Gas Exchange and Ventilatory Responses to Hypoxia and Hypercapnia in Amphisbaena Alba (Reptilia: Amphisbaenia)

Abstract

ABSTRACT Total and cutaneous gas exchange and ventilatory responses to breathing hypoxic and hypercapnic gases were studied in Amphisbaena alba (Linnaeus), a burrowing squamate reptile. This species shows a very low oxygen uptake rate compared with other squamates of the same size (= 15·4, 36·2 and 49·0mlkg−1 h−1, at 20, 25 and 30°C, respectively). Cutaneous gas exchange represents a large fraction of the total uptake. Oxygen uptake was strongly affected by temperature [Q10 = 5·5 (20–25°C); 1·8 (25–30°C); 3·2 (20–30°C)]. A. alba shows a biphasic ventilatory pattern under hypoxic and hypercapnic conditions. A single breathing cycle, consisting of expiration-inspiration, includes a ventilatory period (VP) followed by a non-ventilatory (breath hold) period (NVP) of variable duration. When breathing air at 25°C the NVP typically occupied about 2 min. The ventilatory period occupied only 0·075 parts of a complete breath-to-breath cycle. Breathing hypoxic gases caused a pronounced rise in ventilation volume (VE) from an increase in tidal volume (VT) and frequency (f) at inspired O2 concentrations below 7%. Breathing hypercapnic gas mixtures induced a minor change in VT at CO2 concentrations below 3%, and VE increased mostly because of increases in f. End tidal O2 and CO2 tensions changed with increasing VE while breathing hypoxic and hypercapnic gas. The results are discussed in relation to the fossorial habits of A. alba, and are compared with data from other squamates.