John Wiley & Sons, Ltd.

Temperature‐dependent acute toxicity of methomyl pesticide on larvae of three Asian amphibian species

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Relative to other animal taxa, ecotoxicological studies on amphibians are scarce, even though amphibians are experiencing global declines and pollution has been identified as an important threat. Agricultural lands provide important habitats for many amphibians, but often these lands are contaminated with pesticides. We determined the acute toxicity, in terms of 96‐h median lethal concentrations (LC50), of a carbamate pesticide methomyl on larvae of three Asian amphibian species, Asian common toad (Duttaphrynus melanostictus), brown treefrog (Polypedates megacephalus), and marbled pigmy frog (Microhyla pulchra) at five different temperatures (15, 20, 25, 30 and 35 °C) to examine relationships between temperature and toxicity. We found significant inter‐specific variation in methomyl sensitivity and two distinct patterns of temperature‐dependent toxicity. Because we observed high proportions of malformation among the surviving tadpoles, a further test was carried out on the treefrog to determine effect concentrations using malformation as the endpoint. Concentrations as low as 1.4% of the corresponding 96h‐LC50 at 25 °C were sufficient to cause malformation in 50% of the test population. As the toxicity of pesticides may be significantly amplified at higher temperatures, temperature effects should not be overlooked in ecotoxicological studies and derivation of safety limits in environmental risk assessment and management. This article is protected by copyright. All rights reserved

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