Meeting Abstract
97.4 Wednesday, Jan. 7 Cutaneous water loss and lipids of the skin of tropical and temperater birds RO, J.*; WILLIAMS, J.B.; Ohio State University; Ohio State University ro.25@osu.edu
Skin serves a number of important functions in the vertebrate body: it provides protection from abrasion, defends against chemical insult and pathogens, aids in regulation of body temperate, and forms a barrier to water loss. In mammals and birds, this latter function is accomplished by the outer most layer of the epidermis, stratum corneum (SC), formed by multiple layers of cornified cells embedded in a matrix of lipids. In birds cholesterol, free fatty acids, triacylglycerol, and sphingolipids such as ceramides, and crebrosides are primary constituents of the intercellular lipid matrix. Previous studies have suggested that lipid composition of the intercellular spaces of the SC influences rates of water loss through the skin. However our understanding of how lipids in the SC influence water permeation through the skin, and how environment affects these lipid domains, remains rudimentary. In this study we measured cutaneous water loss and lipid composition of the SC in 13 species of temperate birds and 14 species of tropical birds (n =140 individuals). We used thin layer chromatography to identify and quantify lipid classes and APPI mass spectrometry to identify individual lipid molecules. Results thus far indicate that birds from temperate regions have lower rates of cutaneous water loss than birds from humid lowland tropical environments. Low rates of cutaneous water loss in temperate birds were associated with a dramatic increase in the quantity of sphingolipids in their SC: temperate birds had a mean ceramide concentration of 87.5 mg/g dry SC, whereas tropical birds had 12.2 mg/g dry SC. In sharp contrast, the amount of cholesterol per unit SC was not significantly different between temperate and tropical birds. Our use of mass spectrometry has thus far revealed over 600 molecular species of sphingolipids in the SC of birds.
