Department of Anthropology, University of Arkansas, Fayetteville, Arkansas, United States.
Department of Anatomy, Arkansas College of Osteopathic Medicine, Arkansas Colleges of Health Education, Fort Smith, Arkansas, United States.
Am J Biol Anthropol. 2024 Oct;185(2):e25006. doi: 10.1002/ajpa.25006. Epub 2024 Jul 24.
Cortical bone geometry is commonly used to investigate biomechanical properties of primate mandibles. However, the ontogeny of these properties is less understood. Here we investigate changes in cortical bone cross-sectional properties throughout capuchin ontogeny and compare captive versus wild, semi-provisioned groups. Tufted capuchins (Sapajus spp.) are known to consume relatively hard/tough foods, while untufted capuchins (Cebus spp.) exploit less mechanically challenging foods. Previous research indicates dietary differences are present early in development and adult Sapajus mandibles can resist higher bending/shear/torsional loads.
This study utilized microCT scans of 22 Cebus and 45 Sapajus from early infancy to adulthood from three sample populations: one captive Cebus, one captive Sapajus, and one semi-provisioned, free-ranging Sapajus. Mandibular cross-sectional properties were calculated at the symphysis, P, and M. If the tooth had not erupted, its position within the crypt was used. A series of one-way ANOVAs were performed to assess differences between and within the sample populations.
Mandible robusticity increases across ontogeny for all three sample populations. Sapajus were better able to withstand bending and torsional loading even early in ontogeny, but no difference in shear resistance was found. Semi-provisioned, free-ranging Sapajus tend to show increased abilities to resist bending and torsional loading but not shear loading compared to captive Sapajus.
This study helps advance our understanding of the primate masticatory system development and opens the door for further studies into adaptive plasticity in shaping the masticatory apparatus of capuchins and differences in captive versus free-ranging sample populations.
皮质骨几何形状常用于研究灵长类下颌骨的生物力学特性。然而，这些特性的发育过程还不太清楚。本研究调查了卷尾猴属（Sapajus spp.）皮质骨横截面积特性在整个发育过程中的变化，并比较了圈养和半散养、有补充食物供应的群体。已知戴帽卷尾猴（Sapajus spp.）食用相对坚硬/坚韧的食物，而无帽卷尾猴（Cebus spp.）则以机械挑战性较低的食物为食。之前的研究表明，饮食差异在发育早期就存在，并且成年萨氏卷尾猴的下颌骨能够抵抗更高的弯曲/剪切/扭转负荷。
本研究利用来自三个样本群体的 22 只 Cebus 和 45 只 Sapajus 的微 CT 扫描，从婴儿期到成年期：一个圈养的 Cebus 群体，一个圈养的 Sapajus 群体，以及一个半散养、自由放养的 Sapajus 群体。在下颌联合处、P 和 M 处计算下颌骨的横截面特性。如果牙齿尚未萌出，则使用其在牙槽中的位置。进行了一系列单向方差分析，以评估样本群体之间和内部的差异。
所有三个样本群体的下颌骨粗壮度都随着发育而增加。即使在发育早期，萨氏卷尾猴也能更好地承受弯曲和扭转负荷，但在剪切阻力方面没有差异。与圈养的 Sapajus 相比，半散养、自由放养的 Sapajus 往往表现出更强的抵抗弯曲和扭转负荷的能力，但在抵抗剪切负荷方面没有差异。
本研究有助于提高我们对灵长类咀嚼系统发育的理解，并为进一步研究卷尾猴咀嚼器官的适应性可塑性以及圈养与自由放养样本群体之间的差异开辟了道路。
