The smallest known brain of any vertebrae is the translucent Danionella cerebrum, measuring only 12 mm in length.
Scientists researching the species in Berlin, Germany, first became aware of the sound while they were passing by the fish tanks and heard sounds.
Subsequently, scientists installed high-speed cameras in a fish tank to precisely determine the situation.
Lead researcher Verity Cook told New Scientist, “The fish are so loud that, even when just walking past their tanks, you can hear audible pulsing sounds.”
The fish makes a “drumming sound” when one of its ribs is sucked into its swim bladder.
The males are the only ones who create noise, and Ms. Cook speculates that it could be for communication and mutual location in dark environments.
