An Ecological study of the Crabs inhabiting the Estuaries in southern Kanto District

Abstract

Inquiries have been made into the ranges of crabs found in the estuaries of the southern Kanto district (Tokyo Metropolis and Kanagawa Prefecture). Only a few number of species may be seen in the river mouth of the torrential rivers such as, Hayakawa, Sakawagawa, Hanamizugawa and Sagamigawa. They are Varuna litterata, Eriocheir japonicus, Sesarma haematocheir, S. dehaani and S. intermedia all belonging to estuarine crabs. On the other hand, in the estuaries of the slowly flowing rivers such as, Sakaigawa, Namerigawa, Tagoegawa, Moritogawa, Hirasakugawa, Tamagawa and Arakawa, som marine crabs such as, Philyra pisum, Charybdis japonicus and Hemigrapsus penicillatus may be seen together with those estuarine crabs mentioned above. Among these estuarine crabs the habitat of Paracleistastoma, Scopimera and Ilyoplax extend towards fresh water region, and those of Sesarma haematocheir and its relatives (S. denhaani and S. intermedia) into the swamns and marshes and further towards the land near the river.