Environmentally relevant concentrations of benzo[a]pyrene affect steroid levels and affect gonad of male scallop Chlamys farreri

• Exposure to B[a]P resulted in high accumulation in scallop spermary.
• Sex steroid levels in male gonad and sperm numbers are affected by B[a]P exposure.
• Environmentally relevant concentrations of B[a]P induced gonad impairment in scallop.

Sexually mature male Chlamys farreri were exposed to benzo[a]pyrene for 10 days at four concentrations at 0, 0.025, 0.5 and 10 μg/L. Fluctuations in sex steroids during the exposure period were observed, which indicated that sex steroids have a role in gamete development. Exposure to B[a]P altered levels of 17β-estradiol, testosterone, and progesterone. Furthermore, B[a]P treatments induced oxidative stress in a dose-dependent manner on spermary of scallop and led to delayed development and damaged spermatid in germinal epithelium of spermary. Overall, B[a]P affected the steroid levels and induced gonadal toxicity at environmentally relevant concentrations.