中间球海胆野生和养殖群体遗传结构的微卫星分析

Genetic structure analysis of wild and cultured populations of the Japanese sea urchin(Strongylocentrotus intermedius) using microsatellites

利用28对微卫星DNA分子标记对中间球海胆的1个野生和1个养殖群体进行了遗传多样性分析。结果表明：在28个基因座中，共检测到91个等位基因，每个基因座位检测到的等位基因数为2～6个，2个群体的平均等位基因数均为3．0714，平均有效等位基因数分别为2．2319、2．2271，平均观察杂合度分别为0．5234、0．5365，平均期望杂合度为0．4868、0．4993，平均多态信息含量为0．4477、0．4396，群体间的多态性差异不显著。2个群体间的遗传相似系数为0．7587，遗传距离为0．2762。经Hardy—Weinberg平衡的卡方检验，有50％的位点显著偏离Hardy—Weinberg平衡。通过F检验发现，两个群体均处于不同程度的杂合子过剩状态。群体间发生分化程度很弱，遗传变异主要来自群体内个体之间。

In this research, we have analyzed the genetic diversity of wild and cultured populations of 28 polymorphic microsatellite markers for Japanese sea urchin （Strongylocentrotus intermedius） via mining EST database of relative species （S. purpuratus ）. S. intermedius belongs to Echinodermata, Eleutheroze and Echinodea, which is distributed in the northeastern Japan, the Korean Peninsula and the Far East coast of Russia. It was introduced into China by Dalian Fisheries University in 1989 and has been breeding for more than 6 generations. EST-SSRs recently have been commomly used in genetic investigations. The flanking sequence of EST-SSRs is so highly conserved that the primers can be tansferred between similar species. Therefore, in this experiment, the primers were designed with the EST sequence of S. purpuratus from the database in GenBank （http：//www. ncbi. nlm. nih. gov/dbEST/index, html ）, then polymerase chain reaction （PCR） was used to identify the effective primers that matched with the S. intermedius which was related to S. purpuratus. Results showed ： A total of 91 different alleles were found and the number of alleles in each locus ranged from 2 to 6. In the 2 populations, the average number of alleles was both 3. 071 4; the number of mean valid alleles was 2. 231 9 and 2. 227 1 respectively; the value of average observed and expected heterozygosity were 0. 523 4,0. 536 5 and 0. 486 8,0. 499 3 respectively; the mean PIC was 0. 447 7 and 0.439 6. The difference in genetic diversity among the 2 populations was not significant. The genetic similarity coefficient of the 2 populations was 0. 758 7, and the genetic distance of the populations was 0.276 2. Chi-square test was used to analyze the genotypes based on Hardy-Weinberg equilibrium,the P value showing that 50% loci departed from Hardy-Weinberg equilibrium. The results of the F-test suggested that both the two populations have surplus heterozygous, and there is no obvious inbreeding phenomenan in the two populations. The results also displayed low genetic differentiations between the 2 populations, and the variance was mainly due to individual difference among the populations. Although the cultured population has been breeding for several generations, there is no significant difference on genetic polymorphism with the wild population.