The Present Status of Marine Alien Benthos in Japan, Based on a Survey of Collections in Museums and Aquaria

The Committee for the Preservation of the Natural Environment and the Japanese Association of Benthology investigated the history and present status of marine alien benthic invertebrates and algae on the basis of lists or computer databases of catalogued specimens in the collections of museums and aquaria in Japan. Through the cooperation of 31 museums and aquaria, we recognized 24 marine alien species in 780 lots, including two gastropods, 12 bivalves, two polychaetes, five crustaceans, two ascidians, and one chlorophyte. These species include one cryptogenic species and two species introduced from other parts of Japan. A bivalve, Mytilus galloprovincialis, comprises 245 lots, followed by the striped barnacle Balanus amphitrite (100 lots), the slipper snail Crepidula onyx (75 lots), the ivory barnacle Balanus ebruneus (57 lots), and the European barnacle B. improvisus (55 lots). Most specimens of alien species were collected after 1980 in or around the Seto Inland Sea and Tokyo Bay. The results of this study are not exhaustive, and more extensive research is essential to catalogue the existence of all specimens of marine alien species in Japanese museums and aquaria.