Oxygen consumption and lipid content in red and white muscles of antarctic fishes

Antarctic nototheniid fishes have red muscle which is restricted to the pectoral girdle region of the body. The muscle masses articulate the pectoral fins whose movement propels the fish during sustained low speed cruising. Both the rate of oxygen consumption and lipid content are higher in the red muscle masses than in white muscle. Electron microscope observations reveal large numbers of lipid droplets and mitochondria arranged in close association with one another. These findings support the hypothesis that red muscle is used for long, sustained swimming motion, and that lipid, rather than glycogen, is the main energy source for this activity.