Morphological differences and genetic differentiation level between populations of Trapezium liratum in Lake Obuchi and Lake Nakaumi

Species redetermination of Trapezium liratum inhabiting Lake Obuchi

Abstract

A comparison of the species thought to be Trapezium liratum inhabiting brackish Lake Obuchi in Aomori Prefecture with those inhabiting Lake Nakaumi shows some morphological differences, i.e., maximum shell size, shell width/shell length ratio, and surface pigmentation. We therefore conducted an isozyme polymorphism analysis to determine whether the species inhabiting Lake Obuchi is composed of the same species as those in Lake Nakaumi. Twelve different marker enzymes, AAT, ACP, CK, FDH, FUM, αGPD, IDH, LAP, MDH, ME, PGM and SOD, were detected, and fifteen loci were hypothesized from the populations in the two lakes. The allele frequency, average heterozygosity per locus (H), genetic identity (I), and genetic distance (D) were obtained. The level of genetic differentiation between the two populations revealed that each had a unique gene pool, but that this genetic differentiation was not at a level that would qualify them as different species. It was determined that the Trapezium liratum inhabiting both lakes are composed of the same species.