在電影《大白鯊》中,，當(dāng)這條兇惡的鯊魚在水中游弋時(shí)，約翰·威廉姆斯那帶有不祥預(yù)感的音樂便會(huì)響起。然而水虎魚卻有著它們自己的伴奏。

紅腹水虎魚（Pygocentrus nattereri，如圖）在進(jìn)行捕獵時(shí)會(huì)發(fā)出惱人的噪音,。為了搞清這種小魚是如何在水下發(fā)聲的，比利時(shí)列日大學(xué)生物學(xué)家Sandie Millot在一個(gè)魚缸中對(duì)它們進(jìn)行了觀察,。

研究人員發(fā)現(xiàn),，這種兇猛的獵食者會(huì)發(fā)出3種聲音：首先，當(dāng)一條水虎魚同對(duì)手面對(duì)面時(shí),，它們會(huì)發(fā)出急促的叫聲,，就如同犬吠一般。而在兩條魚搏斗的整個(gè)過程中,，水虎魚往往會(huì)發(fā)出兩聲低沉的吼叫,。

斗志旺盛的水虎魚利用肌肉快速擊打自己的魚鰾——幫助它們漂浮的氣室——來發(fā)出這兩種聲音,。

而第三種叫聲則最令人厭惡——水虎魚會(huì)不停地撞擊它們的牙齒以驅(qū)趕其他的魚遠(yuǎn)離自己的晚餐。研究人員在本月出版的《實(shí)驗(yàn)生物學(xué)期刊》上報(bào)告了這一研究成果,。(生物谷 Bioon.com)

doi:10.1242/?jeb.061218
PMC:
PMID:
Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study

Sandie Millot*, Pierre Vandewalle and Eric Parmentier

Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or trapped in a gill net. These sounds are generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder. The piranha swimbladder is thought to play an important role in sound production as an impedance-matching device and as a resonator. However, the vibratory capacities of the cranial and caudal sacs and the exact role of both sacs in sound production remain poorly understood. In this study, three sounds were each associated to a specific behaviour. The first sound (type 1) was produced during frontal display; it had numerous pulses and lasted 140!±17 ms, with a fundamental frequency of 120±4 Hz. It corresponded to the sound made by hand-held fishes. The second sound (type 2) was produced during circling and fighting behaviour; it was a single pulse lasting 36±8 ms, with a fundamental frequency of 43±10 Hz. The third sound (type 3) corresponded to chasing behaviour and comprised three to four pulses, each lasting 3±1 ms, with a fundamental frequency of 1739±18 Hz. Using a laser vibrometer to study the swimbladder displacement when stimulated at different frequencies, it was demonstrated that the first two sounds corresponded to the swimbladder mechanism. By contrast, the third sound was associated with the jaw mechanism. The vibrometer indicated that the swimbladder is a highly damping structure, simply copying the sonic muscle contraction rate. This study provides two interesting insights. First, it shows the relationships between three kinds of piranha sound and three specific behaviours. Second, using muscle stimulation at different rates, it shows which simultaneous conditions are required for production of sound in this species. Swimbladder calls were produced by a muscle contraction rate of approximately 100 Hz because this periodicity allowed the swimbladder to vibrate. At this frequency range, the contraction–relaxation cycles of the swimbladder muscles engendered wall displacements that had short amplitudes and with only a small variability between them.