Toxic Effects Of Butachlor On Tadpoles Of Three Anuran Species

Butachlor is a kind of herbicides which is widely used in paddy fields in south of China. Many studies have shown that it is seriously harmful to farmland ecosystem. Rana zhenhaiensis, Bufo melanostictus and Fejervarya multistriat are widely distributed species in the south of China. They play important roles in maintaining the balance of farmland ecosystem. However, in recent years, the numbers of the three kinds of frogs are significantly reduced. This may be related to the long-term application of herbicides butachlor. Therefore Rana zhenhaiensis tadpoles, Bufo melanostictus tadpoles and Fejervarya multistriat tadpoles are chosen in my study. Exposed to Butachlor, at different times and under different concentrations, the sub-chronic toxic effects (body length and body weight) of three kinds of tadpoles were observed. Physiological activity (SOD and CAT activity, T-AOC capability), the impact of metabolism (LDH and EST isozyme) and genotoxic effects (red blood cell micronucleus and DNA damage) were also observed and detected in my study.The results are as follows:sub-chronic toxicity results show that growth and development of tadpoles were serious impacted by Butachlor. Body length and body weigh in all experimental groups are smaller than control group in different degrees. And with the increased concentration and time extension, tadpoles'growth and development are more obvious inhibited. Physiological activity results show that antioxidant systems of three kinds of tadpoles are destructed by butachlor. SOD, CAT activity and T-AOC capability of tadpoles are sensitive to butachlor, and they can be effective indicators in evaluating external contamination. Genotoxicity results show that erythrocyte micronuclei, nuclear anomalies and DNA damage were observed in three kinds of tadpoles which were exposed to butachlor. Physiological metabolism experimental results show that Butachlor changed tadpoles'zymogram of EST and LDH enzymes, affecting the metabolism of isozyme.Based on the above, toxic effects of low concentration of butachlor to Rana zhenhaiensis tadpoles, Bufo melanostictus tadpoles and Fejervarya multistriat tadpoles would be observed. Therefore, safe and reasonable use of herbicides butachlor and protecting farmland ecosystem should be done immediately. It also shows that amphibians and their larvae can be used as biological indicator for monitoring environmental pollution.