John Wiley & Sons, Ltd.

Deciphering mechanisms of malathion toxicity under pulse exposure of the freshwater cladoceran Daphnia magna

0
The organophosphate pesticide (OP) malathion is highly toxic to freshwater invertebrates including the cladoceran Daphnia magna, a widely used test organism in ecotoxicology. To assess whether toxic effects of malathion are driven primarily by exposure concentration or exposure duration, Daphnia magna was pulse exposed to equivalent integrated doses (duration x concentration), i.e. 3h x 16 µg/L, 24h x 2 µg/L and 48h x 1 µg/L. Following recovery periods of 3h, 24h and 48h the toxicity of malathion on different biological levels in Daphnia magna was examined by analyzing the following endpoints: survival and immobilization; enzyme activities of acetylcholinesterase (AChE), carboxylesterase (CbE), and glutathione S‐transferase (GST); and AChE gene expression. The results showed no difference in survival among equivalent integrated doses. Adverse sub‐lethal effects were driven by exposure concentration rather than pulseduration. Specifically, short pulse exposure to a high concentration of malathion resulted in more immobilized daphnids, lower AChE and CbE activities and a higher transcript level of AChE gene compared to long pulse exposure to low concentration. The expression of the AChE gene was up‐regulated, indicating a compensatory mechanism to cope with enzyme inhibition. The study shows the need for obtaining a better understanding of the processes underlying toxicity under realistic exposure scenarios, so this can be taken into account in environmental risk assessment of pesticides. This article is protected by copyright. All rights reserved

Customer comments

No comments were found for Deciphering mechanisms of malathion toxicity under pulse exposure of the freshwater cladoceran Daphnia magna. Be the first to comment!