The composition and distribution of pelagic ostracods (Ostracoda: Myodocopa) in the Sea of Japan

In the waters of the subarctic structure of the Sea of Japan, the fauna of planktonic ostracods of the Halocyprididae family occurs within the oceanic zone of the sea. In contrast to halocypridids of other Far Eastern seas of Russia, this fauna is depauperated and isolated from the Pacific fauna. Deep-water species of halocypridids are absent; the only inhabitant of deep water is an interzonal eurytopic, Discoconchoecia pseudodiscophora (Rudjakov, 1962), which is found in the open part of the Sea of Japan from the surface to great depths. The maximum abundance of pelagic ostracods in the Sea of Japan was observed in the mesopelagic zone. The northern boundary of the distribution of tropical-subtropical species of halocypridid ostracods runs along 38°–40° N in the southern Sea of Japan and along the La Perouse Strait in the eastern part of the sea (based on the data for the 1970s–1980s). Benthic ostracods of the families Philomedidae and Cypridinidae (which are found in the meroplankton only during their spawning period) inhabit the neritic zone of the cold-water and warm-water parts of the Sea of Japan.