Ethusa zurstrasseni Doflein, 1904

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 : 545

Ethusa zurstrasseni Doflein, 1904

( Fig. 15 )

Ethusa zurstrasseni Doflein, 1904: 28 , 291 (list), pl. 13, figs 3, 4, 64. — Ihle 1916b: 153 (list), 156 (list). — Serène 1968: 40 (list). — Chen 1987: fig. 4; 1993: 318 (key), 319 (list).

Ethusa madagascariensis Chen, 1987: 683 , fig. 3, pl. 2, figs A, B; 1993: 318 (key), 319 (list).

TYPE MATERIAL. — Holotype of Ethusa zurstrasseni Doflein, 1904 : cl 7.2 mm, cw 6.8 mm, Deutsche Tiefsee Expedition, Valdivia , stn 254 ( ZMB 13629).

Type material of Ethusa madagascariensis Chen, 1987 : holotype: cl 7.0 mm, cw 6.6 mm, Vauban , stn CH 52 ( MNHN-B 18271 ) ; allotype: cl 8.9 mm, cw 8.9 mm, Vauban , same station ( MNHN-B 18366 ) ; paratypes: 1 cl 6.1 mm, cw 5.4 mm; 1 cl 8.6 mm, cw 9.2 mm, same station ( MNHN-B 18360 ) .

TYPE LOCALITY. — Somalia, off southern coast, 0°29.3’S, 42°47.6’E, 977 m.

MATERIAL EXAMINED. — Somalia. Deutsche Tiefsee Expedition, Valdivia , stn 254, 0°29.3’S, 42°47.6’E, 977 m, 1 holotype ( ZMB 13629).

Madagascar. Vauban, stn CH 52, 15°21.0’S, 46°12.5’E, 150 m, 8.XI.1972, 1 holotype of E. madagascariensis ( MNHN-B 18271), 1 allotype of E. madagascariensis ( MNHN-B 18366), 1 paratype of E. madagascariensis , 1 paratype of E. madagascariensis ( MNHN-B 18360).

DISTRIBUTION. — Somalia ( Doflein 1904) and Madagascar (Chen 1987). Depth: 150-977 m ( Fig. 34 ).

SIZE. — Maximum size: cl 7.0 mm, cw 6.6 mm ( MNHN-B 18271), cl 8.9 mm, cw 8.9 mm ( MNHN-B 18366).

REMARKS

Diagnostic to Ethusa zurstrasseni are slender, almost triangular and distinctively acute outer orbital teeth that almost reach as high as the frontal teeth ( Doflein 1904: pl. 13, fig. 3; Chen 1987: figs 3a, 4a, as E. madagascariensis ), the anterior border of the endostome extends above the antennular fossae of the basal antennular articles, and the presence of conspicuous granules throughout the carapace and abdomen.

The G1 of the holotype ( ZMB 13629) were illustrated by Chen (1987: fig. 3e) but no details of the distal portion were given. Details of the tip of the same holotype pleopod are given in Figure 15 . The G1 remains the most reliable way to differentiate between E. zurstrasseni and E. sinespina Kensley, 1969 , another western Indian Ocean species.

Ethusa madagascariensis Chen, 1987 is clearly a junior subjective synonym of E. zurstrasseni . The two species were differentiated only by the presence of swollen cheliped propodi in E. madagascariensis , a character that varies widely with size, sex, and particularly if the chelipeds were regenerated. The cheliped propodi are indeed swollen in the holotype of E. madagascariensis ( MNHN- B 18271; Chen 1987: fig. 3c) but not in the cheliped of the smaller male paratype ( MNHN-B 18360) of the same species or in the holotype of E. zurstrasseni , which was examined by Chen (1987: fig. 4b).

Figures

FIG. 15. — Ethusa zurstrasseni Doflein, 1904, holotype cl 7.2 mm, cw 6.8 mm, southern Somalia, Deutsche Tiefsee Expedition, Valdivia, stn 254, 977 m (ZMB 13629), right G1, distal part, ventrolateral (left) and dorsolateral (right) views. Scale bar: 1 mm.

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