Lipids and the permeability of epidermis from snakes

Evaporative water loss was measured in vitro from shed epidermis of 11 species of snakes from widely ranging habitats. Permeability of epidermis was inversely related to habitat aridity and increased 1.9‐ to 31.3‐ fold when lipids were extracted prior to measurements. The quantity of lipids extracted from epidermis varied severalfold among species, and was significantly greater in xeric‐adapted, terrestrial species than in aquatic species. However, there was no significant correlation between lipid quantity and the increase of permeability produced by extraction of lipids. Both quantity and composition of lipids are likely involved in evolutionary or physiological adjustments to habitat. Lipids were demonstrated histochemically to be located primarily in the mesos layer of the epidermis, with some lipids also present in the alpha and beta keratin. Alteration of keratin without lipid extraction increased permeability only 20% if that produced by lipid extraction in the same species. The data corroborate other recent findings indicating that epidermal lipids play a major role in regulating the permeability of reptilian integument.