MU�OZ-GARCIA, A.*; WILLIAMS, J.B.*; The Ohio State University; The Ohio State University: Lipids of the stratum corneum vary with cutaneous water loss in House Sparrows (Passer domesticus) from arid and mesic environments

Terrestrial vertebrates that live in extremely arid environments are challenged to control for excessive water losses in order to maintain their water homeostasis. In this hard conditions, the integument plays a crucial role as the interface between the organism and the environment. Lipids in the stratum corneum, the outer layer of the epidermis, act as a barrier minimizing the amount of water evaporated through the skin. We measured cutaneous water loss (CWL) in two groups of House sparrows (Passer domesticus), one living in a mesic environment (Ohio, USA), and another living in Taif (Saudi Arabia), a desert environment, and we found that CWL was lower in the desert individuals. We hypothesized that changes in lipid composition of the stratum corneum could affect CWL. Preliminary results showed that desert animals have a higher amount of ceramides and a lower proportion of cholesterol in their stratum corneum than mesic birds. This suggests that lipids in the stratum corneum are more densely packed and in a less fluid state in desert sparrows, thus configuring a more effective water barrier.