Meeting Abstract

P1.73  Sunday, Jan. 4  Cutaneous water loss and lipids covalently bound to corneocytes in house sparrows after acclimation to high and low humidity CLEMENT, M.E.*; MUNOZ-GARCIA, A.; WILLIAMS, J.B.; Ohio State University; Ohio State University; Ohio State University clement.33@osu.edu

Lipids of the stratum corneum (SC), the outer layer of the epidermis of birds and mammals, provide a barrier to water vapor diffusion through the skin. The SC of birds consists of flat dead cells, called corneocytes, and two lipid compartments: an intercellular matrix and a monolayer of covalently bound lipids (CBL) attached to the outer surface of corneocytes. We previously found two classes of sphingolipids, ceramides and cerebrosides, covalently bound to corneocytes in the SC of house sparrows and that these were associated with cutaneous water loss (CWL). Desert house sparrows had a lower ratio of covalently bound ceramides to cerebrosides than mesic birds, which resulted in lower CWL rates. In this study, we collected adult and nestling house sparrows from Ohio, acclimated them to either a high or low humidity environment, and measured their rates of CWL. We then evaluated the composition of the CBL of the SC using thin layer chromatography. CWL was higher in nestlings than in adult house sparrows, and higher in dry-acclimated than in humid-acclimated birds. Adults had a greater proportion of covalently bound cerebrosides than nestlings. There was no change in the composition of CBL between dry and humid acclimated birds for either adults or nestlings. CWL decreased as the ratio of covalently bound ceramides to cerebrosides decreased, consistent with our previous findings. We also found that nestlings had greater variability in the ceramide:cerebroside ratio than adults. These results suggest that the composition of CBL in the SC changes with ontogeny but not in response to acclimation.