Skinner Mark Fretson, Asami Mao, Skinner Matthew M, Kato Akiko
Archeology, Simon Fraser University, Burnaby, British Columbia, Canada.
Center for the Evolutionary Origins of Human Behavior, Kyoto University (EHUB), Kyoto, Japan.
Am J Primatol. 2025 Jan;87(1):e23713. doi: 10.1002/ajp.23713.
Japanese macaques are ideal to advance understanding of a wide-spread pattern of recurrent developmental distress in great apes, preserved as repetitive linear enamel hypoplasia (rLEH). Not only are they numerous, unendangered, and well-studied, but they are distributed from warm-temperate evergreen habitats in southern Japan to cool-temperate habitats in the north, where they are adapted behaviorally and phenotypically to winter cold and seasonal undernutrition. We provide a pilot study to determine if enamel hypoplasia exists in Japanese macaques from the north and, if temporal patterns of enamel hypoplasia are consistent with seasonal cold, undernutrition and/or exposure to secondary plant compounds. High-resolution casts of canine teeth from 15 males obtained from Shimokita Peninsula (latitude 41.3° N) between 2012 and 2014, whose skeletons are curated at the Center for the Evolutionary Origins of Human Behavior, Kyoto University, were imaged by confocal and scanning electron microscopy. Perikymata, the surface expression of regularly deposited imbricational layers of enamel, provide an estimate of time between and within hypoplastic enamel defects. Based on histological sections from five individuals, we determined Retzius periodicity to be 7 days. Evidence for recurrence, duration, and severity of 68 LEH defects was collected from perikymata counts as well as measurements of LEH angle of onset, depth and width. Male canine teeth show four to five recurrent, evenly-spaced enamel defects per crown with a median of 54.8 (range 18-74) perikymata between defects; lasting on average 8.7 (range 1-20) perikymata. These translate into repetitive developmental distress averaging every 1.05 years, lasting 8.7 weeks, less than local winter foraging conditions (100 days). We conclude that linear enamel hypoplasia recurs circ-annually among high-latitude male monkeys from Japan. The triad of cold, hunger and anti-feedants can be differentiated in future study through recourse to provisioned and un-provisioned populations throughout the Japanese archipelago.
日本猕猴是增进对大型猿类中广泛存在的反复发育应激模式理解的理想对象，这种模式表现为重复性线性釉质发育不全（rLEH）。它们不仅数量众多、未濒危且研究充分，而且分布于日本南部的暖温带常绿栖息地到北部的寒温带栖息地，在那里它们在行为和表型上适应了冬季寒冷和季节性营养不良。我们进行了一项初步研究，以确定来自北方的日本猕猴是否存在釉质发育不全，以及釉质发育不全的时间模式是否与季节性寒冷、营养不良和/或接触次生植物化合物一致。2012年至2014年间从下北半岛（北纬41.3°）获得的15只雄性猕猴的犬齿高分辨率铸型，其骨骼保存在京都大学人类行为进化起源中心，通过共聚焦和扫描电子显微镜成像。釉质的规则沉积叠层的表面表达——釉质横纹，可用于估计发育不全釉质缺陷之间以及内部的时间。基于五个个体的组织学切片，我们确定芮氏周期为7天。从釉质横纹计数以及发育不全起始角度、深度和宽度的测量中收集了68个线性釉质发育不全缺陷的复发、持续时间和严重程度的证据。雄性犬齿每颗牙冠显示出四到五个反复出现、间隔均匀的釉质缺陷，缺陷之间的釉质横纹中位数为54.8（范围18 - 74）；平均持续8.7（范围1 - 20）个釉质横纹。这转化为平均每1.05年出现一次反复发育应激，持续8.7周，短于当地冬季觅食期（100天）。我们得出结论，线性釉质发育不全在来自日本高纬度地区的雄性猕猴中每年循环出现。在未来的研究中，可以通过研究日本列岛有食物供应和无食物供应的种群，来区分寒冷、饥饿和拒食剂这三者的影响。
