BOWDEN, RM*; EWERT, MA; NELSON, CE: Variation in Yolk Hormones in Follicles of the Painted Turtle

Maternally derived yolk hormone levels vary seasonally in the painted turtle, Chrysemys picta, and this variation is correlated with offspring sex ratios in the laboratory. We examined variation in the concentration of three steroid hormones in three follicle size classes both within a female at one point during the nesting season and among females across the nesting season. Female C. picta were collected at four points that encompassed the entire nesting season. Follicles and shelled eggs were harvested for hormone analysis. We found that progesterone levels did not vary across the nesting season, and that recently ovulated follicles (in shelled eggs) had significantly more progesterone than unovulated follicles. Testosterone concentrations were low and did not vary either among size classes or seasonally. Larger follicles had lower estradiol concentrations, but total estradiol levels increased across the nesting season. We conclude that hormone concentrations vary among follicles, that the pattern varies among hormones, and that the variation in the distribution of these maternally derived yolk hormones may have implications for offspring sex determination. Preliminary data will also be presented from a longitudinal study of seasonal yolk hormone variation within individual females.