Heat tolerance in ectotherms scales predictably with body size

This study analyses how heat stress varies with body size in ectothermic organisms. The analytical approach is based on thermal death time (TDT) curves, which take into consideration both the intensity and the duration of a thermal stress, and result in a linear relationship between temperature and the logarithm of time. We analyzed two separate heat tolerance datasets measured in mollusk, arthropod, fish, amphibian and reptile species, covering nearly 9 orders of magnitude in size. Datasets ware intrinsically different but ultimately convey the same type of information on thermal tolerance. The first dataset comprised individual measurements of heat stress (i.e., data points expressed in temperature and time coordinates) whereas the second dataset described the intercept and slope of TDT curves. In both cases, smaller organisms exhibited a higher tolerance to an acute heat stress than larger ones, but their tolerance declined faster in time.We then combined the results from our scaling...