The Evolution of Bat Vestibular Systems in the Face of Potential Antagonistic Selection Pressures for Flight and Echolocation
The Evolution of Bat Vestibular Systems in the Face of Potential Antagonistic Selection Pressures for Flight and Echolocation
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DOI：
10.1371/journal.pone.0061998
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发表时间：
2013-04-24
期刊：
影响因子：
3.7
通讯作者：
Rossiter, Stephen J.
中科院分区：
文献类型：
--
作者：
Davies, Kalina T. J.;Bates, Paul J. J.;Rossiter, Stephen J.
前庭系统维持着身体的平衡感，因此，在运动的进化转变过程中，可能受到了强烈的选择。在哺乳动物中，蝙蝠具有独特的特征，这对它们的前庭系统提出了不寻常的要求。首先，蝙蝠有动力飞行的能力，在鸟类中，这与扩大的半规管有关。其次，许多蝙蝠都有与回声定位相关的增大的耳蜗骨，耳蜗管和半规管在岩骨中共享一个空间。为了确定蝙蝠前庭系统在这些压力下是如何进化的，我们使用微型CT扫描来比较不同物种之间的管状形态，这些物种具有不同的飞行和回声定位能力。我们没有发现蝙蝠的管道半径与获得动力飞行有关，但管道半径确实与蝙蝠亚目蝙蝠的体重有关，也与来自翼亚目的非回声定位的东半球果蝠的体重相关。在使用喉部回声定位的翼翼翼手目成员中没有发现这种趋势，尽管在这一组中，管半径与翼尖圆形有关。我们还发现，前庭系统随着耳蜗大小而扩大，尽管这种关系在使用恒定频率回声定位的物种中有所不同。在所有蝙蝠中，前管和侧管的形状分别与较大的耳蜗大小和较小的身体大小有关，这表明每个管的空间约束取决于其在头骨中的方向。因此，在许多回声定位蝙蝠中，体型小和耳蜗大的组合似乎共同作用于前庭系统的主要力量。两个主要的回声定位蝙蝠群体表现出不同的管状形态，其大小和形状与身体质量和耳蜗大小有关，因此表明了独立的进化路径，并为多次获得回声定位提供了试探性支持。
The vestibular system maintains the body's sense of balance and, therefore, was probably subject to strong selection during evolutionary transitions in locomotion. Among mammals, bats possess unique traits that place unusual demands on their vestibular systems. First, bats are capable of powered flight, which in birds is associated with enlarged semicircular canals. Second, many bats have enlarged cochleae associated with echolocation, and both cochleae and semicircular canals share a space within the petrosal bone. To determine how bat vestibular systems have evolved in the face of these pressures, we used micro-CT scans to compare canal morphology across species with contrasting flight and echolocation capabilities. We found no increase in canal radius in bats associated with the acquisition of powered flight, but canal radius did correlate with body mass in bat species from the suborder Yangochiroptera, and also in non-echolocating Old World fruit bats from the suborder Yinpterochiroptera. No such trend was seen in members of the Yinpterochiroptera that use laryngeal echolocation, although canal radius was associated with wing-tip roundedness in this group. We also found that the vestibular system scaled with cochlea size, although the relationship differed in species that use constant frequency echolocation. Across all bats, the shape of the anterior and lateral canals was associated with large cochlea size and small body size respectively, suggesting differential spatial constraints on each canal depending on its orientation within the skull. Thus in many echolocating bats, it seems that the combination of small body size and enlarged cochlea together act as a principal force on the vestibular system. The two main groups of echolocating bats displayed different canal morphologies, in terms of size and shape in relation to body mass and cochlear size, thus suggesting independent evolutionary pathways and offering tentative support for multiple acquisitions of echolocation.