Ethusa dilatidens Chen, 1997

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 : 519-520

Ethusa dilatidens Chen, 1997

( Fig. 7 )

Ethusa dilatidens Chen, 1997: 615 , fig. 3.

TYPE MATERIAL. — Holotype: cl 11.8 mm, cw 12.1 mm, KARUBAR, stn CP 83 ( MNHN-B 22887 ).

TYPE LOCALITY. — Indonesia, Tanimbar Islands, 09°23’S, 131°00’E, 285- 297 m.

MATERIAL EXAMINED. — Philippine Islands. Visayan Sea, MUSORSTOM 3, stn CP 144, 11°12’N, 124°15’E, 379-383 m, 7.VI.1985, 1 ( MNHN-B 18280), 1 ( MNHN-B 18281), 1, 4 ( MNHN-B 18930).

Indonesia. Tanimbar Islands, KARUBAR, stn CP 83, 09°23’S, 131°00’E, 285-297 m, 4.XI.1991, 1 holotype ( MNHN-B 22887).

DISTRIBUTION. — Philippine Is (Visayan Sea) and Indonesia (Tanimbar Is) ( Chen 1997). Depth: 285- 383 m ( Fig. 34 ).

SIZE. — Maximum size: cl 18.0 mm, cw 18.0 mm ( MNHN-B 18930), cl 22.1 mm, cw 23.5 mm ( MNHN-B 18930).

REMARKS

Ethusa dilatidens was described from a small male (cl 11.8 mm, cw 12.1 mm, MNHN-B 22887) collected in Indonesia. Diagnostic to this species is the shape of the outer orbital teeth: “broad at base, slightly broader than long, outer borders converging inwards” ( Chen 1997: 618, fig. 3a). More recent material from the Philippine Islands that was examined is larger in size, and the shape of the outer orbital teeth is slightly different from that given in the description. It is narrower at the distal end, with an acute tip. Nevertheless, the other diagnostic characters found in the holotype ( MNHN-B 22887) are evident in all of the specimens: dorsal surface of the carapace covered with very small granules but smooth along the anterior third of its surface, short pubescence through the dorsal surface but long hairs along the anterior and anterolateral borders, moderately inflated branchial regions so that the sides of the carapace are clearly convex, the anterior border of the endostome reaches the level of the posterior bor- der of the antennular fossae of the basal antennular articles, and a semicircular suture between the second and third thoracic sternites (sternal suture 2/3) bordered by a conspicuous anterior prominence. The last two characters were not mentioned in the description.

The G1, however, show some variation. They are short, straight, and slender in the holotype ( Chen 1997: fig. 3g, h) but longer and slightly sinuous ( Fig. 7 ) in the other two much larger male specimens that were examined (cl 18.0 mm, cw 18.0 mm, MNHN-B 18930; cl 17.6 mm, cw 17.5 mm, MNHN-B 18280).

Large specimens show similarities with other species. They may be easily separated from E. latidactyla Parisi, 1914 by the much-inflated branchial regions of E. latidactyla , which gives its carapace a characteristic rounded appearance ( Chen 1985: fig. 7a). In E. sexdentata ( Stimpson, 1858) , in which the proximal region of the outer orbital teeth can be as expanded as in E. dilatidens , the P2 and P3 are relatively much shorter and thicker ( Sakai 1965: pl. 11, fig. 2; 1976: pl. 23, fig. 1; Miyake 1983: pl. 6, fig. 5) than in E. dilatidens .

Figures

FIG. 7. — Ethusa dilatidens Chen, 1997, cl 18.0 mm, cw 18.0 mm, Philippine Islands, Visayan Sea, MUSORSTOM 3, stn CP 144, 379-383 m (MNHN-B 18930), right G1; A, dorsal view; B, C, ventral views. Scale bars: A, C, 0.5 mm; B, 1.0 mm.

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