Abstract
Butylparaben（BuP）is an alkyl hydroxyl benzoate preservative that can be present in aquatic environments, where it can adversely affect the development and reproduction of aquatic organisms due to its estrogenic properties. The BuP concentrations detected in aquatic environments are generally low（ng/L levels）, but few reports have addressed their effects on fish reproduction. Therefore, we exposed mature medaka（Oryzias latipes）to mean measured BuP concentrations of 102, 218, 482, and 979 μg/L for 14 d and assessed the effects on the egg number and fertility of paired medaka during the exposure period. We also assessed vitellogenin-1（VTG-1） gene expression levels in the liver of the exposed fish. The number of eggs produced
and the fertility of the paired medaka exposed to 979 μg/L BuP were significantly reduced compared with those of the control fish. Hepatic VTG-1 levels were significantly increased in all BuP-treated males. The lowest observed effective concentrations （LOECs）of BuP for reproductive impairment（decreased fecundity and fertility）and eliciting estrogenic responses（VTG-1 expression）were 979 and < 102 μg/L, respectively. Since the environmental concentrations of BuP are at least three orders of magnitude lower than the LOEC for population-level effects, BuP alone may not affect the reproduction of wild fish populations.
