Department of Biological Sciences, University of Zimbabwe,
Mount Pleasant, Harare, Zimbabwe

ABSTRACT

The peak of the elevated oxygen consumption following feeding may be preabsorptive in some reptiles, possibly because of the up-regulation of gut function. The question of whether up-regulation has a substantial net cost and accounts for a large part of the cost of the specific dynamic action can be resolved by comparing the response to single and repeated meals. Oxygen consumption of the omnivorous tortoise Kinixys spekii was elevated for 3-4 d after a single meal, and the peak occurred while most food was still in the stomach. The cost of the specific dynamic action varied between diets, being 16%, 21 %, and 30% of the energy absorbed from fungi, leaves, and millipedes, respectively, but was about 0.8 L 0₂ g^-1 absorbed protein for all diets. The specific dynamic action doubled during continuous feeding on leaves and then accounted for 42% of the absorbed energy. The increase after repeated feeding shows that up-regulation of gut function can contribute little to the energy cost of the specific dynamic action in K. spekii; otherwise the cost would fall in subsequent meals.

Physiological Zoology 71: 57-66.