Abstract
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•Honey bees were exposed to mixtures of OP insecticides at field-relevant concentrations.•There were no adverse effects on bee survival or behavior.•Genes involved in detoxification were generally not affected exposure to OP mixtures.
We assessed whether exposure to environmentally-relevant mixtures of four organophosphorus insecticides (OPs) exerted adverse effects on honey bees. Adult and worker bees were orally exposed for five days under laboratory conditions to mixtures of four insecticides, diazinon, malathion, profenofos and chlorpyrifos at two concentrations. Concentration in the mixtures tested were equivalent to the median and 95th centile concentrations of the OPs in honey, as reported in the literature. Effects on survival, behavior, activity of acetylcholinesterase (AChE), and expression of genes important in detoxification of xenobiotics and immune response were examined. Survival of worker bees was not affected by exposure to median or 95th centile concentrations of the OPs. Activity of AChE was significantly greater in worker bees exposed to the 95th centile concentration mixture of OPs compared to the median concentration mixture. Expression of genes involved in detoxification of xenobiotics was not affected by treatment, but the abundance of transcripts of the antimicrobial peptide hymenoptaecin was significantly greater in worker honey bees exposed to the median concentration mixture. Results suggest that short-term exposure to environmentally relevant concentrations of a mixture of OPs do not adversely affect worker honey bees.