A comparative ultrastructural study of the cardiac and skeletal striated muscles of the skink.

Ultrastructural differences between cardiac and striated muscle fibres observed in the ocellated skink (Chalcides ocellatus ocellatus) indicate that functional differences have a structural correlate in the muscle cells. Although the myofibrils of both the cardiac and skeletal muscles displayed the same typical band pattern, differences in mean nuclear diameter and sarcomere length and in the A, I, Z, H, and M bands (discs) were observed. In addition, differences were found in the number, size and distribution of the mitochondria in the two types of muscle fibres. The Golgi complex was indistinguishable in skeletal muscles, but small Golgi vesicles could (with difficulty) be identified in cardiac muscle fibres. Skeletal striated muscle fibres were also found to contain significantly more glycogen granules, smooth sarcoplasm vesicles and heterochromatin than cardiac muscles. Three types of junctional complexes were identified in the cardiac muscles.