Features of an intersex Chinese mitten crab, Eriocheir Japonica Sinensis (Decapoda, Brachyura)

Abstract

According to the review by Du (1987) a male of the mitten crab, Eriocheir jap?nica (De Haan, 1835), infected by Polyascus gregaria (Okada & Miyashita, 1935) (Cirripedia, Rhizocephala) (cf. Glenner et al., 2003) can have five types of an abnormal abdomen with abnormal pleopods. We describe herein a type of parasitism-related intersexuality that has previously not been reported for Eriocheir jap?nica sinensis (H. Milne Edwards, 1853) (cf. Tang et al., 2002, 2003b). A possible mechanism for the origin of the sexual aberrations found in this specimen is also presented. The individual of Eriocheir jap?nica sinensis studied, shows degenerated male features as well as some slightly feminine characteristics, most probably as a result of a parasitic infection by Polyascus gregaria. Though parasitic castration has been reported extensively for many species of crabs (Reinhard, 1950, 1956; H0eg, 1984; O'Brien & Wyk, 1984; Sloan, 1984; Walker, 1985; Weng, 1987; O'Brien & Skinner, 1990; Walker et al., 1992; Alvarez et al., 1995; Grosholz & Ruiz, 1995; Glenner & Werner, 1998; Thresher et al., 2000; Torchin & Mitchell, 2004), we nevertheless consider it important to document the present find in some detail. This is because, in our opinion the features of this specimen allow, to some extent, to trace the possible mechanisms that cause the condition of sexual degeneration under the influence of the parasite.