Histoenzymology and Morphometry of the Masticatory Muscles of Tufted Capuchin Monkey (&lt;i&gt;Cebus apella Linnaeus&lt;/i&gt;, 1758)

Andreo, Jesús Carlos; Oliveira, José Américo de; Navarro, João Adolfo Caldas; Roque, Domingos Donizeti; Roque, José Sidney; Buchain, R.L.

doi:10.2535/ofaj.79.33

Cited by 5 publications

(12 citation statements)

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“…While this finding might initially point to a physiological explanation for the larger jaw-muscle mass in C. apella , most primate jaw muscles studied to date comprise a significant percentage of Type II fibers (Rowlerson et al, 1983; Andreo et al, 2002). Furthermore, Andreo et al (2002) did not clearly define from where they sampled within the muscles. For example, they reported that temporalis samples were taken from the anterior and posterior regions of the muscle.…”

Section: Discussionmentioning

confidence: 95%

“…In a study of C. apella , Andreo et al (2002) found that the masseter and temporalis muscles of tufted capuchins include a predominance of Type II fibers. While this finding might initially point to a physiological explanation for the larger jaw-muscle mass in C. apella , most primate jaw muscles studied to date comprise a significant percentage of Type II fibers (Rowlerson et al, 1983; Andreo et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

“…The morphological, contractile, and metabolic properties of Type II fibers make them better suited for generating force compared to Type I fibers (Close, 1972; Bodine et al, 1987). These physiological differences have led previous investigators to link the predominance of Type II fibers in the jaw muscles of primates to feeding behaviors that require the generation of rapid, forceful bites (Rowlerson et al, 1983; Andreo et al, 2002; Hoh, 2002; Wall et al, 2008). This third pathway could involve environmentally-induced (i.e., plastic) changes in fiber type and size related to increased mechanical loading and enhanced neuromuscular activity (Pette and Staron, 2000) and/or evolutionary (i.e., heritable) changes in fiber type (Komi et al 1977; Staron 1997; Rivero and Barrey 2001).…”

Section: Discussionmentioning

confidence: 99%

“…However, Wall et al (2008) noted substantial differences in fiber type composition between the superficial and deep portions of the temporalis in papionins, with the superficial portion being composed almost entirely of Type II fibers and exhibiting higher levels of EMG recruitment during forceful chewing. Thus, the results from Andreo et al (2002) may partly reflect sampling of areas within the jaw muscles that predominately consist of Type II fibers.…”

Section: Discussionmentioning

confidence: 99%

“…These feeding behaviors would suggest a functional benefit to maintaining a less economical architectural configuration. The metabolic costs might be further exacerbated if the jaw muscles of C. apella are comprised predominately of metabolically-expensive, Type II fibers (Andreo et al, 2002). …”

Section: Discussionmentioning

confidence: 99%

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Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape

Taylor

Vinyard

2009

Journal of Human Evolution

103

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Cebus apella is renowned for its 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 the tufted capuchin (C. apella; n = 12 ) and two "untufted" capuchins (C. capuchinus, 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 C. apella exhibits 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, whole 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 C. apella 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

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Section: Discussionmentioning

confidence: 95%