DISTRIBUTIONS OF ILYOPLAX PUSILLA AND I. DESCHAMPSI(BRACHYURA: OCYPODIDAE)

Abstract

Geographic distributions of two ocypodid crabs of the genus Ilyoplax : I. pusilla and I. deschampsi are summarized from the occurrence records in literatures and unpublished data. I. pusilla is distributed along the coast of mainland Japan and Okinawa, while I. deschampsi ranged along the continental coast of Bo Hai (Gulf of Chihle), Yellow Sea and northern East China Sea. The distributions of the two spesies overlap only at the southern coast of Korea and a part of northern Kyushu of Japan, and both species do not extend into the Japan Sea coast. Along the coast of Ariake Bay in Kyushu, Japan, where both species occurred, their distributions were investigated in detail. I. deschampsi was distributed on the innermost coast, while I. pusilla was on the coast of outer part of the bay, showing clear segregated distributions between them. In habitat conditions, there were some differences between the two species : soil hardness and coarseness of substratum, and salt content of underground water were, on the average, higher in the habitat of I. pusilla than in that of I, deschampsi.