Wacker K, Bartsch P, Clemen G
Institut für Spezielle Zoologie und Vergleichende Embryologie, Universität Münster, Germany.
Ann Anat. 2001 Jan;183(1):37-52. doi: 10.1016/S0940-9602(01)80011-X.
The formation sequence of the tooth-bearing bones and the tooth pattern in early ontogeny of Polypterus senegalus is investigated using transparent preparation, histological sections, and SEM. During the attachment step of the yolk-sac larva the first dermal bones and teeth are formed. Teeth appear simultaneously in the areas of the maxillary, dentary, dermopalatine, prearticular, and coronoid 1 along with the first separate anlagen of these bones. A monostichous arrangement of primary teeth is established on the maxillary, dentary, and dermopalatine. Polystichous tooth arrangements do not occur before the early pterolarval phase, and then only in connection with bones of the palate and inner dental arcades. Especially pronounced is the influence of tooth formation on the structure of the parasphenoid that becomes much thickened by accretion of denticulate platelets, but we found neither evidence for a distinct vomeral contribution to the parasphenoid, nor a composite origin of the ectopterygoid in ontogeny. First replacement teeth are found in association with the maxillary and dentary as early as the late apterolarval phase. Primary teeth are of a single general type, whereas from the pterolarval phase onward three tooth types can be distinguished that are restricted to certain tooth bearing bones. Relatively late in ontogeny, dermo-metapterygoid and entopterygoid become formed and colonised by teeth, whereas first branchial teeth and tooth plates appear earlier during the first phase of extrinsic larval feeding. Characteristics of development of the dentition are discussed in comparison with character states of other better known fossil and recent taxa among Actinopterygii and Sarcopterygii. Compared to the assumed basic pattern of actinopterygian fishes, Polypteriformes show a derived condition with respect to structure, arrangement, replacement, and differentiation of teeth, which arises in sequence during larval development. This also corresponds to observed changes of feeding behaviour and functional demands during larval life.
利用透明标本制作、组织学切片和扫描电子显微镜，对塞内加尔多鳍鱼早期个体发育过程中含牙骨骼的形成顺序和牙齿模式进行了研究。在卵黄囊幼体的附着阶段，最早的真皮骨和牙齿开始形成。在上颌骨、齿骨、腭皮骨、关节前骨和冠状骨1的区域，牙齿与这些骨骼的第一个独立原基同时出现。在上颌骨、齿骨和腭皮骨上，初级牙齿形成单列排列。多列牙齿排列在早期翼状幼体阶段之前不会出现，且仅在与腭骨和内侧牙弓的骨骼相关时才会出现。牙齿形成对副蝶骨结构的影响尤为明显，副蝶骨因齿状小板的堆积而显著增厚，但我们既未发现犁骨对副蝶骨有明显贡献的证据，也未发现外翼骨在个体发育中有复合起源的证据。最早在晚期无翼状幼体阶段，就发现上颌骨和齿骨上有替换牙。初级牙齿属于单一的一般类型，而从翼状幼体阶段开始，可以区分出三种牙齿类型，它们分别局限于特定的含牙骨骼。在个体发育相对较晚的时候，皮鳍骨和内翼骨形成并被牙齿占据，而最早的鳃齿和齿板在外部幼体摄食的第一阶段出现得更早。与其他更知名的辐鳍鱼纲和肉鳍鱼纲化石及现生类群的特征状态相比，讨论了牙列发育的特征。与辐鳍鱼类假定的基本模式相比，多鳍鱼目在牙齿的结构、排列、替换和分化方面表现出一种衍生状态，这种状态在幼体发育过程中依次出现。这也与幼体生活期间观察到的摄食行为和功能需求的变化相对应。
