Ear Institute, University College London, London WC1X 8EE, UK.
Curr Biol. 2011 Apr 26;21(8):658-64. doi: 10.1016/j.cub.2011.03.001. Epub 2011 Mar 31.
The courtship behavior of Drosophilid flies has served as a long-standing model for studying the bases of animal communication. During courtship, male flies flap their wings to send a complex pattern of airborne vibrations to the antennal ears of the females. These "courtship songs" differ in their spectrotemporal composition across species and are considered a crucial component of the flies' premating barrier. However, whether the species-specific differences in song structure are also reflected in the receivers of this communication system, i.e., the flies' antennal ears, has remained unexplored. Here we show for seven members of the melanogaster species group that (1) their ears are mechanically tuned to different best frequencies, (2) the ears' best frequencies correlate with high-frequency pulses of the conspecific courtship songs, and (3) the species-specific tuning relies on amplificatory mechanical feedback from the flies' auditory neurons. As a result of its level-dependent nature, the active mechanical feedback amplification is particularly useful for the detection of small stimuli, such as conspecific song pulses, and becomes negligible for sensing larger stimuli, such as the flies' own wingbeat during flight.
果蝇的求偶行为一直是研究动物通讯基础的长期模型。在求偶过程中，雄蝇扇动翅膀，向雌蝇的触角耳朵发送复杂的空中振动模式。这些“求偶歌曲”在不同物种之间在时频谱组成上存在差异，被认为是蝇类交配前障碍的关键组成部分。然而，这种通讯系统的接收者，即蝇类的触角耳朵，是否也反映出歌曲结构的种间差异，这一点尚未得到探索。在这里，我们展示了黑腹果蝇种组的七个成员，（1）它们的耳朵在机械上被调谐到不同的最佳频率，（2）耳朵的最佳频率与同种求偶歌曲的高频脉冲相关，（3）种间调谐依赖于来自蝇类听觉神经元的放大机械反馈。由于其依赖于水平的性质，主动机械反馈放大对于检测小刺激（如同种歌曲脉冲）特别有用，而对于检测更大的刺激（如飞行中的蝇类自身的拍动翅膀）则变得微不足道。
