Test And Analysis Of Tolerance Under Ammonia Nitrogen And Nitrite From Litopenaeus Vannamei With Different Specifications

White shrimp(Litopenaeus vannamei)is an excellent prawn species in the world.It has the characteristics of high density and high meat content.It is one of the important prawn culture species in China.L.vannamei is a species imported from abroad.At present,domestic seedlings have shown signs of germplasm decline,coupled with relatively backward breeding technology,it is easy to cause excessive levels of toxic factors such as ammonia nitrogen and nitrite in the water body during intensive breeding It has an impact on the sustainable development of the domestic shrimp aquaculture industry.Therefore,it is very important to carry out genetic improvement work of L.vannamei to improve its ability to tolerate ammonia nitrogen and nitrite,and it has important value in the L.vannamei aquaculture industry.This article tested the acute toxicity and safe concentration of ammonia nitrogen and nitrite on cultured waters of L.vannamei(average body length about 1.5 cm,3.0 cm)at a water temperature of 27.0 ±1℃,pH 8.0-8.1,and salinity of 30‰.The heritability of the resistance to ammonia nitrogen and nitrite resistance of the L.vannamei family(about 1.5 cm in length,derived from the L.vannamei family constructed in the breeding room of the Yellow Sea Fisheries Research Institute in 2019)was evaluated.Analyze the correlation between the body length and weight traits of L.vannamei and the traits of tolerance to ammonia nitrogen and nitrite,and compare the breeding values of families with tolerance to ammonia nitrogen and nitrite traits in order to obtain ammonia nitrogen and nitrite All the families with higher tolerance capacity provide data reference value for breeding ammonia-resistant and nitriteresistant varieties of L.vannamei.The research results are as follows:1.Acute toxicity test results of ammonia nitrogen on L.vannamei:The non-ionic ammonia and total ammonia nitrogen on the 1.5 cm L.vannamei at 24,48,72,and 96 h Median lethal concentration(LC50)are NH3-Nm:2.08,1.82,1.77,1.58 mg/L;NH3-Nt:27.81,24.34,23.67,21.13 mg/L.The non-ionic ammonia and total ammonia nitrogen for the 3.0 cm L.vannamei.at 24,48,72,and 96 h LC50 are NH3-Nm:4.49,3.94,3.24,2.78 mg/L;NH3-Nt:60.04,52.69,43.32,37.17 mg/L.The safe concentrations of non-ionic ammonia in the 1.5 cm and 3.0 cm L.vannamei are 0.16 and 0.28 mg/L,respectively,and the safe concentrations of total ammonia nitrogen are 2.11 mg/L and 3.72 mg/L.Acute toxicity test results of nitrite on L.vannamei:24,48,72,96 h LC50 of nitrite nitrogen on L.vannamei is NO2-N:102.56,80.13,71.86,57.07 mg/L.The safe concentration of 1.5 cm L.vannamei to total nitrite nitrogen is 5.71 mg/L.The 3.0 cm L.vannamei is significantly more resistant to ammonia nitrogen than the 1.5 cm L.vannamei.The toxicity of ammonia nitrogen to L.vannamei 1.5 cm is obvious.2.Ammonia nitrogen and nitrite are used as stress conditions for 48 h LC50 concentration of L.vannamei(1.5 cm),respectively,and 1480 tails of L.vannamei(1.5 cm)in 37 families are subjected to ammonia nitrogen and nitrite resistance.According to the test,it is estimated that the ammonia-tolerant and nitrite-tolerant traits of L.vannamei are genetically related to growth traits,respectively.The results showed that the heritability of ammonia nitrogen resistance and nitrite resistance traits were 0.14±0.06 and 0.05±0.02 respectively,both of which belonged to low heritability.The estimated value of the two reached a significant level compared with 0(P<0.05).3.Correlation analysis of ammonia nitrogen tolerance of L.vannamei(1.5 cm).The genetic correlations of ammonia nitrogen tolerance traits are 0.10 and 0.04;the correlations of ammonia nitrogen tolerance phenotypes are 0.20 and 0.12;Low linear positive correlation;statistical test is not significant(P>0.05).The genetic correlations of nitrite-resistant traits are 0.27 and 0.29;the phenotypic correlations of nitrite-resistant traits were 0.36 and 0.36;the genetic correlations and phenotypic correlations are both low-degree linear positive correlations;neither are statistical tests(P>0.05).Since the genetic and phenotypic correlations of ammonia-tolerant traits and nitrite-tolerance are very small,when the selection criteria are ammonia-tolerant and nitrite-tolerant,there will not be a large indirect selection of growth traits of L.vannamei Influence.4.Comparison of the breeding value rankings of the families with ammonia-nitrogen tolerance and nitrite tolerance traits found that among the top 15 families with the same breeding value,there are 11 identical families,namely:K6,J7,I1,L3,B3,L5,13,L6,L2,L1,K7.These 11 families can be used as parental cultures,providing data reference value for breeding of ammonia-resistant and nitrite-resistant L.vannamei strains.