Studies On Molting,Metabolomics And Gut Microbiotas Under Different Foods And Temperatures In Chinese Mitten Crab

Chinese mitten crab?Eriocheir sinensis?,also called river crab,is an omnivorous aquatic animal,and likes to eat aquatic plants and benthic animals?snails,insect larvae?.In natural and cultural condition,aquatic plants and snails are indispensable foods.However,there is few study on the growth of these two natural foods on Chinese mitten crab,as well as on digestion and metabolism.Furthermore,the conditions and facilities for this study were also simple and weak.In this thesis,the Chinese mitten crab new variety-“River&Sea 21”was used as the experimental material,and the individual crab cultivation system-“Dragon Palace”was employed to analyze effects of feeding conditions?temperature,foods?and interference levels on molting and growth of Chinese mitten crab,and to investigate growth differences,haemolymph metabolites and gut microorganism in one molting cycle under the three food types?snails and aquatic plants,snails,aquatic plants?.The aim is to understand the physiological basis of metabolism and digestion of Chinese mitten crab fed with different natural foods.The relevant results are as follows:Part 1.Effects of different feeding conditions and interference levels on molting of Chinese mitten crabTo see the effects of different culture conditions and interfere frequency on molting of Chinese mitten crab?Eriocheir sinensis?,we used the individual crab cultivation system to analyze the differences of weight gain rates and molting intervals of Chinese mitten crab influenced by different temperatures?constant temperature and variable temperature?,feeds?aquatic grass and snail or only formula feed?and blood drawing frequency.The results showed that:molting interval was more concentrated in the constant temperature condition?28.0±1.0??than that in variable temperature condition?8:00²0:00 was28.0±1.0?;20:00ⁿext day 8:00 was 18.0±1.0??.Compared with the crabs fed with formula feed,the survival rate of crabs fed with aquatic grass and snail was 8%higher,weight gain rate was 23.44%higher and molting interval was 16.19d shorter.The interfere of drawing blood at pre-molt stage for one time significantly decreased weight gain rate,but made no significant effect on molting interval.However,the interfere of drawing blood at inter-molt stage for many times significantly decreased weight gain rate and increased molting interval,increased mortality as well.All indicated that:the temperature had no significant effect on survival rates,weight gain rates and molting intervals,but the feed significantly affected the molting of Chinese mitten crab,the interfere at pre-molt stage could make significant effect on weight gain rate,and the interfere at inter-molt stage could make significant effects on weight gain rate and molting interval.Part 2.Metabolomics analysis of Chinese mitten crab under different natural food typesNatural food?snails and aquatic grass?plays an extremely important role in the production of Chinese mitten crab.However,its metabolic and physiological function has been still unknown.This chapter analyzed the metabolomics differences under the three food types?Group A:aquatic grass and snails;Group B:aquatic grass;Group C:snails?.The results showed that group A had the best weight gain rate,group B had the worst weight gain rate.The total of 411 metabolites were detected in all groups,in which,80%was related with lipid metabolites and mainly included six categories:metabolism,organismal systems,human diseases,environmental information processing,genetic information processing and cellular processes.The total of 131 pathways was involved.The results of OPLS-DA showed that there were significant differences in metabolites between the three groups.The content of unsaturated fatty acid,riboflavin,glycine,L-carnitine,cincassiol and perfluoroundecanoic acid in group B were significantly lower than those of group A and group C?P<0.05?,but the content of vitamin D₃ and saturated fatty acid in group B were significantly higher than those of group A and group C?P<0.05?,the content of unsaturated fatty acid and riboflavin in group A were significantly higher than those of group C.This study indicated that different metabolomics existed in Chinese mitten crab under different diets.In group,the lack of animal protein and fat intake resulted in the lowest weight gain rate and survival.Part 3.Analysis of gut microbiome of Chinese mitten crab under different food typesGut microbiome are closely related to growth and development of organisms as well as immunity in animals.In order to understand the influence of different food sources on gut microbiome in Chinese mitten crab,this chapter analyzed the differences of gut microbiome under the three food types?Group A:aquatic grass and snails;Group B:aquatic grass;Group C:snails?.The results showed that the gut microbiome in Chinese mitten crab were mainly Bacteroidetes,Tenericutes,Proteobacteria and Firmicutes.Group C had the highest Shannon diversity index,followed by group A,and group B had the lowest diversity.In group B,the proportion of Proteobacteria in intestinal was significantly higher than that of group A and C?P<0.05?,while Firmicutes was lower than that of group A and C.In group C,the proportion of Sphingobacterium in intestines was significantly higher than that of group A and group B?P<0.05?.The functions analyses of Gut microbiome showed that the group A was mainly involved in protein production and cell division,the group B was mainly involved in glucose metabolism and glucose transport,and the group C was mainly involved in amino acid transport and metabolism.The present study demonstrated that gut microbiome community structure in Chinese mitten crab was strongly affected by food types,and then affected growth and molt of Chinese mitten crab.