Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata)
Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata)
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DOI：
10.1002/jmor.10455
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发表时间：
2006-09-01
影响因子：
1.5
通讯作者：
Sire, Jean-Yves
中科院分区：
文献类型：
--
作者：
Davit-Beal, Tiphaine;Allizard, Francoise;Sire, Jean-Yves
大多数非哺乳动物物种不断更换牙齿（所谓的多齿性），这使得形态和结构的改变在个体发育过程中发生。我们选择了waltl蝾螈，一种易于在实验室培养的蝾螈，作为模型物种，为未来的分子方法建立必要的形态学基础，旨在了解不仅涉及牙齿发育和替换的分子过程，而且还包括它们的变化，特别是在变形过程中，这可能有助于研究进化过程中牙齿形态的改变。为了确定牙齿在个体发育过程中何时（在哪个发育阶段）以及如何（渐进或突然）发生变化，我们集中观察了位于位置I的单一牙齿科，最靠近左下颌联合。我们使用光学（LM），扫描（SEM）和透射电子（TEM）显微镜监测了从10天大的胚胎（牙齿I-1）到成年标本（牙齿I-6）的大生长系列中的六颗第一牙齿的发育和替换。提供了六颗牙齿发育和功能时期的时间表，并比较了幼虫和年轻成虫的牙齿发育。在P. waltl中，第一颗功能牙齿在第二代牙齿形成时不会被取代，这与后一代牙齿形成的情况相反，导致在生命的头两个月里，两颗功能牙齿在一个位置上出现。幼牙I-1与成牙I-6表现出明显不同的特征：牙本质锥体与牙蒂之间出现了分隔区；牙髓腔扩大，可容纳大血管；成牙本质细胞沿牙本质表面排列良好；牙本质中出现小管；牙齿变成了双尖齿。这些变化大多是在一代到下一代之间逐渐发生的，但从单尖牙到双尖牙的变化发生在蜕变期第I-3齿到第I-4齿的过渡期间。
Most nonmammalian species replace their teeth continuously (so-called polyphyodonty), which allows morphological and structural modifications to occur during ontogeny. We have chosen Pleurodeles waltl, a salamander easy to rear in the laboratory, as a model species to establish the morphological foundations necessary for future molecular approaches aiming to understand not only molecular processes involved in tooth development and replacement, but also their changes, notably during metamorphosis, that might usefully inform studies of modifications of tooth morphology during evolution. In order to determine when (in which developmental stage) and how (progressively or suddenly) tooth modifications take place during ontogeny, we concentrated our observations on a single tooth family, located at position I, closest to the symphysis on the left lower jaw. We monitored the development and replacement of the six first teeth in a large growth series ranging from 10-day-old embryos (tooth I-1) to adult specimens (tooth I-6), using light (LM), scanning (SEM), and transmission electron (TEM) microscopy. A timetable of the developmental and functional period is provided for the six teeth, and tooth development is compared in larvae and young adults. In P. waltl the first functional tooth is not replaced when the second generation tooth forms, in contrast to what occurs for the later generation teeth, leading to the presence of two functional teeth in a single position during the first 2 months of life. Larval tooth I-1 shows dramatically different features when compared to adult tooth I-6: a dividing zone has appeared between the dentin cone and the pedicel; the pulp cavity has enlarged, allowing accommodation of large blood vessels; the odontoblasts are well organized along the dentin surface; tubules have appeared in the dentin; and teeth have become bicuspidate. Most of these modifications take place progressively from one tooth generation to the next, but the change from monocuspid to bicuspid tooth occurs during the tooth I-3 to tooth I-4 transition at metamorphosis.