Combined effects of microplastics and flupyradifurone on gut microbiota and oxidative status of honeybees (Apis mellifera L.)

The increasing accumulation of polystyrene microplastics (PS-MPs) and the widespread use of flupyradifurone (FPF) affect honeybee health adversely. However, the combined impact of PS-MPs and FPF toxicity on honeybees remains unknown. In this study, honeybee (Apis mellifera L.) was fed with sucrose solutions containing PS-MPs (0.5 or 5 μm, 50 mg/L), FPF (4 mg/L), or their combination for 21 days under laboratory conditions. The effects of PS-MPs and FPF on honeybee physiology, gut microbiota, and stress-related enzyme activities and genes were measured. The findings showed that concurrent exposure to PS-MPs and FPF significantly reduced honeybee survival, with additive effects, decreased sucrose consumption and body weight, and devastated midgut epithelial cells. FPF was the main stressor affecting survival, while PS-MPs exerted a greater influence on body weight. Co-exposure to PS-MPs (0.5 μm) and FPF disrupted gut microbiota, significantly decreasing Lactobacillus abundance. Supplementation with Lactobacillus helsingborgensis improved honeybee survival, highlighting the protective role of gut microbiota. PS-MPs exposure, alone or combined with FPF, increased oxidative stress and decreased detoxification and immune capabilities in honeybees. These findings suggested the combined toxicity of PS-MPs and FPF on honeybees, underscoring the potential ecology risk posed by multiple stressors.