Huysseune Ann, Hall Brian K, Witten P Eckhard
Biology Department, Ghent University, Belgium.
J Anat. 2007 Oct;211(4):471-84. doi: 10.1111/j.1469-7580.2007.00788.x. Epub 2007 Aug 31.
In this paper we elucidate the pattern of initiation of the first teeth and the pattern of tooth replacement on the dentary of wild Atlantic salmon (Salmo salar L.), throughout nearly all stages of its life cycle, using serially sectioned heads and jaws, cleared and stained animals, and X-rays. The dentary teeth are set in one row. Tooth germs appear around hatching, first in odd positions, followed by even positions. From position 8 further backwards, teeth are added in adjacent positions. The first replacement teeth appear in animals of about 30 mm fork length. On the dentary of early life stages (alevins and fry), every position in the tooth row holds a functional (i.e. attached and erupted) tooth and a replacement tooth. The alternating pattern set up anteriorly in the dentary by the first-generation teeth changes in juveniles (parr) whereby teeth are in a similar functional (for the erupted teeth) or developmental stage (for the replacement teeth) every three positions. This pattern is also observed in marine animals during their marine life phase and in both sexes of adult animals prior to spawning (grilse and salmon), but every position now holds either a functional tooth or a mineralised replacement tooth. This is likely due to the fact that replacement tooth germs have to grow to a larger size before mineralisation starts. In the following spring, the dentary tooth pattern of animals that have survived spawning (kelts) is highly variable. The abundance of functional teeth in post-spawning animals nevertheless indicates that teeth are not lost over winter. We confirm the earlier reported lack of evidence for the existence of an edentulous life phase, preceding the appearance of so-called breeding teeth during upstream migration to the spawning grounds, and consider breeding teeth to be just another tooth generation in a regularly replacing dentition. This study shows how Atlantic salmon maintains a functional adaptive dentition throughout its complex life cycle.
在本文中，我们利用连续切片的头部和颌骨、透明和染色的动物标本以及X射线，阐明了野生大西洋鲑（Salmo salar L.）在其几乎整个生命周期中，齿骨上第一颗牙齿的萌出模式和牙齿替换模式。齿骨牙齿排成一排。牙胚在孵化前后出现，首先出现在奇数位置，随后是偶数位置。从第8个位置往后，牙齿在相邻位置添加。第一批替换牙齿出现在叉长约30毫米的鱼体内。在早期生命阶段（仔鱼和幼鱼）的齿骨上，齿列中的每个位置都有一颗功能性（即附着且已萌出）牙齿和一颗替换牙齿。第一代牙齿在齿骨前部建立的交替模式在幼鱼（稚鱼）阶段发生变化，此时每三个位置的牙齿处于相似的功能阶段（对于已萌出的牙齿）或发育阶段（对于替换牙齿）。这种模式在海洋动物的海洋生活阶段以及产卵前的成年动物（降海洄游鲑和鲑鱼）两性中也有观察到，但现在每个位置要么有一颗功能性牙齿，要么有一颗矿化的替换牙齿。这可能是因为替换牙胚在矿化开始前必须长得更大。在接下来的春天，产卵后存活的鱼（产后亲鱼）的齿骨牙齿模式高度可变。然而，产后动物中功能性牙齿的数量表明牙齿在冬季不会脱落。我们证实了先前报道的，在洄游到产卵场的上游过程中所谓繁殖齿出现之前，不存在无齿生命阶段的证据，并认为繁殖齿只是定期替换齿列中的另一代牙齿。这项研究展示了大西洋鲑如何在其复杂的生命周期中维持功能性的适应性齿列。
