Distribution Pattern of Muscle Fiber Type in Musculus Biceps Brachii of White-Handed Gibbon

Abstract

Histochemical examinations of muscle fiber types by Sudan black B staining were made on m. biceps brachii of male and female white-handed gibbon (Hylobates lar). Three types of muscle fibers could be discriminated in terms of the reaction to the pigment and the cellular diameter: red muscle fiber (type I) with a positive reaction and a small diameter; white muscle fiber (type II) with a weak reaction and a large diameter; intermediate muscle fiber (type III) with an intermediate reaction and diameter. Of 4648 muscle fiber cells, in average of male and female, scanned in the cross-section, red muscle fibers accounted for 44.1%, white muscle fibers 28.3%, and intermediate muscle fibers 27.6%, respectively. White muscle fibers were clearly localized in the external layers of both heads of m. biceps brachii. In contrast, red muscle fibers were more evenly distributed throughout the muscle though moderately localized in the regions adjacent to the sulcus bicipitalis medialis. Intermediate muscle fibers showed no specific localization at all. These results suggest that m. biceps brachii of the gibbon, an acrobatic armswinger, is inclined to be a red muscle that is fatigue-resisting rather than power-generating.