Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich 8057, Switzerland.
Applied and Analytical Palaeontology, Institute of Geosciences, Johannes Gutenberg University, Mainz 55128, Germany.
Proc Biol Sci. 2019 Oct 9;286(1912):20191921. doi: 10.1098/rspb.2019.1921.
The effect of phytoliths on tooth wear and function has been contested in studies of animal-plant interactions. For herbivores whose occlusal chewing surface consists of enamel ridges and dentine tissue, the phytoliths might particularly erode the softer dentine, exposing the enamel ridges to different occlusal forces and thus contributing to enamel wear. To test this hypothesis, we fed guinea pigs (; = 36 in six groups) for three weeks exclusively on dry or fresh forage of low (lucerne), moderate (fresh timothy grass) or very high (bamboo leaves) silica content representing corresponding levels of phytoliths. We quantified the effect of these treatments with measurements from micro-computed tomography scans. Tooth height indicated extreme wear due to the bamboo diet that apparently brought maxillary incisors and molars close to the minimum required for functionality. There were negative relationships between a cheek tooth's height and the depth of its dentine basin, corroborating the hypothesis that dentine erosion plays an important role in herbivore tooth wear. In spite of lower body mass, bamboo-fed animals paradoxically had longer cheek tooth rows and larger occlusal surfaces. Because ever-growing teeth can only change in shape from the base upwards, this is a strong indication that failure to compensate for wear by dental height-growth additionally triggered general expansive growth of the tooth bases. The results suggest that enamel wear may intensify after enamel has been exposed due to a faster wear of the surrounding dentine tissue (and not the other way around), and illustrate a surprising plasticity in the reactivity of this rodent's system that adjusts tooth growth to wear.
植物硅酸体对牙齿磨损和功能的影响在动植物相互作用的研究中一直存在争议。对于那些咀嚼面由釉质脊和牙本质组织组成的食草动物来说，植物硅酸体可能特别会侵蚀较软的牙本质，使釉质脊承受不同的咬合力，从而导致釉质磨损。为了验证这一假设，我们用低（紫花苜蓿）、中（新鲜黑麦草）和高（竹叶）硅含量的干草或鲜草（分别代表相应水平的植物硅酸体）连续喂养 3 周豚鼠（每组 36 只）。我们通过微计算机断层扫描的测量来量化这些处理的效果。牙齿高度表明，由于竹叶饮食导致的极度磨损，上颌切牙和磨牙显然接近功能所需的最小高度。臼齿的高度与其牙本质窝的深度之间呈负相关关系，这印证了牙本质侵蚀在食草动物牙齿磨损中起着重要作用的假设。尽管竹叶组动物的体重较低，但它们的颊齿列却更长，咬合面也更大。由于不断生长的牙齿只能从根部向上改变形状，这强烈表明，由于牙齿高度生长无法补偿磨损，牙齿基部的整体扩张生长也会发生。这些结果表明，由于周围牙本质组织磨损更快，在釉质暴露后可能会加剧釉质磨损，而不是相反，并且说明了这种啮齿动物系统的惊人的可塑性，它可以根据磨损情况调整牙齿生长。
