Fiber architecture of the intrinsic muscles of the shoulder and arm in semiterrestrial and arboreal guenons
Article first published online: 8 APR 2003
Copyright © 2003 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 122, Issue 1, pages 51–65, September 2003
How to Cite
Anapol, F. and Gray, J. P. (2003), Fiber architecture of the intrinsic muscles of the shoulder and arm in semiterrestrial and arboreal guenons. Am. J. Phys. Anthropol., 122: 51–65. doi: 10.1002/ajpa.10269
- Issue published online: 11 AUG 2003
- Article first published online: 8 APR 2003
- Manuscript Accepted: 13 JAN 2003
- Manuscript Received: 25 JUL 2002
- National Science Foundation. Grant Number: DBS-9221795
- Chlorocebus aethiops;
- Cercopithecus ascanius
The internal organization of myofibers and connective tissues has important physiologic implications for muscle function and for naturalistic behavior. In this study of forelimb muscle morphology and primate locomotion, fiber architecture is examined in the intrinsic muscles of the shoulder (musculi deltoideus, infraspinatus, supraspinatus, subscapularis, teres major, and t. minor) and arm (m. coracobrachialis, biceps brachii, brachialis, and triceps brachii) in the semiterrestrial vervets (Chlorocebus aethiops) and arboreal red-tailed guenons (Cercopithecus ascanius). Wet weights and lengths of whole muscles, lengths of fasciculi and their associated proximal and distal tendons, and angles of pinnation were measured to estimate morphologic correlates of physiologic properties of individual muscles: force, velocity/excursion, energy expense, and relative isometric or isotonic contraction. Neither mean total-shoulder:total-arm ratios for muscle mass nor total reduced physiological cross-sectional area exhibited significant (P < 0.05) interspecific differences, thus emphasizing the importance of fine-tuning musculoskeletal analyses by the data collected here. The results generally support those previously published for quadriceps femoris and triceps surae of the hind limb in these species (Anapol and Barry  Am. J. Phys. Anthropol. 99:429–447). The fiber architecture of the semiterrestrial vervets is largely suited for higher velocity while running on the ground. By contrast, the architectural configuration of red-tailed monkeys implies relatively isometric muscle contraction and passive storage of elastic strain energy for exploitation of the compliant canopy, where substrate components are situated beneath the sagittal plane of the animal. With respect to relative distribution of maximum potential force output among muscles of either shoulder or arm groups in these otherwise hind limb-dominated quadrupedal primates, statistically significant interspecific differences are best interpreted in light of braking, climbing, and, for vervets, the transition between ground and canopy.
The interspecific differences shown here for the intrinsic muscles of the shoulder and arm underscore the significance of intramuscular morphology in reconciling structure and function with regard to locomotor behavior. Its analysis and interpretation lend support to consideration of “semiterrestrial” as a bona fide locomotor category uniquely different from what is practiced by dedicated arboreal and terrestrial quadrupeds that occasionally visit the habitat of one another. Data from a more committed terrestrial species would clarify this enigma. Am J Phys Anthropol, 2003. © 2003 Wiley-Liss, Inc.