Study On The Effects Of Alkaline Stress On The Alkali Resistance Of Hybrids Of Leuciscus Argentatus And Their Parent

In this study,the average body weight of 3-month-old juvenile Leuciscus waleckii was（12.3±1.34g）and the average body weight of tall juvenile Leuciscus idus was（17.1±0.05 g）.The effects of alkalinity of sodium bicarbonate（NaHCO₃）with different concentration gradients on the toxicity of Leuciscus waleckii,Leuciscus idus and"Ya long yu"were analyzed.The results showed that,By using probability unit method and linear regression method,the LC₅₀of half lethal concentration for 12,24,48,72 and 96 h were 144.40,138.25,131.43,130.64 and 126.71,respectively mmol·L^-1 and 114.80,109.15,103.99,103.28,90.86 mmol·L^-1,The semi-lethal concentration LC₅₀ for Leuciscus idus was 89.46,78.13,72.11,68.25,68.25 mmol·L^-1 and 73.09,67.64,65.33,61.63,61.63 mmol·L^-1.The safe concentrations（SC）were 35.63 mmol·L^-1 and 28.32mmol·L^-1 and 18.43 mmol·L^-1 and 18.28 mmol·L^-1,The semi-lethal concentration LC₅₀of"Ya long yu"was 124.87,103.39,91.10,82.34,73.81mmol·L^-1 and 117.33,87.42,77.51,71.07,64.54 mmol·L^-1,respectively.Safe concentrations（SC）were 21.31 mmol·L^-1 and 18.28 mmol·L^-1,respectively.respectively.The LC₅₀ value calculated by linear regression method is lower than that of the probability unit method.In conclusion,Leuciscus waleckii,Leuciscus idus and"Ya long yu"have strong salt-alkali tolerance characteristics,and are excellent germplasm of medium alkalinity(10～30 mmol·L^-1)carbonate salt-alkali water-enhanced culture.In order to comprehensively evaluate the alkali-resistance of a new hybrid variety"Ya long yu",which takes"Ya long yu"of the Naoer Lake in Inner Mongolia as the mother and"Ya long yu"of the Erqisi River in Xinjiang as the father,the body mass of 180 Leuciscus waleckii,Leuciscus idus of the Erqisi River and their hybrids were first measured.The tolerance test was conducted at50 mmol/L sodium bicarbonate（NaHCO₃）alkaline water for 7 days.From the perspective of blood physiology:The activities of blood ammonia（Amon）,blood urea nitrogen（BUN）,alkaline phosphatase（AKP）,glutamate dehydrogenase（GDH）,glutamine synthetase（GS）and sodium-potassium ATP（NKA）in branchial tissue of Leuciscus waleckii,Leuciscus idus and the new hybrid""Ya long yu""under carbonate alkalinity stress were determined.From the perspective of gene expression,the relative mRNA expression levels of AKP,GDH,GS,NKα1-like,NKα3,RHBG and RHCG1 in the gill tissues of Leuciscus waleckii,Leuciscus idus and the new hybrid variety"Ya long yu"under carbonate alkalinity stress were determined.From the perspective of protein:Under carbonate alkalinity stress,the branchial tissues of Leuciscus waleckii,Leuciscus idus and the new hybrid"Ya long yu"were stained with immunofluorescence to see the localization results of NKA,RHBG and RHCG1.The results showed that the trend of enzyme activity in serum was consistent with the trend of relative expression levels of each gene in branchial tissue,showing an up-regulation trend.The activity of enzyme and relative expression levels of mRNA of hybrid were between male and female except that the content of GS was slightly lower than that of male and female.In immunofluorescence staining,NKA was located in the same position as RHBG and RHCG1 at the base of branchial lamella.To sum up,the results showed that the hybrids inherited better genes from the parents,which could provide better economic effects for aquaculture in the future.