A Histophysiological Study of the Red and White Muscles of the Mackerel

The red and white muscles of the Mackerel, Rastrelliger kanagurta Russell, were studied with respect to their fat content and enzyme (lipase and succinic dehydrogenase) concentrations. It was found that the red muscle, concentrated along the lateral line had a considerably higher amount of extraas well as intra-cellular store of fat and lipase activity in the fibres. Histochemical observations showed that succinic dehydrogenase was localized in the mitochondria which were numerous in the red and sparse in the white muscle fibres. The red muscle was thus found to be well adapted for an aerobic metabolism to use fat as the chief fuel for muscular activity and the white for an anaerobic metabolism to use mainly glycogen. The respective roles of the two muscle types in the migratory travel of this fish as well as of others are suggested.