A Blue View: The Electric Eel

Did you know that the electric eel is not technically an eel at all?

Published May 10, 2016

National Aquarium – Electric Eel

Its slender, serpentine body may resemble a true eel, but scientifically speaking, the electric eel is actually a knifefish—a cousin of the carp and catfish.

Electric eels generate power with three organs containing 6,000 power-storing cells, called electrocysts. Those organs take up a lot of real estate. The eel’s other vital organs—like the heart and liver—are crammed in near the head, occupying just one-fifth of its body.

The electric eel can generate nearly 600 volts of electricity, stunning small fish and worms with ease. It can also emit a low-level charge of just a few volts, which functions like radar to identify nearby prey, compensating for the eel’s poor eyesight.

With that much power coursing through its body, you may be wondering how the electric eel keeps from shocking itself. The truth is, scientists don’t know. The mechanism by which electric eels protect themselves from their own charge hasn’t been extensively studied, but most hypotheses are based on the eel’s biological and physiological characteristics.

For more shocking facts about the electric eel, check out this week’s A Blue View podcast:

Episode Transcript

There’s no better word to describe the electric eel than, well, shocking. Part of that shock, as it turns out, was the discovery that it isn’t even a real eel. It has a long, smooth, snake-like body, but scientifically it’s classified as a knifefish, a cousin to the carp and the catfish—only with maximum voltage.

Using electricity for predation, as the electric eel does, is a rarity among electric-fish lineages.

The electric eel is a fish that's like a Taser—except that while a Taser delivers 19 high-voltage pulses per second, the electric eel produces 400 pulses per second.

This eel can discharge bursts of electricity five times the power of a standard U.S. wall socket—that’s at least 600 volts. It uses this electric technique to stun its prey: worms, crustaceans and small fish. But it can't see what it stuns, because it has poor eyesight. In fact, it’s basically blind.

Electric eels are commonly found in the freshwater murk of the swamps and creeks of the Amazon and Orinoco river basins in South America and are typically solitary animals. Nonetheless, there is a word to describe a group of them: they’re called a swarm.

It navigates by electrolocation, emitting a low-level electric discharge of less than 10 volts, which it uses like radar to find prey.

The volley of an eel's jolt induces immobilizing muscle contraction. That's the scientific definition. For the rest of us, it’s just a big “ouch.”

The electric eel is one of the most sophisticated predators in the aquatic realm. So how does it get its wallop?

Electric eels can be massive, up to 8 feet long and weighing more than 40 pounds, but their vital organs are jammed into the front 20 percent of their bodies to make room for three electric organs. These contain over 6,000 power-storing, battery-like cells called electrocysts.

The genome of the electric eel was sequenced in 2014, revealing to scientists that the eel's complex electric organs evolved from simple muscle cells. Over time, the fish became capable of generating a punch-packing electrical field.

Research shows that we should be grateful we're not small fish in the Amazonian basin. The electric eel hacks its prey's nervous system, leaving it defenseless and easily slurped into the eel’s mouth.

And, in addition to being shocking, the eel—despite its size—is fast. It can strike and swallow a worm or small fish in about a tenth of a second. Most animals it consumes never know what hit them.

The electric eel actually inspired Alessandro Volta, father of the unit of electricity known as the volt. In 1800, using a stack of disks of copper and zinc, Volta built a model that could store electricity. He called it an artificial electric fish. Today, we call it a battery.

The electric eel continues to inspire real-world applications in technologies like biobatteries, which provide the power to run implanted medical devices, like pacemakers or insulin pumps. Who knows? In the fullness of time, many of us just may be thanking a shocking knifefish for our continued health and long lives.

More fascinating facts about the electric eel’s stunning power—and how it avoids electrocuting itself—are available at aqua.org/ablueview.

A Blue View is produced for WYPR by the National Aquarium, whose mission is to inspire conservation of the world’s aquatic treasures. For the National Aquarium, I’m John Racanelli.

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