Biologists figured out the history of the electrification of fish

(ORDO NEWS) — Able to create an electrical discharge, fish use a special organ for this. Biologists figured out its evolution and found that “fish electricity” arose independently in different groups of animals due to the doubling of the sodium channel gene, which originally worked in the muscles.

Electric rays, eels and catfish belong to very different groups of fish and live in different parts of the Earth. However, they are united by a formidable weapon: they and some other fish are able to create strong discharges.

So, electric rays (genus Torpedo ) generate voltage up to 220 volts, electric catfish ( Malapterurus electricus ) – twice as much.

These predators use electricity of their own production, paradoxically as it may sound, to drown out the fish – their victims.

However, “fish shock” also serves for self-defense and is closely related to the organs of electroreception. They allow many fish (mostly primitive ones) to sense charges in their environment. Some successfully combine “electrical reconnaissance” with “electrical assault”.

Biologists have turned to the example of the so-called weakly electric fish, which are not created by such strong discharges as the famous “striker” fish.

However, they successfully use electricity to distinguish between members of their species and communicate while in muddy water and darkness.

These are the so-called mormirs ( Mormyroidea ) from Africa and the gymnotes ( Gymnotiformes ) from South America. Scientists figured out their evolutionary past and found out that the electric organs of these two groups have a very similar history.

Biologists figured out the history of the electrification of fish 2
Electric discharges of fish can be species-specific

It turns out that the basis for “fish electricity” was sodium channels – membrane proteins that selectively and in response to a special signal pass sodium ions. They are usually found in the muscles and cause them to contract.

More precisely, the whole point here is in the corresponding genes, which are doubled in all fish, that is, they are represented by two copies. During the evolution of electric fish, one of the copies of the sodium channel gene in some muscle tissues ceased to function.

However, then she again earned, so to speak, at full capacity – already in the electric organ, which just represents modified muscles.

The amazing invention of evolution is due to the change in gene regulation. According to the new paper, it is associated with a specific section of the sodium channel amino acid sequence, about 20 “letters” long, that can change or even disappear from the protein.

“It’s amazing because we’re seeing how a small change in a gene can completely change where it’s active,” said Harold Zakon, professor of neuroscience at the University of Texas and lead researcher.

He also emphasized that it was especially important for fish to “split” the regulation of two copies of the gene in muscles and an electrical organ, to make them independent. Otherwise, the fish would damage their own muscles.


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