Morphology and Histochemistry of Flight Muscles in Free-Tailed Bats, Tadarida brasiliensis

Abstract

Three primary and two accessory flight muscles of Tadarida brasiliensis were studied using gross dissection and histochemical analysis. The pectoralis, subscapularis, and serratus ventralis thoracis muscles were composed entirely of fast oxidative fibers (FO), except for a restricted caudal portion of the latter muscle that included a small percentage of slow fibers (SO). The accessory flight muscles, triceps brachii and biceps brachii, included predominantly FO fibers except for deep-lying fascicles where a mixture of FO and SO fibers occurred. The exclusive presence of FO fibers in the primary flight muscles reflects the metabolic demands for high-speed flight over extended periods of time. The monotypic histochemical profile in these muscles represents a one-gear mechanical system for force production. Mixed populations of fiber types in the accessory flight muscles reflect the maintenance of postural or tonic role within these muscle groups. No fast glycolytic (FG) fibers were observed in any of the muscles studied, thus emphasizing the importance of oxidative metabolism in the flight muscles.