Meeting Abstract

73.9  Sunday, Jan. 6  Cutaneous water loss and sphingolipids in the stratum corneum of house sparrows from desert and mesic environments MU�OZ-GARCIA, Agust�*; RO, Jennifer; BROWN, Johnie C; WILLIAMS, Joseph B; OSU; OSU; Applied Biosystems; OSU munoz-garcia.1@osu.edu

Because cutaneous water loss (CWL) represents over a half of the total water loss in birds, selection pressures might have acted to reduce CWL in desert birds. We previously found that CWL of house sparrows from a desert population was 25% lower than that of individuals from a mesic environment. The stratum corneum (SC), the outer layer of the epidermis of birds, has a fundamental role in the formation of a barrier to water vapor diffusion through the skin. The avian SC is formed by layers of cells embedded in a lipid matrix with cholesterol, free fatty acids and two classes of sphingolipids, ceramides and cerebrosides. The SC of birds also serves a thermoregulatory function, allowing high CWL rates. The presence of cerebrosides in the avian SC could be related to the dual role that the SC has in birds. In this study, we characterized the biochemical properties of the approximately 200 different sphingolipids that we identified and quantified in the SC of house sparrows from desert and mesic environments using high-performance liquid chromatography coupled with atmospheric pressure photoionization-mass spectrometry. We used principal components analysis (PCA) to reduce the number of variables in our data. To evaluate the functional significance of the differences in lipid composition between desert and mesic sparrows, we tested the association between principal components and CWL in both populations. Our study indicated that a reduction in CWL found in desert sparrows was the result of modifications in chain length and polarity of the sphingolipids, changes that apparently determine the interactions of the lipid molecules within the SC.