北太平洋周辺地域におけるカワシンジュガイとサケ科魚類の寄主特異性及びその進化

抄録

1. The criteria used by Zhadin (1938) as specific characters in Margaritifera (Unionacea ; Margaritiferidae) are valid. 2. All Japanese Margaritifera belong to M. laevis (Haas, 1910), known only in Sakhalin, Kuril Islands, Hokkaido and Honshu. 3. All Margaritifera in western North America belong to M. falcata (Gould, 1855), and are more closely related to M. laevis than to the species in eastern North America. 4. The salmonid fishes that act as larval hosts of these two species of Margaritifera are close relatives phyletically even though they are classified in different genera, Oncorhynchus and Salmo. 5. At some time in Tertiary a Salmo-like fish, acting as larval host, and a species of Margaritifera were found on both sides of the North Pacific, on island arc of north eastern Asia and on the mainland of northwestern America. After a separation of this range into two parts, the biological system fish-and-mussel changed at different rates so that the fishes are classified in separate genera, the mussels in separate species. 6. Host-specificity of the larval glochidium stage of Margaritifera to a young Salmo-like fish has been more persistent than the morphological attributes of the adult fishes. This is in correlation with the morphological similarity of young Oncorhynchus to young Salmo, and supports the belief that host-parasite relationships may aid in tracing phylogeny.