Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
Proc Biol Sci. 2011 Dec 22;278(1725):3762-8. doi: 10.1098/rspb.2011.0656. Epub 2011 May 11.
Acoustic signals play essential roles in social communication and show a strong selection for novel morphologies leading to increased call complexity in many taxa. Among vertebrates, repeated innovations in the larynges of frogs and mammals and the syrinx of songbirds have enhanced the spectro-temporal content, and hence the diversity of vocalizations. This acoustic diversification includes nonlinear characteristics that expand frequency profiles beyond the traditional categorization of harmonic and broadband calls. Fishes have remained a notable exception to evidence for such acoustic innovations among vertebrates, despite their being the largest group of living vertebrates that also exhibit widespread evolution of sound production. Here, we combine rigorous acoustic and mathematical analyses with experimental silencing of the vocal motor system to show how a novel swim bladder mechanism in a toadfish enables it to generate calls exhibiting nonlinearities like those found among frogs, birds and mammals, including primates. By showing that fishes have evolved nonlinear acoustic signalling like all other major lineages of vocal vertebrates, these results suggest strong selection pressure favouring this mechanism to enrich the spectro-temporal content and complexity of vocal signals.
声学信号在社会交流中起着至关重要的作用，并表现出强烈的选择新颖形态的倾向，导致许多类群的叫声变得更加复杂。在脊椎动物中，青蛙和哺乳动物的喉和鸣禽的鸣管的反复创新增强了声谱-时间内容，从而增加了发声的多样性。这种声学多样化包括非线性特征，这些特征将频率谱扩展到传统的谐波和宽带叫声之外。尽管鱼类是现存脊椎动物中最大的群体，并且在声音产生方面也表现出广泛的进化，但它们仍然是证明脊椎动物中存在这种声学创新的一个显著例外。在这里，我们结合了严格的声学和数学分析以及对发声运动系统的实验性沉默，展示了一种蟾鱼的新型鳔机制如何使其能够发出具有非线性的叫声，这些叫声与青蛙、鸟类和哺乳动物（包括灵长类动物）中发现的叫声相似。这些结果表明，鱼类已经进化出了像所有其他主要发声脊椎动物谱系一样的非线性声学信号，这表明强烈的选择压力有利于这种机制来丰富发声信号的声谱-时间内容和复杂性。
