ULTRASTRUCTURE OF CARDIAC MYOCYTES IN THE GREATER BANDICOOT RAT (BANDICOTA-INDICA)

Cardiac myocytes in the left ventricle and atrium of the greater bandi coot rat (Bandicota indica) were examined by transmission electron mic roscopy. The fine structure showed typical features of mammalian cardi ac myocytes. In atrial myocytes, however, the areas occupied by mitoch ondria were much smaller than that filled with myofibrils. The decreas e in mitochondria and the abundance of myofibrils are thought to be an ultrastructural adaptation to the large body size of this species. Ma ny conducting myocytes were observed in both atrium and ventricle. The atrial conducting myocytes were ultrastructurally :different from the Purkinje fibers of the ventricle. We suggest that the abundance and t he ultrastructural variation of conducting myocytes are related to the physiological aspects, such as body size, of this animal.