The morphology of the lung of the black mamba Dendroaspis polylepis (Reptilia: Ophidia: Elapidae). A scanning and transmission electron microscopic study
The black mamba (Dendroaspis polylepis) belongs to the family Elapidae that also includes the cobras, kraits and coral snakes. Generally, these snakes are extremely venomous and occur in the warmer parts of the world (Parker, 1977). They belong to the infraorder Caenophidia, which includes the most highly developed snakes (Webb, Wallwork & Elgood, 1978). The black mamba is a diurnal and only sparingly arboreal snake (Skinner, 1973). It is the fastest land snake, attaining speeds of 16-19 km/hr for short bursts (Wood, 1980). The structure of the ophidian lung is remarkably different from that of the other reptiles (Luchtel & Kardong, 1981) and the variation in the nature of the pulmonary morphology in this reptile group is remarkable (Porter, 1972; Duncker, 1978). This feature is clearly illustrated in the family Boidae where in the subfamily Boinae the left lung is well developed with the right lung being smaller, while in Tropidophinae only the right lung is developed; both lungs are equally well developed in Bolyeriinae (Goin & Goin, 1962). Further, in the family Colubridae the left lung is drastically reduced in size, whereas in Viperidae the left lung is largely absent, the right lung being extremely elongated (Cope, 1894; Butler, 1895). These variations show well the notable adaptive radiation this reptilian group has undergone (Brongersma, 1949, 1951; Underwood, 1967, 1976; Pohunkova & Hughes, 1985). The morphological variations in the pulmonary anatomy of the Ophidia have been used to evaluate the systematic relationships within this reptilian taxon (Cope, 1894, 1900; Underwood, 1967, 1976). In this respect, extensive and detailed comparative studies on the ophidian lungs are essential for any meaningful systematic use of this differing morphology. The study of the ophidian lung covers a long period of time (Cope, 1894, 1900; Butler, 1895; Marcus, 1937; Varde, 1951; George & Shah, 1956). These elegant early studies, however, are largely descriptive of gross anatomy or are histological. Apart from the detailed ultrastructural account of the lung of the rattlesnake (Luchtel & Kardong, 1981) and the garter snake (Pohunkova & Hughes, 1985), apparently only brief accounts of the ultrastructure of the snake lung are available (Okada et al. 1962; Nagaishi, Okada, Ishika & Daido, 1964; Brooks, 1970). Stinner (1982) gave an excellent account of the morphometry of lung of the colubrid snake Pituophis melanoleucus. The present study was intended to supplement these investigations by examining the lung of the black mamba.