Menoplax, 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 : 657-660

Genus Menoplax n. gen.

Carcinoplax – Chen 1984: 188; 1998: 266 (part).

TYPE SPECIES. — Carcinoplax longispinosa Chen, 1984 (by present designation; gender feminine).

SPECIES INCLUDED . — Menoplax longispinosa ( Chen, 1984) n. comb.

The genus is restricted to the Indo-West Pacific region.

ETYMOLOGY. — From mene, Greek for “moon” or “crescent”, in reference to the diagnostic crescent-shaped vulva, and plax, Greek for “plate” or “tablet”, which is derived from the generic name Carcinoplax (from karkinos, Greek for “crab”) to denote that the type species of the new genus was formerly included in Carcinoplax sensu lato.

DESCRIPTION

Carapace ( Guinot 1989: fig. 40, pl. 13, figs A, B, D, E, as C. longispinosa ) transversely rectangular, slightly wider than long, widest at junction of anterolateral, posterolateral borders; front lamellar, straight, not marked by median notch or projection. Barely discernible notch between front, inner edge of supraorbital border; orbits narrow, not expanded distally; supraorbital borders short, slightly sinuous; suborbital borders rounded, with short, blunt inner tooth not visible dorsally; anterolateral borders convex; posterolateral borders long, arched. Dorsal surface of carapace smooth, strongly convex, without clear indication of regions. Outer orbital angle with short, triangular tooth; 2 anterolateral teeth on each side of carapace, first reduced or obsolete in females, second conspicuous, acute, long, dorsally oriented. Basal antennal article long, slender, distalmost (third) article reaches front. Eye peduncles short, much shorter than front (0.2 front width); cornea spherical, only slightly expanded distally. Anterior border of endostome well demarcated from buccal cavern, ridges faint but clearly defined.Third maxillipeds completely close the buccal cavern. No obvious stridulating mechanism other than possible rubbing of proximal portion of cheliped (P1) merus against pterygostomial ridge. Thoracic sternum wide. Median sulcus on thoracic sternite 4 absent; sutures 4/5, 5/6, 7/8 interrupted medially, 6/7 complete ( Fig.12 ). Anterior end of sterno-abdominal cavity anterior to thoracic sternite 4. Cheliped fingers ( Chen 1984: fig. 7-1, 7-2, as C. longispinosa ; Guinot 1989: pl. 13, fig. C, as C. longispinosa ) slender, slightly longer than propodus, darker in colour. Carpus with acute tooth on inner margin. Ambulatory leg (P2-P5) meri, carpi, propodi long, slender; dorsal margins unarmed; dactyli long, slender, carinated, setose. Male abdomen ( Chen 1984: fig. 7-3, as C. longispinosa ) with 6 freely-movable somites plus telson, narrowly triangular, somites 4-6 gradually decreasing in length from somite 3 (widest somite). Telson wider than long. Somite 3 covers space between P5 coxae, somite 2 slightly narrower than 3 so that somites 1, 2 only leave small portion of thoracic sternite 8 visible. G1 ( Chen 1984: figs 7-4-7-6, as C. longispinosa ; Guinot 1989: fig. 32A, as C. longispinosa ) stout, with small denticles, truncated tip. G2 ( Chen 1984: figs 7-7 to 7-9, as C. longispinosa ; Guinot 1989: fig. 32B, as C. longispinosa ) slender, much shorter than G1, flagellum much shorter than basal part, with basal denticles, tip pointed. Penis arising from P5 coxa, large; broad, soft proximal expansion.Female abdomen with 6 freely-movable somites, relatively narrow. Telson broadly triangular, wider than long. Somite 3 covers space between P5 coxae, somite 2 as wide as somite 3, thoracic sternite 8 not visible. Vulva of mature females ( Fig. 12 ) oblique, crescent shaped, extending from suture 5/6 to suture 6/7, vulvar cover in the form of swollen section of thoracic sternite 6 covering outer margin.

REMARKS

Menoplax n. gen. is being described as a monotypic genus for Carcinoplax longispinosa Chen, 1984 . In contrast to Carcinoplax , the new genus is characterized by a stout, truncated G1 with an acuminate tip (slender, thin, with a typically rounded tip in Carcinoplax ), a G2 that is much shorter than the G1 (typically as long as the G1, never much shorter as in Carcinoplax ), the presence of a crescent shaped vulva provided with a vulvar cover ( Fig. 12 ) (vulva greatly enlarged and without a vulvar cover in Carcinoplax ), a female abdomen narrower than that of Carcinoplax , a complete 6/7 suture (incomplete in Carcinoplax ), conspicuously slender and long fingers, carinated dactyli of ambulatory legs (smooth in Carcinoplax ), slender basal antennal article that is longer than that in Carcinoplax , and a strongly convex carapace armed with long second anterolateral teeth unlike any species of Carcinoplax . Other differences are given in the Remarks for M. longispinosa n. comb. (see below).

Menoplax longispinosa ( Chen, 1984) n. comb. ( Fig. 12 )

Carcinoplax longispinosa Chen, 1984: 189 [in key], 196, 197, 201, fig. 7, pl. 1, fig. 5 [East and South China seas];

1998: 266 [in key]. — Guinot 1989: 311, figs 32, 40, pl. 13, figs A-E [ Madagascar, Philippine Is].

TYPE MATERIAL. — ♂ holotype ( IOAS K69B-31), ♂ paratype ( IOAS Ky11B-31).

TYPE LOCALITY. — South China Sea, 18°30’N, 113°30’E, 1100 m.

MATERIAL EXAMINED. — Madagascar. Off northwest coast, trawling 135, 13°01’S, 48°01’E, 1075-1110 m, A. Crosnier coll., 21.I.1975, 1 pre-adult ♀ ( MNHN-B 10208). — Trawling 142, 13°45.6’S, 47°34.2’E, 1250- 1300 m, A. Crosnier coll., 28.II.1975, 1 ♀ ( MNHN-B 10207).

Philippine Islands. South China Sea, MUSORSTOM 1, stn CP 47, 13°41’N, 120°30’E, 658-757 m, 25.III.1976, 1 ♂ ( MNHN-B 10187). — Stn CP 49, 13°49’N, 120°00’E, 750-925 m, 25.III.1976, 1 ♀ ( MNHN-B 10206).

Indonesia. Tanimbar Is, KARUBAR, stn CP 91, 08°44.54’S, 131°03.10’E, 884-890 m, 5.XI.1991, 1 ♂ ( MNHN-B 29364).

Solomon Islands. SALOMON 1, stn CP 1858, 09°37.0’S, 160°41.7’E, 435-461 m, 7.X.2001, 1 ♀ ( MNHN-B 29359).

SALOMON 2, stn CP 2176, 09°09.4’S, 158°59.2’E, 600-875 m, 21.X.2004, 1 ♂ ( MNHN-B 30084). — Stn CP 2181, 08°46.9’S, 159°39.8’E, 645-840 m, 22.X.2004, 1 ♀ ( MNHN-B 30085). — Stn CP 2197, 08°24.4’S, 159°22.5’E, 897-1057 m, 24.X.2004, 1 ♂, 4 ♀♀ ( MNHN- B 30086). — Stn CP 2215, 07°44.3’S, 157°42.3’E, 718-880 m, 26.X.2004, 1 ♂ ( MNHN-B 30087). — Stn CP 2219, 07°58.3’S, 157°34.4’E, 650-836 m, 27.X.2004, 1 pre-adult ♀, 1 ♀ ( MNHN-B 30105). — Stn CP 2220, 07°58.1’S, 157°33.9’E, 632 m, 27.X.2004, 1 pre-adult ♀ ( MNHN-B 30104). — Stn CP 2246, 07°42.6’S, 156°24.6’E, 664-682 m, 1.X.2004, 1 ♂ ( MNHN- B 30110). — Stn CP 2247, 07°44.9’S, 156°24.7’E, 686-690 m, 1.XI.2004, 2 ♂♂, 3 ♀♀ ( MNHN-B 30107). — Stn CP 2248, 07°42.5’S, 156°24.8’E, 650- 673 m, 1.XI.2004, 2 ♂♂ ( MNHN-B 30096). — Stn CP 2252, 07°28.4’S, 156°17.5’E, 1059-1109 m, 2.XI.2004, 1 ♀ ( MNHN-B 30106). — Stn CP 2267, 07°48.0’S, 156°50.0’E, 590-600 m, 4.XI.2004, 4 ♂♂, 3 ♀♀ ( MNHN-B 30083). — Stn CP 2269, 07°45.1’S, 156°56.3’E, 768-890 m, 4.XI.2004, 1 ♂ ( MNHN-B 30113). — Stn CP 2270, 07°37.9’S, 156°58.8’E, 970- 1060 m, 4.XI.2004, 1 ♂ ( MNHN-B 30075).

Vanuatu. MUSORSTOM 8, stn CP 956, 20°33.41’S, 169°35.95’E, 1175-1210 m, 20.IX.1994, 1 ♂ ( MNHN- B 29337) ; 1 ♂ ( MNHN-B 30139 ). — Stn CP 990, 18°51.63’S, 168°50.98’E, 980-990 m, 24.IX.1994, 1 ♂, 1 ovig. ♀ ( MNHN-B 29407 ) ; 1 ♂ ( MNHN-B 301142 ). — Stn CP 991, 18°51.26’S, 168°52.19’E, 936- 910 m, 24.IX.1994, 1 ♂, 1 ♀ ( MNHN-B 29335 ). — Stn CP 992, 18°52.34’S, 168°55.16’E, 775- 748 m, 24.IX.1994, 2 ♂♂, 1 ♂ parasitised by Sacculina , 1 ♀ ( MNHN-B 29328 ). — Stn CP 993, 18°48.78’S, 168°54.04’E, 780-783 m, 24.IX.1994, 1 ♂ ( MNHN-B 29336 ). — Stn CP 1007, 18°51.97’S, 168°55.92’E, 720- 830 m, 25.IX.1994, 1 ♂ ( MNHN-B 29334 ). — Stn CP 1008, 18°53.29’S, 168°52.65’E, 919-1000 m, 25.IX.1994, 1 ♂, 1 ♂ parasitised by Sacculina , 1 ovig. ♀, 1 ♀ parasitised by Sacculina ( MNHN-B 29333 ). — Stn CC 1034, 17°54.85’S, 168°42.04’E, 690-750 m, 29.IX.1994, 4 ♂♂ ( MNHN-B 29331 ). — Stn CP 1035, 17°56.02’S, 168°44.06’E, 765-780 m, 29.IX.1994, 5 ♂♂, 1 ♀ ( MNHN-B 29329 ). — Stn CP 1036, 18°01.00’S, 168°48.20’E, 920-950 m, 29.IX.1994, 6 ♂♂, 3 ♀♀ ( MNHN-B 29332 ) ; 1 ♂ ( MNHN-B 29363 ). — Stn CP 1037, 18°03.70’S, 168°54.40’E, 1058-1086 m, 29.IX.1994, 8 ♂♂, 3 ♀♀ ( MNHN-B 29330 ) .

Chesterfield Islands. MUSORSTOM 5, stn DW 313, 22°24.31’S, 159°57.53’E, 780-930 m, 13.X.1986, 1 ♀ ( MNHN-B 29245 ). — Stn DC 321, 20°40’S, 158°02.20’E, 1000 m, 14.X.1986, 1 ♂ ( MNHN-B 29428 ). — Stn CP 323, 21°18.52’S, 157°57.62’E, 970 m, 14.X.1986, 17 ♂♂, 8 ♀♀, 4 ovig. ♀♀ ( MNHN-B 29362 ) ; 1 ♂ ( MNHN-B 29311 ) ; 1 ♂ ( MNHN-B 29312 ). — Stn CP 324, 21°15.01’S, 157°51.33’E, 970 m, 14.X.1986, 16 ♂♂, 7 ♀♀, 1 ovig. ♀ ( MNHN-B 29308 ) ; 1 ♂ ( MNHN-B 29313 ) ; 1 ♀ ( MNHN-B 30055 ). — Stn CC 390, 21°00.90’S, 160°50.30’E, 745-825 m, 22.X.1986, 1 ♂ ( MNHN-B 29310 ) ; 1 ♂ ( MNHN-B 29184 ) .

CORAIL 2, stn DE 14, 21°00.69’S, 160°57.18’E, 65- 660 m, 21.VII.1988, 1 ♂ ( MNHN-B 29342).

EBISCO, stn CP 2557, 21°15.01’S, 157°51.33’E, 970 m, 14.X.2005, 2 ♂♂, 1 pre-adult ♀, 5 ♀, 2 ♀♀ parasitised by Sacculina ( MNHN-B 30129). — Stn CP 2616, 19°35’S, 158°52’E, 786-836 m, 19.X.2005, 1 ♂ ( MNHN-B 30134). — Stn CP 2648, 21°32’S, 162°30’E, 750- 458 m, 23.X.2005, 1 pre-adult, 9 ♂♂, 9 ♀♀ ( MNHN-B 30116). — Stn CP 2649, 21°31’S, 162°33’E, 775-792 m, 23.X.2005, 1 pre-adult ♀, 1 ♀ ( MNHN-B 30130). — Stn CP 2650, 21°27’S, 162°33’E, 825-894 m, 23.X.2005, 1 ♀ ( MNHN-B 30141).

New Caledonia. BIOCAL, stn CP 75, 22°19’S, 167°23’E, 825-860 m, 4.IX.1985, 1 ♂ ( MNHN-B 10411).

BATHUS 1, stn CP 651, 21°41.8’S, 166°40.1’E, 1080- 1180 m, 11.III.1993, 2 ♀♀ ( MNHN-B 29424).

BATHUS 2, stn CP 751, 22°24.35’S, 166°12.83’E, 1300- 150 m, 15.V.1993, 1 ♀ ( MNHN-B 29349).

Fiji. BORDAU 1, stn CP 1490, 18°51’S, 178°32’W, 785- 820 m, 11.III.1999, 1 ♀ ( MNHN-B 29361). — Stn CP 1491, 18°50’S, 178°27’W, 777-787 m, 11.III.1999, 6 ♂♂, 2 ♀♀ ( MNHN-B 29501). — Stn CP 1493, 18°43’S, 178°24’W, 429-440 m, 11.III.1999, 1 ♀ ( MNHN-B 29367). — Stn CP 1502, 18°21’S, 178°27’W, 640-660 m, 13.III.1999, 1 ♂ ( MNHN-B 29360).

Tonga. BORDAU 1, stn CP 1565, 20°58’S, 175°16’W, 869-880 m, 9.VI.2000, 2 ♂♂, 1 ♂ parasitised by Sacculina , 1 ♀ ( MNHN-B 29562). — Stn CP 1625, 23°28’S,

Castro P.

176°22’W, 824 m, 19.VI.2000, 5 ♂♂, 3 ♀♀, 1 ovig. ♀, 1 ♀ parasitised by Sacculina , 1 ♀ parasitised by bopyrid ( MNHN-B 29557).

DISTRIBUTION. — Madagascar ( Guinot 1989) and the western Pacific Ocean from East and South China seas ( Chen 1984) to the Philippine Is ( Guinot 1989) and now from Indonesia (Tanimbar Is), Solomon Is, Vanuatu, Chesterfield Is, New Caledonia, Fiji, and Tonga. Depth: 429-1300 m. Also dredged from stations recorded at 65-660 m and 150-1300 m.

COLOUR

Photographs of freshly collected specimens from the Chesterfield Is showed an almost transparent light-pink male ( MNHN-B 29428) and a light orange-pink female ( MNHN-B 29362).

REMARKS

Menoplax longispinosa n. comb. shows a marked sexual dimorphism in the shape of the carapace, which is unusual for a carcinoplicine crab. The first anterolateral tooth is reduced in females (see Guinot 1989: pl. 13, figs D, E, as Carcinoplax longispinosa ), while the conspicuous, acute second tooth tends to be slightly shorter than that in males (see Guinot 1989: fig. 40, pl. 13, figs A, B, as C. longispinosa ). The length and orientation of the second, horn-like tooth, however, varies among individuals of both sexes, even between the right and left teeth in some specimens.

The morphology of two small females ( MNHN- B 10207, 10208) from Madagascar, also examined by Guinot (1989: 312), does not depart from other specimens collected elsewhere in the Indo-West Pacific region. The species has not yet been recorded from elsewhere in the Indian Ocean but it is most probably found in deep water across the ocean.

There is a superficial resemblance between the carapaces of M. longispinosa n. comb. and C. ischurodous ( Stebbing, 1923) . Carcinoplax ischurodous has a long anterolateral tooth somewhat similar to the second anterolateral tooth of M. longispinosa n. comb. There is only one anterolateral tooth in C. ischurodous , however, and its G1, G2, and vulva are characteristic of Carcinoplax : slender G1, G2 with long flagellum (see Guinot & Richer de Forges 1981b: fig. 10A-D), and an enlarged, oval vulva covered by a soft membrane.

Figures

FIG. 12. — Menoplax longispinosa (Chen, 1984) n. comb., ♀, cl 10.0 mm, cw 13.7 mm, Chesterfield Is, MUSORSTOM 5, stn CP 324, 970 m (MNHN-B 30055), thoracic sternum and vulva.