Analyzing Major Sources of Variation in the Relation Between Metabolic Heat Production and Respiratory Gas Exchange

Arizona State University, Scottsdale AZ

Investigators

Abstract

Energy is vital for both the propagation and maintenance of organisms. Thus, the use of metabolic energy and the heat that is produced as its byproduct is a major theme in modern biology. Animal energy usage is usually measured by "indirect calorimetry" that relies upon the exchange of respiratory gases by the organism (e.g., oxygen consumption or carbon dioxide production). An important complication in such analyses is that the relationship between respiratory gas exchange at the lungs and metabolic heat production is variable. These variations could have important consequences for our understanding of energy use by animals by producing substantial (e.g., >30%) errors in energetic analyses. This project will quantify the relationships between metabolic heat production in animals and their respiratory gas exchange, and determine the sensitivity of these relations to variables most likely to importantly affect energy metabolism. Critical variables to be explored include diet composition, intensity of metabolism, time of day relative to the animal's physiological cycles, and extent of time spent feeding or fasting. The most likely physiological bases of currently unexplainable variation in the relations between respiratory gas exchange and metabolic heat production will be explored. This portion of the research will focus on quantifying the various fates of the carbon dioxide that is produced by animal metabolism (e.g., exhaled through the lungs, stored in the body). This research will be conducted using a broad range of animals (insects, reptiles, birds) in order to evaluate the extent of biological variation in these basic energy relations.