Meeting Abstract

P3.22  Monday, Jan. 6 15:30  Characterization of yolk glucocorticoids and their metabolism during the embryonic development of the red-eared slider (Trachemys scripta) TREIDEL, LA*; PAITZ, RT; BOWDEN, RM; Illinois St. Univ.; Univ. of Illinois; Illinois St. Univ. latreid@ilstu.edu

Oviparous vertebrate eggs contain a number of steroids, including glucocorticoids, at the time of laying. During embryonic development, maternally derived glucocorticoids can act to modify the offspring’s phenotype, while embryonically produced glucocorticoids are important for hatching. The multiple roles of glucocorticoids make it likely that regulating the timing of embryonic exposure throughout development is necessary for proper offspring development and hatching. Yet, little is currently known about the mechanisms by which this occurs, especially in oviparous reptiles such as the red-eared slider (Trachemys scripta). In our first study, we characterized the changing concentrations of yolk corticosterone occurring during embryonic development. Eggs from ten clutches were sampled throughout incubation and yolk corticosterone was quantified via a radioimmunoassay. We found that while prior to the start incubation only trace amounts of corticosterone are present, late in development, yolk corticosterone levels spike. Next, to investigate the metabolism and movement of corticosterone during embryonic development, we topically applied 150,000 cpm of tritiated corticosterone to eggs. Using eggs sampled at different points in development, an ether extraction was used to separate and quantify ether soluble and water soluble metabolites in the yolk, extraembryonic fluid, and embryo. From this study we found that applied corticosterone is rapidly metabolized during development and remains as metabolites mostly in the yolk and extraembryonic fluid. Together, these two studies suggest that the glucocorticoid environment is subject to modulation prior to the embryonic production of glucocorticoids.