A new genus and species of bopyrid isopod (Crustacea, Isopoda, Bopyridae, Orbioninae) parasitic on Sicyonia (Crustacea, Decapoda, Penaeoidea) from New Caledonia

Asymmetrorbione drepanopleon n. gen., n. sp., a highly asymmetrical orbionine bopyrid isopod, is described from specimens of two species of Sicyonia H. Milne Edwards, 1830, shrimp collected by the MUSORSTOM expeditions in New Caledonia; it is the seventh genus included in the Orbioninae. This genus can be characterized by the female having coxal plates well developed on the longer side of the body, a pleon with five pleomeres plus pleotelson, pleomeres I-V having biramous pleopods and uniramous lateral plates, the short side of the body with reduced lateral plates and the long side of the body with lateral plates elongated on pleomeres I and II, all lateral plates smooth, and uniramous uropods. The male has all pleonal segments plus the pleotelson fused into a single segment and lacking midventral tubercles, pleopods, and uropods. A second species, Orbione kempi Chopra, 1923, is also transferred to the new genus. Comparisons are made between Asymmetrorbione n. gen. and Anisorbione Bourdon, 1981, females of which differ in having only five pleonal segments and biramous uropods, and Orbione Bonnier, 1900, females of which differ in their lack of pronounced asymmetry of the pleon and lateral plates and in the presence of tubercles on the lateral plates.