Using fluorescent AFLP-markers, the genetic diversity and structure of six geographical populations of the swimming crab,Portunus trituberculatus(Miers, 1876), from the coast of China were analysed to assess their genetic resource state. Eight primer combinations generated 925 loci among 85 individuals, and revealed a high polymorphism within these populations that varied from 57.41% (Zhoushan population) to 76.86% (Dalian population). According to the combination of percentage of polymorphic loci (PPL) and Shannon’s information index (I), the populations from Zhangzhou, Dongying and Dalian showed more genetic variation than the Lianyungang, Zhanjiang and Zhoushan populations. The gene flow () and across all populations overall were 1.935 and 0.205, respectively, showing moderate genetic differentiation. Differentiation was highest in the Zhoushan and Zhanjiang populations, and the geographical distribution and UPGMA cluster tree were not fully accordant. Neutrality test results revealed that the Zhangzhou population faced a smaller selective pressure than the other five populations (). In general, a high genetic diversity among theP. trituberculatuspopulations was observed along the coast of China, especially in the Zhangzhou, Dongying, Dalian and Lianyungang populations, while a pronounced level () of genetic differentiation has occurred between the Zhoushan population and the other populations. Therefore, these findings have the following implications for conservation and genetic improvement: (1) high diversity levels and good genetic resources, especially in the Zhangzhou population, which could lay the foundations for breeding research and genetic improvement; (2) the importance of preventing species escape and gene pool contamination in ex-situ conservation and species introduction programs in the Zhoushan population.
Physicochemical characteristics of chitosan from swimming crab (Portunus trituberculatus) shells prepared by subcritical water pretreatment
