Meeting Abstract

22.5  Thursday, Jan. 3  Yolk steroid movement early in development: Finding a familiar face in an unfamiliar place PAITZ, RT*; BOWDEN, RM; Illinois St. Univ.; Illinois St. Univ. rpaitz@ilstu.edu

Yolk steroids influence a variety of offspring traits and have been studied as a means by which females may differentially modify offspring phenotypes. While numerous studies have examined the effect on offspring, few have focused on how these effects are produced. We investigated the mechanism(s) underlying yolk steroid effects by following exogenously applied steroids as they are processed by the egg. Red-eared slider (Trachemys scripta) eggs were divided between treatments with estradiol, tritiated estradiol, or ethanol and sampled every five days through the first 15 days of development. Estradiol levels were measured in the albumen, yolk and embryo of the estradiol and ethanol treated eggs using RIAs. For the eggs treated with tritiated estradiol, liquid scintillation spectrophotometry was used to quantify radioactivity in the organic and water phases of albumen, yolk and embryo. Yolk estradiol concentrations declined through development in both the estradiol and ethanol treated eggs with the estradiol treated eggs having elevated concentrations at each sampling point. Estradiol levels in the albumen of treated eggs were lower than those in yolk, while estradiol could not be detected in the albumen of ethanol treated eggs at any point of development. However, in the tritiated estradiol treated eggs, radioactivity levels in the albumen were higher than those in the yolk. Additionally, for all three egg components, radioactivity levels in the water phase following extraction with diethyl ether were higher than those of the organic phase. Together these results indicate that estradiol is converted to a water-soluble form early in development. We propose that this conversion is responsible for the decline observed in endogenous steroid levels and may facilitate movement of steroids within the egg.