Effects Of Aquatic Plants On Growth, Nutritional Quality And Gene Expression Of Chinese Mitten Crab, Eriocheir Sinensis

Chinese mitten crab(Eriocheir sinensis),which is also known as river crab,is an unique aquatic economic species in China.During the artificial culture we found aquatic plants has the vital function on the growth of Chinese mitten crab,but the mechanism of this function still unknown.With the Elodea as the experimental variables in crab breeding,culture biology and molecular biology were conducted to study the effects of water grass on the growth and nutritional quality of crab and related gene expression in this study and to explore the intrinsic mechanism of the effect of aquatic plants for crabs.The results are presented as follows:Part 1.Effects of Elodea nuttallii on the growth and nutritional quality of Chinese mitten crab,Eriocheir sinensisAquatic plants have become one of the most important ecological factors in aquaculture practice of Chinese mitten crab.However,the effects of aquatic plants on the growth of Chinese mitten crab have not been quantitatively evaluated,and its effects on the nutritional quality are still vague.In this paper,we studied the influence of aquatic plants(Elodea nuttallii)on the growth and nutritional quality of Chinese mitten crab,and compared the amino acid and fatty acid composition,and growth of adult Chinese mitten crab reared in the concrete ponds with Elodea nuttallii and without Elodea nuttallii.The results showed that there were significant differences(P<0.05)in the growth rate of body weight,carapace length,carapace width and conditional factor between Chinese mitten crabs reared with and without Elodea nuttallii,but there were no significant differences(P>0.05)in the hepatopancreas index and the gonad index between two rearing environments.The contents of amino acids,essential amino acids and flavor amino acids contained in the muscle of Chinese mitten crab reared in ponds with Elodea nuttallii were significantly higher than in ponds without Elodea nuttallii(P<0.05).The flavor amino acid contents in hepatopancreas of female crab reared with Elodea nuttallii were significantly higher than that without Elodea nuttallii(P<0.05),but no significant difference appear in male(P>0.05).The fatty acid composition and content in the muscles displayed no significant difference between the two ponds.However,the contents of saturated fatty acids(SFA),fatty acids(MUFA)and polyunsaturated fatty acids(PUFA)in hepatopancreas were significant higher in the Elodea nuttallii ponds than those in the ponds without Elodea nuttallii(P<0.05).This study indicated that the Elodea nuttallii not only would be useful to the growth of Chinese mitten crab,but also should be helpful to improve the nutritional quality of Chinese mitten crab.Part 2.Transcriptome analysis of effects of aquatic plants on Eriocheir sinensisApplying the high-throughput sequencing technologies,we obtained the transcriptome data of the mixed samples of Chinese mitten crab muscle,eyestalk,hepatopancreas and gonad in the environment with and without aquatic macrophytes breeding in this chapter.A total number of 47167 transcripts were assembled,in which 33133 transcripts were annotated in NCBI-nr database,and 26792 transcripts in Uniport database.Transcriptomic comparison analysis showed that there were 35 differentially expressed genes in Chinese mitten crab between the crabs reared with and without aquatic plants.Among these differentially expressed genes,there were 13 genes up-regulated in watergrass-crab and 12 genes up-regulated in no aquatic plants crab.GO function enrichment results showed that no aquatic plants crabs have some genes which effect atpase activity and Wnt pathways.Compared with no aquatic plants crab,these high expression genes associated with ribosomal protein,myosin heavy chain in watergrass crab,which is conducive to the development of the crab,gonad and individual growth and adaptation to environment.The preliminary study showed that the aquatic plants had a certain influence on the gene expression pattern of Chinese mitten crab,which provided the molecular biological basis for revealing the mechanism of effect of the aquatic plants to Chinese mitten crab.Part 3.Effects of aquatic plants on growth,molting and digestive enzyme gene expression of Eriocheir sinensisIn this chapter,we put larval crab in the separate cages and culture in the same water environment.The real grass,plastic grass and no aquatic plants were settled as three experiment groups.After two molts,count the weight gain rate,survival rate,each molt period and the gene expression regulation of some digestive enzymes.The results indicated that the weight gain rate of three experiment groups has no significant difference(P>0.05),but the survival rate of real grass group and the plastic grass group were significantly higher than that of no aquatic plants group after the first molt(P<0.01).After the second molt,the weight gain rate,survival rate,fatness during real grass group and plastic grass group has no significant(P>0.05),and both of them were significantly higher than no aquatic plants group(P<0.05).The average molt period of real grass group was shorter than the other two groups(P<0.05),and the plastic grass group was significantly shorter than no aquatic plants group(P<0.01).In the expression of intestinal digestive enzymes,there was no significant difference among the three groups.To sum up,in the same water environment,the effects of aquatic plants on Eriocheir sinensis were not only the significantly increase of weight gain rate and survival rate,but also short the molting period.