Avian epidermal differentiation II. Adaptive response of permeability barrier to water deprivation and replenishment

Abstract

Zebra Finches are the epitome of desert-adapted avian species; i.e. they are able to survive without drinking water for over a year. Whereas transepidermal water loss (TEWL) in naked Zebra Finch nestlings is lower than in adults, and desert adaptation is accompanied by intercellular deposition of epidermal multigranular body (MGB) contents, MGB secretion is reduced as nestlings mature into feathered adults, indicative of less stringent barrier requirements. Here, removal of drinking water resulted in increased intercellular deposition of MGB contents, and TEWL progressively decreased. In contrast, MGB intercellular deposition decreased when birds were rehydrated, with TEWL returning towards normal within 5 days of rehydration. Finally, water-deprivation caused significant changes in epidermal lipid composition that returned toward control levels with rehydration. These studies show that adult Zebra Finches adapt to xeric stress by increased secretion of multigranular bodies resulting in reduced TEWL.