Comparison of natural and pharmacological hypothermia in animals: Determination of activation energy of metabolism |
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Affiliation: | 1. Evolutionary Physiology and Animal Ecology Laboratory, Department of Biology, Dalhousie University, Halifax, B3H 1J8, Nova Scotia, Canada;2. Fish Ecology and Aquaculture Laboratory, Department of Biology, Mount Allison University, Sackville, E4L 1E4, New Brunswick, Canada;3. Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental and Interdisciplinary Sciences, Carleton University, Ottawa, Ontario, Canada;4. US Fish and Wildlife Service, Abernathy Fish Technology Center, Longview, 98632, WA, USA;5. Fisheries and Oceans Canada, Cooperative Resource Management Institute, School of Resource and Environmental Management, Simon Fraser University, Vancouver, V5A 1S6, British Columbia, Canada;6. Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, V6T 1Z4, British Columbia, Canada |
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Abstract: | The constancy of the activation energy of metabolism (E) for all living organisms is one of the most impressive, though controversial, statements of the modern metabolic theory of evolution. According to WBE-theory suggested by West, Brown, and Enquist, E should be in the range from −0.6 to −0.7 eV. However, there are many examples of significant deviations of E from the predictions of the theory. Now we have conducted a study of this value using rats in different types of pharmacological hypothermia: 1. Short-term (for several hours) hypothermia induced by anesthetic xylazine; 2. Daily torpor-like state induced by the pharmacological composition developed in our previous study. It has been found that in pharmacological daily hypothermia E = −0.56 ± 0.03 eV, which was close to that in daily heterotherms found in literature, E = −0.57 ± 0.04 eV. In short-term hypothermia E was substantially lower, E = −0.17 ± 0.071 eV. Our analysis revealed that in short-term hypothermia, changes in body temperature may lag behind changes in metabolic rate for a period Δt, affecting E. We propose an approach for estimating Δt and obtaining an adjusted E = −0.68 ± 0.17 eV, which corresponds to theoretical predictions. We assume that a similar consideration of Δt should be done when calculating E of daily heterotherms. We assume that in ectotherms, when the ambient temperature changes rapidly, changes in metabolic rate may lag behind changes in body temperature for a period (−) Δt, that should also be considered in E calculations. The proposed approach may contribute to the further development of the metabolic theory of evolution and may be useful in comparing artificial and natural hypothermia, as well as in studying the energy transformations in ecosystems. |
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Keywords: | Allometry Energetics Hibernation Heterotherms Endotherms Ectotherms Metabolism Metabolic theory of ecology Torpor body mass activation energy of metabolism I" },{" #name" :" keyword" ," $" :{" id" :" kwrd0075a" }," $$" :[{" #name" :" text" ," _" :" whole-organism metabolic rate FWHM" },{" #name" :" keyword" ," $" :{" id" :" kwrd0080" }," $$" :[{" #name" :" text" ," _" :" full width at half maximum Boltzmann constant coefficient of determination PITS" },{" #name" :" keyword" ," $" :{" id" :" kwrd0110" }," $$" :[{" #name" :" text" ," _" :" Pharmacologically Induced Torpor-like State MTE" },{" #name" :" keyword" ," $" :{" id" :" kwrd0120" }," $$" :[{" #name" :" text" ," _" :" Metabolic Theory of Ecology WBE" },{" #name" :" keyword" ," $" :{" id" :" kwrd0130" }," $$" :[{" #name" :" text" ," _" :" West Brown and Enquist theory |
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