Scientists have used numerous techniques to measure organismal metabolic rate, including assays of oxygen (O2) consumption and carbon dioxide (CO2) production. Relatively few studies have directly compared estimates of metabolic rate on the same groups of animals as determined by different assay methods. This study directly compared measures of the metabolic rate of three lines of Drosophila simulans as determined either from direct measures of CO2 production using infrared gas analysis (IRGA), or from estimates of O2 consumption based on manometeric techniques. Determinations of metabolic rate of the same cohorts of flies using these two methods produced results that often differed widely. Typically metabolic rate as determined by the manometric method was significantly greater than that determined by CO2 output. These differences are difficult to explain by simple biotic or abiotic factor(s). Because of the idiosyncratic nature of these differences it is not possible to use a simple factor to convert from metabolic rate measurements done using manometric techniques to those expected from direct measures of CO2 output or O2 consumption. Although manometric devices are simple to construct and use, measurements of metabolic rate made with this method can vary significantly from measurements made by directly assaying CO2 production or O2 consumption.
Bibliographical noteFunding Information:
Funds were provided by National Science Foundation Grant DEB-0444766, and National Institutes of Health RO1 grant GM067862-01 to J.W.O.B. and a National Cancer Institute MSI CCP NCI U56 CA96286 and 1U54132238 to W.V.V. Funds were provided to J.B.W. by NSF grant IBN 0212092. Two anonymous reviewers supplied very helpful comments on the original manuscript.
- Metabolic rate
- Oxygen consumption