Meeting Abstract
Even though most organisms are exposed to variable bouts of warm temperatures, we know relatively little about how the timing and continuity of heat exposure influences biological processes. If heat waves increase in frequency and duration as predicted by climate change models, it is important to understand how these bouts of warmer temperatures could affect thermally sensitive species, including reptiles with temperature-dependent sex determination. We hypothesized that 1) the continuity of exposure to warm temperatures would affect resulting sex ratios in Trachemys scripta hatchlings, and 2) the duration of exposure to warm temperatures would affect the expression of two genes in the sex-determination cascade, aromatase and Dmrt1. To test the first hypothesis, eggs were initially exposed to daily fluctuations of 25±3°C (which produce all males) and then two 7-day heat wave days of 29.5±3°C separated by varying amounts of days at 25±3°C (sex ratio data to be collected October 2019). To test the second hypothesis, we exposed eggs to a 9-day heat wave (same thermal parameters), and sampled embryonic gonads on the last day of the heat wave as well on days 1, 3, 5, and 7 after the end of the heat wave. Surprisingly, neither Dmrt1 nor aromatase increased in expression following the heat wave. Expression of both genes slightly decreased after the last heat wave day, and then gradually increased back to initial levels. These data suggest that the response of some sex-determining genes to fluctuating temperatures may be slower than has been defined by constant temperature studies and underscore the importance of accounting for natural variation in temperature when studying such phenomena in the laboratory.
