The electric eel was first described by the scientist Carl Linnaeus in 1766. For about 250 years scientists counted only one kind of electric eel, but as of November 2026, scientists know of at least three species, and one is named Electrophorus varii for the late Smithsonian fish scientist Richard Vari, and another is named E. voltai for Alessandro Volta. The three species look nearly alike, but each has its own skull shape, pectoral fin features and pattern of body pores, and a scientist used their DNA to tell them apart. As of November 2026, E. electricus lives only on the Guiana Shield highlands, E. voltai mostly on the Brazilian Shield, and E. varii in the lowland Amazon basin, and a few Guiana Shield streams hold both E. voltai and E. varii. By DNA, the lowland species split from the other two about 7.1 million years ago, and the two highland species split about 3.6 million years ago, at about the time the Amazon River took its modern path across the continent.
As of November 2026, the strongest discharge known from any living animal is 860 volts, which scientists measured from one Volta's electric eel and that is higher than the 650 volts that had been cited before for electric eels. The 860-volt measurement comes from a single eel that was 1,219 millimeters long. In a 2019 study, scientists read the peak voltage of an eel's high-voltage volley with an oscilloscope, with the eel lying on a dry plastic sheet so the water was not part of the circuit. The bigger an electric eel is, the stronger its discharge, with shocks from E. varii eels ranging from 151 volts for a 200 mm eel to 572 volts for a 609 mm eel, and 480 volts from an Electrophorus electricus 760 millimeters long. As of November 2026, sources give different top voltages for electric eels: 600, 650, 800 and 860 volts. In lowland waters full of minerals, electricity travels farther, but in the clear water of the highlands the eel's discharge does not travel as far.
An electric eel makes electricity with special cells called electrocytes, and it has thousands of them, and in an electrocyte, a nerve signal opens channels so sodium ions flow in and potassium ions flow out, which changes the voltage across the cell membrane. At rest, the two ends of an electrocyte cancel each other out, but when the cell fires, the back membrane switches and the cell makes about 150 millivolts. The electrocytes work like a stack of batteries, and large electric eels stack thousands of electrocytes in series, so the small voltages add up to over 600 volts. The stacks run along the rear 80 percent of the body, and the electric organ is made of hundreds of thousands of flat cells connected in a line. An electric eel has three electric organs: the two larger organs, called the Main and Hunter's organs, make the strong shock, and the small Sachs organ makes the weak pulses.
In a burst of shocks, an electric eel can send out as many as 400 pulses a second, and the shock is high in voltage but low in current, about one amp. The shock works on the nerves of the eel's food, which makes the muscles tighten. Scientist Kenneth Catania found that two or three quick pulses make hidden prey twitch, and the eel senses the twitch. Catania tested the nerve idea with fish that had been treated with a drug called curare, which blocks nerves from reaching muscles, and these fish did not twitch when the eel sent out pulses. After the shock, the eel opens its mouth to make suction and takes in its food. An eel can curl around prey it is holding, which brings its head and tail close together, and in a test this more than doubled the strength of the electric field.
In experiments, electric eels used their high-voltage pulses to find and track moving objects, as well as to stun. To test how eels track prey, scientists put a small metal conductor on a spinning disk, and the eels followed it while giving off high-voltage pulses. When a water-movement cue and an electric cue were put in different places, eels struck first toward the water-movement cue and later toward the conductor.
When an electric eel is cornered by a large object sticking out of the water, it can leap up and press its chin against it while giving off a series of shocks. When an eel leaps, its voltage and current rise as it goes higher, and the current goes from the eel's chin straight into the target, instead of spreading out through the water. The leap was seen in eels over about 60 centimeters long, and it appears to be common in the larger eels. The leap may have evolved in steps, and each step, from getting closer to touching to rising out of the water, adds more power to the shock.
An electric eel is a fish, but it is not a true eel, and it is more closely related to catfish and carp than to true eels. More than 220 species of South American knifefish in the electric eel's lineage use electric pulses to communicate and sense, and electric organs have evolved at least six times in different kinds of fish. Electric eels evolved from weakly electric fish, so they still have the weak electric output used for sensing, and they use weak electric pulses to talk to each other. Electric eels are the only electric fish in South America that use their electricity to hunt and to defend themselves.
For a long time scientists thought electric eels hunted alone. Then more than 100 adult electric eels, 1.2 to 1.8 meters long, gathered in a Brazilian lake, and scientists watched them for 72 hours. The eels were seen herding small fish into a tight ball, and then smaller groups of up to 10 eels sent out shocks together. At dawn and dusk, one group hunt lasted about an hour and included five to seven high-voltage bursts, and the eels rested almost still in deeper water the rest of the day. As of November 2026, hunting in groups is rare among fishes, and only nine other fish species were known to do it in 2021. In the 2021 report on group hunting, the combined voltage of the group bursts had not been measured. Researchers think group hunting may happen only in places with plenty of prey and enough shelter for many adult eels.
An electric eel has gills like other fish, but it cannot live without air, and it gets about 80 percent of its oxygen by gulping air at the surface. Electric eels live in rivers and ponds in South America, and many live in quiet, slow-moving, muddy water in the Amazon and Orinoco river basins, where the water can be low in oxygen, so an eel has to come to the surface for a breath at least every ten minutes. In the dry season the water in the rivers drops, and electric eels can be left in small pools. When the rainy season comes and the rivers swell, young electric eels spread out into new areas.
Words to know
- electrocytes: power cells
- oscilloscope: voltage-reading machine
- curare: nerve-blocking drug
- lineage: family line
