Bemis Katherine E, Burke Samantha M, St John Carl A, Hilton Eric J, Bemis William E
Department of Fisheries Science, Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, Virginia.
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York.
J Morphol. 2019 Jan;280(1):78-94. doi: 10.1002/jmor.20919.
Atlantic Cutlassfish, Trichiurus lepturus, have large, barbed, premaxillary and dentary fangs, and sharp dagger-shaped teeth in their oral jaws. Functional teeth firmly ankylose to the dentigerous bones. We used dry skeletons, histology, SEM, and micro-CT scanning to study 92 specimens of T. lepturus from the western North Atlantic to describe its dentition and tooth replacement. We identified three modes of intraosseous tooth replacement in T. lepturus depending on the location of the tooth in the jaw. Mode 1 relates to replacement of premaxillary fangs, in which new tooth germs enter the lingual surface of the premaxilla, develop horizontally, and rotate into position. We suggest that growth of large fangs in the premaxilla is accommodated by this horizontal development. Mode 2 occurs for dentary fangs: new tooth germs enter the labial surface of the dentary, develop vertically, and erupt into position. Mode 3 describes replacement of lateral teeth, in which new tooth germs enter a trench along the crest of the dentigerous bone, develop vertically, and erupt into position. Such distinct modes of tooth replacement in a teleostean species are unknown. We compared modes of replacement in T. lepturus to 20 species of scombroids to explore the phylogenetic distribution of these three replacement modes. Alternate tooth replacement (in which new teeth erupt between two functional teeth), ankylosis, and intraosseous tooth development are plesiomorphic to Bluefish + other Scombroidei. Our study highlights the complexity and variability of intraosseous tooth replacement. Within tooth replacement systems, key variables include sites of formation of tooth germs, points of entry of tooth germs into dentigerous bones, coupling of tooth germ migration and bone erosion, whether teeth develop horizontally or immediately beneath the tooth to be replaced, and how tooth eruption and ankylosis occur. Developmentally different tooth replacement processes can yield remarkably similar dentitions.
大西洋带鱼（Trichiurus lepturus）具有大型、带倒刺的前颌骨和齿骨獠牙，以及口腔颌骨中锋利的匕首状牙齿。功能性牙齿牢固地融合在齿骨上。我们使用干燥骨骼、组织学、扫描电子显微镜（SEM）和显微计算机断层扫描（micro-CT）扫描，研究了来自北大西洋西部的92个大西洋带鱼标本，以描述其齿列和牙齿替换情况。根据牙齿在颌骨中的位置，我们确定了大西洋带鱼骨内牙齿替换的三种模式。模式1与前颌骨獠牙的替换有关，其中新的牙胚进入前颌骨的舌面，水平发育，然后旋转到位。我们认为，前颌骨中大型獠牙的生长是通过这种水平发育来实现的。模式2发生在齿骨獠牙的替换中：新的牙胚进入齿骨的唇面，垂直发育，然后萌出到位。模式3描述了侧牙的替换，其中新的牙胚沿着齿骨嵴进入一个沟槽，垂直发育，然后萌出到位。硬骨鱼物种中这种独特的牙齿替换模式尚属未知。我们将大西洋带鱼的替换模式与20种鲭亚目鱼类进行了比较，以探索这三种替换模式的系统发育分布。交替牙齿替换（新牙在两颗功能性牙齿之间萌出）、融合以及骨内牙齿发育在竹荚鱼和其他鲭亚目鱼类中是原始特征。我们的研究突出了骨内牙齿替换的复杂性和变异性。在牙齿替换系统中，关键变量包括牙胚形成的部位、牙胚进入齿骨的入口点、牙胚迁移与骨侵蚀的耦合、牙齿是水平发育还是在待替换牙齿的正下方发育，以及牙齿萌出和融合的方式。发育上不同的牙齿替换过程可以产生非常相似的齿列。
