Danionella cerebrum is a popular species for scientific study because it is transparent, meaning that scientists can easily observe its brains and internal organs.
Verity Cook, the lead author of the research and a PhD student at the university, told the BBC: “People were just walking past the fish tanks, and they could hear these sounds, and were wondering where they were coming from.
“It turned out that they’re coming from the fish themselves. And it’s extraordinary because they’re so tiny and so loud.”
Experts believe the sounds are generated by the fish as a form of communication and to locate each other – the species is native to Myanmar, where it inhabits murky, muddy waterways in a mountain range.
Or it may be to do with mating behaviour – only the males make the sound.
The tiny fish makes the noise by contracting its muscles and pulling on a rib which creates tension with a strip of cartilage. When that cartilage is released, it beats against the swim bladder, the gas-filled organ that all fish have, producing a drumming sound.
‘Rapid, loud pulses’
The fish’s muscles are particularly resilient to fatigue, allowing frequent beats against the swim bladder.
“We found that it possesses a unique sound production apparatus, involving a drumming cartilage, specialised rib and fatigue-resistant muscle, which allows the fish to accelerate the drumming cartilage at extreme forces and generate rapid, loud pulses,” scientists said in their findings, which were published in the scientific journal Proceedings of the National Academy of Sciences.
“Such an amplitude is highly unusual for an animal of its size.”
Scientists measured the volume with underwater microphones.
There are noisier species of fish known to science, but they are all much bigger than the pipsqueak Danionella cerebrum.
“In terms of communication signals, I couldn’t find another animal of this size that makes sounds this loud,” Ms Cook said.
The little fish has another claim to fame – it has the smallest known brain of any vertebrate in the world.
