The average shock from an electric eel lasts about two-thousandths of a second. The pain isn’t searing — unlike, say, sticking your finger in a wall socket — but isn’t pleasant: a brief muscle contraction, then numbness.
For scientists who study the animal, the pain comes with the professional territory.
“I remember the first time I was shocked,” said Carlos David de Santana, an ichthyologist at the National Museum of Natural History in Washington, D.C., who recalled falling into the water and dropping his equipment. “I was scared.”
De Santana has suffered several high-voltage attacks in his years studying electric eels, including one close to 400 volts.
He is the lead author of a study published Tuesday in Nature Communications describing the discovery of a new species of electrical eel, Electrophorus voltai. Named after Alessandro Volta, the Italian physicist who invented the battery, it can generate an electric shock as high as 860 volts, the strongest of any known animal.
In the process, the researchers realized that what for centuries had been considered a single species of electric eel is actually three.
“It’s quite literally shocking, when you discover new diversity in such an eye-catching fish first described 250 years ago,” de Santana said. He became enamored of the serpentine freshwater fish during childhood summers on his grandparents’ farm, where he observed them while wading in the nearby Amazon River.
The electric eel has long excited the popular imagination. But its biodiversity has been vastly underestimated, owing in part to the difficulty of catching and studying the creature, which can grow to 8 feet long and weigh up to 44 pounds. (“Eel” is also technically a misnomer; the electric variety is part of the knifefish family.)
The discovery resulted from an effort by de Santana and his colleagues, along with a wider network of researchers, to create a tree of life for South American electric fishes, which the team hopes to use for study of the region’s evolutionary history.
From 2014 to 2017, the group traveled to the Greater Amazon region — including Brazil, French Guiana, Guyana and Suriname — where they collected 107 live electric eel specimens, tested their voltage, and extracted muscle samples for later genetic analysis.
The team then looked for morphological, genetic and electrical differences between the specimens. Luiz Antonio Wanderley Peixoto, an author of the study and a postdoctoral intern at the University of São Paulo, said it was the first time electric voltage has been used to differentiate animal species.
The genetic analysis revealed that the specimens represented at least three distinct species. One striking physical difference between the three was in the shape of their skulls. The head of Electrophorus electricus looks like the letter “u,” whereas that of E. voltai was more ovular — an egghead.
The biggest surprise came when the researchers measured each eel’s electrical discharge — a delicate process that involved placing an electrode on each animal’s head and tail. They measured an 860-volt discharge from E. voltai; previously the highest known discharge was 650 volts, which is four times the voltage of a standard U.S. wall socket. The amperage is too low to cause serious harm to humans.
Electric eels possess a specialized nervous system that synchronizes the activity of electricity-producing cells called electrocytes. An eel has about 6,000 electrocytes, packed into three organs called the main organ, Hunter’s organ and Sachs’ organ, and can discharge them simultaneously to produce a powerful current. Angel Caputi, a computational neuroscientist at the Institute for Biological Research in Uruguay, has written that the electrocytes line up “like a series of batteries piled into a flashlight.”
The eel employs this current to detect other fish, disrupt nearby electric signals from other fish and even paralyze prey. Electric eels were once thought to be solitary animals, but de Santana and his team have seen eels coordinate their predatory activity like lions on the hunt.
“This social behavior is quite unusual,” said Naercio Aquino Menezes, of the University of São Paulo’s Zoology Museum and the study’s lead investigator. “They come together in a school, surround the fish they feed on, release electricity and kill it.”
Menezes said the team hopes to soon film a coordinated electric-eel attack, which he believes has never been caught on camera.
De Santana said the study could have applications for biotechnology research, perhaps as a model for the creation of medical implants. Scientists have long marveled at the eel’s unique ability to turn its body into a battery pack. In 2017, researchers at the University of Fribourg in Switzerland designed an “eel-inspired” artificial organ that might eventually power small medical devices, from pacemakers to prosthetics.
“The interest in these fish goes beyond biodiversity,” de Santana said. “They could inspire new technology. They’re one of the few fish in the world that really carry magic.”