But that didn't deter Sandie Millot, Pierre Vandewalle and Eric Parmentier from the University of Liège, Belgium. 'You just have to pick them up and they make sounds,' says Parmentier. However, it wasn't clear when and why piranhas produce sounds naturally.
Intrigued by fish acoustic communication and the mechanisms that they use to generate sound, the team monitored the behaviour of small groups of captive red-bellied piranhas and publish their discovery that the fearsome fish have a repertoire of three combative sounds in The Journal of Experimental Biology at http://jeb.biologists.org.
Suspending a hydrophone in the piranhas' tank, Millot and Parmentier recorded the fish's sounds and filmed them as they cruised around and competed for food. According to Parmentier, the well-fed fish were relatively peaceful – attacking each other occasionally – although they were not averse to nipping at near-by fingers. 'We both visited the hospital because we were bitten and Sandie's finger was nearly cut in half,' recalls Parmentier.
Comparing the soundtrack with the movie, the team found that the fish were generally silent. However, they became quite vocal as soon as they entered into a confrontation – producing the same barking sound that they had produced when held in the scientists' hands. 'At first we thought there was only one sound,' admits Parmentier, but then it became apparent that the piranhas produce two more: a short percussive drum-like sound when fighting for food and circling an opponent; and a softer 'croaking' sound produced by their jaws when they snap at each other.
Having convinced themselves that the fish had a wider acoustic repertoire than they had initially thought, the team decided to find out how the fish produce the sounds.
Parmentier explains that piranhas were already known to produce noises using muscles attached to their swim bladders; however, it wasn't clear how the swim bladder was involved in sound production. So, the team stimulated the muscles to contract, measured the swim bladder's vibration and found that instead of resonating – and continuing to vibrate after the muscles ceased contracting – the swim bladder stopped vibrating as soon as the muscles finished contracting. In other words, the muscles were driving the swim bladder's vibration directly and the frequency (pitch) of the bark and drum sounds was determined by the muscles' contraction frequencies: not the swim bladder's own intrinsic resonant properties. They also found that the rear half of the swim bladder did not vibrate, so only the head portion of the swim bladder contributed to sound production.
Now that they have discovered that aggressive piranhas are quite vocal, the team is keen to find out whether amorous piranhas are vocal too. However, Parmentier suspects that the team will have to relocate to Brazil to answer that question. 'It is difficult for the fish to reproduce in the tank, so I am sure we have to deploy hydrophones in the field to have the sounds that are produced during mating,' says Parmentier.
IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org
REFERENCE: Millot, S., Vandewalle, P. and Parmentier, E. (2011). Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study. J. Exp. Biol. 214, 3613-3618.
This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT firstname.lastname@example.org
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences