Cytochemical differentiation of muscle fibers by succinic dehydrogenase (SDH) activity in the respiratory muscles of an air-breathing fish, Channa punctatus (Bloch).

1. A cytochemical study on the succinic dehydrogenase activity of the respiratory muscles of Channa punctatus reveals that the Adductor mandibularis is made up entirely of white muscle fibers. 2. The Adductor, Dilator and Levator operculi are composite muscles and composed of white as well as red fiber bundles. However, these composite muscles are dominated by white muscle fibers. 3. The interior of the Protractor hyoideus is dominated by red and medium fibers whereas its superficial part is dominated by white muscle fibres. 4. The muscles innervated by the branches of V trigeminal nerve (Adductor mandibularis, Dilator operculi) are dominated by white fibers, whereas those innervated by the VII facialis (Adductor and Levator operculi and Protractor hyoideus) show dominance of red fibers.