Ladich Friedrich, Winkler Hans
Department of Behavioural Biology, University of Vienna, Althanstrasse 14, Vienna 1090, Austria
Konrad Lorenz-Institute of Comparative Ethology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna 1160, Austria.
J Exp Biol. 2017 Jul 1;220(Pt 13):2306-2317. doi: 10.1242/jeb.132944.
Sound propagates much faster and over larger distances in water than in air, mainly because of differences in the density of these media. This raises the question of whether terrestrial (land mammals, birds) and (semi-)aquatic animals (frogs, fishes, cetaceans) differ fundamentally in the way they communicate acoustically. Terrestrial vertebrates primarily produce sounds by vibrating vocal tissue (folds) directly in an airflow. This mechanism has been modified in frogs and cetaceans, whereas fishes generate sounds in quite different ways mainly by utilizing the swimbladder or pectoral fins. On land, vertebrates pick up sounds with light tympana, whereas other mechanisms have had to evolve underwater. Furthermore, fishes differ from all other vertebrates by not having an inner ear end organ devoted exclusively to hearing. Comparing acoustic communication within and between aquatic and terrestrial vertebrates reveals that there is no 'aquatic way' of sound communication, as compared with a more uniform terrestrial one. Birds and mammals display rich acoustic communication behaviour, which reflects their highly developed cognitive and social capabilities. In contrast, acoustic signaling seems to be the exception in fishes, and is obviously limited to short distances and to substrate-breeding species, whereas all cetaceans communicate acoustically and, because of their predominantly pelagic lifestyle, exploit the benefits of sound propagation in a dense, obstacle-free medium that provides fast and almost lossless signal transmission.
声音在水中的传播速度比在空气中快得多，传播距离也更远，这主要是由于这两种介质密度不同。这就引出了一个问题：陆生动物（陆地哺乳动物、鸟类）和（半）水生动物（青蛙、鱼类、鲸类）在声学交流方式上是否存在根本差异。陆生脊椎动物主要通过在气流中直接振动发声组织（声带）来产生声音。青蛙和鲸类对这种机制进行了改良，而鱼类产生声音的方式则大不相同，主要是利用鱼鳔或胸鳍。在陆地上，脊椎动物用轻薄的鼓膜接收声音，而在水下则必须进化出其他机制。此外，鱼类与所有其他脊椎动物的不同之处在于，它们没有专门用于听觉的内耳终器。比较水生和陆生脊椎动物内部以及它们之间的声学交流可以发现，与更为统一的陆生动物声学交流方式相比，不存在“水生动物声学交流方式”。鸟类和哺乳动物表现出丰富的声学交流行为，这反映了它们高度发达的认知和社交能力。相比之下，声学信号在鱼类中似乎是个例外，显然仅限于近距离和在水底繁殖的物种，而所有鲸类都进行声学交流，并且由于它们主要生活在远洋环境中，因而受益于声音在密度大、无障碍物的介质中传播，这种介质能实现快速且几乎无损耗的信号传输。
