Respiration in the African lungfish Protopterus aethiopicus. I. Respiratory properties of blood and normal patterns of breathing and gas exchange.

Members of the three existing genera of lungfishes represent different stages in the transition from aquatic to aerial breathing. Neoceratodus, the Australian lungfish, is primarily aquatic and utilizes gill breathing, while its lung offers an accessory means for O2 absorption (Lenfant, Johansen & Grigg, 1966; Johansen, Lenfant & Grigg, 1967). Conversely, the South American lungfish, Lepidosiren paradoxa, is a typical air breather and the much reduced gills are of little or no importance for O2 absorption but may have some functional significance for elimination of CO2 (Johansen & Lenfant, 1967). The African lungfish, Protopterus, resemble L. paradoxa in being primarily an air breather. The purpose of the present paper is to evaluate the status of P. aethiopicus in the transition from aquatic to aerial breathing by analysis of the respiratory properties of blood and of the normal pattern of breathing and gas exchange.