Multi-organ toxicity and systemic metabolic disruption underlying low-concentration broflanilide-induced developmental and cocooning defects in Bombyx mori.

The novel meta-diamide insecticide broflanilide exhibits high efficacy against diverse agricultural pests, yet its physiological impacts at low concentration on non-target lepidopterans, particularly the economically important silkworm Bombyx mori, remain poorly defined. In this study, we systematically evaluated the low-concentration toxicity (LC10: 0.038 mg/L; LC25: 0.075 mg/L) of broflanilide in the silkworm, B. mori, and elucidated the underlying molecular mechanisms through integrated histopathological, transcriptional, and metabolomic approaches. Exposure to low-concentration broflanilide, particularly at LC25, significantly reduced mulberry consumption, body weight, survival and cocooning performance, indicating a marked decline in overall fitness. Histopathological analysis revealed severe structural damage to both the silk gland and the midgut tissues. These phenotypic alterations were accompanied by dysregulated expression of core silk protein genes, apoptosis-related genes in the silk gland, and detoxification-related genes in the midgut. Furthermore, untargeted hemolymph metabolomics identified significant shifts in the abundance of L-Carnitine, L-Proline, and lysophosphatidylserine following low-concentration broflanilide exposure. Pathway enrichment analysis revealed that arginine and proline metabolism and ABC transporters were enriched among the total differentially expressed metabolites (DEMs), aminoacyl-tRNA biosynthesis among downregulated DEMs, and histidine metabolism among upregulated DEMs. These findings identify candidate physiological and molecular markers for detecting broflanilide exposure in sericulture and contribute to the ecological risk assessment of meta-diamide insecticides in agricultural landscapes.