Ethusina stenommata, 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 : 575-577

Ethusina stenommata n. sp.

( Fig. 26 )

Ethusina robusta – Chen 1993: 342 (part) (not E. robusta ( Miers, 1886)) .

TYPE MATERIAL. — Holotype: cl 12.0 mm, cw 11.1 mm, MUSORSTOM 7, stn CP 564 ( MNHN-B 28731 ); paratypes: cl 11.7 mm, cw 11.1 mm, MUSORSTOM 7, stn CP 567 ( MNHN-B 28732 ); cl 13.3 mm, cw 13.7 mm, cl 12.3 mm, cw 12.6 mm, MUSORSTOM 5, stn CP 323 ( MNHN-B 19062 ).

TYPE LOCALITY. — Wallis and Futuna Is, Tuscarora Bank, 11°46’S, 178°27’W, 1015-1020 m.

MATERIAL EXAMINED. — New Caledonia. MUSORSTOM 5, stn CP 323, 21°18. 52’S, 157°57.62’E, 970 m, 14.X.1986, 2 paratypes ( MNHN-B 19062).

Fiji. BORDAU 1, stn CP 1460, 16°47’S, 178°47’W, 750-767 m, 6.III.1999, 1 ( MNHN-B 28666).

Wallis and Futuna Islands. MUSORSTOM 7, stn CP 564, 11°46’S, 178°27’W, 1015-1020 m, 20.V.1992, 1 holotype ( MNHN-B 28731), 1, 2 juv.

( MNHN-B 28730), 1 ( MNHN-B 28733). — Stn CP 567, 11°47’S, 178°27’W, 1010-1020 m, 20.V.1992, 1 paratype parasitized by Sacculina sp. ( MNHN-B 28732). — Stn DW 620, 12°34’S, 178°11’W, 1280 m, 28.V.1992, 1 ( MNHN-B 28665).

ETYMOLOGY. — From stenos, Greek for narrow, and omma, Greek for eye, in reference to the relatively narrow eyes.

DISTRIBUTION. — Known from New Caledonia, Fiji, and the Wallis and Futuna Is. Depth: 750-1280 m ( Fig. 34 ).

SIZE. — Maximum size: cl 12.0 mm, cw 11.1 mm ( MNHN-B 28731), cl 14.0 mm, cw 14.8 mm ( MNHN-B 28666).

DESCRIPTION

Carapace ( Fig. 26A ) slightly longer than broad in males, slightly broader than long in females; dorsal surface with very short, scant setae, small granules. 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. 26A ) with triangular, slender, acutely tipped, slightly outwardly directed outer orbital teeth, reaching about half as high in males, juvenile females, or slightly below frontal teeth in adult females. Frontal teeth slightly longer in males than in females; lateral frontal teeth slender, nearly equal in females, slightly longer than triangular in males, acutely tipped median frontal teeth, obtuse in some females. Orbital sinuses broad, V-shaped in males, juvenile females, U-shaped in adult females; inner margins nearly straight and with slight basal swelling in males, juvenile females, slightly curved in adult females, outer J-shaped to nearly straight, not prominently acute; lateral frontal sinuses U-shaped, broader, shallower in females than in males; median frontal sinus V-shaped, broader in females, wider than lateral frontal sinuses but as wide as orbital sinuses. Anterolateral borders and outer margins of outer orbital teeth without hairs. Eye peduncles ( Fig. 26B ) relatively narrow, slightly longer than cornea, immobile. Most of eye peduncles, eyes visible dorsally.

Anterior border of endostome lies well below posterior border of antennular fossae of basal antennular articles.

Male chelipeds (P1) smooth, equal or nearly equal; propodi slightly swollen, almost as long as fingers; fingers slender, no teeth or defined cutting edges. Female chelipeds similar to male chelipeds except more slender propodi, broad cutting edges in juveniles.

P2, P3 ( Fig. 26A ) relatively slender and thin; smooth; length of P2 meri 0.8-1.0 times cl, P2 meri 8.6-8.8 times longer than broad in males, 7.3-7.7 in adult females. P4, P5 with few hairs; dactyli relatively slender, curved, dactyli of P5 with thick, slender spines.

Male abdomen with four somites (3-5 fused, basal half swollen), circular telson. Somite 1 very narrow, length 5.7 times as broad, somite 6 rectangular. Female abdomen with six somites, broad, triangular telson; somite 3 broadest, somite 6 longest.

G1 ( Fig. 26C ) slender; distal third much narrow- er than proximal, straight, fringed proximaly by long setae, few spines, each tip obtuse, short spines along ventral surface; G2 long, distal third straight, each distal end with acute tip.

REMARKS

Ethusina stenommata n. sp. shares the presence of relatively short and triangular outer orbital teeth with E. crenulata n. sp. (see below). They can be differentiated, however, by the presence in E. crenulata n. sp. ( Figs 26 ; 27 ) of a vertical fissure at the dorsal lower margin of each orbital sinus, a granular carapace, and stouter P2 and P3. Two female specimens of the new species (cl 13.3 mm, cw 13.7 mm, cl 12.3 mm, cw 12.6, paratypes, MNHN-B 19062) were erroneously identified as E. robusta ( Miers, 1886) by Chen (1993: 342). E. stenommata n. sp. can be differentiated from E. robusta by having nearly straight, more slender, and longer outer orbital teeth, longer and relatively more slender P2 and P3, and slightly shorter, stouter P2-P5 dactyli than E. robusta ( Miers 1886: pl. 29, fig. 2).

All preserved specimens were very light in colour, almost cream white, in contrast to various shades of light yellow or tan in specimens of the other species that had been preserved for approximately the same time.

Figures

FIG. 26. — Ethusina stenommata n. sp., holotype cl 12.0 mm, cw 11.1 mm, Wallis and Futuna Islands, Tuscarora Bank, MUSORSTOM 7, stn CP 564, 1015-1020 m (MNHN-B 28731); A, dorsal surface of carapace and P2; B, ventral view of anterior surface of carapace; C, right G1, ventral views. Scale bars: A, 5 mm; B, 2 mm; C, 1 mm.

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

FIG. 27. — Ethusina crenulata n. sp., paratype cl 10.1 mm, cw 10.0 mm, French Polynesia, Marquesas Islands, Eiao, MUSORSTOM 9, stn CP 1276, 800-805 m (MNHN-B 28718).