Madsen P T, Payne R, Kristiansen N U, Wahlberg M, Kerr I, Møhl B
Department of Zoophysiology, Institute of Biological Sciences, University of Aarhus, Building 131, 8000 Aarhus C, Denmark.
J Exp Biol. 2002 Jul;205(Pt 13):1899-906. doi: 10.1242/jeb.205.13.1899.
Delphinoids (Delphinidae, Odontoceti) produce tonal sounds and clicks by forcing pressurized air past phonic lips in the nasal complex. It has been proposed that homologous, hypertrophied nasal structures in the deep-diving sperm whale (Physeter macrocephalus) (Physeteridae, Odontoceti) are dedicated to the production of clicks. However, air volumes in diving mammals are reduced with increasing ambient pressure, which seems likely to influence pneumatic sound production at depth. To study sperm whale sound production at depth, we attached ultrasound time/depth-recording tags to sperm whales by means of a pole and suction cup. We demonstrate that sperm whale click production in terms of output and frequency content is unaffected by hydrostatic reduction in available air volume down to less than 2% of the initial air volume in the nasal complex. We present evidence suggesting that the sound-generating mechanism has a bimodal function, allowing for the production of clicks suited for biosonar and clicks more suited for communication. Shared click features suggest that sound production in sperm whales is based on the same fundamental biomechanics as in smaller odontocetes and that the nasal complexes are therefore not only anatomically but also functionally homologous in generating the initial sound pulse.
海豚类动物（海豚科，齿鲸亚目）通过迫使加压空气经过鼻腔复合体中的发声唇来产生音调声音和滴答声。有人提出，深海潜水的抹香鲸（Physeter macrocephalus）（抹香鲸科，齿鲸亚目）中同源的、肥大的鼻腔结构专门用于产生滴答声。然而，随着环境压力的增加，潜水哺乳动物体内的空气量会减少，这似乎可能会影响在深度条件下的气动发声。为了研究抹香鲸在深度条件下的发声情况，我们通过杆子和吸盘将超声时间/深度记录标签附着在抹香鲸身上。我们证明，就输出和频率成分而言，抹香鲸的滴答声产生不受鼻腔复合体中可用空气量静水压降低的影响，直至降至初始空气量的不到2%。我们提供的证据表明，发声机制具有双峰功能，既允许产生适合生物声纳的滴答声，也允许产生更适合交流的滴答声。共同的滴答声特征表明，抹香鲸的发声基于与较小齿鲸相同的基本生物力学原理，因此鼻腔复合体不仅在解剖学上而且在产生初始声脉冲的功能上是同源的。
