The Study Of Toxicological Impacts Of Three Kinds Of Pesticides On Tadpoles Of Four Anuran Species

In this study, we chose tadpoles of four anuran species--Hylarana guentheri, Polypedates megacephalus, Bufo melanostictus and Bufo gargarizans as the research objects. Acute toxicity, sub-chronic toxicity, physiological toxicity and genetic toxicity of three kinds of pesticides, Emamectin benzoate, Beta cypermethrin and Paraquat were studied adopting common determination technique of aquatic biological toxicity. So that to reveal the toxic impact of these three pesticides on farmland tadpoles, to provide scientific bases for protecting the amphibians and setting up an environmental monitoring system of aquatic ecosystem that takes the amphibian as an indicator.The result of acute toxic tests showed that Emamectin benzoate was highly-toxic level to tadpoles of Bufo melanostictus and Bufo gargarizans, the LC50in96h is124.3μg/L and546.5μg/L; Beta cypermethrin was hyperoxic to tadpoles of Hylarana guentheri, Polypedates megacephalus and Bufo melanostictus, while it was medium-toxic to tadpoles of Bufo gargarizans, the LC50in96h in order is0.734μg/L,0.137μg/L,20.84μg/L and1079μg/L; Paraquat was medium-toxic to tadpoles of Polypedates megacephalus and Bufo melanostictus, the LC50in96h is1207μg/L and2035μg/L.The result of sub-chronic toxic test showed that the enhanced body weights and lengths of Polypedates megacephalus and Bufo gargarizans tadpoles was restrained by Beta cypermethrin to a certain extent, and the inhibition was dose-dependent. The longer was the toxic time, the significant difference induced by the lower Beta cypermethrin concentration was found.The impacts of Beta cypermethrin on LDH and EST isoenzymes of Polypedates megacephalus tadpole tissues were studied. The activity of LDH was activated at first, then recovered to normal level, at the same time, part bands lost; The activity of EST was inhibited, the Rf of bands changed. The activation effect of low concentration Beta cypermethrin to CAT, T-AOC and GSH activity of three kinds of tadpoles were obvious, while the inhibitory effect of high concentration Beta cypermethrin to those enzymatic activity were obvious. Follow the increase of toxic time, the Beta cypermethrin could reduce those enzymatic activity, and the the peak value was advanced. Micronuclear Test result showed that Emamectin benzoate had strong induction effect on the micronuclei and nuclear anomalies in erythocytes of Bufo melanostictus and Bufo gargarizans tadpoles, the same as Beta cypermethrin on Polypedates megacephalus tadpoles. The micronuclei and nuclear anomalies in erythocytes of Bufo melanostictus and Bufo gargarizans tadpoles could be improved by increment of Emamectin Benzoate concentration and prolongation of the exposed time. After exposed to Beta Cypermethrin, it was found that the micronuclei and nuclear anomalies in erythocytes of Polypedates megacephalus tadpoles presented the trend of first increase then decrease with the increase of the exposed time.Single cell gel-electricity (SCGE) was used to study the effect of DNA damage induct by Beta cypermethrin on erythocytes of Polypedates megacephalus tadpoles. With the concentration increasing, the damaged degree of erythrocyte DNA increase gradually. In statistic sense, significant linear relationships between the rate of tailing cell and Beta Cypermethrin concentration, the same as between the damaged degree of erythrocyte DNA and Beta Cypermethrin concentration.