Carcinoplax tenuidentata, Castro, 2007

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 645-648

Carcinoplax tenuidentata n. sp.

( Figs 4 ; 5 )

TYPE MATERIAL. — MUSORSTOM 10, stn CP 1320, ♂ holotype, cl 9.1 mm, cw 10.8 mm ( MNHN-B 29496). — Stn CP 1325, ♂ paratype, cl 12.0 mm, cw 14.5 mm ( MNHN-B 29497). — MUSORSTOM 8, stn CP 1123 ♀ paratype, cl 14.3 mm, cw 17.1 mm ( MNHN-B 29797). — BATHUS 4, stn DW 883 ♀ paratype, cl 11.4 mm, cw 13.4 mm ( MNHN-B 29493).

TYPE LOCALITY. — Fiji, Bligh Water, 17°16.8’S, 177°53.6’E, 290- 300 m.

MATERIAL EXAMINED. — Vanuatu. MUSORSTOM 8, stn DW 1004, 18°48.96’S, 168°59.24’E, 319-350 m, 25.IX.1994, 1 ♂ ( MNHN-B 29405). — Stn CP 1123, 15°07.19’S, 166°55.20’E, 262-552 m, 9.X.1994, ♀ paratype ( MNHN-B 29797).

BOA 1, stn CP 2445, 18°08.0’S, 166°55.3’E, 231-285 m, 10.IX.2005, 2 ♂♂ ( MNHN-B 30124).

New Caledonia. LAGON, stn DW 835, 20°46.8’S, 165°17.3’E, 135-150 m, 11.I.1987, 1 pre-adult ♀ ( MNHN-B 29774).

Passe de Boulari, 400 m, 20.III.1988, 1 ♂, 1 ♀ ( MNHN-B 29775).

BATHUS 1, stn DW 641, 21°52.18’S, 166°49.06’E, 240- 258 m, 10.III.1993, 1 ♂ ( MNHN-B 29551). — Stn DW 654, 21°17.11’S, 165°56.77’E, 237-298 m, 12.III.1993, 1 ♀ ( MNHN-B 29490). — Stn DW 659, 21°16.98’S, 165°56.82’E, 275 m, 12.III.1993, 1 ♂ ( MNHN-B 29809). — Stn CP 668, 20°57.21’S, 165°34.57’E, 205-219 m, 14.III.1993, 1 ♂ ( MNHN-B 29491). — Stn CP 713, 21°45.28’S, 166°36.83’E, 250 m, 19.III.1993, 1 ♀ ( MNHN-B 29492).

HALIPRO 1, stn CP 853, 21°45’S, 166°37’E, 241-250 m, 19.IV.1994, 1 ♂ parasitised by Sacculina ( MNHN-B 29810).

BATHUS 4, stn DW 883, 22°03.43’S, 165°56.03’E, 450-600 m, 1.VIII.1994, 1 ♀ paratype ( MNHN-B 29493). — Stn CP 899, 20°16.68’S, 163°50.26’E, 500-600 m, 3.VIII.1994, 1 ♀ ( MNHN-B 29494).

Fiji. MUSORSTOM 10, stn CP 1320, 17°16.8’S, 177°53.6’E, 290-300 m, 6.VIII.1998, 1 ♀ ( MNHN-B 29495), ♂ holotype ( MNHN-B 29496). — Stn CP 1325, 17°16.4’S, 177°49.8’E, 282-322 m, 7.VIII.1998, 1 ♂ paratype ( MNHN-B 29497). — Stn CP 1328, 17°16.8’S, 177°50. 4’E, 248-277 m, 7.VIII.1998, 2 ♀♀ ( MNHN-B 29498).

BORDAU 1, stn CP 1402, 16°38’S, 179°36’E, 260-279 m, 25.II.1999, 1 pre-adult ♀ ( MNHN-B 29499 ). — Stn CP 1403, 16°40’S, 179°36’E, 220-224 m, 25.II.1999, 1 ♀ ( MNHN-B 29500 ) ; 1 pre-adult ♂ ( MNHN-B 29807 ) .

ETYMOLOGY. — From tenuis, Latin for “thin”, and dens, Latin for “tooth”, in reference to the slender, short anterolateral teeth characteristic of the species.

DISTRIBUTION. — Southwestern Pacific Ocean: Vanuatu, New Caledonia, and Fiji. Depth: 135- 720 m.

DESCRIPTION

Carapace ( Figs 4A ; 5 ) quadrate, slightly wider than long (1.2 as wide as long in holotype), anterolateral borders arched, inflated, giving carapace globose appearance. Carapace convex, without clear indication of regions. Front lamellar, straight, not marked by median notch. Slight notch between front, inner edge of supraorbital border. Supraorbital borders sinuous, margins granular. Suborbital borders granular, each with short, blunt inner tooth not visible dorsally. No tooth on outer orbital angle other than the curved, granular border of the orbit; 2 slender, spinous, acute-tipped anterolateral teeth on each side of carapace. Posterolateral borders arched.

Subhepatic, pterygostomial regions, pterygostomial crest, pterygostomial lobe, merus, ischium of third maxilliped endopod with short, conspicuous granules.

Eye peduncles ( Figs 4A ; 5 ) short (0.2 front width), distal margin granular, cornea slightly expanded distally.

Chelipeds (P1) ( Fig. 5 ) nearly equal in males, females, slightly more slender in males; fingers

Revision of Goneplacinae ( Crustacea, Brachyura)

slender, as long as propodus in males, much shorter in females, with blunt teeth, less than half of distal portion of fingers dark brown. Broad, curved, acute-tipped tooth on inner (ventral), proximal margin of carpus, smaller tooth on outer (dorsal), distal margin. Ambulatory legs (P2-P5) moderately long, slender, smooth; many long simple setae along inner, outer margins of P5 propodus, dactylus, outer margin of P5 carpus, shorter along P2-P4, some long simple setae along P2-P4 meri, carpi, propodi; P5 dactylus long, slender, smooth; length of P5 merus 0.5-0.6 cl.

Male abdomen ( Fig. 4B ) narrowly triangular, with 6 freely-movable somites plus telson; telson slightly wider than long, somite 3 covers space between P5 coxae. Somites 1, 2 slightly narrower than somite 3, small portion of thoracic sternite 8 visible. G1 ( Fig. 4C ) long, slender, straight; pointed tip with scattered spinules. G2 ( Fig. 4D ) slender, nearly equal or slightly longer than G1, slightly curved flagellum, tip with 2 lateral spinules.

Female abdomen wide. Telson slightly wider than long. Somites 1, 2 cover space between P5 coxae, thoracic sternite 8 not visible. Vulva of mature females greatly expanded, extending from edge of slightly deflected suture 5/6 to suture 6/7; membrane covers aperture leaving space open along anterior margin.

Colour

The holotype specimen ( MNHN-B 29496) was photographed soon after collection. The carapace was orange and the ambulatory legs transparent and banded with orange.

REMARKS

The overall morphology of the new species is remarkably similar, almost identical, to that of Pycnoplax bispinosa ( Rathbun, 1914) n. comb. Both species have two relatively short, slender, and acute anterolateral teeth ( Figs 4A ; 5 for C. tenuidentata n. sp.; Fig. 13B for P. bispinosa n. comb.). The teeth are seemingly dorsal, just at the border of a conspicuously inflated section of the carapace. The legs are slightly longer and more slender (distal end of the merus of the folded P5 reaches the proximal portion of the second anterolateral teeth in both species but not in the largest specimens of P. bispinosa n. comb.). There are also short setae on the ventral surface of the carapace, third maxilliped, abdomen, and ambulatory legs (P2-P5).

The most obvious difference between the new species and P. bispinosa n. comb. is in the pterygostomial region on the ventral surface of the carapace. In C. tenuidentata n. sp. the pterygostomial and subhepatic regions are about the same relative height. In contrast, in P. bispinosa n. comb. the pterygostomial region is much higher than the subhepatic region and the two regions are separated from each other by a conspicuous pterygostomial ridge. Other differences are listed in the Remarks section for P. bispinosa n. comb. (see below).

Unusual for a species of Carcinoplax is that the orbital border does not continue into a lobe or tooth. It ends as a rounded and granular border well above the first anterolateral tooth ( Fig. 4A ).

Figures

FIG. 4. — Carcinoplax tenuidentata n. sp., ♂ holotype, cl 9.1 mm, cw 10.8 mm, Bligh Water, Fiji, MUSORSTOM 10, stn CP 1320, 290-300 m (MNHN-B 29496): A, dorsal surface of the carapace; B, abdomen; C, left G1, dorsal view; D, left G2, ventral view. Scale bars: A, 5 mm; B, 3 mm; C, D, 1 mm.

FIG. 5. — Carcinoplax tenuidentata n. sp., ♂ holotype, cl 9.1 mm, cw 10.8 mm, Bligh Water, Fiji, MUSORSTOM 10, stn CP 1320, 290-300 m (MNHN-B 29496).

FIG. 13. — A, Pycnoplax surugensis (Rathbun,1932) n. comb., ♂, cl 14.7 mm, cw 20.6 mm,off southern coast of New Caledonia,BATHUS 2, stn DW 719,22°47.57’S,167°14.58’E,444-455 m (MNHN-B 29412);B, Pycnoplax bispinosa (Rathbun, 1914) n. comb., ♀, cl 9.0 mm, cw 11.2 mm,off Rendova I., SALOMON 2,stn CP 2287,253-255 m (MNHN-B 30088);C, Thyraplax crosnieri (Guinot & Richer de Forges, 1981) n. comb., ♀, cl 10.6 mm, cw 13.5 mm, off southern coast of New Caledonia, MUSORSTOM 4, stn DW 222, 410-440 m (MNHN-B 29422).