Effect of temperature on control of breathing in the cryophilic rhynchocephalian reptile, Sphenodon punctatus

Abstract

1. 1. The metabolic rate of Sphenodon, measured as CO 2 production, was low in comparison with lizards and snakes, but similar to values from chelonians at similar body temperature. 2. 2. Breathing patterns were studied using X-ray cinematography and impedance pneumography, and revealed regular, periodic breathing with non-ventilatory periods decreasing as body temperature was raised. 3. 3. Ventilation was independent of inspired oxygen, but was rapidly depressed by carbon dioxide inhalation, indicative of respiratory control by intrapulmonary receptors. 4. 4. The air convection requirement of Sphenodon was high and suggests an inefficient system of pulmonary gas transfer across its simple, unicameral lung. 5. 5. Ventilation in the sole surviving rhyncocephalian reptile is discussed in relation to its cryophilic preference.