Mechanism of Low-Concentration Chlorantraniliprole Exposure Defects and Molting in Bombyx mori Larvae Based on Ca²⁺...

Chlorantraniliprole (CAP), a novel anthranilic diamide insecticide, has been extensively used in agricultural pest management. Given their environmental persistence, low-concentration CAP residues warrant a systematic assessment of their safety risks. The silkworm (Bombyx mori) is the lepidopteran model insect. This study was conducted to characterize the changes in Ca²⁺ levels and the expression of the molting-related gene Ftz-f1 in the midgut of fourth-instar B. mori after exposure to low-concentration CAP at different time intervals (CAP 0-24 h, CAP 24-48 h, and CAP 48-72 h). Low-concentration CAP exposure significantly reduced the molting rate of fourth-instar silkworms in the CAP-exposed groups to 97%, 92%, and 80% of the control group, respectively (p < 0.001), and the percentage proportion of newly molted fifth instar in the CAP-treated groups to 92%, 82%, and 67% of the control group, respectively (p < 0.001). CAP exposure disrupts intracellular Ca²⁺ homeostasis and induces dysregulation in the transcription of Ca²⁺-regulating genes, consequently suppressing both transcription and protein expression of the molting target gene Ftz-f1, which ultimately leads to molting defects in silkworms. The present study reveals the molecular mechanism of the impaired molting of fourth-instar molting defects caused by low-concentration CAP exposure, which provides critical evidence for the safety evaluation of low-concentration CAP residues and the sublethal toxicity to the lepidopteran insect.