Microsatellite DNA polymorphism to reveal genetic divergence in ayu, Plecoglossus altivelis

Six (CA)n and one (CT)n(CA)n microsatellite loci were isolated from a size- selected genomic library of ayu Plecoglossus altivelis altivelis. Primers f or PCR amplification were designed for the microsatellite loci and the loci characterized by screening polymorphisms in the amphidromous form of ayu. All loci displayed a high degree of length polymorphism, as observed in the total number of alleles per locus (2-21), and a high degree of heterozygos ity ranging from 0.414-1.000. Distinct differences were observed between am phidromous and landlocked populations of ayu, in the frequency distribution s of the alleles. The primers developed for ayu Plecoglossus a. altivelis w ere also tested for their ability to amplify homologous sequences in endang ered subspecies of Ryukyu-ayu, Plecoglossus altivelis ryukyuensis. Genetic variability was obviously low in both average number of alleles per locus a nd average heterozygosities. These microsatellite loci show great potential as indicators for genetic variability and divergence among populations of ayu species.