The morphology of the lung of the East African tree frog Chiromantis petersi with observations on the skin and the buccal cavity as secondary gas exchange organs.

Abstract

The class Amphibia consists of three distinct Orders, the Anura - the tailless amphibians; the Urodela - the tailed amphibians, and the Apoda - the snake-like amphibians also called caecilians. The anurans inhabit both aquatic and terrestrial environments, the urodeles are predominantly aquatic, whereas the caecilians are largely fossorial terrestrials. To varying extents the amphibians exhibit bimodal breathing, basically utilising the skin and the lungs for gas exchange. The organisation of the lung of the anurans has been investigated by Czopek (1955), Okada et al. (1962), Dierichs (1973), Meban (1973, 1977), Hutchison, Whitford & Kohl (1968), Smith & Rapson (1977), Bils & Hughes, (1978), Welsch (1983), Pohunkova & Hughes (1985) and Goniakowska-Witalinska (1985, 1986); that of the urodeles has been examined by Czopek (1962), Hughes (1970), Hightower, Burke & Haar (1975), GoniakowskaWitalinska (1978, 1980 a, b, c, d, 1982) and Stark-Vancs, Bell & Hutchison (1984); the caecilian lung has been studied by Welsch & Storch (1973), Pattle, Schock, Creasey & Hughes (1977), Welsch (1981) and Maina & Maloiy (1988). Comparative studies on the morphology of the amphibian lungs have been carried out by Czopek (1955), Szarski (1962, 1964) and Tenney & Tenney (1970). The amphibian lung exhibits remarkable structural variation (Smith & Rapson, 1977; Goniakowska-Witalinska, 1985), with the more energetic species, largely the anurans, having more elaborate septate lungs and those of the urodeles being simple with a smooth saccular internal surface. The structure of the amphibian lung, particularly among the anurans, has not been thoroughly investigated (GoniakowskaWitalinska, 1985). Goniakowska-Witalinska (1985, 1986) examined the lung of the tree frog Hyra arborea. This species is known to be highly metabolically active and the lungs are richly vascularised (Czopek, 1965; Goniakowska-Witalinska, 1973). In the present study the lung of the East African tree frog Chiromantis petersi which, together with Chiromantis xeraphelina, is probably the most xerophilous of all anuran amphibians (Loveridge, 1970, 1976) has been investigated using the scanning and transmission electron microscopes with the purpose of supplementing the available knowledge on the design of the anuran lung and in general that of the amphibians. The buccal cavity and the skin, areas of great importance in gas exchange in amphibians, have also been examined.