Integrated toxicity of neonicotinoid Cycloxaprid in the Apis mellifera intestinal system: Oxidative damage, immune...

Bees serve as primary pollinators and sensitive indicators of environmental pollution. Cycloxaprid (CYC), a novel neonicotinoid insecticide, has been shown to exert substantial physiological effects on the olfactory systems of bees. This study further investigated the bee sensitivity to CYC, its impact on the intestinal system and the underlying mechanisms involved, using a 10-day chronic exposure at 30 μg/L. The results indicated that young bees and foragers exhibited the highest sensitivity to contact and oral exposure to CYC, respectively. Additionally, CYC significantly induced oxidative stress, detoxification, immune responses, and lipid peroxidation in bees, which ultimately led to gut tissue apoptosis. Non-targeted metabolomics revealed that CYC disrupted the metabolic balances in the midgut by reducing the abundance of Fructobacillus and Alternaria. However, changes in the composition or diversity of gut bacteria and fungi were not significant. In summary, this study demonstrated that chronic exposure to CYC impairs intestinal health in bees at both physiological and molecular levels, and highlights the need to develop new pesticides with consideration for combined risks to bees.