Skin Lipids, Water Loss, and Energy Metabolism in a South American Tree Frog (Phyllomedusa sauvagei)

Evaporative water loss in Phyllomedusa sauvagei is very low at ambient temperatures up to 30 C but increases precipitously between 35 and 40 C. Standard metabolic rate shows a constant Q10 (ca. 2.4) between 10 and 38 C. At ambient temperatures of 38–40 C there are pulsatile releases of clear fluid on the skin, and skin and core temperatures are maintained at 35–37 C. Some skin secretions of P. sauvagei contain lipids which are mainly wax esters. A film of the lipid retards evaporation from a water surface at temperatures below 35 C but is relatively ineffective at 38 C and above. This lipid appears to have a transition temperature strategically placed to minimize evaporative losses up to the point where thermal considerations outweigh those of water conservation.