Kralick Alexandra E, Loring Burgess M, Glowacka Halszka, Arbenz-Smith Keely, McGrath Kate, Ruff Christopher B, Chan King Chong, Cranfield Michael R, Stoinski Tara S, Bromage Timothy G, Mudakikwa Antoine, McFarlin Shannon C
Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, Washington, DC, 20052.
Department of Anthropology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104.
Am J Phys Anthropol. 2017 May;163(1):129-147. doi: 10.1002/ajpa.23192. Epub 2017 Mar 2.
While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda.
In 43 individuals (0.0-14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees.
Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees.
Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.
虽然牙齿发育对生活史研究很重要，但来自已知年龄野生大猩猩的数据却很稀少。我们报告了对野生维龙加山地大猩猩牙齿发育的首次放射学检查，使用了在卢旺达回收的已知年龄骨骼样本。
对43只个体（年龄范围为0.0至14.94岁），我们收集了下颌磨牙的X光片，并在可能的情况下进行了锥形束CT扫描。使用两种既定的分期系统评估磨牙冠和牙根的钙化状态，并使用多项式回归生成年龄预测方程。将结果与已知年龄的圈养和野生黑猩猩的现有数据进行比较。
山地大猩猩的发育阶段通常落在已报道的圈养黑猩猩的分布范围内或超过它们，在同等放射学发育阶段表现出更老的年龄。差异反映出与圈养黑猩猩相比，山地大猩猩第二磨牙冠发育的起始延迟和/或持续时间延长，以及第一和第二磨牙牙根发育延长。然而，与野生黑猩猩相比，磨牙牙根发育持续时间的差异不太明显。
尽管存在样本限制，我们的研究结果扩展了已知的大猩猩磨牙形成时间放射学估计的变化范围，并提供了一种基于野生样本的新的年龄预测技术。然而，与黑猩猩相比，山地大猩猩在磨牙形成的放射学评估中似乎没有加速，而在其他生活史特征方面它们是加速的。未来的研究应旨在解决物种差异、野生与圈养环境和/或抽样现象对这里观察到的模式的影响，以及更普遍地，它们如何与牙齿大小、萌出时间和发育生活史的变化相关。
