| Eriocheir sinensis, as a commercially important acquatic species, is naturally distributed widely in C hina. However, due to overfishing, land reclamation from mashes, water pollution and other human factors, as well as the Yangtze River large water conservancy construction, ecological and environmental factors about the survival and migration of the C hinese mitten crab was severely damaged. The natural resources sharply declined. In order to restore the natural resources of the C hinese mitten crab, in recent years, The provinces and cities near the Yangtze River have taken measures, such as artificial reproduction and releasing, especially the pro-crab proliferation releasing activities in Yangtze Estuary achieved good effect. At present, the research concentrated on the labeling methods, the number, area and time of releasing, and seed size, etc. The method of the enhancement effect of C hinese mitten proliferation are traditional, mainly including marking the releasing individual and analysising recapture rate, the enhancement effect of proliferation, the genetic relationship between the released and wild populations, and how and whether releasing groups will alter the genetic diversity of wild populations in natural waters, have become an issue of concern. In this study, the mitochondrial DNA molecular markers is used to research the pro-comparative genetic diversity analysis of Estuary C hinese mitten crab in the Yangtze, as well as its enhancement effect of evaluation. The results of the present study were as follows:1. Genetic analysis of released and wild populations of Eriocheir sinensis in the Yangtze EstuaryIn this study, Mitochondrial Cytochrome Oxidase Subunit I(CO I) fragments of released and wild Eriocheir sinensis from the Yangtze Estuary were amplified via PCR, then PCR products were purified and sequenced. We analyzed the population genetic diversity and structure by sequencing the mitochondrial COI gene of 77 individuals. Among the total 15 haplotypes, Hap-1 appeared most frequently in released and wild Eriocheir sinensis and was shared with two populations. The total genetic diversity indexs were high. Haplotype diversity index(H)was 0.825, nucleotide diversity index(π)was 0.00466,and the average number of nucleotide variation index was 2.910. Analyzing separately the genetic diversity of the two populations, we known that haplotype diversity and nucleotide diversity index of the wild population were higher than the released populations. The haplotype diversity index of two populations were 0. 833 and 0.810. Analysis of molecular variance( AMOVA) showed the genetic differentiation index(FST)of two populations was 0.03466(P >0.05), indicating that there were no obvious genetic differences among the released and wild individuals, and the genetic variation mainly existed within populations index of genetic differentiation(FST) and gene flow(Nm) between released population and wild population were 0.03466 and 13.93. The values of F ST and Nm indicated that there were more frequent gene flow between two populations(Nm = 75.05> 1).2. The identification of the non-released individuals among released parents Eriocheir sinensis based on mitochondrial D-loop tag in the Yangtze River EstuarySequences of mitochondrial control region were used as a genetic tag to evaluate the effect of Eriocheir sinensis stock enhancement. Among 119 individuals near the recaptured sites in the Yangtze Estuary, 27.73% were preliminarily excluded as wild individuals through haplotype comparison among all the pro-crabs and recaptured crabs. When haplotype comparison was respectively divided into four groups(CS1、CS2、CS3、CS4) based on the recaptured sites, 31.03%, 22.67%, 23.33% and 22.15% recaptures were excluded as wild individuals. The relatively high exclusion rate indicated that mitochondrial control region was an effective tag to evaluate releasing effect of Eriocheir sinensis.3. Enhance ment effects of released parent Eriocheir sinensis in the Yangtze Estuary based on Mitochondrial DNA molecular marke rsAll 72 samples of released parent and wild juvenile E. sinensis populations in 2014 and 2015 were studied based on mitochondrial COI and D-loop gene sequences. Results showed a clear bias of the base composition that gene fragment of A and T content was significantly higher than that of G and C content. Based on analysis of mitochondrial D-loop sequences, the total variable sites, the number of haplotypes, haplotype diversity, nucleotide diversity and average number of nucleotide variation of two groups were higher than those based on mitochondrial COI sequence analysis of the results. The results of the two gene sequences all showed lower pro-crab population genetic diversity compared with wild progeny population genetic diversity. Mitochondrial D-loop and COI gene could be all used as effective markers to detect the population genetic diversity of Chinese mitten crab, but the sensitivity of mitochondrial D- loop as a reflection of C hinese mitten crab populations was higher than that of COI gene. Sequence molecular variance(AMOVA) analysis based on D- loop and COI gene all showed that there is higher genetic differentiation between releasing pro-crab and wild progeny population, and the genetic variation ma inly existed within populations, more than 98%. So there were almost no impacts on genetic diversity and genetic structure by released pro-crab on wild progeny populations in this study. |
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