The morphology of the masticatory apparatus facilitates muscle force production at wide jaw gapes in tree-gouging common marmosets (Callithrix jacchus)
The morphology of the masticatory apparatus facilitates muscle force production at wide jaw gapes in tree-gouging common marmosets (Callithrix jacchus)
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DOI：
10.1242/jeb.029983
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发表时间：
2009-12-15
影响因子：
2.8
通讯作者：
Taylor, A. B.
中科院分区：
文献类型：
--
作者：
Eng, C. M.;Ward, S. R.;Taylor, A. B.
普通的绒猴（Callithrix jacchus）在用前牙刨树时会产生宽的下颚，以引起树的分泌物流出。近亲棉顶绢毛猴（Saguinus oedipus）不挖树，但共享相似的饮食，包括分泌物。从理论上讲，最大限度地打开下颚会降低绒猴在刨削过程中产生的咬合力。为了研究在刨削过程中下颌肌肉结构和颅面位置如何影响肌肉性能，我们将联合收割机头骨和下颌肌肉结构特征结合起来，在这两个物种的一系列下颌张口中模拟肌肉力量的产生。我们结合关节力学，休息肌节长度和肌肉结构的估计，从咬肌和颞肌模型肌肉偏移，肌节长度和相对张力作为关节角度的函数。从咬合到估计最大功能性张口度55 °的肌肉偏移。在C. jacchus与S.伊底帕斯除了后颞肌。由于分布在串联的更多肌节（即较长的纤维）上的肌肉偏移减少，C的肌节长度操作范围较小。jacchus下颚肌肉在这个范围的张口。这种配置允许C. jacchus在更大的间隙作用于长度-张力曲线的更有利的部分，从而在这些肌肉中产生相对更大的张力。俄狄浦斯我们的研究结果表明，咬性能在树刨普通绒猴改善肌肉骨骼配置，减少肌肉拉伸在宽的gapes，同时促进相对较大的肌肉力量在极端的下巴打开。
Common marmosets (Callithrix jacchus) generate wide jaw gapes when gouging trees with their anterior teeth to elicit tree exudate flow. Closely related cotton-top tamarins (Saguinus oedipus) do not gouge trees but share similar diets including exudates. Maximizing jaw opening theoretically compromises the bite forces that marmosets can generate during gouging. To investigate how jaw-muscle architecture and craniofacial position impact muscle performance during gouging, we combine skull and jaw-muscle architectural features to model muscle force production across a range of jaw gapes in these two species. We incorporate joint mechanics, resting sarcomere length and muscle architecture estimates from the masseter and temporalis to model muscle excursion, sarcomere length and relative tension as a function of joint angle. Muscle excursion from occlusion to an estimated maximum functional gape of 55 deg. was smaller in all regions of the masseter and temporalis of C. jacchus compared with S. oedipus except the posterior temporalis. As a consequence of reduced muscle excursion distributed over more sarcomeres in series (i.e. longer fibers), sarcomere length operating ranges are smaller in C. jacchus jaw muscles across this range of gapes. This configuration allows C. jacchus to act on a more favorable portion of the length-tension curve at larger gapes and thereby generate relatively greater tension in these muscles compared with S. oedipus. Our results suggest that biting performance during tree gouging in common marmosets is improved by a musculoskeletal configuration that reduces muscle stretch at wide gapes while simultaneously facilitating comparatively large muscle forces at the extremes of jaw opening.