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EVALUATION OF METHOXYCHLOR AS AN ENDOCRINE DISRUPTOR IN FATHEAD MINNOWS (PIMEPHALES PROMELAS)
Citation:
Jensen, K M., M D. Kahl, J J. Korte, E A. Makynen, G W. Holcombe, AND G T. Ankley. EVALUATION OF METHOXYCHLOR AS AN ENDOCRINE DISRUPTOR IN FATHEAD MINNOWS (PIMEPHALES PROMELAS). Presented at 16th Annual Sigma Xi Scientific Poster Exhibition, Univ. of Minnesota-Duluth, Duluth, MN, Feb. 21-25, 2000.
Description:
Recent concerns over the possible effects of endocrine-disrupting chemicals (EDCs) on humans and wildlife has resulted in considerable interest in environmental contaminants that adversely affect aspects of sexual reproduction and early development. The U.S. Environmental Protection Agency (EPA) is required to develop, validate, and implement a screening program for identifying potential EDCs. An advisory troup to EPA (EDSTAC) recommended a suite of screening-level assays, including a short-term in vivo fish assay, to help comply with this mandate. To evaluate the utility of the proposed screening assay to detect potential endocrine disruption in fish, reproductively-active fathead minnows were exposed to the insecticide, methoxychlor, which exhibits weak estrogenic properties in other vertebrate models. Spawning fish were continuously exposed to aqueous concentrations of 0, 0.55, or 3.55 ng methoxychlor/ml for 21-d. Endpoints assessed included plasma sex steroid concentrations , vitellogenin, gonadalsomatic indices (GSIs), gonad histology, secondary sex characteristics, fecundity, and larval survival. Whole body residues of methoxychlor and metabolites were also determined in the parental fish. Preliminary results indicate that exposure to methoxychlor caused both a dose-dependent vitellogenin induction in the male fathead minnow, gonad histopathology, and a marked decrease in egg production. GSI was not significantly affected. This study provides insights into the application of the recommended screening assay and evaluation of various reproductive endpoints for assessing the effects of EDCs in fish.