| The Eriocheir populations, E.sinensis, E.hepuensis and E.japonica were analyzed by using isozyme and mtDNA sequencing techniques to detect the genetic variation of populations. The genetic results were compared with the results of morphology study in order to discuss the relationship of these populations. The main results of this dissertation were listed below:1. The electrophoresis system suited for Eriocheir study was founded and 11 enzymes were obtained. These enzymes assayed were AAT, GPI, G3PDH, HK, IDHP, LDH, LAP, MDH, MPI, PGDH and SOD.2. Of the 11 enzymes assayed routinely, 17 gene loci were found, i.e., AAT-1 , AAT-2*, GPI*, G3PDH*, HK*, IDHP-1*, IDHP-2*, LDH*, LAP-1*, LAP-2*, MDH-1*, MDH-2*, MPI-1*, MPI-2*, PGDH*, SOD-1* and SOD-2*. There were 8, 6 and 4 polymorphic loci (AAT-1*, AAT-2*, GPI*, G3PDH*, IDHP-1*, IDHP-2*, MDH-1*, MDH-2*and AAT-1*, AAT-2*, GPI*, IDHP-1*, MDH-1*, MDH-2*, and AAT-1*, AAT-2*, GPI*, IDHP-1*) in E.sinensis, E.hepuensis and E.japonica, respectively.3. The value of Ae, Ho, He, and p were 1.0815, 0.0384, 0.0871, 47.06%; 1.0551, 0.0433, 0.0861, 35.29% and 1.0337, 0.0252, 0.0451, 17.65% in E.sinensis, E.hepuensis and E.japonica, respectively. The values of Ho were lower than those of He, and the values of Ho were at a low level in these three species.4. The genetic distance values were 0.0010, 0.0027 and 0.0016 between E.sinensis and E.hepuensis, between E. sinensis and E. japonica, between E. hepuensis and E. japonica, respectively. The distance value between E.sinensis and E.hepuensis was the smallest than the others, which indicated that the relationship was closer between E.sinensis and E.hepuensis.5. The primers of Eriocheir species were designed by using the DNA sequence of Daphnia pulex, Drosophila yakuba and Artemia franciscana. The mitochondrial DNA 12S rRNA and ND2 regions were amplified.6. The mtDNA sequencing analysis showed that the sequence lengths of 12S rRNA were 416bps in the E.sinensis, E.hepuensis and E.japonica, and were 417bps in the E.okninawa. The base contents were similar and the average A, T, G, C contents were 34.9%, 40.0%, 10.6%, 14.4%, respectively. There were 0-2 bases variation in intrapopulations and 2-11 bases vaiations in interpopulations, and the variability of base were 0-0.48% in intrapopulations and 0.48-2.63% in interpopulations , respectively.The sequence lengths of ND2 were 376bps in all the Eriocheir populations, and the base contents were similar and the average A, T, G, C contents were 29.4%, 44.7%, 7.1%, 18.8%, respectively. The sequences were AT rich and biased.7. The maximum distance were 0.72% in intrapopulations and 2.4% in interpopulations by 12S rRNA sequence analysis, and the value were 0.80% and 3.99% by ND2 sequence analysis, respectively. The E.okninawa populations occupied a distinct status in the phylogeny tree, and the other populations clustered together all by themselves.8. The Eriocheir crabs were divided into three independent groups by individual cluster analysis and each group was on behalf of one species. There were no individual crossover among different species, while the different individual were crossed together in E.japonica populations. E.sinensis and E.hepuensis were clustered together firstly, which indicated the relationship was closer between the two species.9. One-Way ANOVA results showed there were significant difference in 10(C/B, D/A, F/A, G/A,H/I, J/A, K/A, M/L, M/N, O/P, 10 (C/B, E/A, F/A, G/A ,H/I, J/A, K/A, M/L, M/N, O/P) and 9 (C/B, D/A, G/A, H/I, J/A, K/A, M/L, M/N, O/P)variables in E.sinensis, E.hepuensis and E.japonica, respectively.
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