Ethusina ocellata, 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 : 566-568

Ethusina ocellata n. sp.

( Fig. 23 )

Ethusina brevidentata – Chen 1997: 624 (not E. brevidentata Chen, 1993 ).

TYPE MATERIAL. — Holotype: parasitized by Sacculina sp. , cl 5.9 mm, cw 5.9 mm, SALOMON 1, stn CP 1783 ( MNHN-B 28708 ); paratypes:

cl 7.3 mm, cw 7.2 mm, SALOMON 1, stn 1858 ( MNHN-B 28624); parasitized by Sacculina sp. cl 5.8 mm, cw 5.8 mm, cl 8.5 mm, cw 8.9 mm,

cl 8.4 mm, cw 9.0 mm, cl 7.6 mm, cw 8.2 mm, SALOMON 1, stn CP 1783 ( MNHN-B 28709).

The specimen chosen as the holotype was a male parasitized by Sacculina sp. It was nevertheless the only male specimen with a complete set of pereopods. There was no evidence of abnormalities in the G1 and G2.

TYPE LOCALITY. — Solomon Islands, Indispensable Strait W of Malaita island, 08°32.8’S, 160°41.7’E, 399- 700 m.

MATERIAL EXAMINED. — Indonesia. Kai Islands, KARUBAR, stn CC 21, 05°14’S, 133°00’E, 688- 694 m, 25.X.1991, 1 damaged ( MNHN-B 22882). Solomon Islands. SALOMON 1, stn CP 1783, 08°32.8’S, 160°41.7’E, 399-700 m, 29.IX.2001, 1 holotype parasitized by Sacculina sp. ( MNHN-B 28708), 1, 1 juv., 1, 2 ovig. paratypes ( MNHN-B 28709), 1 juv. cl 5.9 mm damaged, 1 ovig. cl 8.6 mm, cw 9.1 mm, 2 parasitized by Sacculina sp. cl 8.7 mm, cw 9.3 mm and cl 8.7 mm, cw 9.0 mm respectively ( MNHN-B 28676). — Stn CP 1858, 09°37.0’S, 160°41.7’E, 435-461 m, 7.X.2001, 1 paratype ( MNHN-B 28624).

ETYMOLOGY. — From oculus and ocellata (Latin for eye and having small eyes, respectively) in reference to the relatively small, concealed eyes that result from shorter eye peduncles, a character that clearly separates the new species from Ethusina brevidentata Chen, 1993 , a close species.

DISTRIBUTION. — Indonesia (Kai Is) ( Chen 1997) and the Solomon Is. Depth: 399-700 m ( Fig. 34 ).

SIZE. — Maximum size: cl 5.9 mm, cw 5.9 mm (MNHN-B 28708), cl 8.7 mm, cw 9.3 mm (MNHN-B 28676).

DESCRIPTION

Carapace ( Fig. 23A ) almost as broad as long in males, small females, slightly broader than long in large females; dorsal surface with microscopic granules. Urogastric, cardiac regions slightly elevated, bordered by grooves, deep along lateral borders of metagastric region and posterior borders of protogastric region; two distinct, often round depressions on posterior protogastric region, more conspicuous in large individuals; cervical, branchial grooves shallow. Branchial regions slightly inflated along sides.

Anterior border of carapace ( Fig. 23A ) with small, obtuse to slightly acute, straight outer orbital teeth, slightly shorter or nearly equal than but not reaching lateral frontal teeth. Frontal teeth nearly triangular, lateral frontal teeth much shorter than median frontal teeth. Orbital sinuses broad, oblique, slightly sinuous in males, round- ed in large females; lateral frontal sinuses U-shaped; median frontal sinus V-shaped, wider than lateral frontal sinuses but slightly narrower than orbital sinuses.

Eye peduncles ( Fig. 23B ) shorter than cornea, 0.6-0.7 times eye diameter, mobile. Eyes completely concealed by outer orbital margin, not visible dorsally.

Anterior border of endostome ( Fig. 23B ) lies well below posterior border of antennular fossae of basal antennular articles.

Male chelipeds (P1) smooth, equal; slightly swollen propodi, almost as long as fingers; fingers with broad, round teeth. Female chelipeds similar to male chelipeds but slightly unequal in some specimens, no teeth but broad cutting edges on fingers of some.

P2, P3 relatively short; length of P2 meri 1.0- 1.2 times cl, P2 meri 8.1-8.6 times longer than broad. P4, P5 with few short hairs on dactyli, propodi; P5 dactyli thick, curved.

Male abdomen with four somites (3-5 fused, basal half swollen), rounded telson. Somite 1 length 3.2 times as broad, somite 6 square. Female abdomen with six somites, broad, round- ed telson; somite 3 broadest, somite 6 longest.

G1 ( Fig. 23C ) short, stout; each distal end slightly blunt with two lateral fringes of spines; G2 relatively short, each distal part narrower; thick, flattened, pointed tip.

REMARKS

There are close similarities between Ethusina ocellata n. sp. and E. brevidentata Chen, 1993 , on account of their very small outer orbital teeth and the morphology of their G1. Close examination, however, reveals several important differences. Diagnostic to E. ocellata n. sp. are very short eye peduncles ( Fig. 23B ) that conceal the eyes from dorsal view (longer eye peduncles, thus eyes are visible dorsally beyond inner margins of orbital sinus in E. brevidentata [ Chen 1993: fig. 16a, b]); lateral frontal teeth ( Fig. 23A ) that are much smaller than the median frontal teeth (only slightly smaller or about the same size in E. brevidentata [ Chen 1993: fig. 16a, b]); outer orbital teeth directed dorsally (directed outwardly in E. brevidentata ); lateral frontal sinus very narrow, much narrower than median frontal sinus (lateral frontal sinus wide, almost as wide as median frontal sinus in E. brevidentata ); dorsal surface of carapace, frontal and anterolateral borders, and P2 and P3 (particularly meri) smooth (all conspicuously granular in E. brevidentata ); slightly thicker P2 and P3, merus of P2 8.1-8.6 times longer than broad (8.9-9.0 in E. brevidentata ); and relatively short dactyli of P4 and P5 (longer and more slender in E. brevidentata ). The G1 are very similar. Setation in the G1 of E. ocellata n. sp., however, is more conspicuous ( Fig. 23C ) than in E. brevidentata ( Chen 1993: fig. 16g-i).

Figures

FIG. 23. — Ethusina ocellata n. sp., holotype cl 5.9 mm, cw 5.9 mm, Solomon Islands, west of Malaita, SALOMON 1, stn CP 1783, 399-700 m (MNHN-B 28708); A, dorsal surface of carapace; B, ventral view of anterior portion of body; C, left G1, ventral view. Scale bars: A, 3 mm; B, 2 mm; C, 1 mm.

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