| Portunus triberculatus is a commercially important species widely spread along the coast waters of China. In recent decades, the wild population has been constantly decreased due to overfishing and habitats destruction. To protect and recover the P.tirtuberculatus resources,a large scale of stock enhancement has been carried out in the coastal waters of China. Liaoning Province carried on enhancement programs from 2012 year for the restoration of existing resources.As the stock enhancement activities may change the genetic variability and genetic composition of the recipient wild populations, it is necessary to carry out genetic monitoring of broodstocks and wild populations for long term sustainability of the swimming crab resources. In this study, genetic diversity and population structure of 4 wild populations(CXD,YK,JZ and SZ) and 2 broodstock populations(XRD and PJ) were detected according to the sequence of mitochondrial control region. 96 mtDNA haplotpes were observed in 129 wild Portunus trituberculatus individuals and 50 mtDNA haplotpes were observed in 67 broodstocks individuals. The haplotype diversity was high for all wild populations, with values from 0.9657 to 0.9905;and the broodstock populations haplotype diversity were 0.9635 and 0.9828. The nucleotide diversity of wild populations and broodstock populations both ranged from 0.0160 to 0.0228, both of them showed a high level of genetic diversity. The result of AMOVA suggested that 92.92% of the genetic differention within populations. The Fst values between wild populations ranged from-0.00893 to 0.01043,which indicated a little genetic differentiation and no significant genealogical structure among 4 wild populations, but the broodstock populations between wild populations had significant differentiations. And no pedigree branch corresponding to different populations(except the PJ broodstock population) was observed in the neighbor-joining tree. The mismatch distribution of pairwise nucleotide and the negatively selective neutrality test suggested that P.tirtuberculatus of Liaodong Bay has experienced demographic or spatial expansion history. To sum up, the broodstock populations and the wild populations in Liaodong Bay had abundant genetic diversity and relatively similar genetic structure, which reflected good quality of the germplasm resource.It is important to consider the difference in contribution to reproduction between parents when assessing the effectiveness of enhancement programs. We used 10 microsatellite markers to estimate genetic diversity, the Probability of Exclusion(PE), paternity test accuracy, and the parental contribution of nine female parents, based on a sample of one hundred and seventy nine offspring of swimming crab(Portunus trituberculatus). The average heterozygosity of offspring and polymorphic information content(PIC) etc were lower than that of their parents, and significant difference existed in He between adult broodstock and offspring(P<0.05, Wilcoxon signed-rank test). When using 4 microsatellite markers, the PE was ?0.998 and accuracy was 56.98%. When using 6 microsatellite markers, the PE was ?0.9999 and accuracy was 97.21%, and between 8-10 microsatellite markers, the accuracy was 100%. We found that the number of microsatellite markers increased and the accuracy increased, too. In this experiment all nine female parents contributed to the offspring. Different parents showed large variance in parental contributions(P<0.05, Nonparametric chi-square test). The highest parental contributions were 29.61% but the lowest only were 3.35%. In this study, the difference of parental contributing to reproduction is one of the reasons for loss of genetic variability in hatchery populations. Research shows that the microsatellite markers as an effective means can be used for assessing the genetic diversity of swimming crab in enhancement programs enhancement. The experimental results provide scientific basic data for the scientific development of China's crab breeding and releasing. |
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