Effects Of Ammonia Nitrogen Stress On Growth,Physiological And Biochemical Properties,Gill And Hepatopancreas Gene Expression And Microstructure Of Penaeus Vannamei

The quality of aquaculture water directly affects the growth and survival of prawn,thus affecting the economic benefits of farmers.Ammonia nitrogen is the most common water quality monitoring index.The increase of ammonia nitrogen content in water refers to the increase of nitrogen in the form of free ammonia?NH₃?and ammonium ion?NH₄⁺?.The size of prawns used in this experiment is relatively large,the results of this experiment can provide some data reference for the management of shrimp farmers in the culture.This experiment involves growth,survival,physiology and biochemistry,histopathology,gene relative expression level and so on.It comprehensively explores the toxic effect of ammonia nitrogen stress on Litopenaeus vannamei.In this study,we investigated the response of shrimp to ammonia nitrogen stress from the aspects of growth,survival rate,physiology and biochemistry,damage of gill and hepatopancreas microstructure,and relative expression level of ammonia transporter and hemocyanin genes.Explore the effect of ammonia nitrogen stress on the growth and survival rate of Litopenaeus vannamei,the experimental ecological method was used to explore.The ammonia nitrogen stress concentration was set into 6 groups:control group,4mg/L,6mg/L,8mg/L,12mg/L,16mg/L,and the stress time was 20d.After 20 days,the growth rate of body length,the weight gain rate and the survival rate were measured under the conditions of different concentrations of ammonia nitrogen.Results:on the 20th day,the weight gain rate of prawn in each group decreased in turn with the increase of ammonia nitrogen concentration?P<0.05?.On the 20th day,the growth rate of prawn body length in each group decreased in turn with the increase of ammonia nitrogen concentration.On the 15th day,the survival rate of prawn in each group decreased in turn with the increase of ammonia nitrogen concentration The survival rate of prawn in each group was still significantly lower than that in the control group?P<0.05?,and the survival rate decreased with the increase of ammonia nitrogen concentration gradient.The results showed that the increase of ammonia nitrogen concentration had a great effect on the growth and survival of prawn.Explore the effects of ammonia nitrogen stress on the contents of ammonia nitrogen,urea nitrogen and hemocyanin in hemolymph of Litopenaeus vannamei,as well as the activities of Na⁺/K⁺-ATPase in gill.On the 16th,17th,18th,19th and 20th day of ammonia nitrogen stress,the contents of ammonia nitrogen,urea nitrogen,hemocyanin and Na⁺/K⁺-ATPase activity in gill were measured.With the prolongation of ammonia nitrogen stress time,ammonia nitrogen and urea nitrogen in haemolymph were significantly higher than those in the control group?P<0.05?,and the content of hemocyanin in each group was significantly lower than that in the control group?P<0.05?.The results showed that the NH₃-N in hemolymph increased first and then decreased with time,and was positively correlated with the concentration of NH₃-N.The results showed that with the increase of ammonia nitrogen content in shrimp hemolymph,part of ammonia nitrogen may be converted into urea nitrogen.The general trend of the content of hemocyanin was that all stress groups were decreased,and each group changed slightly with time.The activity of Na⁺/K⁺-ATPase in gill decreased with the increase of ammonia nitrogen concentration,indicating that the enzyme activity was inhibited,which may affect the normal exchange of ions and the osmotic regulation.Explore the effect of ammonia nitrogen stress on the relative expression level of Rh protein gene on gill and hepatopancreas hemocyanin gene of Litopenaeus vannamei.The relative expression levels of Rh protein gene and hepatopancreas hemocyanin gene on gills were measured on the 16th and 20th day of ammonia nitrogen stress.Compared with the control group,the expression of hemocyanin gene decreased significantly?P<0.05?,indicating that there was a certain correlation between ammonia nitrogen stress and the expression of hemocyanin gene.The relative expression level of Rh protein gene in gill was significantly different between the ammonia nitrogen stress group and the control group?P<0.05?.In the fourth part,in order to explore the damage of the gill and hepatopancreas microstructure of Litopenaeus vannamei under ammonia nitrogen stress,the damage of the gill and hepatopancreas microstructure was observed after 20 days of ammonia nitrogen stress.The results showed that after 20 days of ammonia nitrogen stress,the damage was serious,the gill filaments were swollen,nuclear pyknosis,local vacuolation,incomplete structure,and the gill respiratory epithelial cells were large Area falling off.The arrangement of the hepatic tubules is disordered,the boundary is fuzzy,the hepatic tubules are ruptured,the cell volume is increased,a large number of cells are disintegrated,and the lumen is enlarged.The metabolic dysfunction of hepatopancreas may lead to stress death of prawn.The gill and hepatopancreas of Litopenaeus vannamei were seriously damaged by high concentration ammonia nitrogen stress for a long time.