Meeting Abstract
As ambient temperature (TA) increases, many animals increase total evaporative water loss (TEWL) to maintain a constant body temperature. In Passerine birds, the increase in TEWL is mainly attributed to an increase in respiratory water loss, whereas water lost through the skin as cutaneous water loss (CWL) increases only modestly. However, pigeons and doves (Columbidae) exhibit an opposite trend, greatly increasing CWL with only a small increase in respiratory water loss. The unique ability of pigeons and doves to greatly increase CWL at high TA may be attributed to the inherent thermal properties of the skin barrier. In birds, the barrier to CWL is the stratum corneum (SC), the outermost layer of skin comprised of dead cells called corneocytes embedded in a matrix of lipids packed together in layers called lamellae. The ability of lipid molecules to pack tightly together in an ordered arrangement determines the permeability of the SC to water and thus CWL. We measured the CWL of pigeons (Columba livia) at 25, 30, 35, 40, and 45° C. We then isolated the SC and used Fourier transform infrared spectroscopy to assess lipid ordering and phase state at the same temperatures. Our results indicate that CWL in pigeons increases as TA increases, and this increase is associated with a concurrent increase in lipid disorder. Furthermore, lipids in pigeon SC undergo a greater increase in disorder than Passerine birds, further supporting the hypothesis that thermal properties of skin lipids determine an organism’s physiological response to increased TA.
