Boone Michelle D
Department of Zoology, 212 Pearson Hall, Miami University, Oxford, Ohio 45056, USA.
Environ Toxicol Chem. 2008 Jul;27(7):1561-8. doi: 10.1897/07-520.1.
Although aquatic communities frequently are exposed to a number of pesticides, the effects of chemical mixtures are not well understood. In two separate studies, I examined how insecticide mixtures influenced the likelihood of unpredictable, nonadditive effects on American toad (Bufo americanus) and green frog (Rana clamitans) tadpoles reared in outdoor aquatic communities. I exposed tadpoles to single or multiple insecticides at approximately half the reported median lethal concentrations using insecticides that were either acetylcholinesterase inhibitors (carbaryl or malathion) or a sodium-channel disruptor (permethrin). I found that combinations of insecticides with the same mode of action were more likely to have nonadditive effects on amphibian metamorphosis compared with those having different modes of action. Additionally, in one study, a commercial formulation of permethrin led to near-complete elimination of American toads, suggesting that this formulation could have adverse effects on aquatic communities. Many community studies exploring the ecological effects of expected environmental concentrations of pesticides have suggested that indirect effects in the food web, rather than direct effects on individual physiology, have the largest effect on amphibians. The present study indicates that direct effects of pesticides may become particularly important when insecticides with the same mode of action are present in the environment.
尽管水生生物群落经常接触多种农药，但化学混合物的影响尚未得到充分了解。在两项独立研究中，我研究了杀虫剂混合物如何影响在室外水生群落中饲养的美洲蟾蜍（Bufo americanus）和绿蛙（Rana clamitans）蝌蚪产生不可预测的非加和效应的可能性。我使用乙酰胆碱酯酶抑制剂（西维因或马拉硫磷）或钠通道破坏剂（氯菊酯），以约半数报告的半数致死浓度，将蝌蚪暴露于单一或多种杀虫剂中。我发现，与具有不同作用模式的杀虫剂组合相比，具有相同作用模式的杀虫剂组合对两栖动物变态更有可能产生非加和效应。此外，在一项研究中，氯菊酯的商业配方导致美洲蟾蜍几乎完全灭绝，这表明该配方可能对水生生物群落产生不利影响。许多探索预期环境浓度农药生态效应的群落研究表明，食物网中的间接效应而非对个体生理的直接效应，对两栖动物影响最大。本研究表明，当环境中存在具有相同作用模式的杀虫剂时，农药的直接效应可能会变得尤为重要。
