A proposed multigeneration protocol for Japanese medaka (Oryzias latipes) to evaluate effects of endocrine disrupters

Definitive data on reproductive impairment of chronically exposed populatio ns may be required to assess the appropriateness of the existing test metho ds for hazard identification and prioritization of endocrine modulators. Mu ltigeneration toxicity testing protocols for wildlife receptors are lacking . To help address this gap we describe a multigeneration fish assay using t he freshwater fish, Japanese medaka (Oryzias latipes). This test species ha s been used for the evaluation of carcinogenic, teratogenic and reproductiv e effects and is sensitive to estrogen exposure producing ovo-testis, alter ed biochemical parameters and phenotypic characteristics. Due to the short life cycle, a multigeneration test with medaka can be conducted in I year. Endpoints evaluated include: survival, growth, sex ratio, fecundity, embryo nic lesion occurrence, embryonic stage development, gonadal and hepatic som atic indices, histopathology and biochemical parameters. As new endpoints a re developed they can be incorporated into the protocol. Results of a posit ive control (17 beta-estradiol) study are presented to give an indication o f the baseline associated with various test endpoints and to highlight the importance of nutrition in the experimental design. 17 beta-Estradiol treat ment induced vitellogenin production in male and female medaka, feminized m ales, and disrupted egg production. The proposed protocol provides research ers with an effective multigeneration fish test that can be used to examine potential effects of stressors at the population, individual, cellular and subcellular level. (C) 1999 Elsevier Science B.V. All rights reserved.