Ref ID : 6648
Ohtaka Akifumi and Nishino Machiko; Studies on the aquatic oligochaete fauna in Lake Biwa, central Japan. II. Records and taxonomic remarks of nine species. Hydrobiologia 406:33-47, 1999
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At least 41 taxa of aquatic oligochaetes including five new records have been recorded from the ancient Lake Biwa in Japan. The lake is characterized by eurybathyal occurrence of Branchiura sowerbyi. The posterior gill filaments of B. sowerbyi develop normally in lagoons adjacent to the lake, while in the lake they weakly develop or often disappear at littoral and sublittoral depths shallower than 30 m, and they almost completely disappear in the profundal zone. The profundal population of B. sowerbyi also differs from other populations in eastern Asia in having fewer and shorter hairs, and simple-pointed crotchets, or bifid crotchets with parallel teeth, in dorsal bundles of chaetae. This suggests that an intralacustrine speciation is progressing in the profundal population. An aberrant modification is found in the pectination of dorsal crotchets in Tubifex tubifex occurring at deep profundal depths of the lake. The ventral chaetae in segment II of Teneridrilus mastix are rarely modified in Lake Biwa. This requires cancellation of the modification of chaetae in II as a diagnostic characteristic of the genus Teneridrilus. Limnodrilus amblysetus, previously known only from China, is recorded from Lake Biwa. Descriptions and taxonomic remarks are provided for Haemonais waldvogeli (new to Japan), Pristina longiseta, Stephensoniana trivandrana and Ripistes parasita (new to Lake Biwa), and Ophidonais serpentina, based on Lake Biwa material.