Researchers have figured out how clownfish make “pop-pop-pop” noises at each other. The secret turns out to be an unusual tooth-clacking mechanism that scientists had never before documented.
Plenty of fishes make noises, explains Eric Parmentier of the University of Liège in Belgium. Most species either scrape bones together or vibrate air-filled swim bladders.
Those mechanisms don’t generate sound with the right frequencies or other qualities to explain the noises of the clownfish Amphiprion clarkii, says Parmentier. These striped reef fish chirp or pop during courtship or daily life around the reef, or when an intruder looms.
To study the sounds in that last scenario, Parmentier and his colleagues worked with Michael Fine of Virginia Commonwealth University in Richmond. The lab team combined a high-speed video camera with X-ray equipment and recorded the fish’s bone movements at 500 frames per second, 20 times the speed of a typical movie.
When a male clownfish sees an intruder, he opens his jaws and then lifts his head, causing unusual ligaments to snap the jaws shut. The popping sound comes from the front teeth smacking together. The researchers tested the idea by sabotaging the ligament. When its jaw couldn’t snap shut, the fish was mute, they report in the May 18 Science.
Fish have evolved diverse ways of making sound, says Parmentier, and he predicts that the cichlids that he’s studying now use yet another mechanism.