Adaptive Plasticity of Fish Locomotory Muscle

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The locomotory muscles of fishes have an extraordinary ability to alter their biochemical, physiological, and performance characteristics in response to ontogenetic, physiological, and environmental influences. Dr. Somero and his colleagues will experimentally modify the biochemical properties of white- and red muscles to establish clearer links between biochemical status and locomotory capacity. They will vary muscle biochemical state through altered dietary regimen and, then, quantitate enzymatic activities and swimming performance. They will determine how variations in transcriptional and translational activity and in protein turnover establish final concentrations of ATP generating enzymes. They will swim fishes at different intensities and measure how the intracellular localization--the compartmentalization-- of enzymes varies. Measurements of pH and of effectors that influence enzyme compartmentalization will be made concomitantly. Body size influences the levels of ATP generating enzymes in muscle and the regulatory mechanisms and will be evaluated. The regulatory mechanisms responsible for these size-dependent ("scaling") changes will be studied using techniques to quantify RNA concentrations and to measure protein synthesis and protein degradation. Deep-sea fish will be maintained in the laboratory to determine the extent to which the greatly reduced metabolic rates and swimming capabilites of these fishes are due to intrinsic, genetically-based factors, on the one hand, and dietary factors, on the other. They will attempt to bring the muscle biochemical robustness (e.g., enzyme levels and RNA concentrations) to the highest possible levels in these deep-living forms to establish their ultimate potential for activity and growth. The goal is an understanding of the biochemical and physiological basis for variations in locomotor capacity in fish.