Trimodal gas exchange in the large aquatic salamander, Siren lacertina (Linnaeus)

Abstract

1. 1. Pulmonary, cutaneous and branchial gas exchange ( V ́ O2 and V ́ CO2 ) was determined on the large aquatic salamander Siren lacertina acclimated to 5, 15 and 25°C. 2. 2. Gas exchange was predominantly aquatic at 5°C (86 per cent of the total V ́ O2 and 98 per cent of the total V ́ CO2 ). At 25°C the lungs assumed a greater role in gas exchange and accounted for 50–75 per cent of the total V ́ O2 and up to 60 per cent of the total V ́ CO2 ; the latter value shows that Siren lungs are the most efficient of any amphibian thus far investigated. 3. 3. The gills of Siren did not contribute materially to the total V ́ O2 . The gills showed a greater participation in V ́ CO2 (18 and 12 per cent of the total V ́ CO2 at 15 and 25°C, respectively). Most of the aquatic gas exchange in Siren occurs via the integumentary surfaces. 4. 4. The air-dried lungs of Siren are extremely long, about two-thirds of the body length, and show a considerable degree of septation. The increased infolding of the lung tissues increases the respiratory surface area some fourfold. 5. 5. The efficient pulmonary respiration in Siren is an adaptation for survival in shallow, weed-choked, and often hypoxic and hypercarbic waters.