Abstract
The genetic variation in populations of the diamond-shaped squid Thysanoteuthis rhombus in the Pacific was examined through mitochondrial DNA analysis. Part of the cytochrome oxidase subunit I gene was amplified with the polymerase chain reaction (PCR) and sequenced for 23 individuals, five from each of three samples collected off Kyoto/Fukui, Okinawa Island, and the Ogasawara Islands in the western Pacific, and also for eight individuals from a sample caught off Galapagos Islands in the eastern Pacific. Resultant sequence data showed that there were seven variable nucleotide positions in the 399 base-pair segment of the gene and that all 23 sequences were grouped into six haplotypes. No marked genetic difference was observed between populations on both sides of the Pacific. The PCR-mediated SSCP (single-strand conformation polymorphism) analysis applied to a larger number of individuals of more than 200 from adjacent waters around Japan (off Kyoto/Fukui and Okinawa Island) revealed no divergence in haplotype frequency between these two regional samples.
