Respiratory function in the South American lungfish, Lepidosiren paradoxa (Fitz).

Few animal species have aroused as much excitement upon their discovery as the South American lungfish. Its possession of distinct piscine as well as amphibian characters made the animal a link in the transition of vertebrate life from water breathing to air breathing. Its special attributes are clearly reflected in its name, Lepidosiren paradoxa. Physiological experimentation on respiratory function in this fish is very scarce (Cunningham, 1934; Carter & Beadle, 1930; Carter & Beadle, 1931; Cunningham & Reid, 1932; Sawaya, 1946). No measurements of pulmonary-gas concentration and blood-gas tensions have come to our notice. The present investigation concerns the respiratory properties of the blood and the dynamics of gas exchange as well as the relative importance of branchial and aerial respiration. The experiments were also designed to elucidate possible regulatory mechanisms in the breathing pattern of Lepidosiren paradoxa.