Evaluating Population Genetics Of Important Economic Marine Organism Coelomactra Antiquate (spengler)

Coelomactra antiquata, which is of great commercial importance, is a valuable bivalve mollusk along the coast of China. However, the natural resource of C. antiquata has been destroyed due to different reasons (e.g. pollution to its living environment, overexploitation). Up till now, there still exist some problems considering the low survival rate of juveniles shellfish which is considered to be the main reason that restrict the development of aquaculture, though analyses about the artificial breeding of C. antiquata are systemic. The studies concerning the genetic diversity and differentiation of C. antiquata are so important to the protection of its germplasm resource together with the selective breeding. Our study used both the allozyme and AFLP technologies to analysis the genetic diversity and differentiation of C. antiquata which are mainly distributed along the coast of China in order to provide scientific basis for the sustainable utilization and protection the resource of C. antiquata as well as its selective breeding.1. Polyacrylamide gel electrophoresis (PAGE) was used to analyze the population genetics of three wild C. antiquata populations from Qidong (Jiangsu Province), Zhanggang (Fujian Province) and Beihai (Guangxi Province) respectively. The results showed that a total of 7 enzymes were measured and 12 loci were found. Four loci (Sod-1,Mdh-1,Est-1,Est-3) were polymorphic, while the other eight loci (Aat-1,Me-1,Est-2,Est-4,Acp-1,Acp-2,Amy-1,Amy-2) were monomorphic. The results also showed that Sod-1 and Est-1 from Zhanggang population and the Sod-1 from Beihai population are accorded with Hardy-Weinberg equilibrium (P>0.05). All loci from Qidong population, Mdh-1 and Est-3 loci from Zhanggang population and Mdh-1,Est-1,Est-3 from Beihai population deviate from Hardy-Weinberg equilibrium obviously (P<0.01). Besides, all other polymorphic loci, expect for the Est-1 from the Qidong and Zhanggang population which showed heterozygote deficiency (F>0), showed heterozygote excess (F<0).2. In general, the results analyzed by allozyme method showed that the average of the mean number of alleles per locus (A) was 1.7500, the average of the mean effective number of alleles per locus (A_e) was 1.3939, and the average of percentage of polymorphic loci (P) was 33.33%. The average of observed heterozygosity (H_o) was 0.2750, ranging from 0.2389 to 0.3083, and the average of expected heterozygosity (H_e) was 0.1765, ranging from 0.1496 to 0.2041. The G_ST values (G_ST) among three populations was 0.0719, and the genetic distances ranged from 0.0164 to 0.0302. The results showed that the germplasm resource condition of C. antiquata in China was good.3. Amplified fragment length polymorphism (AFLP) was used to analyze the four wild C. antiquata from Qindao (Shandong Province), Qidong (Jiangsu Province), Zhanggang (Fujian Province), and Beihai (Guangxi Province) together with one cultured population from Zhanggang (Fujian Province). 618 loci were found by nine pairs of selective primers. The results showed that the mean number of alleles per locus (A) ranged from 1.3916 to 1.6036, with an average of 1.5000. The mean effective number of alleles per locus (Ae) ranged from 1.1733 to 1.2431, with an average of 1.2124. The mean of the percentage of polymorphic loci (P) was 49.98%, ranging from 39.16% to 60.36%, the mean of Shannon's information index (I) was 0.2067, ranging from 0.1684 to 0.2354, and the mean of Nei's gene diversity (H) was 0.1320, ranging from 0.1073 to 0.1506. Besides, the genetic diversity of four wild populations was higher than that of the cultured population. In general, the genetic differentiation of the five populations was large. The average of GST value of the five populations was 0.3318, ranging from 0.0996 to 0.4835, and the average of genetic distance among the five populations was 0.1858, ranging from 0.0365 to 0.2937. Cluster analysis suggested that Qingdao population (Shandong) and Qidong population (Jiangsu) clustered into one group, and Zhanggang population (Fujian) and Beihai population (Guangxi) grouped into another group. Combined with the genetic distance and the GST value, it is considered that the two groups may represent two distinct subspecies which was also evident in the AFLP results of fifteen makers in three primer pairs (E-ACA/M-CGT, E-ACT/M-CGT, E-AGA/M-CGT). In general, the results of the allozyme analysis and the AFLP analysis both showed that although the natural resources of C. antiquate has been destroyed severely, it has not had a great effect on the genetic diversity of the population. So it is necessary to take proper protection measures in order to provide germplasm resources for the artificial culture in the future.5. Using the FIASCO (Fast Isolation by AFLP of Sequences COntaining repeats) method, we constructed the (CA)_n, (CT)_n enriched library for C. antiquate which from Zhanggang Fujian. A total of 768 colonies was contained in the (CT)_n enriched library for C. antiquate, 140 colonies which size were between 500 and 1200bp were sequenced, 30 tandem repeat sequences (n≧4) were obtained, which contains 11 Minisatetllite sequences and 19 microsatellite sequences, the rate of positive clones was 13.57%. 8 microsatellite loci were were polymorphic, which will be helpful to researches for population genetics of C. antiquate.