In any vertebrate group, tooth shape is known to fit with a biological function related to diet. However, little is known about the relationships between diet and tooth microstructure and composition in teleost fishes. In this work, we describe the external morphology, internal microstructure and elemental composition of the oral teeth of three representative species of the family Serrasalmidae having different feeding habits (herbivorous vs. omnivorous vs. carnivorous). We used backscattered-electron imaging and low vacuum environmental scanning electron microscope to compare the organization and mineralization of tooth layers as well as energy dispersive X-ray microanalysis and Raman microspectrometry to investigate the elemental composition, Ca/P ratio and mineralogy of the most superficial layers. Oral teeth of each serrasalmid species have the same internal organization based on five distinctive layers (i.e. pulp, dentine, inner enameloid, outer enameloid and cuticle) but the general tooth morphology is different according to diet. Microstructural and compositional variation of the cuticle and iron-enrichment of superficial layers were highlighted between herbivorous and carnivorous species. Iron is more concentrated in teeth of the herbivorous species where it is associated with a thicker cuticle explaining the more intense red-pigmentation of the cutting edges of oral teeth. The iron-enrichment is interpreted as a substitution of Ca by Fe in the hydroxyapatite. These traits are discussed in the light of the evolutionary history of the family. Further considerations and hypotheses about the formation and origin of the mineralized tooth layers and especially the iron-rich superficial layers in teleost fishes are suggested.

中文翻译：

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Pacu和食人鱼牙齿的微观结构和成分变化与饮食专业化有关（Teleostei：Serrasalmidae）。

在任何脊椎动物群体中，已知牙齿形状都具有与饮食有关的生物学功能。但是，关于硬骨鱼的饮食与牙齿微观结构和成分之间的关​​系知之甚少。在这项工作中，我们描述了具有不同喂养习惯（食性，杂食性与肉食性）的锯齿状沙门氏菌的三个代表性物种的口腔外部形态，内部微观结构和牙齿成分。我们使用背散射电子成像和低真空环境扫描电子显微镜来比较牙齿层的组织和矿化以及能量色散X射线显微分析和拉曼光谱法研究最表层的元素组成，Ca / P比和矿物学层。每种serrasalmid物种的口腔牙齿具有基于五个不同层（即牙髓，牙本质，内同种异体，外同种异体和表皮）的相同内部组织，但根据饮食的不同，其总体牙齿形态也有所不同。在草食性和食肉性物种之间，表皮的微观结构和组成变化以及表层的铁富集被突出显示。铁更多地集中在草食动物的牙齿中，铁与较厚的表皮结合在一起，这说明口腔齿的切割边缘出现了更强烈的红色色素沉着。铁的富集被解释为羟基磷灰石中的Fe替代了Ca。这些特征是根据家族的进化史进行讨论的。