| Litopenaeus vannamei, also known as the Pacific white shrimp, is an importantmarine species naturally distributed along the Pacific coast of Central and SouthAmerica. As an economically valuable marine crustacean in aquaculture, numerousselective breeding programs have been initiated in the past decade. A greater numberof broodstocks are required to set up basic families in selective breeding programs.However, the small number of foreign imports does not meet the current demand.Compared with the shrimp imported, inbreeding would be more obvious if thecultured shrimp were used as broodstocks, resulting in inbreeding depression of someimportant traits. Therefore, more stocks from different companies must be introducedto expand the number of broodstocks. In such a scenario, it is necessary to conductdetailed genetic diversity and differentiation analyses to avoid inbreeding and otherundesirable effects.Fenneropenaeus chinensis is the main cultured species in shrimp farmingindustry naturally distributed along China’s coastal area. With the effect of humanfactors, such as overfishing, environmental pollution, mismanagement and so on, theresources have been quickly depleted. Fisheries resource enhancement and releasingrestored the fisheries resources effectively and was widely used in multiple aquaticspecies. Evaluation of resources enhancement and releasing in Chinese shrimp hasbeing unable to assess accurately because of the restriction of marking techniques andtagging methods. With characteristics of co-dominance, high reproducibility,polymorphism richness and a ubiquitous genome distribution, microsatellite markersare suitable for recognize the “internal standard” individuals in the recapture species.This method could calculate the recapture rate accurately and evaluate the effects of stock enhancement.The purpose of this study is the molecular relationships in seven stocks ofLitopenaeus vannamei introduced to China and the molecular marker based resourceenhancement effect assessment of Fenneropenaeus chinensis in Jiaozhou Bay andBohai Bay (Hangu).In the present study, seven stocks of Litopenaeus vannamei introduced to Chinawere analyzed using seven microsatellites markers, to evaluate the genetic diversityand levels of inbreeding depression. For all stocks,82alleles were detected over allseven microsatellite loci. The total number of alleles per locus ranged from4to21,with an average of11.7, and varied in size from154to525bp. Newas lower than Nain all stocks. The value of PIC per locus ranged from0.593to0.952, with an averageof0.766, indicating a high level of polymorphism (PIC>0.5) that would be effectivefor further analyses. The average observed heterozygosity (Ho) of the seven stockswas ranged from0.552to0.754. The expected heterozygosity (He) varied between0.600and0.802and was slightly greater than Ho. According to the49tests forHardy-Weinberg equilibrium, deviation（sP <0.05）were observed for37tests (75.5%)due to the heterozygotes deficiency. Estimates of Fst(0.0498～0.1156), with a meanof0.0834, indicated that there was moderate differentiation among the stocks. Fisvalues were positive at five loci, suggesting that there was a relatively high degree ofinbreeding among the stocks. Pairwise Fstvalues ranged from0.0225to0.151, andmost of the stock pairs were moderately differentiated. Genetic distance and clusteranalysis using UPGMArevealed a close genetic relationship for L. vannamei betweenUA1and UA2. AMOVA indicated that the genetic variation among stocks (11.3%)was much lower than that within stocks (88.7%). Although the seven stocks had acertain degree of genetic differentiation and a rich genetic diversity, there is anincreased risk of decreased performance due to inbreeding depression in subsequentgenerations.2507from Jiaozhou Bay and3232from Bohai Bay (Tanggu) were recaptured inthe fisheries resource enhancement and releasing of Fenneropenaeus chinensis. Withtwo established groups of microsatellite quadruple PCR reaction systems, which primers inside the groups were marked with fluorescence, alleles of recapturedindividuals were detected. Combined with the software Cervus3.0and the alleles ofthe parents, the “internal standard” individuals in the recapture species were identified.Firstly, the low temperature reaction system group was used for genetic alleles inrecaptured individuals from Jiaozhou Bay. Then use the high temperature reactionsystem group to verify the results. At last,8“internal standard” individuals from4families were confirmed from the6releasing families in Jiaozhou Bay. Similar wayswere used in the Bohai Bay (Hangu) recaptured population. However the hightemperature group was used first this time. Four “internal standard” individuals fromthree families were confirmed from the six releasing families in Bohai Bay (Hangu).Recapture rate could be calculated to evaluate the releasing effect. |
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