Meeting Abstract

S5-1.2  Saturday, Jan. 5  Early hormonal influences on temperature dependent sex determination in turtles BOWDEN, R.M.*; CLAIRARDIN, S.G.; PAITZ, R.T.; Il. St. Univ.; Il. St. Univ.; Il. St. Univ. rmbowde@ilstu.edu

In reptiles with temperature dependent sex determination (TSD), treatment with exogenous steroids, particularly estrogens, during the middle third of development have well documented effects on sex determination. Less well understood are the effects of maternal or endogenous steroids on development, despite the fact that eggs have a rich supply of maternal steroids at oviposition. Because embryos are exposed to steroids very early in development, understanding the fate of those compounds, and potential effects on development are critical to revealing the link between early exposure to steroids and steroid effects. To this end, we have been investigating embryonic metabolism of maternal steroids, how timing of exposure influences steroid effects, and more recently, the effects of endocrine disrupting compounds during early development in the red-eared slider turtle Trachemys scripta. We have found that the embryo and its associated membranes are responsible for the metabolism of maternal steroids, and that estradiol is converted to several estrogen sulfates that are present in both the yolk and albumen egg compartments. Interestingly, at least some of these sulfonated products are capable of influencing sex determination, as we have demonstrated with exogenously applied estradiol sulfate. When the endocrine disruptor Bisphenol-A is applied to eggs, the rate and end products of estrogen metabolism, and sex determination are altered. The metabolism of maternal estrogens is important to modulating the influence of steroids on development, and disruption of this process may help explain how the estrogenic effects chemicals such as Bisphenol-A are elicited.