Genetic Diversity Analysis Of Procambarus Clarkii Population In The Middle And Lower Reaches Of The Yangtze River

The red swamp crayfish, Procambarus clarkii, native to south-central United States and Northeastern Mexico, has been transplanted to Hawaii, Japan, Europe and even the River Nile. They were introduced to Nanjing. China from Japan in 1930s. This crayfish has rapidly spread to most provinces of China, and has established dense populations due to translocation by humans for food and lack of local predators. The red swamp crayfish has great market demand and high price due to its tender flesh and good taste in recent years, thus it has become one of the most important freshwater aquaculture species in China. With the natural population spreading and aquaculture of Procambarus clarkii, the red swamp crayfish have widely distributed in most of provinces of eastern and central regions, especially in Yangtze River basin. In this study, both microsatellite molecular markers and COI gene of mitochondrial DNA were used to study the genetic structure and genetic diversity of eight crayfish populations in the middle and lower reaches of the Yangtze River. The eight crayfish populations were Nanjing population. Xuyi population. Hefei population, Nanchang population. Yuanjiang population, Wuhan population, Qianjiang population and Yaowan population, respectively. We hope that this study will be useful in resource protection and genetic beeding of red swamp crayfish. The main results of this study are as follows:(1) Seventeen microsatellite loci were used to evaluate genetic variation in 8 geographic populations of red swamp crayfish. The results shows:①Average heterozygosity observed from 17 microsaterllite loci varied from 0.4221 to 0.5170. average expected heterozygosity varied from 0.4024 to 0.6121, and polymorphism information content varied from 0.3408 to 0.5624. These results proved that the genetic diversity of red swamp crayfish population in the middle and lower reaches of the Yangtze River was at a medium level. The highest and the lowest genetic diversity among the 8 populations are NJ population and HF population, respectively.②The gene flow of the 8 populations varied from 0.9890 to5.9161, F-Statistics from 0.0405 to 0.2018, genetic similarity indexes from 0.5960 to 0.8997. the genetic distances from 0.1057 to 0.5175. Cluster's analysis showed that the first group contained NJ. NC and XY populations; the second group contained YJ, WH. QJ and YW populations; HF population comprised a third group. (2) As an important and useful polymorphic DNA marker, mitochondrial cytochrome Oxidase subunit I (COI) gene was used to analyze the genetic diversity and genetic structure of 8 geographic populations of red swamp crayfish. The result shows:①25 variable nucleotide positions are detected in analyzed 1386bp COI sequences, and 42 haplotypes are defined among 8 populations. The variable nucleotide positions of the 8 populations varied from 15 to 23: the haplotype diversity from (0.491±0.175) to (0.964±0.077). the nucleotide diversity from (0.00288±0.00142) to (0.00680±0.00117). The highest and the lowest genetic diversity among the 8 populations are HF population and YJ population, respectively.②AMOVA analysis showed that the F-Statistics of 8 populations is 0.0989, These results proved that the genetic differentiation of red swamp crayfish population in the middle and lower reaches of the Yangtze River was at a medium level.(3) In this study, microsatellite molecular markers and COI gene of mitochondrial DNA result shows that the genetic diversity of red swamp crayfish population in the middle and lower reaches of the Yangtze River was at a medium level, genetic differentiation between eight populations was obviously. People should protect the genetic diversity of red swamp crayfish in resource protection and genetic beeding .