BIOCHEMICAL-STUDY OF THE POPULATION HETEROGENEITY AND DISTRIBUTION OFTHE OVAL SQUID SEPIOTEUTHIS-LESSONIANA COMPLEX IN SOUTHWESTERN JAPAN

The three taxa of the Sepioteuthis lessoniana (Lesson, 1830) complex, AKAIKA, SHIROIKA, and KUAIKA, are genetically and reproductively indep endent and coexistent without hybridizing along the coast of Ishigaki Island, Okinawa. The present study analyzed 554 specimens of Sepioteut his collected from 11 localities in inshore waters of southwestern Jap an to elucidate the distributional patterns and population structures by means of horizontal starch gel electrophoresis at 13 genetic loci e ncoding for ten enzymes. The results showed that each of the three tax a has a different distributional pattern. SHIROIKA is widely distribut ed in the tropical to warm temperate regions throughout southwestern J apan. AKAIKA is distributed in the Ryukyu Islands and also probably oc curs on the Pacific coast of Honshu, mainland Japan. KUAIKA is limited to the tropical region and its latitudinal distribution suggests a cl ose correlation with water temperature. In SHIROIKA and KUAIKA, signif icant genetic differences were detected between the specimens from Oga sawara Islands and those from the other localities suggesting the exis tence of a certain barrier of panmixia between insular localities.