AbstractI measured maximal oxygen consumption (Vo 2max) and standard metabolic rate in ten species of goannas to test whether, as a group, goannas have higher metabolic rates than other lizards. I found significant variation within this group of goannas, and no difference between goannas and other lizards in either measures of metabolic rate. Metabolism within the goannas was also examined with respect to foraging mode and habitat preference. Interspecific comparison of goanna metabolism adds support to the aerobic capacity hypothesis for the evolution of endothermy, and factorial scopes in lizards (≥10) are at least the equivalent of mammalian values.
Ventilation rate was measured concurrently with oxygen consumption in the experiments outlined above. During exercise, the increase in oxygen consumption rate was matched by a similar increase in ventilation rate, such that the ratio between ventilation and metabolism remained constant. This is significant given previous reports of hypoventilation (due to a mechanical constraint) and hyperventilation (in response to either an impairment to gas exchange or increased shunting). There is some evidence supporting the use of gular pumping in these goannas, and strong evidence for mouth breathing during exercise, which prohibits the sampling of nasal expiration only.
The present study is the first to measure pulmonary diffusing capacity (DLco ) during exercise in a reptile. I found that DLco doubled on average due to exercise, however, from five species (four varanids, one agamid) four different responses to exercise were apparent. These differences are most likely related to different behavioural responses to "resting" states, as well as differences in lung anatomy.
I examined the haematological and rheological response to exercise in a range of lizard species. Differences in aerobic ability of these species were not related to either haematology or rheology, with the exception of mean erythrocyte volume. The applications and methods of optimal haematocrit theory are considered.
|Date of Award
|Keith Christian (Supervisor) & Gavin Shane Bedford (Supervisor)