The ventilatory responses of the caecilian Typhlonectes natans to hypoxia and hypercapnia.

Abstract Typhlonectes natans empty their lungs in a single extended exhalation and subsequently fill their lungs by using a series of 10–20 inspiratory buccal oscillations. These animals always use this breathing pattern, which effectively separates inspiratory and expiratory airflows, unlike most urodele and anuran amphibians that may use one to many buccal oscillations for lung inflation and typically mix expired and inspired gases. Aquatic hypoxia had no significant effect on the breathing pattern or mechanics in these animals. Aerial hypoxia stimulated ventilatory frequency and increased the number of inspiratory oscillations but had little effect on inspiratory and expiratory tidal volume. Aquatic hypercapnia elicited a large significant increase in air‐breathing frequency and minute ventilation compared to the small stimulation of minute ventilation seen during aerial hypercapnia. Some animals responded to aquatic hypercapnia with a series of three or four closely spaced breaths separated by long no...