Relation of Body Size and Surface Area to Gas Exchange in Anurans

Abstract

T HE skin, lungs, and buccal cavity may all serve as respiratory surfaces in adult terrestrial amphibians. The relative role of these respiratory surfaces has been shown to be an important consideration in the ecology, geographic distribution, and phylogenetic relationships of caudate amphibians (Whitford and Hutchison, 1963, 1965, 1966, 1967 lung air on which gas exchange with the lung capillaries is dependent and because environmental conditions, particularly temperature, affect the respiratory exchanges and relative role of the respiratory surfaces. Our studies were designed to evaluate the effect of temperature on the role of the skin, pulmonary, and buccopharyngeal surfaces in the respiratory exchanges of a number of anurans representing several families from a variety of habitats; to obtain quantitative measurements of ventilation of the pulmonary surfaces to aid in the interpretation of gas exchange patterns; and to evaluate body size and metabolic rate relationships in anurans. These data are used to evaluate the adaptive significance of differences in respiratory patterns observed with regard to geographic distribution, ecology, and phylogenetic relationships of the forms studied. MATERIAL AND METHODSAll animals were acclimated in constant temperature-photoperiod environmental chambers to the test temperatures and a 16-hr photoperiod for a minimum of 1 week prior to the experiments. Pulmonary (lung and buccopharyngeal) and cutaneous gas exchange were measured separately and simultaneously in constant volume respirometers by a direct manometric method.

Anaerobic metabolism during activity in amphibians

“…These Q! , values for amphibians are generally similar to those reported for resting and actwe oxygen consumption for these and other amphibians (Q,, = 1.3-2.0) (Whitford & Hutchison, 1967;Hutchison et al, 1968;Seymour, 1973).…”

Hepatic confinement of newly produced erythrocytes caused by low-temperature exposure inXenopus laevis

“…In the American toad (Bufo americanus), gas exchange rate decreases to approximately 5% of normal levels at 5°C (Hutchison et al, 1968). The fall in peripheral blood erythrocyte count observed in the present study may occur because a lower oxygen-carrying capacity is required by frogs under hypothermic compared with normal conditions, and is thus important in maintaining proper tissue oxygen tension during hypothermia.…”

A new lungless caecilian (Amphibia: Gymnophiona) from Guyana

“…Consequently, we see no evidence at this time that particularly supports either the 'rheotropic' or the 'buccopharyngeal pump efficiency' scenarios in terms of lung loss in Caecilita. However, we suggest that small body size and high surface-to-volume ratio, the highly vascular tongue, and the presumably low metabolic rate may have facilitated increased dependence on cutaneous/buccal gas exchange (see Elkan 1955Elkan , 1958Czopek 1962;Whitford & Hutchison 1965, 1967Hutchison et al 1968;Bennett & Licht 1973), but for reasons not yet determined. The biology of Caecilita, including lung loss, may have evolved to be similar to that of plethodontids, particularly the slender, elongate, reduced-limbed, burrowing plethodontids (e.g.…”

“…We presume that it has a low metabolic rate typical of caecilians (Mendes 1941(Mendes , 1945Sawaya 1941Sawaya , 1947Bennett & Wake 1974), and it lives in a warm tropical environment. The size of C. iwokramae is well within the size range of lungless plethodontid salamanders, for which the respiratory physiology is relatively well studied and oxygenation is demonstrably obtained via the skin circulation and the buccal capillaries (Elkan 1955(Elkan , 1958Czopek 1962;Whitford & Hutchison 1965, 1967Hutchison et al 1968;Bennett & Licht 1973). The skin of C. iwokramae appears to be typical of that of terrestrial caecilians in terms of epidermis and dermis depth, density of glands and vascularization (see figure 1, Bennett & Wake (1974), for a comparison of the skin of a lungless plethodontid salamander and a terrestrial caecilian with a well-developed lung).…”