| Litopenaeus vannamei,commonly known as white-leg shrimp,belongs to Arthropoda,Crustacea,Decapoda,Penaeidae,Litopenaeus,which is one of the main shrimp culture species in China,has a certain tolerance to high carbonate alkalinity and is one of the main farming species in saline-alkaline water.In order to explore the effects of carbonate alkalinity stress on the survival and growth traits of different families of Litopenaeus vannamei,growth experiments were conducted on L.vannamei in normal alkalinity water and high carbonate alkalinity water,respectively.In this paper,individual physiology and molecular biology experimental methods were used to study growth performance of Litopenaeus vannamei,in low-alkalinity control group(LSW)and a high-alkali stress group(AW,p H of 9.2,salinity of 6,and carbonate alkalinity of 10 mmol/L).The main results are as follows:1.96 h high alkaline stress experiment was conducted to compare the alkaline tolerance of shrimps of selected G10 and G11 generations.And the families with better alkaline tolerance were selected to carry out a 42-day growth experiment.The results showed that in the 96h survival rate of the G10 family in AW group was between 16.2%and 87.5%.The daily weight gain of the LSW group was higher than that of the AW group,and the average daily weight gain of LSW groups of 10002 and10010 families were significantly higher than that of the high alkalinity stress group(P<0.05).In the AW group,the 10002 and 10010 families had better growth performance,their specific growth rates were 1.69%and 1.74%,and their survival rates were 60.42%and 54.17%.The 10012 and 10014 families had poor growth performance,their specific growth rates were only 0.58%and 0.62%.2.In order to study the changes of hemolymph ammonia and the regulation of osmotic pressure of different families of Litopenaeus vannamei under high-alkalinity environment,the high-alkalinity-sensitive families and high-alkalinity-tolerant families selected from G10 and G11 generations were measured under high-alkaline stress for 24h.The results showed that the hemolymph ammonia concentration of G10and G11 sensitive families was significantly higher than that before stress exposure(P<0.05).The recovery degree of hemolymph ammonia was significantly higher than that of the sensitive family shrimp(P<0.05).The serum osmotic pressure of the tested 8 families after 24 hours of alkaline water stress was not significantly different from that before stress exposure(P>0.05).3.In order to explore the response mechanism of the high-alkaline-sensitive family(10014),L vannamei was exposed to LSW and AW for 42d,and intestinal and gill tissues were sampled for gene expression analysis.Transcriptome sequencing is performed on the Illumina platform,and quantitative PCR verification is performed.The results showed that 243 co-differently expressed genes were screened by the gene differential expression analysis of the two tissues,of which 98 were up-regulated and145 were down-regulated.The differently expressed genes in the gut were mainly concentrated in the pathways of glucose metabolism,carbohydrate digestion and absorption,bile secretion,ABC transmembrane transport,and tight junction.The differently expressed genes in gills were mainly concentrated in the pathways of glutathione metabolism,bicarbonate transport,arginine synthesis,sugar metabolism and ion transport.The 10 most significant differently expressed genes were further verified by q PCR.It was found that carbonic anhydrase(CA1,CA10),ecdysone-inducible protein(Eip74EF),β-galactosyltransferase(UGT8)genes in shrimp gills were down-regulated,while Na~+/K~+-ATPase-α(NKA-α),Na~+/K~+Transporting ATPase Interacting(NKAIN),ammonia transporter rhb type(rhbg),and malate dehydrogenase(MDH)were up-regulated,which were consistent with the trend of transcriptome expression.L vannamei showed relatively strong high-alkaline tolerance,which may compensate for alkalosis in vivo by down-regulating the expression of CA in gills,up-regulating Rh ammonia transporter to prevent ammonia accumulation in the body,and up-regulating NKA-related genes to maintain osmotic balance in vivo;The ecdysone function was affected,as manifested by a marked down regulation of ecdysone-inducible protein(Eip74EF).4.The selection index method was used to establish 25 families based on screen5 selected families from the G10 generation,which were raised for 6 weeks and evaluated for 96h high alkaline tolerance and growth performance.The results showed that the heritability of growth traits in G11 generation was 0.37±0.15,and both were significant(P<0.05),and the heritability of survival rate was 0.045±0.018,which was not significant(P>0.05).The correlation coefficient between body weight traits and survival rate traits was 0.39,showing a very significant correlation(P<0.01).It indicated that the effect of genetic improvement of growth traits in G11 generation was significant. |
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