Tropical fish is as loud as a jet plane - Triops Galaxy

Tiny tropical fish is as loud as a jet plane

The expectation that loud animals are also large is often disappointed, especially in the case of males of a tropical fish species. The males of Danionella cerebrum are only around one centimetre in size, but do not conform to the usual cliché, as they can produce a sound pressure similar to that of a fighter jet. Researchers have now decoded the mechanism behind this.

Sound pressure of a jet engine from a distance of 100 metres

This tiny species, which was only described in autumn 2021, lives in the rivers that stretch along the foothills of the Bago Yoma Mountains in Myanmar. The species name D. cerebrum refers to the tiniest known vertebrate brain possessed by the transparent fish. A research team, led by Verity Cook from Charité University Medicine in Berlin, used high-speed cameras to study the process. The study, published in the scientific journal PNAS, shows that a so-called barrel cartilage rushes against the animal’s swim bladder at 2000 times the acceleration of gravity.

Ralf Britz from the Senckenberg Natural History Collections, who first described the species and was involved in the current study, reports that he heard the rattling sounds of the fish in the aquarium. These sounds are used for communication in the murky rivers, where visibility is often very limited. Measurements in aquariums have shown that the animals produce a noise level of 147 decibels at a distance of around one centimetre, which is extremely loud for their size. This is roughly equivalent to the sound pressure of a jet engine at a distance of 100 metres. In comparison, elephants only reach 125 decibels.

To investigate the production mechanism of the sounds, the team observed groups of three to four of these transparent fish in an aquarium, with at least one male present. They filmed the animals with high-speed cameras that can deliver up to 8000 images per second. The sounds are produced so quickly that the team was able to see a contraction of the swim bladder in just one image, which took place within 125 microseconds. As this is much faster than any previously known muscle contraction, the researchers looked for another mechanism and discovered that with each sound, a rib of the animal moves, stops and returns to its original position. They also found a tiny drum cartilage that is also involved in sound production.

Micro-CT images showed that the males of the species each have a drum muscle on the left and right. The contraction of these muscles pulls the fifth rib forwards, causing the drum cartilage to tighten. As soon as the tension is released abruptly, the cartilage rushes against the swim bladder at lightning speed.

Sladjan Lazic

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