Meeting Abstract

S5-1.4  Friday, Jan. 4  Patterns of yolk steroid decline during incubation and potential effects on offspring in species with temperature-dependent sex determination BOWDEN, RM*; PAITZ, RT; Illinois St. Univ.; Illinois St. Univ. rmbowde@ilstu.edu

Steroids, of maternal origin, are present in the yolk of egg-laying reptiles at oviposition. Using two emydid turtle species, the painted turtle (Chrysemys picta) and the red-eared slider turtle (Trachemys scripta), we have shown that (1) yolk steroids decline in concentration throughout development, and (2) they often vary among clutches and across the nesting season. It has been suggested that maternal steroids might be integral to the process of sex determination in species with temperature-dependent sex determination, and if so could be subject to selection as any factor that effects offspring sex would be directly tied to reproductive fitness. Despite the potential for yolk steroids to influence offspring traits, there is limited information on the fate of yolk steroids during development. Recent research indicates that steroid decline can be quite rapid and the timing of this decline may have important implications for how yolk steroids might act upon the developing embryo. In this presentation, we will review the current state of knowledge regarding the effects of yolk steroids in reptiles with temperature-dependent sex determination. We will also discuss how the timing of steroid decline factors into our understanding of the importance of yolk steroids in oviparous species.