Biotransformation causes the sex-specific regulation of polychlorinated biphenyls during metamorphosis of silkworm (Bombyx mori) and their effect on the silkworm development.

The decline in insect populations is indisputable. Currently, the effects of persistent organic pollutants on insect populations have not been sufficiently investigated. Maternal transfer of pollutants is considered to be an inherently correct reason for sex differences in pollutant levels in oviparous organisms. Therefore, in this study, we exposed silkworms (Bombyx mori) to different levels of polychlorinated biphenyls (PCBs) to investigate their effects on silkworm development and the sex-specific regulation of PCBs during metamorphosis. PCB exposure causes disorders in amino acid, energy, nucleotide, and vitamin metabolism and induces neurotoxicity, oxidative stress, and inflammation, leading to lower larval weight, success of cocoon breaking, and egg production, and an elevated ratio of ecdysone to juvenile hormone. During the emergence process, PCBs biotransformation differed in a sex-specific manner in silkworms with a higher degree of biotransformation in females than in males as shown by the compound-specific isotope analysis, which results in lower PCB concentrations in the former. In this case, it is biotransformation rather than maternal transfer that causes the lower PCB levels in females than in males.