Humidity Acclimation and Skin Permeability in the Lizard Anolis carolinensis

Rates of cutaneous evaporative water loss (EWL) were measured in Anolis carolinensis lizards following their exposure to humid (80%-85% RH) or dry (35%-42% RH) environments. After 8 d of acclimation, lizards exposed to dry air had significantly reduced rates of EWL, whereas those exposed to humid air did not. Acclimation of EWL occurred regardless of whether lizards exposed to dry conditions were allowed to dehydrate (to 80% of initial mass) and regardless of whether lizards molted. Evaporation rates measured from isolated dorsal skin in vitro demonstrated that dry-acclimated lizards had a lower skin permeability than did humid-acclimated lizards. The differences in permeability disappeared when lipids were extracted from the skin. Our findings suggest that acclimation of integumentary permeability may result from the gradual deposition of lipids in response to a local stimulus acting at the integument.