| Eriocheir sinensis(Eriocheir sinensis),commonly known as the Chinese mitten crab,is the important feature of aquaculture species.Eriocheir sinensis in the actual production process is divided into three stages: seedling stage,a young crab breeding stage,crab breeding stage.Molt is an important physiological phenomenon of mitten crab.After hatching,the larvae of Eriocheir sinensis in the Yangtze river system need to undergo a total of 21 molt,including 5 in the seedling stage and 11 times of molting and5 times in the culture stage.The energy accumulated by food intake is an important exogenous factor for the smooth molt of the crab.At present,there have been some studies on the molting of Eriocheir sinensis,but these studies mainly focus on the growth index before and after molt or the endogenous regulatory factors such as hormones,genes and so on.However,the effect of molting on the energy demand,protein and lipid demand of the crab is rarely studied at present.According to the characteristics of each molting stage of crab,samples were collected from the hatching period of fertilized eggs to the last reproductive molt stage,using the way of pond cage culture and indoor water tank temporary culture.The changes of dry weight,energy,protein and lipid before and after molting were compared.The effects of various molting on the biochemical indexes of the crab were investigated,which supplemented the theoretical research on molt of crab,and provided more basis for nutrition management of crab culture in different stages.The content and results of the study are as follows:In the first experiment,in order to study the effect of molt on the composition and energy of larvae,from the beginning of hatching,the larvae near the molt were temporarily raised without feeding food,and the larvae before and after each molting shell were collected as samples.The dry matter content,crude protein,total lipid content and energy density of the molt shell were measured.The results showed that thedry matter content after hatching of crab larvae was significantly lower than that of eggs before hatching(p < 0.05),and decreased by 42.7% compared with that before hatching.The dry matter content after the 1st-3rd molting was significantly lower than that before the next molting(p < 0.05).The energy density and crude protein content of larvae dry samples were significantly lower than those before hatching and molting(p < 0.05),and the contents of crude protein were significantly lower than those before hatching and molt(p < 0.05).The energy density and crude protein content of the next molt in hatching to the third molt stage were significantly higher than those in the first molting stage(p < 0.05).Total lipid content of larva dry samples before and after hatching In addition,there was no significant difference in other stages(p > 0.05).The correlation between crude protein and energy density was greater between total lipid and crude protein,which indicated that the change of energy during molting of larvae was mainly influenced by protein supply.Therefore,in order to ensure the energy supply,high-quality protein should be replenished in order to promote the molting of crab seedlings.The second experiment was to study the effect of molting l on the composition and energy of one-year-old juvenile crab.The experiment used the same method to temporarily raise the juvenile crab near the molting shell.The samples of one-year-old young crab before and after molt 11 times were collected and the dry matter content was measured respectively.Crude lipid and protein content,energy density.The results showed that the dry matter content of each molt was significantly lower than that before molt(p<0.05),except before and after the fourth molt(p<0.05).The energy density before molt was significantly higher than that before molt(p<0.05),and the energy density after each molt at inter-molt interval was significantly lower than that before the next molting(p<0.05).After the first molting,the energy density decreased the most,15.9% lower than that before the molting,and the energy accumulated from the 9th molt to the next molting increased by 16.8%.The crude protein content before molting was significantly higher than that after molting(p< 0.05).The content of crude protein in each molt inter-molt was significantly lower than that before the next molt(p<0.05).Before and after the first molting,the protein content decreased the most,15.6%.The crude lipid content of juvenile crab before the first and 8th ~ 11 th molt was significantly higher than that after the molting(p<0.05).There was no significant difference in crudelipid content before and after molting(p>0.05).The content of crude lipid in the 7 ~ 11 molt inter-molt was significantly lower than that before the next molt,but there was no significant difference in the other molt intervals(p > 0.05).The crude lipid content of each molt was significantly lower than that before the next molt(p> 0.05).Before the first molting The crude lipid content before molting decreased the fastest,20.6%.The third experiment was to study the influence of molting shell on the composition and energy of juvenile crab in the culture stage of adult crab.The juvenile crab near molt(during which no feed was fed)was temporarily raised,and the samples before and after molt five times in adult crab culture stage were collected.The dry matter content,crude lipid and crude protein content and energy density were measured respectively.The results showed that the dry matter content after molt of both female and male crabs was significantly lower than that before molt(p< 0.05),except the fourth molt(p<0.05).However,there was no significant difference in dry matter content between female and male crabs at the same molt stage(p>0.05).Except the fourth molt,the energy density after molt of the female crab and the male crab was significantly lower than that before molt.Before the fifth molting,the energy density of female crab was significantly higher than that of male crab(p< 0.05),but there was no significant difference between female and male crab in other stages(p> 0.05).The crude protein content of female crab before the fifth molting was significantly higher than that of male crab(p< 0.05).There was no significant difference in crude protein content between female and male crab at other stages(p> 0.05).Except for the fourth molt,the crude protein content of male and female crab before deciduation was significantly lower than that after molting(p< 0.05).Therefore,the influence of successive molting on the energy,protein and lipid content of crab is different.The energy and nutrients accumulated during the intermolting interval are also different.In order to improve the success rate of culture,the influence of molting shell should be considered in the production process to adjust the culture strategy and feed species. |
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