Meeting Abstract
Reptiles with temperature-dependent sex determination (TSD) may be particularly susceptible to rapid climatic changes, which underscores the importance of investigating environmental and maternal effects on TSD. Numerous studies have demonstrated that estrogens can alter how temperature influences sex determination, such that the incubation temperature required to produce females is altered when exogenous estrogens are applied to the egg. Unfortunately, this phenomenon is almost exclusively studied using supraphysiological doses of estrogens and unnatural constant incubation temperatures. We used the red-eared slider turtle (Trachemys scripta) to examine how natural variation in yolk estrogens (estrogen levels are higher in late-season clutches) influences sex determination under more natural fluctuating incubation temperatures. First, we tested if the effect of temperature on sex determination changed across the nesting season when using fluctuating incubation temperatures. Eggs were incubated at one of three ecologically relevant regimes: 28.0±3, 28.5±3, 29.0±3, or at a constant 29.2 ˚C. Secondly, we tested if the seasonal increase in yolk estrogens is capable of altering the effect of incubation temperature on sex determination. We collected early season clutches and dosed eggs with either a sham (5 µl 70% ethanol) or a mixed estrogen dose (20 ng estradiol + 77.5 ng estrone sulfate/5 µl 70% ethanol), which simulated the seasonal increase in the yolk estrogens. Results from these studies will inform whether variation in yolk estrogens alters how temperature influences sex determination under more natural conditions, thereby providing a mechanistic approach to predicating how reptile species may respond to climatic changes.
