Effects of temperature on metabolism, ventilation, and oxygen extraction in the southern brown bandicoot Isoodon obesulus (Marsupialia: Peramelidae).

The effects of ambient temperatures (T(a)) from 10 degrees to 35 degrees C on metabolism, ventilation, and oxygen extraction were examined for the southern brown bandicoot (Isoodon obesulus). Oxygen consumption (VO2) followed the pattern typical for endotherms, decreasing with increasing T(a) from 10 degrees to 25 degrees C. It did not significantly change between Ta=25 degrees and 35 degrees C (the thermoneutral zone). VO2 was approximately 2.4 times higher at Ta=10 degrees C (0.967 mL O(2) g(-1) h(-1)) compared with basal (0.410 mL O(2) g(-1) h(-1)) at Ta=30 degrees C. While the metabolic rates of the bandicoots were basal at Ta=30 degrees C, respiratory frequency (f(R)) was 24.6 breaths min(-1), tidal volume (V(T)) was 7.79 mL, minute volume (V(I)) was 191.3 mL min(-1), and oxygen extraction efficiency (EO2) was 26.8%. Increased VO2 at Ta< or =25 degrees C was associated with a large increase in V(I) due to increases in V(T) and f(R). A greater proportion of the change was due to the increase in tidal volume. EO2 was constant at approximately 26% for all T(a) up to and including 30 degrees C. At Ta=35 degrees C, EO2 decreased to 17.7%, f(R) increased to 35.6 breaths min(-1), and V(T) decreased to 7.22 mL. The metabolic and ventilatory physiology of the southern brown bandicoot are typical of an unspecialized medium-sized marsupial.