Genetic Differentiation of Calyptogena Bivalves between Seep Areas off Central Honshu and Hydrothermal Vent Fields in the Okinawa Trough

Abstract

The genetic differentiations between seep areas off central Honshu (the Japanese mainland) and hydrothermal vent fields in the Okinawa Trough were examined for two vesicomyid species, Calyptogena okutanii and Calyptogena nankaiensis, on the basis of nucleotide sequences of the mitochondrial gene for cytochrome c oxidase subunit I. For each species, significant genetic differentiation was detected between the two sea areas. Relatively highly diverged haplotypes were detected for both species. An asymmetrical distributional pattern of haplotypes was also shown for C. okutanii. As a similar phylogeographic pattern was revealed for another species inhabiting both sea areas, namely, C. solidissima, the migration of three Calyptogena species between seep areas off central Honshu and hydrothermal vent fields in the Okinawa Trough might be attributable to the same historical events.