Shocking Electric Eel Facts

Illustration of an electric eel
Dorling Kindersley / Getty Images

Most people don't know much about electric eels, except that they produce electricity. Although not endangered, electric eels only live in one small region of the world and are hard to keep in captivity, so most people have never seen one. Some common "facts" about them are just plain wrong. Here's what you need to know.

01
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The Electric Eel Is Not an Eel

A moray eel in a rocky reef
Moray eel.

Humberto Ramirez / Getty Images 

The most important fact to know about electric eels is that, unlike the Moray pictured here, they are not actually eels. Although it has an elongated body like an eel, the electric eel (Electrophorus electricus) is actually a type of knifefish.

It's okay to be confused; scientists have been for many years. The electric eel was first described by Linnaeus in 1766 and since then, has been reclassified several times. At present, the electric eel is the only species in its genus. It is only found in muddy, shallow waters surrounding the Amazon and Orinoco rivers in South America.

02
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Electric Eels Breathe Air

Electric eel
Mark Newman / Getty Images

Electric eels have cylindrical bodies, up to 2 meters (about 8 feet) in length. An adult may weigh 20 kilograms (44 pounds), with males being much smaller than females. They come in a range of colors, including purple, gray, blue, black, or white. The fish lack scales and have poor eyesight but have enhanced hearing. The inner ear is connected to the swim bladder by small bones derived from vertebrae that increase hearing capacity.

While the fish live in water and possess gills, they breathe air. An electric eel needs to rise to the surface and inhale about once every ten minutes.

Electric eels are solitary creatures. When they mass together, the group of eels is called a swarm. Eels mate during the dry season. The female lays her eggs in a nest the male constructs from his saliva.

Initially, the fry eat unhatched eggs and smaller eels. Juvenile fish eat small invertebrates, including crabs and shrimp. Adults are carnivores that eat other fish, small mammals, birds, and amphibians. They use electric discharges both to stun prey and as a means of defense.

In the wild, electric eels live about 15 years. In captivity, they may live 22 years.

03
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Electric Eels Have Organs for Producing Electricity

Electric eels in a tank
Billy Hustace / Getty Images

An electric eel has three organs in its abdomen that produce electricity. Together, the organs make up four-fifths of an eel's body, allowing it to deliver low voltage or high voltage or use electricity for electrolocation. In other words, only 20 percent of an eel is devoted to its vital organs.

The Main organ and Hunter's organ consist of about 5000 to 6000 specialized cells called electrocytes or electroplaques that act like tiny batteries, all discharging at once. When an eel senses prey, a nervous impulse from the brain signals the electrocytes, causing them to open ion channels. When the channels are open, sodium ions flow through, reversing the polarity of the cells and producing an electric current in much the same way a battery works. Each electrocyte only generates 0.15 volts, but in concert, the cells can produce a shock up to 1 ampere of electrical current and 860 watts for two milliseconds. The eel can vary the intensity of the discharge, curl up to concentrate the charge, and repeat the discharge intermittently for at least an hour without tiring. Eels have been known to jump out of the water to shock prey or dissuade threats in the air.

The Sach's organ is used for electrolocation. The organ contains muscle-like cells that can transmit a signal at 10 V of about 25 Hz frequency. Patches on the eel's body contain high frequency-sensitive receptors, which give the animal the ability to sense electromagnetic fields.

04
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Electric Eels Can Be Dangerous

Electric eel
Reinhard Dirscherl / Getty Images

A shock from an electric eel is like the brief, numbing jolt from a stun gun. Normally, the shock can't kill a person. However, the eels can cause heart failure or respiratory failure from multiple shocks or in persons with underlying heart disease. More often, deaths from electric eels shocks occur when the jolt knocks a person in the water and they drown.

Eel bodies are insulated, so they don't normally shock themselves. However, if an eel is injured, the wound can make the eel susceptible to electricity.

05
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There Are Other Electric Fish

Electric catfish
Victoria Stone & Mark Deeble / Getty Images

The electric eel is only one of about 500 species of fish capable of delivering an electric shock. There are 19 species of catfish, which are related to electric eels, capable of delivering an electric shock up to 350 volts. Electric catfish live in Africa, mainly around the Nile River. The ancient Egyptians used the shock from the catfish as a remedy to treat arthritis pain. The Egyptian name for the electric catfish translates as "angry catfish." These electric fish deliver enough electricity to stun an adult human but are not fatal. Smaller fish deliver less current, which produces a tingle rather than a shock.

Electric rays can also generate electricity, while sharks and platypuses detect electricity but don't produce shocks.