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

Ngoc Lâm Trác, Ole Andersen, Annemette Palmqvist

Publikation: Bidrag til tidsskriftTidsskriftartikelpeer review

Abstract

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, D. magna was pulse exposed to equivalent integrated doses (durationconcentration): 3 h16mg/L, 24 h2mg/L, and 48 h1mg/L. After recovery periods of 3 h, 24 h, and 48 h, the toxicity of malathion on different biological levels in D. 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 sublethal effects were driven by exposure concentration rather than pulse duration. 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 ofAChE gene compared with 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. Environ Toxicol Chem 2016;35:394–404.
OriginalsprogEngelsk
TidsskriftEnvironmental Toxicology and Chemistry
Vol/bind35
Udgave nummer2
Sider (fra-til)394-404
Antal sider11
ISSN0730-7268
DOI
StatusUdgivet - 2016

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