Sueur Jérôme, Windmill James F C, Robert Daniel
NAMC-CNRS UMR 8620, Bât. 446, Université Paris XI, 91405 Orsay Cedex, France.
J Exp Biol. 2006 Oct;209(Pt 20):4115-28. doi: 10.1242/jeb.02460.
Cicadas are known to use sound to find a mate. While the mechanism employed by male cicadas to generate loud calling songs has been described in detail, little information exists to explain how their ears work. Using microscanning laser Doppler vibrometry, the tympanal vibrations in the cicada Cicadatra atra are measured in response to acoustic playbacks. The topographically accurate optical measurements reveal the vibrational behaviour of the anatomically complex tympanal membrane. Notably, the tympanal ridge, a distinct structural element of the tympanum that is a link to the receptor cells, undergoes mechanical vibrations reminiscent of a travelling wave. In effect, the frequency for which the maximum deflection amplitude is observed regularly decreases from the apex to the base of the ridge. It is also shown that whilst female ears are mechanically tuned to the male's song, the male's tympanum is only partially tuned to its own song. This study establishes the presence of a peripheral auditory mechanism that can potentially process auditory frequency analysis. In view of the importance of acoustic signalling in cicadas, this unconventional tympanal mechanism may be employed in the context of species recognition and sexual selection.
众所周知，蝉利用声音来寻找配偶。虽然雄性蝉产生响亮求偶歌声所采用的机制已得到详细描述，但关于它们耳朵如何工作的信息却很少。利用显微扫描激光多普勒振动测量法，对蝉科的黑蚱蝉鼓膜振动进行了测量，以响应声学回放。地形精确的光学测量揭示了解剖结构复杂的鼓膜的振动行为。值得注意的是，鼓膜嵴是鼓膜的一个独特结构元素，它与受体细胞相连，会发生类似于行波的机械振动。实际上，观察到最大偏转振幅的频率通常从嵴的顶端向基部逐渐降低。研究还表明，虽然雌蝉的耳朵在机械上能调谐到雄蝉的歌声，但雄蝉的鼓膜只是部分调谐到其自身的歌声。这项研究证实了存在一种可能进行听觉频率分析的外周听觉机制。鉴于声学信号在蝉类中的重要性，这种非常规的鼓膜机制可能在物种识别和性选择的背景下发挥作用。
