1National Research Institute of Far Seas Fisheries, Yokohama, Kanagawa 236-8648, 2National Research Institute of Aquaculture, Yokosuka, Kanagawa 238-0316, 3Marine Fisheries Research and Development Center, Yokohama, Kanagawa 220-6115, Japan
Genetic differentiation between samples of Ommastrephes bartramii collected from the North Pacific (n=50) and the South Atlantic (n=50) was examined using nucleotide sequence variation of 506 bp of the mitochondrial 16S ribosomal RNA gene. Thirteen mtDNA haplotypes were identified: seven in the North Pacific (Ob1-Ob7) and six in the South Atlantic (Ob8-Ob13). No haplotypes were common to the two oceans. An exact test of haplotype frequency showed significant differentiation between the two ocean samples (p>0.001). The genetic distance (the number of net nucleotide substitutions) between the North Pacific and South Atlantic samples was 0.00597, similar to the respective within-ocean values. These findings suggest that the two ocean samples of O. bartramii were genetically differentiated to a lesser degree than the interspecific level.