Studies On Molecular Genetic Variation Of Mitten Crab, Eriocheir Sinensis Populations

Distributed in the coastal waters of China north of 24° N, mitten crab (Eriocheir sinensis) is one of the rare and precious aquatic products and being cultured for food extensively in recent years. Its commercial traits are different among Oujiang, Liaohe, and Yangtze populations, because the three populations differ in growth rate and adult body size. The Yangtze population of the mitten crab is distinguished by faster growth rate, larger body size and therefore, high economic value in the aquaculture. Seed crabs of the other two water systems introduced into the Yangtze system on the huge demand of the seed crabs by the aquaculture has caused severe impacts on aquaculture of mitten crab. Currently the wild seed crab resources are almost exhausted and the identification of the Yangtze population the mitten crab is an urgent need. But the three populations are morphologically difficult to distinguish. RAPD was applied in the studies on genetic variation of Eriocheir sinensis and molecular identification of the three populations. The polymorphic fragments obtained were cloned and sequenced.Among 200 random primers screened, two primers (HX01 and HX02) each generates a fragment (HX01-400bp and HX02-700bp) common in Oujiang and Liaohe populations respectively, whereas they are absent in Yangtze population. Both fragments are reproducible under the 50% changes of the original template DNA concentration, or 25% changes of the MgCl₂ or primer concentration, and were selected as an identification marker of Yangtze population. Using these markers, we found that the cultured crabs in Jiangsu and Anhui are subjected to serious population confusion, even in some seed-crab farms. No molecular marker to distinguish Oujiang population and Liaohe population was found in the present study.Thirty-one reproducible random primers revealed 121 amplified fragments in Liaohe, Oujiang and Yangtze populations. Twenty-seven of the fragments were polymorphic. Intraspecific genetic variation among the populations was low (0=0.004-0.063). Intrapopulation variation of Liaohe population (D=0.018) and Oujiang population (D=0.025) were higher than that of Yangtze population(D=0.013), while the interpopulation variation (D=0.023)between Liaohe...