First specimen-based record of the freshwater crab Geothelphusa dehaani (White, 1847) (Decapoda: Brachyura: Potamidae) in Hokkaido, northern Japan

抄録

Freshwater crabs of the genus Geothelphusa Stimpson, 1858 were collected from a river on Oshima Peninsula, Hokkaido, northern Japan. They were identified as Geothelphusa dehaani (White, 1847) based mainly on structures of the carapace and the male first gonopods. In the study river, G. dehaani occurred in the upper reach of the main stream and in several tributaries but was not found in the middle reach. The presence of brooding females and many immature individuals suggests that the G. dehaani population is established in the river.