Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, 459 Shirahama, Nishimuro, Wakayama 649-2211, Japan; Co-first.
Kushimoto Marine Park Center Ltd, 1157 Arita, Kushimoto, Wakayama 649-3514, Japan; Co-first.
Curr Biol. 2019 Jul 8;29(13):R617-R618. doi: 10.1016/j.cub.2019.05.047.
Many aquatic animals, including mammals, fishes, crustaceans and insects, produce loud sounds underwater [1-6]. Soft-bodied worms would seem unlikely to produce a loud snap or pop because such brief, intense sounds normally require extreme movements and sophisticated energy storage and release mechanisms [5]. Surprisingly, we discovered a segmented marine worm that makes loud popping sounds during a highly stereotyped intraspecific agonistic behavior we call 'mouth fighting'. These sounds - sound pressures up to 157 dB re 1 μPa at 1 m, with frequencies in the 1-100 kHz range and a strong signal at ∼6.9 kHz - are comparable to those made by snapping shrimps, which are among the most intense biological sounds that have been measured in the sea [6]. We suggest a novel mechanism for generating ultrafast movements and loud sounds in a soft-bodied animal: thick, muscular pharyngeal walls appear to allow energy storage and cocking; this permits extremely rapid expansion of the pharynx within the worm's body during the strike, which yields an intense popping sound (likely via cavitation) and a rapid influx of water. Clearly, even soft-bodied marine invertebrates can produce remarkably loud sounds underwater. How they do so remains an intriguing biomechanical puzzle that hints at a new type of extreme biology.
许多水生动物，包括哺乳动物、鱼类、甲壳类动物和昆虫，都会在水下发出响亮的声音[1-6]。柔软的蠕虫似乎不太可能发出响亮的噼啪声或爆裂声，因为这种短暂而强烈的声音通常需要极端的运动和复杂的能量储存和释放机制[5]。令人惊讶的是，我们发现一种分段的海洋蠕虫，在一种高度定型的种内竞争行为中会发出响亮的爆裂声，我们称之为“口斗”。这些声音——在 1 米处的声压高达 157dB 重 1μPa，频率在 1-100kHz 范围内，在 6.9kHz 左右有一个很强的信号——与 snapping shrimp 发出的声音相当， snapping shrimp 是在海洋中测量到的最强烈的生物声音之一[6]。我们提出了一种在柔软身体动物中产生超快运动和响亮声音的新机制：厚实的肌肉咽壁似乎允许能量储存和上发条；这使得在打击过程中，蠕虫体内的咽腔能够极其迅速地扩张，从而产生强烈的爆裂声（可能通过空化）和快速的水流涌入。显然，即使是柔软的海洋无脊椎动物也能在水下发出非常响亮的声音。它们是如何做到的仍然是一个有趣的生物力学谜题，暗示着一种新的极端生物学。
