Deban Stephen M, Richardson Jason C
Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, Science Center 110, Tampa, FL 33620, USA
Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, Science Center 110, Tampa, FL 33620, USA.
J Exp Biol. 2017 Oct 1;220(Pt 19):3588-3597. doi: 10.1242/jeb.165266. Epub 2017 Aug 7.
Desmognathine salamanders possess unusual morphological features for lungless salamanders that have been proposed to aid in burrowing and biting, including well-ossified jaws and skull and a pair of robust ligaments connecting the atlas to the mandible. We evaluated the function of these and other peculiar desmognathine cranial features in biting by examining the morphology, mechanics and biting performance of the large We estimated theoretical biting force using a novel geometric method that we describe. Results provide quantitative evidence to bolster earlier conclusions that the unusual atlanto-mandibular ligaments couple ventral head flexion, a unique desmognathine behavior, with biting performance. Our analysis also reveals that the ligaments not only transmit, but also amplify the force of head flexion when acting together with the unusual stalked occipital condyles, enlarged atlas and massive quadratopectoralis muscles. The geometric model predicts that this mechanism contributes five times the biting force of the three jaw levator muscles combined and predicts that maximum biting force in matches or exceeds forces reported for similarly sized lizards. The biting performance we measured was several times greater in than another plethodontid salamander, , which lacks the unusual morphology and mechanism of desmognathines. The effective biting mechanism of we describe is an emergent property of many of the distinguishing morphological features of desmognathine salamanders and likely plays an important role in their natural history given that desmognathines use biting in feeding, defense and even courtship.
半趾螈属的蝾螈具有一些无肺螈科蝾螈所没有的独特形态特征，这些特征被认为有助于挖掘和撕咬，包括高度骨化的颌骨和头骨，以及一对连接寰椎和下颌骨的粗壮韧带。我们通过研究大型半趾螈属蝾螈的形态、力学和撕咬表现，评估了这些以及其他独特的半趾螈属颅骨特征在撕咬中的功能。我们使用一种新描述的几何方法估算理论撕咬力。结果提供了定量证据，支持了早期的结论，即独特的寰椎 - 下颌韧带将蝾螈特有的头部腹侧弯曲行为与撕咬表现联系起来。我们的分析还表明，这些韧带不仅传递头部弯曲的力量，而且在与独特的带柄枕髁、增大的寰椎和巨大的方胸肌共同作用时，还会放大这种力量。几何模型预测，这种机制产生的撕咬力是三块颌骨提肌合力的五倍，并且预测大型半趾螈属蝾螈的最大撕咬力与同等大小蜥蜴所报道的力量相当或超过其力量。我们测量的大型半趾螈属蝾螈的撕咬表现比另一种无肺螈科蝾螈——红背无肺螈大几倍，后者缺乏半趾螈属蝾螈独特的形态和机制。我们所描述的大型半趾螈属蝾螈有效的撕咬机制是半趾螈属蝾螈许多独特形态特征共同作用产生的特性，鉴于半趾螈属蝾螈在进食、防御甚至求偶中都使用撕咬，这一机制可能在它们的自然历史中发挥重要作用。
