Ventilation and gas exchange in the diamondback water snake,Natrix rhombifera

Abstract

Simultaneous measurements of pulmonary and cutaneous oxygen and carbon dioxide exchange, pulmonary ventilation and heart rate were made on the diamondback water snake,Natrix rhombifera at 28°C using body plethysmography. Resting lung volume, maximum lung volume and tracheal volume were also measured. The following mean values were measured in undisturbed snakes breathing room air: total (pulmonary and cutaneous) O2 uptake 46 μmol · (kg min)−1; total CO2 output, 49 μmol · (kg min)−1; tidal volume, 12 ml (BTPS) · kg−1; ventilatory rate, 6.9 min−1; heart rate, 42 min−1. From the measurements of tracheal volume, the effective (alveolar) ventilation was estimated as approximately 70% of total ventilation resulting in effective pulmonary $$P_{O_2 }$$ and $$P_{CO_2 }$$ of 130 Torr and 20 Torr respectively. Cutaneous exchange accounted for 8.1% of the total $$\dot M_{O_2 }$$ and 12.4% of the total $$\dot M_{CO_2 }$$ . Resting lung volume of anaesthetized snakes was 75 ml (BTPS) · kg−1, maximum lung volume was 341 ml (BTPS) · kg−1 and tracheal volume was 3.9 ml (BTPS) · kg−1.