Differences in degree of homozygosity between seed and sown populations of the Japanese scallop Patinopecten yessoensis.

Abstract

Starch gel electrophoresis for 6 polymorphic isozyme loci was carried out to estimate the level of genetic variation in seed and sown populations of the Japanese scallop Patinopecten yessoensis from Abashiri/Hokkaido, in Japan. The observed heterozygosity was significantly lower than the expected heterozygosity in the seed population, indicating an excess of homozygosity, while such tendency was not observed in the samples of the sown population. Dividing the sampled animals into small and large size groups, the homozygote excess was lower in large size than in the small size. Thus, a decrease of homozygosity during growth is considered to depend on the differentiated survival rate between homozygotes and heterozygotes, probably on the basis of the homozygosity of deleterious recessive alleles.