Enantioselective Toxicity and Multilevel Effects of the Pyrethroid Insecticide Tefluthrin on the Silkworm, Bombyx mori

Chiral pesticides often exhibit enantioselective toxicity, yet the enantiomer-specific effects of tefluthrin on silkworm (Bombyx mori) remain poorly understood. This study evaluated the toxicological impacts of racemic tefluthrin and its enantiomers, (1R,3R)- and (1S,3S)-tefluthrin, on silkworms using multilevel assays. Acute toxicity tests revealed strong enantioselectivity: (1R,3R)-tefluthrin was highly toxic (96-h LC50 = 1.27 mg/L), whereas (1S,3S)-tefluthrin showed low toxicity (LC50 > 200 mg/L). Sublethal exposure to (1R,3R)-tefluthrin and rac-tefluthrin significantly disrupted growth and reproduction, whereas (1S,3S)-tefluthrin exerted minimal effects. Histopathological and biochemical analyses showed that (1R,3R)-tefluthrin induced severe silk gland damage, DNA fragmentation, and oxidative stress, while (1S,3S)-tefluthrin had no significant impacts. Transcriptomic profiling further identified differential expression of genes associated with the p53 signaling pathway, cellular senescence, and voltage-gated sodium channels (Nav). These findings highlight the necessity of enantiomer-specific assessment in the ecological risk evaluation and rational management of chiral pesticides.