QUANTITATIVE STUDIES ON THE MORPHOLOGY OF RESPIRATORY SURFACES IN AMPHIBIANS

Abstract

Morphological studies on the vascular supply of the skin, lungs and mouth of 40 amphibian species demonstrated large differences between particular species in the length of respiratory capillaries computed on the basis of 1 gm of body weight. In urodeles this length ranged from 3.4 m/gm in A. [Ambystoma] means to 17.9 m/gm in T. [Triturus] vulgar is males in full nuptial dress, whereas in anurans it was from 8.5 m/gm in R. [Rana] grylio to 46 m/g in H. [Hyla] arborea. These differences in the length of respiratory capillaries suggest differences in the intensity of gaseous exchange and, consequently, metabolism. Particular species vary in the length of respiratory capillaries per gram of body weight and their distribution between skin and lungs. These differences are unconnected with the systematic position of the amphibians. Some congeners are alike in the length and distribution of respiratory capillaries, e.g., Triturus; others differ in the length, but are similar in the distribution of these capillaries, e.g., Bufo. whereas for still other interrelated species, e.g., members of the family Pelobatidae or genus Bombina, the reverse holds true. Barely 1-3% of respiratory capillaries are in the mouth, whose role in the exchange of gases may therefore be presumed as negligible, except at high temperatures when the buccopharyngeal respiration was found extremely active in Amby-stoma maculatum. Calculated in meters per 1 g of body weight, respiratory capillaries are exceptionally abundant in the youngest stadia of amphibians, e.g., over 90 in R. esculenta, and about 30 in A. mexicanum and S. [Salamandra] salamandra. With growth and on metamorphosis of the larvae, this relative length of the capillaries becomes gradually less. An exception is H. arborea, in which in adults it is double that in just metamorphosed individuals.