These fish are also transparent
Danionella cerebrum may be small fry, but the noises they make are anything but.
Think louder than an elephant.
These tiny fish, which measure up to 12 millimetres long, were the subject of a study published in the journal Proceedings of the National Academy of Sciences on Feb. 24.
Researchers from the Charité Universitätsmedizin, a university hospital in Berlin, and the Senckenberg Society Natural History Collections in Dresden, both in Germany, collaborated on the study.
Their research uncovered the apparatus that allows male Danionella cerebrum fish to make loud, pulsing noises, and theorizes why this behaviour evolved in the first place.
Researchers recorded the fish in a tank. This video is slowed down 10 times to see how they moved. (Video credit: Verity Cook/Charité)
How did the study work?
The researchers put four Danionella cerebrum in a tank.They captured both audio and visual recordings, and performed scans, dissections and gene analyses.
Because these fish have transparent skin, cameras could see and record what happens inside their bodies to make such loud noises.
A study model shows how the Danionella cerebrum creates its sounds. A drumming muscle (green) contracts, pulling the rib (red), which fits into a groove in the cartilage (light blue) and builds tension. The tension is released and the cartilage snaps back into place, striking the swim bladder (purple). (Video credit: Verity Cook/Charité)
First, a special drumming muscle contracts.
It pulls on a rib that moves something called the drumming cartilage out of place — a bit like stretching a rubber band.
Then, suddenly, the drumming cartilage snaps back into position so fast it strikes the swim bladder (a special organ fish have to help them swim).
This impact produces the loud pulse we hear.
Click play on the video at the top of the page to hear the Danionella cerebrum for yourself!
Why so loud?
The noises made by male Danionella cerebrum can be as loud as 147 decibels at a distance of one body length away.
That’s about as loud as a jet engine would sound taking off 100 metres away from you.
The researchers believe these pulses are a way for the fish to communicate.
Danionella cerebrum’s native habitat are shallow, murky waters in Myanmar.
The scientists say this lack of visibility could mean sound communication evolved to help the fish locate mates.
The Danionella cerebrum is about as long as the diameter of a typical AA battery. (Image credit: Senckenberg, with graphic design by Philip Street/CBC)
A unique opportunity
The study broadens our understanding of how animals make noise and why these behaviours might have evolved.
Now, the scientists hope to study the four other species in the Danionella family, to compare how they produce sounds.
Click play to hear the itsy-bitsy fish for yourself!
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TOP IMAGE CREDIT: Senckenberg, with graphic design by Philip Street/CBC
