Meeting Abstract

S2-1.6  Wednesday, Jan. 4  Effects of Developmental Exposure to Ethinyl-Estradiol on Gene Expression and Fitness of the Adult Rivulus, Kryptolebias marmoratus FARMER, J.L.; ORLANDO, E.F.*; University of Maryland, College Park; University of Maryland, College Park eorlando@umd.edu

Concern over endocrine disrupting chemicals found in the aquatic environment and evidence of altered development and reproduction of fishes has suggested a need for further research into the potential effects of these pollutants. Exposure to even low concentrations of some estrogenic compounds, like ethinyl-estradiol (EE2), is known to affect development and reproduction in several fishes. Our study was conducted to determine the effects of EE2 exposure on the reproductive system of rivulus (Kryptolebias marmoratus), a self-fertilizing, simultaneous hermaphrodite. We hypothesized that exposure to EE2 during gonadal differentiation would direct hermaphroditic gonadal development towards a female phenotype in the adult. Expression of seven genes, with known relevance to gonadal development and function (cyp19a1b, cyp19a1a, dmrt1, figα, erα, erβ, and vtg), was measured using real-time quantitative PCR, and the reproductive fitness of fish was evaluated. Gonadal gene expression for cyp19a1a, erα, and dmrt1 decreased in response to EE2 exposure. Vtg expression in the liver was unaffected; however, there was a significant decrease in cyp19a1a gene expression in the brain corresponding to increased EE2 exposure. While the EE2 treated fish showed reduced fertility and gonadal function, each treatment group contained fish that were still capable of internal fertilization; albeit with severely reduced efficiency. It is unclear if 0.1 ppm EE2 significantly affects fitness; however, 0.5 and 1.0 ppm EE2 result in a gonad with reduced testicular function and overall reduced fitness. Additionally, this study provides insight into the endocrine mechanisms regulating development and function of ovarian and testicular tissue in the same gonad.