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Newly discovered species of electric eel can produce most powerful electric shock of any animal

ABC News logo ABC News 4 days ago Suzannah Lyons

It's an update to the electric eel family tree that's been over 250 years in the making.

The electric eel was first described by the famed Swedish scientist Carl Linnaeus in 1766.

But after years of hanging out on its own as the only species in the genus Electrophorus, researchers have now discovered that the electric eel, Electrophorus electricus, is in fact not one species but three.

a close up of a fish: Electrophorus voltai has the most powerful electric discharge of any known animal. (Supplied: L. Sousa) © Provided by Australian Broadcasting Corporation Electrophorus voltai has the most powerful electric discharge of any known animal. (Supplied: L. Sousa) What's more, one of the newly described species of eel, Electrophorus voltai, has been recorded generating an electric shock of 860 volts.

It's far above the 650V previously recorded for the electric eel, making E.voltai the most powerful electricity-generating animal in the world, the authors report in Nature Communications today.

But before you get worried about getting too close, its discharge is high voltage but low amperage they said, so it wouldn't necessarily be dangerous to humans. (If we think of electricity as water flowing through a hose, the amperage (current) is how fast the water is flowing, and the voltage is the water pressure that pushes the water through the hose.)

The findings are the result of an ongoing study aiming to describe most of the species of South America's electric fishes and place them in the fish tree of life, said zoologist and lead author of the paper C. David de Santana of the Smithsonian's National Museum of Natural History.

And that includes one of the continent's most fascinating animals, the electric eel. Fun fact: it's not actually an eel at all, but rather a type of knifefish that grow up to 2.5 metres in length.

"In spite of all the human impact to the Amazon rainforest in the past 50 years we can still discover undescribed giant fishes like two new species of electric eels," Dr de Santana said.

Electric fishes are fish that can generate electricity, or are electrogenic, as opposed to fish which are electroreceptive, meaning they can detect electric fields —although some species can be both.

Other examples of electric fish include electric rays and electric catfish.

Over a period of six years, Dr de Santana and his colleagues collected 107 electric eel specimens from across the Amazon basin and closely examined them.

While the animals looked very similar, the scientists discovered genetic differences in their DNA that showed they were in fact three different species.

They've also determined that the three species live in different parts of the Amazon.

While E. electricus is found in the highlands of the Guiana Shield, and E. voltai call the highlands of the Brazilian Shield home, the third species Electrophorus varii prefers the murky lowland waters.

For Dr de Santana, the finding is the only the beginning of what we might be able to discover in the Amazon's depths.

"The discovery of hidden species diversity of such an eye-catching and long-known organism as electric eels, indicates that an enormous amount of species are waiting to be discovered in the Amazon rainforest," he said.

"Many of which may harbour cures for diseases or inspire technological innovations, reinforcing the critical need to protect Earth's hotspots of biodiversity."

How common are electric animals?

The study suggests that perhaps there are many other animals out there capable of generating electricity that we haven't studied yet, commented Darryl Whitehead of the University of Queensland, who studies electroreception and electric fishes.

Dr Whitehead said we're unlikely to find land-based animals that can generate electricity because air doesn't conduct electricity as well as water, so there's no real reason for them to do so.

© ABC News "But once you're in the water … there you see electrical fields can radiate out, so they can be used for many different things such as defence or [capturing] prey or hunting or communication," he said.

Electric fish use electric organs to generate electricity, which are made of modified muscle cells called electrocytes.

"The ability has been developed at least six times in the fish environment, and these fishes are in no way related to each other," Dr Whitehead said.

It's an example of convergent evolution that even got Charles Darwin's attention, and recent research has looked at whether there could be common genetic factors at play.

Electric eels have three electric organs that can produce strong electrical discharges as well as weak discharges:

  • The Main organ produces more of the strong electric organ discharge
  • Sach's organ generates weak electric discharges
  • Hunter's organ at the front of the animal works as a Main organ, and at the back of the animal as a Sach's organ

"The three organs are arranged as batteries in series inside a flashlight, and fire simultaneously by entire-body muscle contractions caused by the direct stimulation of spinal motor neurons," he said.

From fascination to inspiration

While people have been fascinated by electric eels and other electric fishes for years, we've also been inspired by them.

The ancient Egyptians, Greeks and Romans all used electric fish in early medicine, to numb people or treat conditions like gout or headache.

© ABC News Electric eels inspired the design of Italian physicist Alessandro Volta's first electric battery, said Dr de Santana, and an enzyme extracted from their electric organs has been used as a target for drugs to treat Alzheimer's disease.

More recently, he said, electrical eels have promoted the advance of hydrogel batteries (made of a substance similar to gelatin) that could be used to power medical implants.

Closer to home, scientists have been inspired by an electric ray that lives in Sydney Harbour called the coffin ray (Hypnos monopterygius), said biomedical engineer Alistair McEwan of the University of Sydney.

"They use electrical sensing like a shark to see around them, but not just passively by listening into the electricity, but also by sending out their own electric field to map the world around them," Professor McEwan said.

The researchers have looked at how to emulate this system to sense changes in the heart, for example to monitor internal cardiac surgery, and in the brain.

"We used that in the brain to find different parts of the brain, and maybe a part of the brain that's not working properly, like what would happen in a stroke or epilepsy or a child with cerebral palsy," he said.

Now, Professor McEwan and his colleagues are looking at how they might be able to use the electroreception abilities of the platypus and the echidna.

"We thought the electroreception would only work well with water. It's amazing the platypus works well in fresh water without conductive salt, but even more amazing that the echidna can electrically sense in the dry desert," he said.

"We can use these to inspire new types of communication systems and perhaps new sensing systems for people with disabilities or possibly for anyone who wanted an augmented sense."

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