Toxic Effects Of Two Amide Pedticides On Litopenaeus Vannamei

As a representative and important aquatic resource in the ocean,the Litopenaeus vannamei is closely related to our economy and the health of the people.In this study,enzymology,immunology,histrohistology,transcriptomics and gut intestinal analysis were used to investigate the acute and chronic damage of two amide pescidites,tolfenpyrad（TOL）and tebufenpyrad（TFP）,on Litopenaeus vannamei.The research further evaluated the hazards of these two pesticides within the shrimp and reflected the toxic effects of the pesticides at multiple levels.This study not only provides additional data on the current hazards of pesticides to the marine environment but also offers a reference for the safe use of pesticides.（1）In a 96-hour acute experiment,the effective concentrations of two amide insecticides were investigated.It was found that the median lethal concentrations(LC₅₀)of chlorantraniliprole and bifenazate for Litopenaeus vannamei were 106.3μg/L and 50μg/L,respectively.The chronic experimental concentrations for algae,fish,and daphnia were set based on the reported environmental residual concentrations and the Envirtoxic database’s effect scores..（2）The impact of TOL on Litopenaeus vannamei was investigated through a 42-day chronic toxicity experiment.The results showed that TOL significantly stimulated the weight gain rate of shrimp（P<0.05）,but significantly affected their survival rate.TOL caused an increase in ROS and oxidative stress in shrimp.TOL significantly reduced the Simpson index（P<0.05）and significantly increased the Shannon index（P<0.05）of the bacterial community,significantly increased the relative abundance of Proteobacteria,significantly decreased the relative abundance of Bacteroidetes,and significantly decreased the relative abundance of Actinobacteria in the 20μg/L TOL group.Through PICRUSt 2 functional prediction,it was found that compared with the control group,the biosynthesis of secondary metabolites and the metabolic pathways of gut in different environments were significantly enriched in the 40μg/L TOL group,which changed the structure and diversity of the intestinal tissue bacterial community（3）Study on the toxic effects of TFP on Litopenaeus vannamei.The chronic toxicity experiment found that low concentrations of TFP could stimulate the weight gain rate of shrimp,but the stimulating effect decreased as the concentration of TFP increased.During the exposure period,the SOD and T-AOC activities in the B group of shrimp increased significantly（P<0.05）,while no significant changes were observed in other treatment groups.After TFP treatment,there were no significant changes in the CAT activity of the shrimp.GSH activity in groups B,C,and D increased significantly（P<0.05）,while no significant changes were observed in group E.MDA levels increased significantly with concentration in all treatment groups after pyrimethanil exposure（P<0.05）.During the exposure period,the highest AST and ALT activities were observed in group E,and the activities in groups B,C,and D were significantly higher than those in the control group（P<0.05）.In addition,there was a significant effect of low concentration（group B）on ALT activity（P<0.05）.Histological sections of the hepatopancreas revealed that TFP exposure caused damage to the shrimp’s hepatic tubules,deformation of the lumen,and separation of the basement membrane.Analysis of the intestinal microbiota showed that TFP could induce changes in the richness and evenness of the gut microbiota,as well as enhance the metabolic pathway-related capabilities of the intestinal microbiota（4）After 42 days of chronic exposure to TOL and TFP of Litopenaeus vannamei,growth stimulus was occurred at 40μg/L group TOL and 50/300μg/L group TFP,respectively.Transcriptomic experiments were conducted to explore the molecular mechanism.The results showed that TOL and TFP affected energy metabolism-related circulatory systems such as TCA cycle and glycolytic related genes.In addition,TFP can also cause the involvement of genes related to detoxification in the body.In conclusion,both amide pesticides show chronic toxicity to Litopenaeus vannamei.In this study,TOL and TFP can cause acute toxicity and death to Litopenaeus vannamei,stimulate growth,reduce survival rate,cause oxidative damage,change the diversity and stability of gut flora and cause the disturbance of energy circulation system The study shows that two amide insecticides can act on Marine crustaceans through a multi-clock pathway,and their potential impacts on Marine life should not be ignored.