Study On Appropriate Protein Content And Genetic Diversity Of Procambarus Clarkii

The red swamp crayfish, Procambarus clarkii, a kind of native species in the south-central of United States and the northeastern part of Mexico, has been a dominant species after induced into China from Japan since 1929.With the scale of crayfish industry gradually expand, the study on formula feed, especially the appropriate protein content of feed components has become one of the hotspots.In addition, the main source of seed breeding mode depends on the capture of natural seed, but the large-scale artificial breeding technology is not yet mature, coupled with environmental pollution and other reasons, a significant reduction in the amount of wild resources, so we need to do research on the genetic structure of existing wild population of Procambarus clarkii.In this study, we studied on the appropriate protein content of formula feed on the growth and immunity of Procambarus clarkii. In addition, seven microsatellite markers were applied to investigate the genetic diversity among three wild geographic stocks, comparing with one cultured stock. The main results were as follows:1. There was significant difference Shrimps fed 45% had the lowest survival rate valued 56%, the 5%group had the highest valued74%.The others were all above 70%,and there were no significant difference when the protein level was above 35%.At the end of the experiment, there was significant difference of average total size between the different protein levels on (P<0.05),the maximal body length of stump shrimp is similar with the total size of mode, the minimum body length of stump has the same size as the total size of the shortest in the end.Growth rate and specific growth rate increased with increasing protein level, feed conversion ratio is decreasing. Shrimps fed 41.22% dietary protein had the maximal special growth rate and fed 43.45% dietary protein had the minimal feed conversion, the protein content valued 41.57% had the maximal special growth rate. In this study, the appropriate protein content of Procambarus clarkii (average weight of 0.0238±0.0014g) was between 41.22% and 41.57%.2. When the dietary protein level valued from 5% to 35%, pepsin activity increased gradually by the protein content of formula feed. When the protein content is higher than the 35%, the pepsin activity decreased, but not significant. The change law of Pepsin activity was accord with the growth rate.In order to find out the effect of protein levels on immune-related enzyme activities, acid phosphates (ACP), alkaline phosphates (ALP), Superoxide dismutase (SOD) and peroxides (POD) in muscle were monitored. The dietary protein levels had significant effects on the activity of ALP in the muscle (P<0.05) and had not significant effects on the activities of ACP, SOD and POD in the muscle (P>0.05).3. The genetic diversity of wild population of Procambarus clarkii in the Yangtze River Basin was studied by using seven polymorphic microsatellite markers. The three wild populations were collected in Hongze Lake (HZH), Chaohu Lake (CH)and Poyang Lake (PYH).The cultured population was collected from Xinghua county (XH).The polymorphic information contents (PIC), the expected heterozygosity (He) and the observed heterozygosity (Ho) were ranged from 0.5316 to 0.6788,0.6113 to 0.7399 and 0.5762 to 0.619,respectively.Observed heterozygosity (Ho) of cultured population was only 0.5714.Obviously, the data above showed that the genetic diversity of wild population was a little higher than the cultured population.The results showed genetic differentiation coefficient estimated by Nei’s index between populations was low.There were only 1.11% between CH and PYH population. Coefficient of genetic differentiation was 1.11%～6.61% on average and the majority of genetic variation occurred within population.According to the genetic similarity and distance, PYH and CH population were shortest, while between PYH and HZH population were longest. Cluster’s analysis showed that the first group contained PYH and CH populations;the second group contained HZH and XH populations; The result of cluster’s analysis accorded with it’s region distribution.