Parethusa 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 : 586-587

Genus Parethusa Chen, 1997

Parethusa Chen, 1997: 614 .

TYPE SPECIES. — Parethusa glabra Chen, 1997 by monotypy. Gender: feminine.

DIAGNOSIS. — Dorsal surface of carapace smooth, flat, without conspicuous setae and tomentum; regions not distinct, grooves shallow. Two or four frontal teeth. Basal antennular article moderately large and swollen. Eye peduncles short, “movable”; on ventral surface of carapace. Anterior border of endostome lies well below posterior border of antennular fossae of basal antennular articles.

REMARKS

The presence of four frontal teeth along the anterior border of the carapace in Parethusa hylophora n. sp. (see description below) instead of two in P. glabra , the only known species when the genus was established ( Chen 1997: 614), necessitates an amendment to the diagnosis of the genus. The number of frontal teeth can therefore be two or four instead of the four in the other two genera in the Ethusinae , Ethusa Roux, 1830 and Ethusina Smith, 1884 .

The basal antennular article is larger than that of Ethusa but smaller than in Ethusina . It was described as “not swollen” by Chen (1997: 614, 615).

The genus was described from only one male specimen of P. glabra . The finding of female specimens since the description of the genus now allows the description of additional characters. As in Ethusa and Ethusina (see Guinot & Bouchard 1998: 651), the abdomen-locking mechanism of adult females consists of two low, medium-size tubercles in the middle portion of thoracic sternite 5 and two shallow concavities at each border of the underside (ventral surface) of abdominal somite 6 (level of P2). The paired vulvae are large, slightly raised, and covered by a thin, movable membrane.