Gills Aloud? Small fish were found making very loud noises

A small, transparent fish makes a sound as loud as a jackhammer, scientists have found.

They are prompted to investigate after hearing mysterious noises coming from the fish tanks in their lab.

They found that the fish, Danionella cerebrum, emits a strong rhythm in an organ called the swim bladder.

In the water near the fish, it hits 140 decibels, which is as loud as a gunshot.

Researchers believe the 12mm long species is the loudest fish for its size yet found.

They believe that drumming can be a form of social communication.

In most kingdoms of nature, the bigger the animal, the louder the noise.

Underwater it’s a different story – where the miniscule marine species is now one of the loudest yet discovered.

Scientists know that other creatures, such as the aptly named pistol shrimp can create very loud noises as they hunt other species, up to around 200 decibels.

Danionella is prized by science because its transparency means you can see its brain in action and it allows researchers to closely study its behavior,

But while working with these fish in their lab in Germany, scientists noticed something strange.

“People are just walking around fish tanks, and they hear these sounds, and wonder where they’re coming from,” said Verity Cook, the study’s lead author, and a PhD Student at Charité University, Berlin.

“It turns out they’re from the fish themselves. And it’s rare, because they’re so small and so strong.”

Using an array of microphones and video cameras, the research team soon worked out just how loud.

“At a distance of one body length, the amplitude of the sound is about 140 decibels, that’s how loud we believe the sound is to be detected by other fish,” he told BBC News.

“Sound attenuates with distance, so at one meter away, the amplitude is around 108 decibels.”

That’s still roughly equivalent to the noise made by a bulldozer.

Much of this sound is reflected back into the water so when people stand next to fish tanks, they hear these pulses as a continuous humming sound.

While the fish including the Plainfin Midshipman and the Black Drum and others are stronger, they are all larger than the danionella.

“In terms of communication signals, I can’t find another animal of this size that makes sounds this loud,” Ms Cook added.

Researchers argue that the drumming mechanism used by fish is a very sophisticated instrument.

All slender fish have a swim bladder, a gas-filled organ that helps them stay underwater.

Many species use their muscles to drum on this bladder to produce sounds but danionella goes a few steps further.

When it contracts its muscles, they pull on a rib, creating tension on a piece of cartilage embedded within the muscle.

When the cartilage is released it hits the swim bladder.

Only males of the species make this sound, and they only do it in company. Some are stronger than others.

“We know that when you have eight males together in a big tank, three of them will dominate making the sound and the others will be quiet. So we think there is some sort of hierarchy,” Ms Cook said.

Researchers believe that development in the dark waters in Myanmar played a role in the development of this ability to make a loud noise to help them communicate.

“Evolution has developed a lot of interesting ways to solve a lot of interesting problems,” Ms Cook said.

“And we shouldn’t assume we know how things work, just because of how things work in other species.”

The study was published in the journal, Proceedings of the National Academy of Sciences.