Study On Keeping Procambarus Clarkia Alive Under Water At Low Temperature Dormancy

In this paper,Procambarus clarkii was used as the research object.By studying the effects of cooling rate,dormancy temperature,heating rate and other factors on the survival rate and recovery rate of Procambarus clarkii,the single factor test was used to establish the indoor low temperature dormancy of Procambarus clarkii.The changes of muscle quality and nutrition of Procambarus clarkii under indoor low temperature dormancy and water preservation conditions were studied,and the effects of low temperature dormancy and water preservation on body weight,immunity,antioxidant function and HSP70 gene expression were explored.According to the behavior characteristics of Procambarus clarkii in indoor water environment at different temperatures,the critical dormancy temperature,critical death temperature and ecological ice temperature range of Procambarus clarkii in this environment were obtained : the critical dormancy temperature of Procambarus clarkii was 7 ℃;the critical death temperature of Procambarus clarkii was 0 ℃.The ecological ice temperature range of Procambarus clarkii is 0 ℃ ～ 7 ℃.Then,different single factor experiments were designed : the cooling rate was 2 ℃ / h,3 ℃ / h and 4 ℃ / h,the heating rate was 2 ℃ / h,3 ℃ / h and 4 ℃ / h,and the dormancy temperature was 1 ℃,3 ℃,5 ℃ and 7 ℃.According to the results of single factor test,it was found that the process conditions for keeping the crayfish alive in the low temperature dormancy room were as follows : the initial temperature was 25 ℃,and the water temperature was reduced from 25 ℃ to 5 ℃ with a cooling rate of2 ℃ / h to induce the crayfish to sleep,and then placed in a 5 ℃ incubator to keep alive,and the water temperature was raised to 25 ℃ with a heating rate of 2 ℃ / h to induce the crayfish to recover.Under this condition,the cumulative survival rate of crayfish for 60 days was 70.50 %,and the recovery rate was 96.67 %.By comparing the muscle quality of Procambarus clarkii resting for 0 d and 60 d,it was found that although the water holding capacity and p H of the muscle decreased slightly and the cooking loss rate increased slightly after 60 days of dormancy,there was no significant change compared with the fresh group.In terms of muscle texture,there was no significant change in the elasticity,adhesion,gumminess and chewiness of the muscle after 60 days of dormancy,but the hardness and recovery of the muscle were significantly reduced,indicating that under the condition of low temperature and water,the temperature mutation in the early stage of low temperature dormancy caused a certain stress response.After low temperature dormancy and water retention,the amino acid content of Procambarus clarkii changed,the glutamic acid,aspartic acid and glycine in the muscle decreased slightly,the alanine increased slightly,the total amount of umami amino acids and essential amino acids increased slightly,indicating that low temperature dormancy and water retention had limited effect on the flavor and nutritional value of Procambarus clarkii muscle.The content of essential amino acids such as isoleucine,leucine,lysine,phenylalanine,threonine and valine increased significantly,while the content of non-essential amino acids such as serine,proline,tryptophan and glutamine also increased significantly.Procambarus clarkii resists low temperature by adjusting the composition and content of essential amino acids during dormancy,and improves its antioxidant and immune ability by adjusting the content of nonessential amino acids such as proline,tryptophan,serine and glutamine.By studying the changes of body weight,ACP activity,AKP activity,SOD activity and MDA content of Procambarus clarkii under different dormancy temperatures,it was found that in the process of low temperature dormancy and water retention,in order to resist the adverse effects of various environmental stresses,the body of Procambarus clarkii will produce energy metabolism reaction to maintain steady state,which is manifested in the decrease of body weight,condition factor,hepatosomatic index and meat yield to varying degrees.The meat yield of each temperature group decreased significantly after 60 days of dormancy,while the other indicators did not change significantly.There were no significant differences in body weight,condition factor,hepatosomatic index and meat yield among different temperature groups.The activities of ACP and SOD in serum and hepatopancreas of Procambarus clarkii showed a trend of increasing first and then decreasing,while the changes of AKP activity were different among different temperature groups,and the changes of MDA activity were different among different tissues.Low temperature dormancy and water preservation will enhance the antioxidant and immune ability of Procambarus clarkii serum and hepatopancreas tissue,thus enhancing the survival ability of Procambarus clarkii during low temperature dormancy and water preservation,but with the extension of dormancy time,its antioxidant and immune ability is also weakened.The expression of HSP70 gene in hepatopancreas of Procambarus clarkii was significantly lower than that before dormancy,but it was affected by low temperature stress.With the prolongation of dormancy time,the expression level of HSP70 gene in hepatopancreas of Procambarus clarkii in each temperature group had a high degree of synchronization,showing a trend of decreasing first,then increasing and then decreasing.This indicates that the extension of dormancy time has an increasing impact on the crayfish.The immune and antioxidant capacity of crayfish is gradually reduced,and the function of reducing reactive oxygen species in cells is gradually weakened.