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Electric fish have for long fascinated humans. The ancient Egyptians used the torpedo, an electric marine ray, in an early form of electrotherapy to treat epilepsy.
Much of what Benjamin Franklin and other pioneering scientists learned about electricity came from studies of electric fish. In Victorian times, parties were organized where guests would form a chain to experience the shock of an electric fish.
Worldwide, there are hundreds of species of electric fish in six broad lineages. Charles Darwin himself cited electric fish as prime examples of convergent evolution, where unrelated animals independently evolve similar traits to adapt to a particular environment or ecological niche.
Researchers on Thursday unveiled a genetic blueprint of the electric eel, a fearsome denizen of South America that can zap you with an electric field of up to 600 volts, as well as detailed genetic data on two other types of electric fish.
Even though six groups of electric fish have evolved independently in far-flung locales like the muddy waters of the Amazon and murky marine environments, they all seem to have reached into the same genetic toolbox to fashion their electricity generating organ, they said.
The new study found that various electric fish rely on the same genes and biological pathways to build their electric organs from skeletal muscle despite the different appearance and body location of their organs.
The electric organ is used by fish to communicate with mates, navigate and stun prey as a shocking defense. There are so many species that have this ability that Darwin said electric fish were an example of convergent evolution where unrelated animals independently develop the same traits. All muscle and nerve cells can potentially be electric, muscle contractions release a small amount of voltage. Some fish started to amplify this potential between 100 and 200 million years ago.
Although all muscle cells demonstrate electrical potential, groups of electric fish have evolved specialized muscle cells called electrocytes. Developing over millions of years, these electrocytes are capable of generating electric fields that have a much higher voltage than typical muscle cells. The electric eel, for example, is capable of producing an electric field of up to 600 volts.
“The electric organ is used by fish to communicate with potential mates, navigate murky environments, mark territory, stun prey and evade predation. These electric fish use electric fields to navigate in much the same way that bats use echolocation to sense their environment,” says James Albert, a professor of biology at the University of Louisiana.
“Evolution has removed the ability of muscle cells to contract and changed the distribution of proteins in the cell membrane, now all electrocytes do is push ions across a membrane to create a massive flow of positive charge,” Lindsay Traeger, U-W graduate student and co-author of the study said in the news release.
The six groups include: South American knife fishes, African electric catfish, African elephant fish, stargazers, some skates and some rays. Scientists think the electric organ first appeared in a fish 150 million to 200 million years ago, Gallant added.
The study was published in the journal Science.