Influence of Body Size and Temperature on the Critical Oxygen Tension of Some Plethodontid Salamanders

Abstract

Salamanders of the family Plethodontidae are characterized in part by the absence of lungs and the reduction or loss of structures normally associated with pulmonary ventilation. All gas exchange occurs either through the skin or through the lining of the buccopharyngeal cavity. Thus a twofold limitation in their respiratory capacity exists: (1) they have no means of increasing their respiratory surface area independent of alterations in body size (surface-to-volume ratio); (2) their anatomical opportunities for increasing ventilation rate are restricted to the relatively unimportant bucco-pharyngeal surface. Whitford and Hutchison (1965) suggested that the relative inefficiency of these respiratory mechanisms may determine their distribution. We may expect to find a distributional size cline corresponding to respiratory requirements if respiratory efficiency in smaller animals is significantly greater than in larger species, because of increased surface-to-volume ratio.