Enantioselective toxicity of the neonicotinoid dinotefuran on honeybee (Apis mellifera) larvae

Abstract

The threat of neonicotinoids to insect pollinators, particularly honeybees (Apis mellifera), is a global concern, but the risk of chiral neonicotinoids to insect larvae remains poorly understood. In the current study, we evaluated the acute and chronic toxicity of dinotefuran enantiomers to honeybee larvae in vitro and explored the mechanism of toxicity. The results showed that the acute median lethal dose (LD50) of S-dinotefuran to honeybee larvae was 30.0 μg/larva after oral exposure for 72 h, which was more toxic than rac-dinotefuran (92.7 μg/larva) and R-dinotefuran (183.6 μg/larva). Although the acute toxicity of the three forms of dinotefuran to larvae was lower than that to adults, chronic exposure significantly reduced larval survival, larval weight, and weight of newly emerged adults. Analysis of gene expression and hormone titer indicated that dinotefuran affects larval growth and development by interfering with nutrient digestion and absorption and the molting system. Analysis of hemolymph metabolome further revealed that disturbances in the neuroactive ligand-receptor interaction pathway and energy metabolism are the key mechanisms of dinotefuran toxicity to bee larvae. In addition, melatonin and vitellogenin are used by larvae to cope with dinotefuran-induced oxidative stress. Our results contribute to a comprehensive understanding of dinotefuran damage to bees and provide new insights into the mechanism of enantioselective toxicity of insecticides to insect larvae.