Chewing or not? Intraoral food processing in a salamandrid newt
Chewing or not? Intraoral food processing in a salamandrid newt
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DOI：
10.1242/jeb.189886
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发表时间：
2019-03-01
影响因子：
2.8
通讯作者：
Konow, Nicolai
中科院分区：
文献类型：
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作者：
Heiss, Egon;Schwarz, Daniel;Konow, Nicolai
食品加工是指食物在吞咽前的任何形式的机械分解。在所有主要的噬牙动物群体中都可以发现这种行为的变化。咀嚼是迄今为止最常用的口腔内加工机制，涉及有节奏的下颌和鳃下（舌）运动。咀嚼发生在软骨鱼类（鲨鱼和鳐鱼）、放线鱼类（鳍状鱼类）、肺类（肺鱼）以及羊膜动物身上，并且涉及肌肉活动模式和进食装置运动的相似之处。有人认为，羊膜动物的咀嚼是四足动物陆地入侵的一部分，它涉及下颚和肌肉舌头的运动相互作用。然而，人们对非两栖动物的食物加工机制知之甚少，它们可能保留了许多祖先四足动物的特征。在这里，我们在蝾螈（Triturus camifex）身上发现了一种加工机制，在捕获猎物后，它会随着有节奏的下颌和舌头运动而周期性地摆动头部。我们使用高速透视，解剖重建和胃内容物的分析来显示蝾螈，虽然不使用下颚，部署一种衍生的处理机制，在舌头的环形运动的驱动下，猎物有节奏地撞击口腔顶部的牙列。然后，我们比较了颌口和舌头运动的模式和协调，得出结论，这种蝾螈的食物加工与鱼类和羊膜动物的加工机制有共同的特征。这一发现使蝾螈成为重建鱼类-四足动物分裂过程中口内加工机制进化的有希望的模型。
Food processing refers to any form of mechanical breakdown of food prior to swallowing. Variations of this behaviour are found within all major gnathostome groups. Chewing is by far the most commonly used intraoral processing mechanism and involves rhythmic mandibular jaw and hyobranchial (tongue) movements. Chewing occurs in chondrichthyans (sharks and rays), actinopterygians (rayfinned fishes), dipnoi (lungfishes) as well as amniotes and involves similarities in the patterns of muscle activity and movement of the feeding apparatus. It has been suggested that amniote chewing, which involves the interaction of movements of the mandibular jaw and the muscular tongue, has evolved as part of the tetrapod land invasion. However, little is known about food-processing mechanisms in lissamphibians, which might have retained many ancestral tetrapod features. Here, we identified a processing mechanism in the salamandrid newt, Triturus camifex, which after prey capture displays cyclic head bobbing in concert with rhythmic jaw and tongue movements. We used high-speed fluoroscopy, anatomical reconstructions and analyses of stomach contents to show that newts, although not using their mandibular jaws, deploy a derived processing mechanism where prey items are rasped rhythmically against the dentition on the mouth roof, driven by a loop motion of the tongue. We then compared patterns and coordination of jaw and tongue movements across gnathostomes to conclude that food processing in this newt species shares traits with processing mechanisms in fish as well as amniotes. This discovery casts salamanders as promising models for reconstructing the evolution of intraoral processing mechanisms at the fish-tetrapod split.