Document Detail

Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape.
MedLine Citation:
PMID:  19875148     Owner:  NLM     Status:  MEDLINE    
Tufted capuchins (sensu lato) are renowned for their dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between C. apella (n=12) and two "untufted" capuchins (C. capucinus, n=3; C. albifrons, n=5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that tufted capuchins exhibit architectural properties of their jaw muscles that facilitate relatively large forces including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P(0)). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P(0). As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in tufted capuchins primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear to have increased jaw-muscle and bite forces without markedly compromising muscle excursion and contraction velocity. One performance advantage of this morphology is that it promotes relatively large bite forces at wide jaw gapes, which may be useful for processing large food items along the posterior dentition. We further hypothesize that this morphological pattern may have the ecological benefit of facilitating the dietary diversity seen in tufted capuchins. Lastly, the observed feeding on large objects, coupled with a jaw-muscle architecture that facilitates this behavior, raises concerns about utilizing C. apella as an extant behavioral model for hominins that might have specialized on small objects in their diets.
Andrea B Taylor; Christopher J Vinyard
Related Documents :
7977678 - Jaw muscle function and wishboning of the mandible during mastication in macaques and b...
9021318 - Coordinated electromyographic activity of the human masseter and temporalis anterior mu...
9533608 - Measurement of muscle hardness: a methodological study.
19488478 - Effects of the unilateral removal and dissection of the masseter muscle on the facial g...
4092408 - Muscle carnitine deficiency in old age. case report and therapeutic results.
8385638 - Rapid preparation of subsarcolemmal and interfibrillar mitochondrial subpopulations fro...
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2009-10-28
Journal Detail:
Title:  Journal of human evolution     Volume:  57     ISSN:  1095-8606     ISO Abbreviation:  J. Hum. Evol.     Publication Date:  2009 Dec 
Date Detail:
Created Date:  2009-11-27     Completed Date:  2010-02-12     Revised Date:  2014-09-21    
Medline Journal Info:
Nlm Unique ID:  0337330     Medline TA:  J Hum Evol     Country:  England    
Other Details:
Languages:  eng     Pagination:  710-20     Citation Subset:  IM    
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Bite Force
Cebus / anatomy & histology*,  physiology,  psychology
Feeding Behavior*
Jaw / physiology
Masseter Muscle / anatomy & histology*,  physiology
Mastication / physiology
Muscle Fibers, Skeletal / cytology*,  physiology
Muscle Strength
Temporal Muscle / anatomy & histology*,  physiology
Grant Support
R24 HD050837/HD/NICHD NIH HHS; R24 HD050837-01/HD/NICHD NIH HHS; R24 HD050837-01/HD/NICHD NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Transformation of the water soluble fraction from "alpeorujo" by Coriolopsis rigida: The role of lac...
Next Document:  Testing hypotheses of dietary reconstruction from buccal dental microwear in Australopithecus afaren...