Comparison of ethinylestradiol and nonylphenol effects on reproduction of Chinese rare minnows (Gobiocypris rarus).

Breeding pairs of rare minnows were exposed to 5, 10, 20 microg/L 4-nonylphenol (NP) or 4 ng/L 17alpha-ethinylestradiol (EE(2)) for 21 days. Among reproductive parameters investigated, fecundity, fertility, and laying interval were significantly affected by 4 ng/L EE(2), but were not affected at any exposure level of NP. These effects coincided with male feminization, ova-testis, increased plasma VTG in both males and females as well as the accumulation of eosinophilic material in kidneys and livers. Histopathologic evaluation revealed severe kidney lesions in both EE(2) and NP-exposed fish. The bioassay succeeded in demonstrating that EE(2) was several orders of magnitude more potent than the industrial chemical NP. The rare minnow was more sensitive to EE(2) than medaka, but comparable to zebrafish in terms of sensitivity. The results of the present investigation indicated that a short-term reproductive bioassay is feasible using the Chinese rare minnow as the test species.