Ethusa Roux, 1830

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 : 506-507

Genus Ethusa Roux, 1830

Ethusa Roux, 1830 : pl. 18. — H. Milne-Edwards 1837: 161. — Miers 1886: 328. — Alcock 1896: 281; 1899: 31. — A. Milne-Edwards & Bouvier 1902: 39. — Ihle 1916b: 137, 150 (list). — Balss 1922: 119; 1957: 1610. — Rathbun 1937: 77. — Monod 1956: 84. — China 1966: 255. — Serène & Lohavanijaya 1973: 33. — Guinot 1978: 249; 1979a: 103, 129, 139, 155; 1979b: fig. 2B1, 2B2, 2B3. — Manning & Holthuis 1981: 38. — Williams 1984: 268. — Hendrickx 1997: 61. — Chen & Sun 2002: 237.

Pridope Nardo, 1869: 307 .

TYPE SPECIES. — Cancer mascarone Herbst, 1785 , by subsequent designation ( Fowler 1912: 590; see Holthuis 1962: 236; Melville & Smith 1987: 91). Gender: feminine. Name 1622 in Official List ( China 1966).

DIAGNOSIS. — Dorsal surface of carapace granular, often tomentose; some regions distinct, limited by grooves. Four frontal teeth. Basal antennular article normal, not large, swollen. Eye peduncles relatively long, clearly “movable”, on inner margin of orbit, clearly visible dorsally. Anterior border of endostome, formed by efferent branchial channels, reaches various levels in relation to posterior border of antennular fossae, from well below fossae to well above it. P2, P3 relatively short (short and stout meri), not extending well over frontal teeth when folded.

REMARKS

The relative mobility of the eye peduncles should not be used to distinguish between Ethusa and Ethusina because of difficulties in determining their relative mobility (see Remarks for Ethusina below). Yet, the eye peduncles are clearly movable when pushed in Ethusa due to their relatively greater length.

Serène & Lohavanijaya (1973) placed what they originally identified as Ethusina gracilipes Miers, 1886 in the genus Ethusa on the basis of the “ambiguity” in the characters they used to separate the two genera (i.e. the relative size of the basal antennular articles and eye peduncles). As a result, these authors placed Ethusina as a junior subjective synonym of Ethusa (see Remarks of Ethusina below). Their specimen, although apparently lost, most probably belonged to Ethusa indica Alcock, 1894 (see Remarks of E. indica below).

The presence of arthrobranchs at the base of P 3 in Ethusa and their absence in Ethusina ( Smith 1884; A. Milne-Edwards & Bouvier 1902) is a variable character.

Rathbun (1897: 167) clarified the use of Ethusa instead of Aethusa , which was used by some of the earlier authors.