Animals

Scientist Allows Himself to Be Shocked by an Electric Eel

The painful experiment reveals the voltage and current of an electric eel and is helping researchers better understand electromotive forces.

Biologist and neuroscientist Kenneth Catania of Vanderbilt University is such a victim, since he was accidentally shocked a few times while working around small electric eels. Asked how it felt, Catania told Seeker, “The best comparison is probably an electric fence on a farm.”

Since he lived to tell the tales, Catania reasoned that he could accurately measure the high-voltage discharges of an electric eel attack by having a small one shock him in a controlled experiment.

Prior research determined that the eels may increase their powers by either curling their bodies around perceived predators or by attacking as they leap out of water. The stunning leaps prevent the eels’ electrical discharges from weakening as they dissipate through the water.

To study the dynamics of the electrical circuit that develops during such leaps, Catania submerged his arm in a tank containing a small, juvenile electric eel. He touched the back of his hand to a cup-like plastic container on the bottom of the tank. The cup was lined on the inside and out with conductive aluminum tape. Wires were affixed via the tape and were run to a device called an ammeter that measures electrical currents.

Catania then withstood multiple attacks.

“About ten,” he estimated.

The measurements, reported in the journal Current Biology, show that this tiny eel’s total voltage was 198 volts. The Taser-like jolt to Catania’s arm peaked at 40–50 milliamps, which is more than enough to cause a victim considerable pain, but not enough to cause permanent damage.

In real life, however, humans and animals may encounter much larger electric eels. A fish twice the size of the one used in the study would likely discharge twice as much electric current.

“As the eels get longer, their voltage and current both increase, meaning there is more electrical power,” Catania explained.

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The eels’ clever techniques for increasing the strength of their currents are helping Catania and others to better understand the science underlying electromotive forces. He suspects that the height of an eel’s leap is significant, since greater leaps may maximize a current’s jolt and conserve energy.

“Probably one reason they leap up to attack is that they may have a limited amount of energy before becoming exhausted,” Catania said. “So delivering that energy efficiently is important.”

The primary electric eel goal is to deter predators, which does not necessarily mean killing them. Catania agrees with Humboldt, who suspected that the two horses in the account from the 1800s died as a result of drowning while trapped in the water with the electric eels.

The fisherman temporarily paralyzed by the eels in the 1600s had a better outcome. His comrades boated out to him, tied him to a rope, and dragged him back to shore — wincing but alive. 

“Many people have been shocked by large eels,” Catania said. “I don’t know of any report going back 200 years of anyone who was killed from the shocks. But drowning is more likely, because the eel can cause temporary paralysis.”

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The eel’s natural deterrent appears to be working.

“My guess is that electric eels are not common prey for most species,” Catania said.

These animals are also not endangered, although numbers are likely much lower than historic populations due to their deaths as by-catch and intentional killings by humans.

Human skin has little evolved resistance to the electric eel’s defense. During the study, Catania tried hard to keep his arm still, but it would reflexively pull back at times.

 
Luckily, most of us are not in situations where we would encounter these electrified fish. Marine mammals, as well as alligators and crocodiles, however, frequently encounter electric eels.

Catania theorizes that fur on marine mammals and scales on crocodilians could help these predators to better withstand electric eel attacks. It is unclear if encounters between these animals affected their evolution over the millennia.

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Catania is one of the world’s leading authorities on electric eels and has studied everything from star-nosed moles to tentacled snakes, using them as model systems for understanding basic rules of science that could be applied to new technologies as well as medical treatments. For example, his studies on moles are helping to reveal how touch is represented in the neocortex and how mammalian brains evolved.

He has studied electric eels for years, and yet he remains fascinated by their shocking ways.

“Although I’m supposed to be an expert,” he said, “I am always surprised by the abilities of any animal I study.”

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