Scientists from the Charité University in Germany were studying a little fish called Danionella cerebrum when they started noticing strange noises. It sounded like insects buzzing or chirping. They soon realized the sound was coming from the tanks full of fish.
The scientists found that D. cerebrum can make sounds by squeezing a muscle attached to one of its ribs. This stores potential energy. When the fish relaxes the muscle, the stored energy turns into kinetic energy—the energy of motion. This causes the rib to hit a gas-filled organ called a swim bladder, making a loud sound. Up close, this noise can reach up to 140 decibels—as loud as fireworks!
The next step is figuring out why the fish makes these noises, says Verity Cook, a neuroscientist, or scientist who studies the brain, who helped make this discovery. “No one has looked at this fish before,” she says. “Every single question is brand-new.”