The effect of dehydration on the metabolic rate and locomotor performance of two species of tree frogs found in Southern California (Pseudacris regilla and P. cadaverina)

Abstract

Pacific tree frogs (Psedacris regilla) and California tree frogs (P. cadaverina), native to Southern California, have adapted to frequent periods of drought. These tree frogs show both behavioral and physiological adaptations that help diminish water loss to their environment. However, despite these adaptations, tree frogs may still experience periods of dehydration in their natural habitat. Dehydration significantly decreases aerobic scope in amphibians; frogs being more susceptible than toads. When dehydrated, semi‐aquatic frogs rely heavily on anaerobic metabolism, which has been shown to induce hyperglycemia and decreased organ ATP levels. In this study we are interested in evaluating the effects of dehydration on the aerobic scope of P. regilla and P. cadaverina, two highly terrestrial treefrogs. Furthermore we will investigate the effects of dehydration on the respiratory quotient of these frogs. Evaporative water loss in frogs can lead to a loss of 6–9% of initial body mass per day on land. In this study 8 frogs from each species were dehydrated to 5, 10, 15% of their initial body weight and then placed in a respiratory chamber so that standard metabolic rates were measured. After metabolic rates were recorded, hoping speed and the time it took for animals to right themselves were measured. After an exercise bout, the metabolic rate of all frogs was once again measured in all animals to determine the effect of dehydration on aerobic scope. Previously we have reported that P. regilla drinks water opportunistically whereas P. cadaverina must reach at least 18% dehydration before water absorption behaviors are consistently employed. Since there are significant differences in the levels of dehydration that each frog can endure before rehydration is normally established we expect to see differences in both aerobic scope, locomotion performance and the time it takes for frogs to switch to carbohydrates as the primary fuel for metabolism.Support or Funding InformationTitle V STEM Grant