| Macrobrachium nipponense distributes widely in natural waters in China. It is also one of important freshwater spawns for aquaculture. Because of inbreeding, serious retrogression of genetic traits appeared in Macrobrachium nipponense. It’s necessary to study the conservation of genetic resources and genetic improvements of Macrobrachium nipponense.RAPD (Random Amplified Polymorphic) analysis was applied to detect the genetic diversity of four populations of Macrobrachium nipponense Sampled from Huzhou, Suzhou, Wuxi, Yixing around the Taihu Lake. Under the pre-optimized conditions,16effective primers were selected from50random primers.117clearly and stable loci, with92polymorphic loci, ranging from200bp to2000bp in length, were detected. The percentages of polymorphic loci of four populations were49.57%,60.68%,53.85%,57.26%.Their mean expected heterozygosity ranged from0.2077to0.2163, and their Shannon Information Index ranged from0.2967to0.3053. Index of genetic diversity Gst ranged from0.1644to0.2002. Results of Analysis of Molecular Variation (AMOVA) revealed that16.67%of the variances were from inter-population, Pst analysis indicated that the variance of inter-population significantly affected the total variance. The genetic distance indicated that genetic divergence existed between four populations. The maximum genetic distance occurred between Suzhou and Yixing populations (0.1481), and the minimum between Wuxi and Yixing populations (0.1141). Results of cluster analysis based on UPGMA indicated that the closest relationship was found between Wuxi and Yixing populations, then was Huzhou and Suzhou populations. This study was not only in favor of protecting and using of genetic resources, but also provided guides for genetic improvement and selection of breeding materials.Cell electro fusion were successfully applied to nuclear transfer of fish, but difficult to use in genetic improvement of fish because of its low rate of success. The success of electrofusion is affected by many factors. The unfertilized eggs were activated spontaneously at the time contacting with water. The longer they stayed in water, the lower the ability to fertilize.Unfertilized oocytes of loach were dipped in synthetic ovarian fluid (SOF) and Holfreter’s solution for15minutes,20minutes or30minutes respectively before fertilization. The results showed that SOF effectively delayed activation time of oocytes after being in water; and Holfreter’s solution also had some effects, but not so efficient as SOF. Using the oocytes which were digested by different concentrations of Trypsin as recipient, fusion experiments indicated that0.5%Trypsin in SOF, in comparison with the control group (Holfreter’s solution), noticeably raised the development rate of fused eggs to blastula stage. The statistical analysis showed the difference is obvious (P<0.05). The ratios of fused oocytes developed to gastrula and hatching stages, however, were not so different with the control group. In addition, when the Trypsin concentration were0.2%and0.1%, the ratios of fused oocytes developed to various stages were all lower than those of the control group, the statistical analysis indicated the differences were significant (P<0.05). This paper demonstrated that the types of solutions and concentrations of Trypsin have obvious effects on the development of electrofusion oocytes. The delay activation time of recipient oocytes would raise the fusion rate, but would not raise the hatching rate. The recipient oocytes treated using0.2%Trypsin administrated by Holfreter’s solution might achieve higher rate of fused fish. |
