title: Activity affects intraspecific body-size scaling of metabolic rate in ectothermic animals.
abstract: Metabolic rate is commonly thought to scale with body mass (M) to the 3/4 power. However, the metabolic scaling exponent (b) may vary with activity state, as has been shown chiefly for interspecific relationships. Here I use a meta-analysis of literature data to test whether b changes with activity level within species of ectothermic animals. Data for 19 species show that b is usually higher during active exercise (mean +/- 95% confidence limits = 0.918 +/- 0.038) than during rest (0.768 +/- 0.069). This significant upward shift in b to near 1 is consistent with the metabolic level boundaries hypothesis, which predicts that maximal metabolic rate during exercise should be chiefly influenced by volume-related muscular power production (scaling as M (1)). This dependence of b on activity level does not appear to be a simple temperature effect because body temperature in ectotherms changes very little during exercise.
authors.affiliation: Department of Biology, Juniata College, Huntingdon, PA, 16652, USA. glazier@juniata.edu
authors.forename: Douglas Stewart
authors.initials: DS
authors.lastname: Glazier
mesh_terms: D000818:Animals; D001001:Anura / Q000033:anatomy & histology / Q000502:physiology; D001481:Basal Metabolism / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D016001:Confidence Intervals; D003445:Crustacea / Q000033:anatomy & histology / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D004777:Environment; D005399:Fishes / Q000033:anatomy & histology / Q000502:physiology; D016018:Least-Squares Analysis; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D012104:Reptiles / Q000033:anatomy & histology / Q000502:physiology; D014714:Vertebrates / Q000033:anatomy & histology / Q000502:physiology*