Mechanism of lung ventilation in the caecilian Dermophis mexicanus

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Abstract
The pattern of lung ventilation in the terrestrial caecilian Dermophis mexicanus was investigated by recording pressure changes of buccal and pleuroperitoneal cavities and activity of the buccal musculature. This species uses a fairly typical sarcopterygian buccal pumping system to inflate its single lung. What distinguishes it from other amphibians is the large number of buccal pumping cycles that occur in each ventilatory cycle. Up to 29 buccal cycles were observed to occur in a single respiratory cycle, with a mean of 16.1 ± 3.0 buccal cycles. This long series of buccal cycles avoids the sarcopterygian pattern of rebreathing expired air because only the first buccal cycle pumps expired air back into the lung. The series of buccal cycles also generates pleuroperitoneal pressures that are three to ten times greater than those observed in other amphibians. We suggest that these high pleuroperitoneal pressures are necessary for the maintenance of body form and locomotor function in terrestrial caecilians.