Field‐dose fenitrothion impairs gut function and survival in the bumble bees ( Bombus terrestris )

BACKGROUND Fenitrothion is a widely used insecticide, yet its effects on the health of bumble bees ( Bombus terrestris ) have not been reported until now. We carried out experiments to investigate the impact of field‐realistic concentrations of fenitrothion on food consumption, body weight, survival probability, gut structure, gut detoxification enzyme activity, gut microbial diversity, gut transcriptional and gut metabolic profiles of Bombus terrestris . RESULTS Exposure to 500 μg kg −1 fenitrothion significantly reduced survival probability, induced gut damage as evidenced by hematoxylin and eosin staining, decreased cytochrome P450 (P450) activity while increasing glutathione S‐transferase (GST) activity, and down‐regulated AChE1 expression in gut tissue. Furthermore, 16S rRNA sequencing revealed a decline in gut microbial diversity, while transcriptomic and metabolomic analyses indicated disruptions in gut gene and metabolic expression. Molecular docking revealed that fenitrothion binds within a hydrophobic pocket formed by residues Trp148, Ser186, Tyr185, and Gly182 of the AChE1 protein. CONCLUSION These multiple sublethal alterations in bee behavior and physiology indicate that fenitrothion is likely to exert complex yet detrimental effects on Bombus terrestris health under field conditions.