Meeting Abstract

22.4  Thursday, Jan. 3  Seasonal patterns in maternal and yolk hormones in the loggerhead sea turtles Caretta caretta ROSTAL, DC*; DAVIS, TS; PAITZ, RT; ZIMMERMAN, L; BOWDEN, R; Georgia Southern University; Georgia Southern University; Illinois State University; Illinois State University; Illinois State University Rostal@georgiasouthern.edu

A variety of functions have been suggested for yolk hormones in oviparous tetrapods. In species with temperature dependent sex determination, the role of these yolk hormones is only recently been studied. No studies to date have investigated yolk hormones in species that produce more than 2 clutches of eggs per season. This study examined the variation of maternally derived egg yolk hormones of the loggerhead sea turtle Caretta caretta within a clutch and across the nesting season. 17-estradiol (E2), testosterone (T) and progesterone (P) were measured by RIA in maternal blood plasma and egg yolk. Temperature dataloggers were placed in the nests to estimate hatchling sex ratios based upon incubation temperatures. Egg yolk estradiol and testosterone within a clutch did not vary significantly due to position, while yolk progesterone was significantly higher in eggs collected from the bottom of the egg chamber. There was an inverse relationship observed between female plasma steroid and yolk steroid levels. The ratio of E2 to T in egg yolk increased significantly as the season progressed and with higher nesting events. This differential allocation of yolk hormones corresponded with increased nesting events, higher incubation temperatures and predicted female biased hatchling ratios based on incubation temperatures. In addition to higher temperatures, late season nests also experience greater environmental fluctuations in temperature and humidity due to increased rain events and storm surges. The relationship of increased yolk steroids will discussed relative to changes in the nesting and post-hatching environment experienced across the nesting season.