Effects of estrone on full life cycle of Java medaka (Oryzias javanicus), a new marine test fish.

Estrone is a natural estrogen detected in sewage treatment works effluents and in estuarine waters. However, there is little information on the effects of estrone on marine fish. This study investigated the effects of estrone on reproduction of the estuarine fish, Java medaka (Oryzias javanicus). Java medaka were exposed to concentrations of 39, 198, 484, 1,188, and 3,701 ng/L of estrone from embryonic stages up to adult stages for 239 d after hatching. The fertility and egg numbers of Java medaka exposed to 1,188 and 3,701 ng/L were significantly lower than that of control. The hepatic vitellogenin concentrations in male Java medaka exposed to estrone greater than 484 ng/L were significantly higher than that of control. Oocytes in testis (testis-ova) were not detected in the males in any of the exposure groups. The lowest-observed-effect concentration and no-observed-effect concentration for Java medaka were 484 and 198 ng/L of estrone. These results suggest that in relatively low estrone concentrations, 39 and 198 ng/L, Java medaka will not be affected by exposure to estrone.