Measuring Anolis thermal tolerances has been a hallmark of many studies since the heydays of thermal physiological studies in the mid-to-late 1900’s. However, studies examining the factors affecting thermal tolerances of embryos are still relatively sparse. In the symposium “Beyond CTmax and CTmin: Advances in Studying the Thermal Limits of Reptiles and Amphibians” at the ninth World Congress of Herpetology, Joshua Hall – PhD candidate in the Warner lab at Auburn University – explored critical thermal maximum temperatures in Anolis sagrei during development. He sought to determine (1) How we should measure embryonic CTmax? (2) What is the ecological relevance of embryonic CTmax? And (3) Are there differences between acute and chronic CTmax?

Previous work from Pruett and Warner, determined that constant incubation temperatures resulted in a chronic CTmax of 35°C for A. sagrei. Meanwhile, Joshua tested three methodologies of creating an acute CTmax during incubation including: heat shock, thermal ramp, and thermal fluctuations. All three methodologies showed an acute CTmax of ~45/46°C; there was consistency across methodologies as well as an extremely large difference found between chronic and acute CTmax. Additionally, Josh examined what data were available via the Reptile Developmental Data Base to examine chronic CTmax in nine other squamate species (ranging from 28-36°C). Of those nine species from previously collected data, four had measures of acute CTmax, and in all four cases the acute CTmax was higher than the chronic CTmax. Lastly, Josh recommends that researchers use the terminology acute and chronic when describing CTmax and that more work should be done to better determine the relationships between chronic and acute CTmax in an ecological context. Super cool work, looking into the future of thermal physiological work!