BIMODAL RESPIRATION IN AQUATIC AND TERRESTRIAL APODAN AMPHIBIANS

New data on resting metabolism, aerobic capacity, respiratory morpholo gy and bimodal breathing capacities of four caecilian species were com bined with previously known data on caecilian and amphibian biology to discern differing or unifying themes of gas exchange within the Gymno phiona and among the Amphibia. Discoveries include 1) a uniform restin g metabolism among caecilians that is distinctly lower than that of an urans and urodeles, 2) an aerobic capacity following activity that riv als or exceeds that of other amphibians, and 3) despite previous sugge stions to the contrary, a substantial contribution of the skin to resp iratory gas exchange, apparently sufficient to sustain the low resting metabolism. In contrast, pulmonary gas transport appears to dominate during metabolic recovery from exercise, which is comparatively fast. The contributing roles of the skin and lungs to this extreme scope of respiratory needs in caecilians are further discussed in light of the structural nature of and circulatory supply to each respiratory bed, a nd the respiratory properties of caecilian blood.