The first finding of the introduced barnacle Amphibalanus variegatus (Darwin) in Tokyo Bay

Amphibalanus variegatus (Darwin) is an introduced species in Japan that was first recorded here in 1936 in Kumamoto Prefecture. Several occurrences were reported afterwards, mainly in the southwestern part of Japan, but not after 1970. During our investigation of sessile organisms in Tokyo Bay, which began in 2004, we obtained two individuals of A. variegatus, identified based on the characteristics of the surface of the shell, the form of the opercular valves, and the structure of the shell. It is unclear whether A. variegatus has successfully established a local population in Tokyo bay. The possibility of this would seem to be low, however, because several recent studies on barnacles in the bay have failed to record this species.