The bathymetric ranges of the same deep-sea (2000 m) species in the Sea of Japan and outside it are compared. Among 85 deep-sea species of the Sea of Japan mega- and macrofauna, 25 species are known outside the sea at the depths greater than 2000 m and 45 species are known outside the sea only from the sublittoral and bathyal (2000 m). Remaining 14 species are endemic to the Sea of Japan. The species of the first group, together with eurybathic Sea of Japan endemics (8 species) are classified as pseudoabyssal. The term pseudoabyssal species is used here for eurybathic (sublittoral-abyssal or bathyal-abyssal) species, the distribution of which is restricted to a relatively small area in the abyssal, in present case, to the abyssal within the Sea of Japan. The share of pseudoabyssal species in the abyssal basin of the Sea of Japan (64%) is larger than in any other abyssal region. It is suggested that the large share of pseudoabyssal species is the result of local submergence of the sublittoral-bathyal fauna into the abyssal zone of the Sea of Japan. The abyssal basin of the Sea of Japan is distinguished as a biogeographic province within the abyssal biotic zone.
A review of genetic intra- and interspecific relationships of deep-sea Buccinum and Neptunea species around Japan (with special reference to the Sea of Japan)
