Abstract
We determined the nucleotide sequences of the 3′ region (~400 base pairs) of the mitochondrial control region for 97 individuals of the deep-sea demersal fish species Bothrocara hollandi, which were collected at five sites in the northwestern Pacific off Tohoku District, the northeastern part of the Japanese mainland. Phylogenetic analysis based on the sequences showed that these fish form a monophyletic group with individuals of the Okhotsk Sea, which have completely deviated from those fish of the Japan Sea. Furthermore, genetic diversity of fish in the northwestern Pacific was higher than that in the Okhotsk Sea. The population of the northwestern Pacific was shown to have experienced a recent population expansion. Nine of 97 individuals had only one non-coding unit, and the remaining individuals had two units between mitochondrial genes for tRNAThr and tRNAPro; however, neither of these groups of individuals formed a monophyletic group in the Okhotsk Sea or the northwestern Pacific, while monophyly of individuals with more than one unit was shown in the Japan Sea. The differences between the populations of the Japan Sea and neighboring sea areas might be attributed to the occurrence of repeated environmental changes and corresponding population bottleneck events in the Japan Sea.
