PAITZ, Ryan*; JANZEN, Fredric; BOWDEN, Rachel; Illinois State Univ.; Iowa State Univ.; Illinois State Univ.: Relationship between plasma and egg yolk steroid levels in the painted turtle
In species that undergo rapid egg formation (e.g., birds), steroid concentrations in plasma and those in yolk often closely match. In contrast, in species in which the process of egg formation is not rapid (e.g., turtles), the likelihood of direct correspondence between plasma steroid levels in the female and steroid levels in the yolk should be lower. For those species, yolk accumulates over a series of months and may reflect both past and present steroid levels of the female. Previous research in turtles has detected age-related differences in yolk steroid levels, indicating the possibility of ontogenetic variation in plasma levels as well. We investigated the relationship between plasma steroid levels and yolk steroid levels in multiply nesting painted turtles (Chrysemys picta) from different age classes across the nesting season. We collected plasma and eggs immediately following each nesting event. Progesterone (P), testosterone (T), and estradiol (E) were measured in the plasma and the yolk, while corticosterone (B) was measured only in the plasma. We did not detect any age-related differences in plasma or yolk steroid levels, although we did observe seasonal patterns in the yolk and plasma. Plasma levels of P and T decreased from first to second clutches. B did not vary seasonally and E was not detectable. In the yolk, P and E increased from first to second clutches while T did not vary seasonally. These data are consistent with previously reported studies of plasma and yolk steroid profiles for turtles during the nesting season, and indicate that single plasma sampling events are insufficient to determine the relationship between plasma and yolk steroid levels in species with non-rapid yolk accumulation.