Digestion in an Ectothermic Herbivore, the Green Iguana (Iguana iguana): Effect of Food Composition and Body Temperature

Abstract

In laboratory experiments, the effect of food composition and body temperature on digestive efficiency was investigated in the lizard Iguana iguana on Curacao (Netherlands Antilles). In a series of experiments the animals were kept in cages with a temperature gradient and different foods were offered ad lib. Mean selected daytime body temperatures were 35.0-degrees-36.4-degrees-C (mean 24 h T(b): 31.8-degrees-33.7-degrees-C). Mean apparent dry-matter digestibility (DDM) varied from 30.0% to 84.2%, depending on the kind of food. Mean DDM and digestible energy were significantly inversely related to the cell wall components lignin and cutin, and these components could explain most of the variance in DDM (r = 0.88). The amount of digestible protein was significantly correlated with crude protein content in the food. Mean transit time of food through the digestive tract varied from 3.9 (berries) to 8.5 (leaves) d. A second series of experiments, in which body temperatures were varied (T(b)) range: 30.0-degrees-36.1-degrees-C), showed that an increase in body temperature induced a significant curvilinear decrease of the transit time from 10 d down to 3 d. Dry-matter digestibility, however, was not affected by a change in body temperature. Maximal fresh-food intake was inversely related at a significant level to the transit time. It is argued that body temperature affects the potential digestive capacity of the green iguana.