Plasticity in thermoregulatory behavior and performance in response to hyperoxia in Iberolacerta bonnali

Thermal physiology, hyperoxia, Iberolacerta bonnali, plasticity, thermoregulation, climate change

As climate change worsens and temperatures rise, the ability to respond to novel environments is becoming essential for all life on Earth. Ectotherms, or “cold-blooded” animals, are particularly vulnerable to environmental changes, as they rely on environmental temperatures to maintain their body temperature. Ectotherms that reside at higher elevations are facing warmer temperatures while also dealing with high-elevation hypoxia (oxygen deprivation). To study the effect oxygen availability has on ectothermic thermal physiology, we collected Pyrenean rock lizards (Iberolacerta bonnali) from high-elevation habitats. These lizards were then split into two treatments: one group was maintained at the same high elevation environment and one group was transplanted to lower elevation. We then conducted thermal preference trials on both groups in thermal arenas with a gradient of 20-60℃. We predicted that lizards transplanted from high to low elevations would prefer a warmer environment, as the increased oxygen availability would aid in maintaining a higher metabolism. While inside these arenas, thermal imaging cameras (FLIR C3 models) were used to take thermographs of each lizard every five minutes. From these thermographs, I extracted both body and head temperature data, and then analyzed it to test the effects of oxygen availability on the thermal preferences for each lizard. This data was also analyzed to test for the presence of regional heterothermy (a physiological strategy wherein ectotherms keep different regions of their bodies at different temperatures) in I. bonnali. These results are important because they can give insight into unknown mechanisms of the I. bonnali’s thermal physiology and help in understanding the mechanisms of how they adapt and respond to the novel environments created by climate change. 

As climate change worsens, temperatures around the world continue to fluctuate, creating novel environments. The ability to respond and adapt appropriately to these new environments is quickly becoming an essential part of every organism's life. One group of organisms that are especially vulnerable to these new climatic conditions are ectotherms, or “cold-blooded” organisms, as they rely heavily on their surrounding environment to maintain their body temperature. Ectotherms that reside at higher elevation habitats have an even harder time adjusting to rising temperatures, as they have unique struggles that have been exacerbated by climate change, such as extreme temperatures, intense radiation, and hypoxia (oxygen deprivation) One type of defense lacertid lizards like I. bonnali have in defense to these dangers is regional heterothermy, a physiological strategy to  maintain different regions of their bodies at different temperatures. This regulates the highly temperature sensitive nervous system of ectotherms. To study the effects of oxygen availability on ectothermic thermal physiology and performance, we collected groups of Pyrenean rock lizards (Iberolacerta bonnali), a threatened species endemic to high elevations, and tested how their thermoregulatory behavior and sprint performance responded to different environments. 

We predict that lizards transplanted to low elevation would exhibit higher thermal preferences and voluntary thermal maxima, as the increased oxygen availability would aid in maintaining a higher metabolism. Additionally, we predict that maximum sprint speed and the optimal temperature for sprint speed would increase in the transplanted lizards, corresponding with a shift in the shape of the thermal performance curve.  In terms of regional heterothermy, we predict that the head temperature will will remain more consistent relative to the body, due to brain tissues’s sensitivity to temperature changes.