The Comparative Study Of Toxic Effects Of A New Insecticide Spirotetramat On Xenopus Tropicalis And Bufo Bufo Gargarizans

In recent decades, pesticides improved crop produce and economic benefits, but also broughttremendous negative impact. Studies have proved that the number of amphibian populationsdramatically declined was related with pesticides pollution. In this paper, the toxic effects of Xenopustropicalis tadpoles and Bufo bufo gargarigans tadpoles exposed to a new insecticide spirotetramat wascomparatively studied by acute toxicity test, developmental toxicity, and biochemical test; the effects ofgene expression of antioxidant enzymes in Xenopus tropicalis tadpoles also examined. The results of theexperiment will enrich the toxicological research of spirotetramat acting on amphibian.Firstly, the results of acute toxicity of spirotetramat on Xenopus tropicalis tadpoles and Bufo bufogargarigans tadpoles showed that spirotetramat was moderately toxic to two kinds of tadpoles. The96hLC50were4.35mg/L and6.45mg/L, respectively. Moreover, Xenopus tropicalis tadpoles were moresensitive to spirotetramat than Bufo bufo gargarigans tadpoles.Secondly, the results of the growth toxicity showed that spirotetramat affect the growth of tadpoles.The results showed that the tadpoles’ body weight and body length were greatly affected, and thechanges of body weight than that of body length were more affected by spirotetramat. In addition, lowconcentration spirotetramat can significantly delay develpoment of Xenopus tropicalis tadpoles, theirbody lengh and weight can act as indicators for assessing the toxicity of spirotetramat.Thirdly, the Xenopus tropicalis tadpoles and Bufo bufo gargarigans tadpoles exposed tospirotetramat for the measurement of the antioxidant enzymes (SOD, CAT, and GSH-PX) activity andlipid oxidation products MDA content. The results showed spirotetramat can change antioxidant defensesystem of tadpoles in varying degrees, activate or restrain the activity of SOD, CAT, and GSH-PX,resulting in the content of MDA increased and finally cause toxic effects. The results showed that theSOD, CAT, GSH-PX activity and MDA content all can be considered good indicators as assessment ofenvironmental pollution. And the GSH-PX activity of Bufo bufo gargarigans tadpoles was the mostsensitive parameter.Finally, the impacts of gene expression of two antioxidant enzymes (SOD and CAT) of Xenopustropicalis tadpoles, which were evaluted through real-time quantitative PCR (RT-PCR) test. The resultsshowed spirotetramat can affect SOD and CAT gene expression on the Xenopus tropicalis tadpoles.Gene CAT exerts a dose-response relationship, indicating that spirotetramat can cause changes in geneexpression of antioxidant enzymes. Moreover, the changes of CAT gene expression were mostly inaccordance with those of enzyme activity, yet the SOD changes were not. The results showed CAT canserve as an effective index for toxic assessment of spirotetramat.This study discussed comparatively the toxic effects of new insecticide spirotetramat on Xenopustropicalis tadpoles and Bufo bufo gargarigans tadpoles, indicating that spirotetramat has centain toxiceffects of action, growth, physiological and biochemical on amphibian. This paper provides basic datafor toxicology studies of spirotetramat on amphibians and scientific basis for ecological risk assessment.