The evolution of bat vestibular systems in the face of potential antagonistic selection pressures for flight and echolocation

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 Yinpterochiro...

前庭系统（vestibular system）维持着身体的平衡感，因此在运动方式的进化转变过程中可能受到了强烈的选择压力。在哺乳动物中，蝙蝠具有独特的特征，这些特征对其前庭系统提出了特殊的要求。首先，蝙蝠能够进行动力飞行——这一能力在鸟类中与半规管（semicircular canals）扩大相关。其次，许多蝙蝠拥有与回声定位相关的扩大耳蜗（cochleae），且耳蜗与半规管共同占据颞骨岩部（petrosal bone）内的空间。为探究蝙蝠前庭系统在这些压力下的进化方式，我们利用显微CT扫描（micro-CT scans），对具有不同飞行能力和回声定位能力的物种间的半规管形态进行了比较。我们发现，蝙蝠获得动力飞行能力并未伴随半规管半径的增大，但在阳翼手亚目（Yangochiroptera）的蝙蝠物种中，以及在阴翼手亚目（Yinpterochiro...）的非回声定位旧大陆果蝠中，半规管半径与体重存在相关性。