Introduction and spread of Philine auriformis (Gastropoda: Opisthobranchia) from New Zealand to San Francisco Bay and Bodega Harbor

Specimens of Philine auriformis have been observed in the southern portion of San Francisco Bay, California, since summer 1992. Specimens from Bodega Harbor were first discovered from intertidal mudflats in April 1994 and probably represent the spread of the San Francisco Bay population to a neighboring estuary. Their numbers have increased steadily and the species is now well established in both estuaries. Examination of the anatomy of specimens collected from California was compared with that described from New Zealand. No significant differences in anatomy were detected in animals from these different localities. It is suggested that the species was introduced into California waters by release of ballast water from international shipping.