How much starvation, desiccation and oxygen depletion can Drosophila melanogaster tolerate before its upper thermal limits are affected?

Heat tolerance is commonly assessed as the critical thermal maximum (CTmax) using the dynamic method exposing organisms to a gradually increasing (ramping) temperature until organisms fall into a coma. The CTmax estimate is dependent on the ramping rate, with decreased rates leading to longer treatments and ultimately lower CTmax estimates. There is a current discussion surrounding the physiological dynamics of the effect of the time of exposure by temperature interaction on these estimates. Besides temperature the time of exposure to limited food (starvation), desiccation, and reduced levels of oxygen or increased levels of CO2 may, in interaction with ramping rate, act as confounding factors when assessing upper thermal limits using the dynamic method. Here we test the role of the different potentially confounding factors for assaying thermal tolerance using a ramping assay under four different ramping rates, varying from 0.01°C/min to 0.2°C/min. We find that CTmax values are higher a...