Meeting Abstract

P1.71  Sunday, Jan. 4  Cutaneous water loss and lipids in the stratum corneum of mesic horned larks (Eremophila alpestris praticola) and five species of desert larks CHAMPAGNE, A.M.*; MUNOZ-GARCIA, A.; WILLIAMS, J.B.; The Ohio State University; The Ohio State University; The Ohio State University champagne.7@osu.edu

The stratum corneum (SC), the outer layer of the epidermis in birds and mammals, forms a barrier to water vapor diffusion through the skin. The avian SC is composed of corneocytes embedded in a lipid matrix of cholesterol, free fatty acids, triglycerides, ceramides, and cerebrosides. Cutaneous water loss (CWL) accounts for over half the total water loss in birds. Because birds in deserts face a hot, desiccating environment, selection to reduce CWL at moderate ambient temperatures may have been stronger in desert birds than in mesic birds. Previous studies in our lab have shown that changes in the ratios of lipid classes in the SC may influence CWL in birds. Appropriate ratios of ceramides, cerebrosides and free fatty acids seem necessary for the formation of intercellular lipid bilayers, called lamellae. The molecular organization of these lamellae affects CWL. In this study, we compared rates of CWL and SC lipid composition of horned larks from central Ohio (Eremophila alpestris praticola) with those of five species of larks from deserts. E.a. praticola had higher rates of CWL at thermoneutral temperatures and a higher ratio of ceramides to cerebrosides in the SC than desert larks, a result consistent with our findings in other bird species. We also found that the lipid composition of the SC was associated with CWL in horned larks.