Temperature dependence of regional heterothermy in a diminutive ectotherm.

Regional heterothermy describes when body regions differ in temperature, which can have important ramifications for performance because most biological processes are temperature dependent. However, the relationship between regional heterothermy and environmental temperature is not well known, particularly for ectotherms. The relationship between environmental heterogeneity and regional heterothermy might also yield insight into how the latter is regulated. We examined the thermal dependence of regional heterothermy (between the head and the cloaca) in live ring-necked snakes (Diadophis punctatus) in both the lab and the field, as well as in one dead and preserved individual. We found that the magnitude of the head-cloaca difference declined with average environmental temperature, that the relationship between head temperature and ambient temperature differed from that of cloaca temperature and ambient temperature, and that the preserved snake specimen did not display a consistent head-cloaca temperature difference. Our results suggest that (1) cloacal and head temperatures are regulated differently, (2) the head-cloaca temperature difference is not merely due to differences in the material properties of the head and cloaca, and (3) this difference may arise from altered circulation and perhaps even endogenous heat-generating mechanisms. Our results also suggest that the thermal dependence of regional heterothermy likely has ramifications for organismal function.