Low-temperature adaptation of oxidative energy production in cold-water fishes

Abstract

This paper addresses the possibility that oxidative energy production in fish muscle is limited by low temperatures. Data are used from species that seasonally acclimatize to low temperatures, and from animals that have adapted to low temperatures over an evolutionary period. It is likely that the inhibitory effect of declining temperatures on the potential rate of oxidative energy production is compensated for largely by increasing the volume of mitochondria in the cell (volume density). For fishes that acclimatize, this increase in mitochondrial volume density may offset diffusion limitations. This is less likely for species that have adapted to low temperatures, because these animals have also developed large-diameter muscle cells. It is suggested that the stimuli for increasing cellular mitochondrial volume density, be they diffusion limitations or catalytic limitations, have not totally been overcome by increased mitochondrial volume density. In addition, a further restriction is concurrently placed upon maximum rates of oxygen uptake by the cell because the increase in mitochondrial volume density occurs at the expense of myofibrillar volume. This has the effect of reducing the maximum rate at which ATP can be used by working muscle.