Meeting Abstract
The power scaling of metabolic rate with body mass is fundamental to animal biology, due to the profound influence that animal size has on ecology and physiology, yet the value of the scaling exponent (b) is highly debated. b has been suggested to be fixed at 0.67 or 0.75, or to vary systematically with cell size and metabolic intensity, within the boundaries of 0.67 and 1. Despite this tremendous interest in the value of scaling exponents, little is known about metabolic scaling within individual animals and how this relates to population-level scaling. We conducted a long-term study that repeatedly characterised the entire metabolic profile of 68 individual fish (cunner, Tautogolabrus adspersus) by measuring their standard metabolic rate (SMR), routine metabolic rate (RMR), active metabolic rate (AMR), and aerobic scope (AS) in five separate trials over 10 months (full fish mass range, 0.5-19.5 g). The mean exponents for the experimental population of fish at any single point in time (i.e., within trials; bSMR=0.89, bRMR=0.89, bAMR=0.94, bAS=0.96) were higher than those characterising the population as it aged (i.e., across all trials; bSMR=0.82, bRMR=0.84, bAMR=0.90, bAS=0.92), and both were higher than the mean exponents for individual fish (bSMR=0.74, bRMR=0.79, bAMR=0.83, bAS=0.85). This variation in scaling pattern, occurring across different levels of community structure, has implications for bioenergetics- and ecosystem models, and suggests that studies on population dynamics should apply metabolic scaling exponents that are significantly higher than those used in studies on individuals.
