Effects of nonylphenol on the gonadal differentiation of the hermaphroditic fish, Rivulus marmoratus

Nonylphenol (NP) is an estrogenic degradation product of alkylphenol polyethoxylate surfactants. In this study, the effects of NP on gonadal differentiation and development in Rivulus marmoratus (Osteichthyes, Cyprinodontiformes), a self-fertilizing, hermaphroditic species, were examined. Starting at hatching, fish were exposed to 150 or 300 mug l(-1) NP (nominal concentrations) in a static system with daily renewal. The measured concentration of NP in the test water decreased rapidly; half-life was 8.0 h. After 60 d of exposure to NP, fish were kept in uncontaminated water for 20 d and were then preserved for histological examination. No fish exposed to 300 mug l(-1) NP (N = 8) and only two of nine fish exposed to 150 mug l(-1) NP developed testicular tissue, compared with nine of 13 water-control fish and five of nine solvent-control fish. Oogenesis was also significantly inhibited by NP. None of the fish exposed to 300 mug l(-1) and only two of nine fish exposed to 150 mug l(-1) NP had vitellogenic oocytes, compared with seven of 11 water-control fish (not including males) and six of nine solvent-control fish. Dysplasia of the gonadal lumen also occurred in fish exposed to 300 mug l(-1) NP. These changes, including testicular agenesis, have not been previously reported in fish exposed to NP. (C) 2002 Elsevier Science B.V. All rights reserved.