Effects of neonicotinoid exposure on molecular and physiological indicators of honey bee immunocompetence
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Bee declines have been associated with various stressors including pesticides and pathogens. We separately exposed immune-challenged adult worker honey bees (Apis mellifera L.) to two neonicotinoid pesticides, thiamethoxam (10 ppb) and imidacloprid (102 ppb), by dietary delivery. We found that whereas neonicotinoid exposure weakly affected transcriptional responses of antimicrobial genes, it did not detectably affect the physiological antimicrobial response as measured by a lytic clearance assay of haemolymph. Our findings add to the evidence that transcriptional responses in immune-related genes are not yet reliable indicators of pesticide impacts on bee health, which suggests caution in their future use as biomarkers in pesticide risk assessment.
Keywordsimidacloprid thiamethoxam immunocompetence antimicrobial peptide gene expression
E.J.C was funded by a joint University of Exeter-Fera studentship. We thank Ben Jones and Joy Kaye for assistance in setting up enzymatic and molecular assays, respectively. We gratefully acknowledge the laboratory support from numerous staff and students in the NBU and CCSS at Fera, York.
All authors conceived and designed experiments; EJC performed experiments and analysis; EJC wrote the paper and all authors participated in the revisions of it and approved the final manuscript.
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