Responses of Goldfish (Carassius auratus, L.) Muscle to Acclimation Temperature: Alterations in Biochemistry and Proportions of Different Fiber Types

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Abstract
The effect of temperature acclimation on the concentration or activity of several proteins from whole epaxial muscle and from subsamples of oxidative and glycolytic fibers from goldfish, Carassius auratus, was measured. Activity of cytochrome oxidase was significantly higher and lactate dehydrogenase lower in muscle tissue of goldfish acclimated to 5 C compared with animals acclimated to 25 C. Markers of aerobic function, succinic dehydrogenase, and myoglobin increased with cold acclimation in both oxidative and glycolytic fibers but were greater in oxidative fibers. Myofibrillar ATPase activity increased significantly with cold acclimation in both classes of muscle fiber but more dramatically in glycolytic fibers. Based on concentrations of biochemical constituents, the proportion of oxidative fibers in epaxial muscle is greater in cold-acclimated goldfish than in those acclimated to warmer temperatures. Increases in both oxidative fiber proportion and myofibrillar ATPase activity of oxidative fibers may explain acclimatory compensation of locomotory performance at low to moderate swimming speeds. Compensation of myofibrillar ATPase activity of white fibers may underlie the homeokinetic nature of burst-speed performance.