Decline in Reproductive Success, Sex Reversal, and Developmental Alterations in Japanese Medaka (Oryzias latipes) after Continuous Exposure to Octylphenol

Japanese medaka (Oryzias latipes) were continuously exposed to concentrations of 0, 2, 20, and 50 μg/L octylphenol, 0.01‰ dimethyl sulfoxide, and 100 ng/L 17β-estradiol from 2 to 4 h postfertilization until maturity. Exposure to ≥2μg/L octylphenol caused a 20–30% increase in mortality both before and after hatch. Growth was significantly decreased in fish exposed to 50 μg/L octylphenol and in the positive control. Sex ratio changed from 42:58 (females:males) in controls to 57:40 at 50 μg/L octylphenol, and 3 and 4% of the medaka exposed to 50 μg/L octylphenol and 17β-estradiol developed testes–ova. In cross-mating experiments, mating of exposed males with control females resulted in an up to 11% lower fertilization rate than in controls. Results indicate that continuous exposure to octylphenol causes a broad variety of reproductive effects, which can be correlated with the xenoestrogenic potential of octylphenol.