Year of Publication

2006

Document Type

Dissertation

College

Arts and Sciences

Department

Biology

First Advisor

David French Westneat

Abstract

Yellow perch (Perca flavescens) exhibit an estrogen stimulated sexual sizedimorphism (SSD) wherein females grow faster and larger than males. In an effort togain better understanding of this phenomenon, several genes associated with sexualdevelopment, reproduction and growth were cloned, including prolactin (PRL),somatolactin (SL), insulin-like growth factor-I (IGF-Ib), the estrogen receptors (ER?? andER??a) and ovarian aromatase (CYP19A1). Real-time quantitative PCR (qPCR) assaysfor all the genes listed above, plus growth hormone (GH), were developed to measuremRNA levels in pituitary, liver and ovary.Adult fish were collected from Lake Erie in the spring (May) and autumn(October) over two years and tissue mRNA levels, body weight, age, gonadasomaticindex (GSI) and hepatasomatic index (HSI) were determined. Sex-specific differencesincluded females having higher body weights, HSI and liver ER?? mRNA levels thanmales and males having higher liver ER??a and liver CYP19A1 mRNA levels thanfemales. Season had a significant effect on growth factors (GH and IGF-Ib), with highermRNA levels in spring, which corresponded with higher liver CYP19A1 mRNA levels.Ovary CYP19A1 mRNA levels, which were higher in autumn, had a significant negativecorrelation with GH and IGF-Ib mRNA levels and liver ER??a mRNA levels had asignificant positive correlation with IGF-Ib mRNA levels.A brood of juvenile yellow perch was sampled through the first year ofdevelopment up to 421 days post-hatching (dph). There was a significant effect of dphon body weight, GH, PRL, SL, IGF-Ib, liver ER??, liver ER??a and ovary CYP19A1mRNA levels. Only liver ER??a mRNA had a significant effect of sex and exhibitedsignificant differences between males and females at 379 and 421 days post-hatching(dph). This work on yellow perch can provide predictive capabilities for estrogendependentphysiological processes in other species, especially teleosts, and can also makeyellow perch an exciting option for future ecotoxicogenomic studies.

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