Toxicity of the Herbicide Butchlor Effects on early period of postembryonic development of Toad Bufo bufo Gargarizans and Bufo naddei Strauch

The present study was undertaken to determine the 24-96h LC₅₀ of herbicide butachlor in the early period of postembryonic development for Bufo bufo Gargarizans and Bufo naddei Strauch and simultaneously observe the developmental changes caused by the toxicity of the herbicide butachlor. At first, 10-20 tadpoles of B. bufo and B.naddei in gosner20 and gosner25 were put into 5 exposure groups and 1 control group respectively, finding their LC₅₀s; then chose 60 tadpoles of B.bufo and B.naddei in gosner20 respectively, in accordance with the concentrations of 1/10, 1/100 and 1/1000 of their LC₅₀s for exposure, measuring the body length of every group for 5 tadpoles after every 3 days. From the start of exposure, we kept continuous observation on the behavior changes. The most typical symptom of tadpoles in the period of acute experiment was the change of tail swing. The LC₅₀ values of butachlor of different concentrations were found respectively. In the period of chronic exposure, the body length of B.bufo and B. naddei was affected significantly by the toxicity of the herbicide butachlor. The study shows that maybe tadpoles in the former stage of the early period of postembryonic development have greater tolerance to herbicide butachlor than the tadpoles in the latter stage; and B.naddei has greater tolerance to herbicide butachlor than B.bufo in the early period of postembryonic development.