One of the world’s smallest fish discovered only three years ago uses a special drumming mechanism to produce sounds as loud as a pneumatic drill, a new study has found.
The translucent fish –Danionella cerebrum – named due to its open skull roof and small brain, is found commonly in small streams along the Bago Yoma mountain range of Myanmar.
Due to its small size, transparent body, and the ease with which it can be studied at the cellular level under a microscope, the fish is widely seen as an emerging model organism in biomedical research.
Since the discovery of the species in 2021, scientists have been perplexed how this fish, measuring less than 12mm in length – just a little longer than a fingernail – could produce sounds exceeding 140 decibels.
Researchers have now found that it possesses a unique sound production apparatus – including a special cartilage, a unique rib, and fatigue-resistant muscle.
These features, scientists say, allow the fish to accelerate its cartilage at extreme forces and generate rapid, loud pulses of sound.
The study found that sound production in the fish corresponds with the rapid compression of its swim bladder and the movement of its fifth rib.
Researchers also found that D cerebrum has specialised muscles that contract to pull the fifth rib.
The muscle contraction happens at record-breaking speeds, exceeding the fastest known such movement in the animal kingdom, scientists say.
Analysing the mechanism further, scientists found that the fifth rib of the fish locks into a groove in a cartilage structure and builds tension by pulling the cartilage.
The cartilage then snaps free, speeding up at 2,000 times the acceleration exerted by gravity, and strikes the swim bladder, producing a short, loud sonic pulse.
Scientists also found that genetic adaptations in the fish resist fatigue in its sonic muscles, allowing the species to produce a long series of sonic pulses.
The findings, published in the journal PNAS on Monday, challenge the conventional notion that the speed of skeletal movement in vertebrate animals is limited by their muscle action.
The results also shed more light on the diversity of adaptions for motion and sound production across animal species.
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