Fiber types distribution in the digastric muscle of tufted capuchin monkey (Cebus apella)

Fiber types distribution in the digastric muscle of tufted capuchin monkey was studied by means of NADH-TR, myosin-ATPase, after alkaline and acid preincubations and SDH histochemical reactions. Three different types of fibers were found presenting an equal distribution. The percentage and types of fibers were as follow: 18.2% SO (Slow Oxidative), 38.4% FOG (Fast Oxidative Glycolytic) and 43.4% FG (Fast Glycolytic). FG fibers revealed the largest area. The relatively high concentration of fast twitch (81.2%) seems to indicate this muscle is involved with the acceleration and fast speed of jaw movements. Aerobic metabolism represented by SO + FOG fibers (56.6%) suggests that this muscle possesses an additional role than that related to the lowering of the jaw.