Meeting Abstract
S10-3 Monday, Jan. 7 09:00 – 09:30 The devil is in the details: natural variation in maternal estrogens and temperature are key to understanding TSD CARTER, AW*; PAITZ, RT; BOWDEN, RM; U Tennessee; Illinois St U; Illinois St U acarte82@utk.edu
Our understanding of biological processes is often based on studies using simplified treatments, like constant temperatures, but incorporating a higher degree of realism in treatment design is crucial to deciphering how biological processes operate in nature. This need is exemplified by ongoing research in temperature-dependent sex determination (TSD), where there is a disconnect between sex ratios produced in the lab and the field. Specifically, lab incubation studies using constant temperatures or consistent diurnal fluctuations do not explain how females are produced under cool field temperatures. We explored how exposing embryos to varying durations of increased temperatures (e.g. heat waves) affect sex determination in Trachemys scripta to help resolve this disparity. Embryos are exceedingly sensitive to heat waves; a 50:50 sex ratio is produced in as few as ~8 heat-wave days (at 29.5 ± 3°C). Surprisingly, if baseline temperatures are dropped from 27± 3°C to 25 ± 3°C, the heat wave duration needed to trigger a 50:50 sex ratio changes minimally (~9.5 days), suggesting that sex determination occurs over relatively few days during incubation and that temperatures outside of this period minimally impact sex determination. We also found that the exposure duration required to trigger ovary development is affected by endogenous concentrations of maternally derived estrogens; late season clutches with higher estradiol concentrations require shorter exposure durations than early season clutches. By integrating natural thermal variation during incubation with maternal estrogens, our data help resolve how sex determination occurs in the field, and more broadly underscore the importance of considering relevant environmental variation in the study of eco-physiology.
