Study On The Toxicity Of Pesticide Stress On Rana Dybowskii At The Complete Metamorphosis Stage

In recent years,with the improvement of agricultural production efficiency,the herbicide Atrazine and the insecticide Chlorpyrifos have been applied more and more widely,the mixed application of the two pesticides has gradually become dominant,and then,the compound pollution extent of pesticides to the ecological environment is intensified,the toxicological evaluation of pesticides to aquatic organisms becomes more complex.Although such pesticide play an important role in agricultural production,but the pesticide can enter water environment in many ways,Impacts on aquatic organisms,and have toxicological effects on the tadpole stage of the growth and the development of amphibians.It is attracting more and more attention to environmental protection and aquatic animal research.The research is relatively late in the field of vertebrate,and the relevant data are somewhat scarce compared with the lower invertebrate.The tadpoles of frogs need to metamorphosis to develop into larvae and adults,during this period,they have undergone drastic changes in their external and internal structures.The changes in structures such as the respiratory organs and digestive organs are more significant,especially the liver.In this paper,the tadpoles of Rana dybowskii were used as test animals to study the single and combined subchronic toxicity of atrazine and chlorpyrifos in the tadpole stage.After metamorphosis,the antioxidant functions include Superoxide dismutase(SOD),catalase(CAT),glutathione peroxide(GSH-Px),malondialdehyde(MDA),biochemical indicators including acetylcholinesterase(Ach E),carboxylesterase(Car E),glutathione-S-transferase(GSTs),histopathology,gene expression(CYP3A gene m RNA)the larvae liver were tested.The results show that:1.Both atrazine and chlorpyrifos alone and in combination lead to liver damage in the larvae of R.dybowskii after metamorphosis,hepatocytes in each treatment group appear uneven,and the changes in liver morphology may affect the physiological function of liver metabolizing toxicants.2.Both atrazine and chlorpyrifos alone and in combination lead to oxidative stress in the liver of the larvae of R.dybowskii after metamorphosis,with the increase of the concentration of atrazine,chlorpyrifos and the combined exposure,lead to a downward trend in the enzyme activities of liver SOD,CAT,and GSH-Px(P < 0.05),and the MDA content showed an upward trend(P < 0.05),and showed a dose-effect relationship.3.Both atrazine and chlorpyrifos alone and in combination lead to changes in detoxification enzymes in the liver of the larvae of R.dybowskii after metamorphosis,with the increase of the concentration of atrazine,chlorpyrifos and the combined exposure,lead to a downward trend in the activities of liver Ach E,Car E,and GSTs(P <0.05),and showed a dose-effect relationship.4.Both atrazine and chlorpyrifos alone and in combination lead to changes in CYP3 A m RNA expression in the liver of the larvae of R.dybowskii after metamorphosis,with the increase of the concentration of atrazine,chlorpyrifos and the combined exposure,as a result,the relative expression of CYP3 A m RNA in the liver showed a downward trend(P < 0.05).In summary,atrazine and chlorpyrifos alone and in combined exposure lead to histopathological damage to the liver of the larvae of R.dybowskii after metamorphosis,inhibit the activity of detoxification enzymes Ach E,Car E and GSTs in liver tissue,which induces oxidative stress,reduces the enzyme activity of SOD,CAT,and GSH-Px,increases the content of MDA,destroys the body's antioxidant defense system and scavenging free radicals,the molecular level also showed that atrazine and chlorpyrifos exposure alone and in combination could lead to the high toxicity of the larval liver of R.dybowskii after metamorphosis.In this paper,the effects of pesticide interference on the growth and development of amphibians were studied by stress on the common pesticides atrazine and chlorpyrifos during the tadpole period of R.dybowskii.It is of great significance to establish the safe concentration of pesticide in the future environment in order to provide basis for the protection of amphibians.