Histochemical and Ultrastructural Features of the Biceps Brachii of the African Chameleon (Chamaeleo senegalensis)

Characteristics of reptilian muscle fibres were investigated in the biceps brachii of the African chameleon, Chamaeleo senegalensis . Fibres were classified as slow and fast. These types of fibre were distinguished on the basis of histochemical staining for myofibrillar ATPase (mATPase). Fast fibres stained dark for mATPase while slow fibres stained light. The patterns of innervation of slow and fast fibres were investigated by staining nerve endings for acetylcholinesterase activity. Slow fibres have a pattern of multiple innervation, whereas fast fibres are associated with individual endplates. The organization of the myofibrils and the sarcoplasmic reticulum in slow muscle fibres from the chameleon biceps brachii was compared with that in fast fibres. Slow fibres lacked an M‐line and the Z‐lines were uneven. They had fibrils that were not clearly separated from each other and the sarcoplasmic reticulum was poorly developed. These features are in sharp contrast to those of fast fibres which had straight Z‐lines, clear M‐lines and well‐developed sarcoplasmic reticulum.