Laboratory larval exposure to mixed-size polystyrene micro/nanoplastics disrupts lipid metabolism and reshapes the hemolymph metabolome and gut microbiota of adult honeybee workers.

Micro/nanoplastics are pervasive contaminants in terrestrial ecosystems, yet their developmental toxicity to pollinators remains insufficiently understood. Here, worker larvae of the honeybee (Apis mellifera) were orally exposed under controlled laboratory conditions to a mixed-size polystyrene micro/nanoplastic (PS-MNP) system containing 50 nm, 100 nm, and 5 μm particles at a 1:1:1 mass ratio across 1-500 mg/L. Survival was assessed using 48 larvae per group, and adult hemolymph metabolomics and gut microbiome analyses were conducted for adults derived from the 10 mg/L larval exposure group using six biological replicates per treatment. Larval PS-MNP exposure reduced survival, transiently increased larval body mass, and disrupted nutrient allocation, as reflected by decreased total protein and free fatty acids but increased glycogen and triglyceride. In the larval fat body, PS-MNPs induced oxidative stress and lipid droplet accumulation, accompanied by transcriptional changes consistent with enhanced lipid storage and impaired lipophagy. These developmental disturbances were followed by post-metamorphic effects. Newly emerged workers exhibited midgut injury and oxidative imbalance. Moreover, adults derived from exposed larvae displayed pronounced hemolymph metabolomic reprogramming and altered gut microbiota after colony reintroduction. More than 1200 differential hemolymph metabolites were detected, with downregulated features enriched mainly in lipid-remodeling, eicosanoid-related, and autophagy-associated pathways. The adult gut microbiota showed depletion of Gilliamella apicola and Bartonella apis and enrichment of Lactobacillus apis and Frischella perrara. Collectively, these findings show that larval-only exposure to a mixed-size PS-MNP system can disturb developmental lipid/redox homeostasis and be followed by intestinal, hemolymph metabolic, and gut microbial alterations after metamorphosis. This integrated cross-stage evidence advances understanding of micro/nanoplastic developmental ecotoxicology in beneficial terrestrial insects and provides evidence for considering developmental windows in future pollinator risk assessment.