Relationship between fish size and metabolic rate in the oxyconforming inanga Galaxias maculatus reveals size-dependent strategies to withstand hypoxia.
The relationship between metabolic rate and body size in animals is unlikely to be a constant but is instead shaped by a variety of intrinsic (i.e., physiological) and extrinsic (i.e., environmental) factors. This study examined the effect of environmental oxygen tension on oxygen consumption as a function of body mass in the galaxiid fish, inanga (Galaxias maculatus). As an oxyconformer, this fish lacks overt intrinsic regulation of oxygen consumption, eliminating this as a factor affecting the scaling relationship at different oxygen tensions. The relationship between oxygen consumption rate and body size was best described by a power function, with an exponent of 0.82, higher than the theoretical values of 0.66 or 0.75. The value of this exponent was significantly altered by environmental P(O2), first increasing as P(O2) decreased and then declining at the lowest P(O2) tested. These data suggest that the scaling exponent is species specific and regulated by extrinsic factors. Furthermore, the external P(O2) at which fish lost equilibrium was related to fish size, an effect explained by the scaling of anaerobic capacity with fish mass. Therefore, although bigger fish were forced to depress aerobic metabolism more rapidly than small fish when exposed to progressive hypoxia, they were better able to enact anaerobic metabolism, potentially extending their survival in hypoxia.
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand; 2Department of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
Mauricio A
MA
Urbina
Chris N
CN
Glover
D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D049628:Body Size / Q000502:physiology*; D005947:Glucose / Q000032:analysis; D000860:Hypoxia / Q000378:metabolism*; D007773:Lactates / Q000032:analysis; D018482:Muscle, Skeletal / Q000378:metabolism; D036441:Osmeriformes / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D012044:Regression Analysis
D007773:Lactates; D005947:Glucose; D010100:Oxygen