN-IU-2013-9048), Makassar Strait , stn CH 203, 01°08.6’S, 117°07.5’E, 25 m, 30.10.1980 ; 1 female (MNHN-IU-2013-9049), stn CH 205, 01°07.8’S, 117°18.7’E, 49 m, 30.10.1980 .

Diagnosis. As for genus.

Remarks. There are some slight differences between the specimens on hand from the western Pacific and Andaman Sea, including Alcock’s figures based on material from the Bay of Bengal ( Alcock & McArdle 1903: pl. 62, figs. 2, 2a, 3, 3a): relatively larger orbits and more quadrate carapace in the western Pacific specimens. Comparison with material from the Andaman Sea showed that these differences (as well as in the granulation of the carapace and the length and general shape of the G1) are not substantial and fall within the range of individual variation. The form of the major male chela also varies, with smaller specimens ( Fig. 40 A) having less gaping fingers, strongly gaping in larger specimens ( Figs. 9 B; 40C). It is therefore best to recognise only one species for the time being.

Rathbun (1910: 340), who treated Chasmocarcinops gelasmoides as a pinnotherid, reported on many specimens from the Gulf of Thailand, mostly from shallow, soft substrates, but she recorded one male specimen that was supposedly found from inside a living scallop Amussium pleuronectes , and she provided a photograph of the crab inside the scallop ( Rathbun 1910: pl. 1, fig. 10). This was listed by Schmitt et al. (1973: 130) in his review of pinnotherids. Serène & Soh (1976: 22) commented:

“ Rathbun (1910), recording 50 specimens from the Gulf of Thailand, mentioned only one of them as having been “in shell of living Amussium pleuronectes ". The crab gelasimoides and the mollusk pleuronectes inhabit the same grounds and are frequently mixed together in the trawl catches of the fishermen. The senior author has observed during the years several hundred specimens, but has never come across a gelasimoides in a shell of living A. pleuronectes and considers that Rathbun's observation must be attributed to chance circumstances. Rathbun did not make her observation in the field, but on preserved material collected by Mortensen several years previously. We believe that the crab and mollusk observed by Rathbun were put alive in the same basket, after being caught; the mollusk having relaxed its muscle, as is usual, the crab penetrated the shell to eat the flesh. At the fixation time, the mollusk closed its shell and kept the crab inside. Our remark on the ethology of the species provides a new reason for removing Chasmocarcinops from the Pinnotheridae .”

Serène (1964a) had earlier transferred the species to the Chasmocarcinidae (as Chasmocarcininae ). We agree with Serène & Soh (1976). All the Singapore specimens were from dredge and grab samples from soft substrates, and all the crabs were free-living. They apparently live buried in the soft mud.

Distribution. Indian (western India, Andaman Sea) and western Pacific (South China Sea to Indonesia) oceans. Depth: 9‒ 49 m.

Figures

FIGURE 9. Overall dorsal view, chela and buccal area of Chasmocarcinops gelasimoides. A, B, Andaman Sea: male (after Alcock 1899 a: pl. 62 fig. 3, 3 a); C, D, Andaman Sea: female (after Alcock 1899 a: pl. 62 fig. 2, 2 a); E, Andaman Sea: male 8.8 × 9.5 mm (PMBC 16849); F, Andaman Sea: female 11.5 × 12.4 mm (PMBC 16894); G, Singapore: male 9.5 × 10.3 mm (ZRC 2000.1341); H, Singapore: female 9.3 × 10.6 mm (ZRC 2013.1411).

FIGURE 40. Chelae of species of Chasmocarcinops and Hephthopelta. A, B, Chasmocarcinops gelasimoides, Andaman Sea: male 8.8 × 9.5 mm (PMBC 16849); C, D, Chasmocarcinops gelasimoides, Singapore: male 9.5 × 10.3 mm (ZRC 2000.1341); E, F, Hephthopelta lugubris, Australia: male 7.9 × 8.3 mm (NMV J 61081); G, H, Hephthopelta occidentalis n. sp., Madagascar: holotype male 6.1 × 6.6 mm, with sacculinid (MNHN-IU- 2010 - 1031).