The effects of body size and temperature on metabolic rate of organisms

Abstract

Multiple regression analyses of previously published data were performed to describe the effect of variations in body mass (M, in grams) and temperature (t, in degrees Celsius) on the rate of oxygen consumption ([Formula: see text], in millilitres O2 per gram per hour). For homeotherms and poikilotherms, the resultant equations describing standard metabolic rate are [Formula: see text] and [Formula: see text], respectively. The metabolic rate of unicells was described by [Formula: see text], although the temperature term was not statistically significant. When solved at 39 °C, the homeotherm equation is essentially similar to previously published relations. At 20 °C, the poikilotherm relation is slightly higher, and the unicell relation considerably lower, than Hemmingsen's widely cited relations. Enough data were available to provide a statistical description of active reptiles and fish: [Formula: see text]; this relationship may be used to approximate the metabolic rate of actively foraging fish and reptiles. Equations for the standard metabolic rate can serve as components in the calculation of minimal metabolic rates of homeotherms and higher poikilotherms in nature; such values could then be increased by estimates of the additional demands associated with movement, feeding, growth, etc. For unicells and lower vertebrates, standard rates also serve as estimates of free-living rates.