Ethusina ciliacirrata, Castro, 2005

Castro, Peter, 2005, Crabs of the subfamily Ethusinae Guinot, 1977 (Crustacea, Decapoda, Brachyura, Dorippidae) of the Indo-West Pacific region, Zoosystema 27 (3), pp. 499-600 : 553-555

Ethusina ciliacirrata n. sp.

( Fig. 18 )

Ethusina robusta – Chen 2000: 430 (part) (not E. robusta ( Miers, 1886)) .

TYPE MATERIAL. — Holotype: cl 12.0 mm, cw 11.8 mm, MUSORSTOM 8, stn CP 1111 ( MNHN-B 27518 ); paratype: cl 14. 0 mm, cw 14.6 mm, BATHUS 1, stn CP 651 ( MNHN-B 28615 ).

TYPE LOCALITY. — Vanuatu, NW of Espiritu Santo island, 14°51.09’S, 167°14.00’E, 1210-1250 m.

MATERIAL EXAMINED. — Vanuatu. MUSORSTOM 8, stn CP 1111, 14°51.09’S, 167°14.00’E, 1210-1250 m, 8.X.1994, 1 ( MNHN-B 27518).

?MUSORSTOM 8, stn DW 1128, 16°02.14’S, 166°38.39’E, 778-811 m, 10.X.1994, 1 juv.

( MNHN-B 27515).

New Caledonia. BATHUS 1, stn CP 651, 21°41.80’S, 166°40.10’E, 1080- 118 m, 11.III.1993, 1 paratype parasitized by Sacculina sp. ( MNHN-B 28615).

ETYMOLOGY. — From cilium, Latin for eyelash, and cirrus, Latin for fringe, in reference to the characteristic fringe of long hairs along the anterior and anterolateral borders of the carapace.

DISTRIBUTION. — Known from Vanuatu and New Caledonia. Depth: 1210-1250 m ( Fig. 34 ); also collected in bottom trawl from 118-1080 m.

SIZE. — Maximum size: cl 12.0 mm, cw 11.8 mm ( MNMN-B 27518), cl 14.0 mm, cw 14.6 mm ( MNHN-B 28615).

DESCRIPTION

Carapace ( Fig. 18A ) slightly longer than broad; dorsal surface with very short setae, small granules; long hairs along anterior, anterolateral borders. Urogastric, cardiac regions elevated, urogastric region bordered by conspicuous lateral grooves; branchial grooves very shallow. Branchial regions slightly inflated along sides.

Anterior border of carapace ( Fig. 18A ) with triangular, slender, acutely tipped, outer orbital teeth, reaching slightly below frontal teeth in male holotype, slightly above in female paratype; outer orbital teeth slightly outwardly directed in male holotype, right one inwardly directed in female paratype. Frontal teeth with acute tips; lateral frontal teeth slender, slightly longer than triangular, acutely tipped median frontal teeth. Orbital sinuses very broad, V-shaped; inner margins oblique, outer nearly straight; lateral frontal sinuses U-shaped, asymmetrical; median frontal sinus U-shaped, wider than lateral frontal sinuses but much narrower than orbital sinuses.

Eye peduncles wide, slightly longer than cornea, immobile. Slight portion of peduncles, eyes visible dorsally in male holotype.

Anterior border of endostome well below posteri- or border of antennular fossae of basal antennular articles.

Chelipeds (P1) of male holotype smooth, nearly equal; propodi swollen, almost as long as fingers; fingers slender, with rounded teeth. Chelipeds of female paratype similar to male chelipeds except slightly more slender propodi; broad, ill-defined teeth on fingers.

P2, P3 relatively long, slender in male holotype, slightly thicker in female paratype; smooth; length of P2 meri 0.8 times cl, P2 meri 6.6 times longer than broad in male holotype, 6.4 times longer in female paratype; P4, P5 with numerous long hairs on all articles except dactyli; dactyli long, slender, slightly curved.

Abdomen of male holotype missing. Abdomen of female paratype with six somites, broad, triangular telson; somite 3 broadest, somite 6 longest.

G1 ( Fig. 18B ) stout, distal third narrower than proximal; slightly twisted, slightly curved, fringed by setae, each tip slightly rounded, short spines along dorsal surface; G2 missing in holotype.

REMARKS

The male holotype ( MNHN-B 28615) of Ethusina ciliacirrata n. sp. was identified as Ethusina robusta ( Miers, 1886) by Chen (2000: 430), who mistakenly referred to it as a female. It is part of a collection of five Vanuatu specimens, none of which actually belong to E. robusta . In contrast to E. robusta , the holotype has broadly triangular, straight or nearly straight outer orbital teeth, and small eyes that are barely seen dorsally. Diagnostic to E. robusta are needle-shaped, outwardly oriented outer orbital teeth ( Fig. 25A ) and males with V-shaped orbital sinuses and eyes that can be partially seen dorsally (Chen & Xu: fig. 9.1, as E. investigatoris ( Alcock, 1896)) . It shares with E. robusta , however, long and slender pereopods and P4 and P5 dactyli, although they are all slightly more slender in E. robusta . Also distinctive of the holotype of E. ciliacirrata n. sp. is the presence of long hairs along the frontal bor- der of the carapace, and rounded teeth along the cheliped fingers.

There are strong similarities with E. coronata n. sp. in regards to the morphology of the G1. As in E. ciliacirrata n. sp. ( Fig. 18B ), the G1 of E. coronata n. sp. are stout, twisted, slightly curved, each with a slightly rounded tip ( Fig. 19B ). In E. coronata n. sp., however, the twist or bend of the G1 is a lot more conspicuous. Furthermore, the triangular outer orbital and frontal teeth are longer and more slender, and the P2 and P3 are shorter and stouter ( Fig. 19A ) than in E. ciliacirrata n. sp.

The soft and incomplete specimen of a juvenile female ( MNHN-B 27515) from Vanuatu, which was also identified as E. robusta by Chen (2000: 430), is questionably identified as E. ciliacirrata n. sp. on account of the broadly triangular, straight, and relatively short outer orbital teeth. Only the P4 and P5 remain complete. They are slender and with slender dactyli as in E. ciliacirrata n. sp.

Figures

FIG. 18. — Ethusina ciliacirrata n. sp., holotype cl 12.0 mm, cw 11.8 mm, Vanuatu, NW of Espiritu Santo, MUSORSTOM 8, stn CP 1111, 1210-1250 m (MNHN-B 27518); A, dorsal surface of carapace, P2, and P4; B, left G1, ventral view. Scale bars: A, 5 mm; B, 1 mm.

FIG. 34. — Bathymetric distribution of Indo-West Pacific ethusine crabs.

FIG. 25. — Ethusina robusta (Miers, 1886); A, lectotype cl 10.0 mm, cw 10.1 mm, Challenger, stn 191, Arafura Sea, 1463 m (BMNH 84.44), dorsal surface of carapace and P2; B, C, cl 8.6 mm, cw 8.2 mm, Solomon Islands, east of Malaita, SALOMON 1, stn CP 1764, 1327-1598 m (MNHN-B 28712); B, left G1, dorsal view; C, left G2, dorsal view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 19. — Ethusina coronata n. sp., holotype cl 12.1 mm, cw 12.0 mm, Solomon Islands, Indispensable Strait west of Malaita, SOLOMON 1, stn CP 1764, 1327-1598 m (MNHN-B 28734); A, dorsal surface of carapace and P2; B, right G1, ventrolateral (left) and dorsal (right) views. Scale bars: A, 5 mm; B, 1 mm.