Range extension of the sesarmid crab Clistocoeloma villosum along the eastern Pacific coast of the Izu Peninsula, Japan

Background: The Pacific coastline along the southern Izu Peninsula, Japan, is strongly influenced by warm tropical waters of the Kuroshio Current. A new easternmost record of the near-threatened sesarmid crab Clistocoeloma villosum is reported from the southern part of Izu Peninsula. Methods: The present study was conducted in August 2014 and February 2015, on tidal flats in the mouth of the Aono River, draining the southern part of Izu Peninsula. Crabs were collected by hand on the tidal flat substrate, under cobble stones and on the periphery of associated mangrove forests. Results and conclusion: Body sizes and morphological characteristics closely matched existing descriptions of C. villosum, the distribution range having been extended ca. 350 km eastward from the Kii Peninsula (traditional eastern boundary of the species), suggesting broad northeastwardly directed planktonic larval transport by the warm Kuroshio Current along the Pacific coast of Japan. The survival and settlement of larvae of this southern species along the southern coast of the Izu Peninsula, is evidence of the suitability of the small gravel dominated tidal flats in the region as habitat for the species.