ABSTRACT
S. D. Bradshaw specifically examined the question of homeostasis in reptiles and drew together published data on vertebrate electrolyte concentrations and tissue fluid distributions in the various reptilian taxa. In terrestrial ophidian reptiles, the epidermal resistance to water loss also increases markedly following the first postnatal ecdysis. Among largely aquatic reptiles, the permeability of the integument to water generally decreases as the salinity of the normal aqueous habitat increases; again, this relationship is found across orders and across species within a single order. The epidermis of reptiles forms the limiting barrier for exchange of water and, in aquatic species, ions with the environment. Transmembrane ion movements require appropriate protein channels or transporters; however, as noted above, significant sodium movement can occur across the skin of aquatic reptiles or even across the skin of terrestrial ophidian reptiles when the shed skin is maintained in an aqueous medium.
