title: Intraspecific variation in aerobic metabolic rate of fish: relations with organ size and enzyme activity in brown trout.
abstract: Highly active animals require a high aerobic capacity (i.e., a high maximum metabolic rate [MMR]) to sustain such activity, and it has been speculated that a greater capacity for aerobic performance is reflected in larger organs, which serve as energy processors but are also expensive to maintain and which increase the minimal cost of living (i.e., the basal or standard metabolic rate [SMR]). In this study, we assessed the extent of intraspecific variation in metabolic rate within a group of brown trout (Salmo trutta L.) and tested whether the observed variation in residual (body-mass-corrected) SMR, MMR, and absolute aerobic scope could be explained by variations in the residual size (mass) of metabolically active internal organs. Residual SMR was found to correlate positively with residual MMR, indicating a link between these two metabolic parameters, but no relationship between organ mass and metabolic rate was found for liver, heart, spleen, intestine, or stomach. Instead, activity in the liver of two aerobic mitochondrial enzymes, cytochrome c oxidase and, to a lesser extent, citrate synthase, was found to correlate with whole-animal metabolic rate, indicating that causes for intraspecific variation in the metabolic rate of fish can be found at a lower organizational level than organ size.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark. tommy.norin@biology.au.dk
authors.forename: Tommy
authors.initials: T
authors.lastname: Norin
authors.forename: Hans
authors.initials: H
authors.lastname: Malte
mesh_terms: D000332:Aerobiosis; D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D016014:Linear Models; D008099:Liver / Q000033:anatomy & histology / Q000201:enzymology / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism; D009929:Organ Size / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D014337:Trout / Q000033:anatomy & histology* / Q000378:metabolism*
chemical_list: D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase