Abstract
Oxygen uptake (Ṁo2), ventilation (V̇E), and arterial pH (pHa) were measured in catheterized, unanesthetized water snakes (Nerodia sipedon) in a head-body plethysmograph, while the snakes breathed either room air or a hypercapnic (5.2% CO2) gas mixture. Measurements were made at 15, 25, and 30 C. Pulmonary ventilation and oxygen uptake increased with body temperature (Tb) during both room-air and CO₂ breathing. However, Ṁo₂ increased in greater proportion, so that the air convection requirement (ACR = V̇E/Ṁo2) decreased with increasing Tb. As a result, arterial pH decreased by −0.012 pH units/°C in animals breathing room air, and the pH changes resulted in a relative constancy of the charge distribution on blood proteins (αPr). Despite the relative hyperventilation seen in snakes, both pHa and αPr are similar to values observed for other reptiles. Snakes breathing CO₂ for 30 min showed a higher ventilation and a lower pHa at each Tb compared with room-air breathers. Temperature-induced changes in V̇E were due largely to changes in respiratory frequency, while CO₂ breathing increased V̇E primarily by increasing tidal volume.
Published Version
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