Genetic Variation among Local Populations of the Japanese Mitten Crab Eriocheir japonica De Haan

Horizontal starch gel electrophoresis was used to investigate the genetic stock structure of the Japanese mitten crab Eriocheir japonica. Twenty-two putative enzyme-coding loci were examined from 1072 crabs at 22 localities from Hokkaido to Okinawa in Japan and 69 Chinese mitten crabs E. sinensis. Nine loci (40.9%) were polymorphic, i.e., AAT-1*, AAT-2*, G3PDH*, GPI*, IDHP-1*, IDHP-2*, MDH-1*, MDH-2* and PGDN*. A geographical cline of allelic frequencies was not clearly recognized at all the loci but the alleles *b and *e at the GPI* locus might be a diagnostic character of the Okinawa populations. The average proportion of polymorphic loci and heterozygosity were 0.149 and 0.020, respectively. Nei's genetic distance was 0.0004 (0-0.0013) which was about 1/140 of the Nei's genetic distance between the Japanese mitten crab and the Chinese mitten crab. Gene diversity analysis indicated that only 1.20% of the variation was between samples. These results indicate that the genetic differentiation of the local populations is small.