Meeting Abstract

P1.119  Monday, Jan. 4  Cutaneous and Respiratory Water Loss of Temperate Passerine Birds RO, J.*; WILLIAMS, J.B.; Ohio State Univ.; Ohio State Univ. ro.25@buckeyemail.osu.edu

Amongst various functions of the vertebrate skin, its ability to impede water loss is critical for survival in terrestrial animals. The outer layer of skin, the stratum corneum is comprised of cornified cells surrounded by an intercellular lipid matrix. Lipids in the SC are thought to be responsible for forming a tight water barrier, but the generality of this idea remains untested. In this study, we measured cutaneous water loss (CWL) and respiratory water loss (RWL) of 12 species of temperate passerine birds from a variety of families. At thermoneutral temperatures, whole organism CWL of temperate birds amounted to, on average, 64.2%, of total evaporative water loss. This emphasizes that CWL is a fundamental component of the water economy of birds. Normalized RWL and CWL among temperate passerines averaged 57.6 mg H2O/g, and 27.8 mg H2O/cm2•d, respectively. Although we found differences in RWL among species, surface specific CWL was statistically indistinguishable across the temperate passerine birds, despite their taxonomic and ecological differences. We hypothesized that water vapor diffusion across the skin was subjected to biological control and tested this idea by comparing CWL of alive and dead birds. When birds were dead, CWL was significantly reduced by 13% suggesting that CWL is under biological influence. The composition of intercellular lipid matrix is influential in determining CWL. We found that ceramides, fatty acid methyl esters, sterol esters and cebrerosides were major constituents of the avian stratum corneum. Variation in CWL was positively associated with amount of ceramide 3 and cerebroside 3, but these combined represented less than 2% of the total lipids.