The gut is the first organ system to be directly affected by changes in food intake and displays incredible plasticity in its response to fluctuating digestive conditions. The gut is energetically expensive to maintain in a functional state and consequently, when most animals are deprived of food their guts are down-regulated to conserve energy. A functionally and morphologically down-regulated gut can potentially impair the subsequent ability of the animal to digest and assimilate nutrients upon re-feeding. Yet, prolonged episodes of food deprivation are routinely undertaken by numerous animal species often as a consequence of natural environmental conditions (e.g. hibernation). In contrast to studies on laboratory rodents, the impact of prolonged food deprivation on the small intestine of animals that naturally undertake prolonged food deprivation episodes and the impact such changes might have on the digestive capabilities of these animals is virtually unknown. Aestivating frogs provide an ideal model to examine the impact of prolonged food deprivation on the gut and any impacts these changes might have on the re-feeding ability of these animals. We have examined the response of the gut of the green striped burrowing frog, Cyclorana alboguttata to natural periods of food deprivation occurring during 3 and 9 months aestivation and have assessed the impact of such changes on the subsequent ability of the animal to re-feed following aestivation.

We are continuing this study to incorporate new molecular tools and expanding upon our existing studies. We are currently investigating the regulation of energy expenditure by the intestine during feeding and aestivation, with a particular focus on Na-K-ATPase. We are also looking at the regulation of intestinal amino acid transport systems in the gut of active and aestivating frogs and their responses to changes in cell turnover rates. This research provides new and exciting insights into the regulation of intestinal function, with particular focus on adaptation to food deprivation in natural model system.

Publications:
Cramp, R. L. and Franklin, C. E. (2003). Is refeeding efficiency compromised by prolonged fasting in the green-striped burrowing frog, Cyclorana alboguttata? J Exp Zool 300A, 126-132.

Cramp, R. L. (2005). The effects of prolonged food deprivation during aestivation and re-feeding on the structure and function of the gut in the green-striped burrowing frog, Cyclorana alboguttata. PhD Thesis, School of Integrative Biology, The University of Queensland.

Cramp, R. L. and Franklin, C. E. (2005). Arousal and re-feeding rapidly restores digestive tract morphology following aestivation in green-striped burrowing frogs. Comp Biochem Physiol A Mol Integr Physiol 142, 451-460.

Cramp, R. L., Franklin, C. E. and Meyer, E. A. (2005). The impact of prolonged fasting during aestivation on the structure of the small intestine in the green-striped burrowing frog, Cyclorana alboguttata. Acta Zool-Stockholm 86, 13-24.