Electric eels live in rivers in South America. But they are not real eels. They belong to a group of fish called knifefish. Most of their body makes electricity.

In 2019, scientists found that there are three kinds of electric eel, not one. One kind made 860 volts. That is more than eight times the voltage of a home outlet in Japan. The eels use electricity to catch fish.

Although their name includes the word "eel," electric eels are actually knifefish from South America. Most of their body is an electric organ made of thousands of cells lined up like batteries. For more than 250 years, scientists thought there was only one species, but a 2019 study showed that there are three.

One of them produced 860 volts, a record for any living animal. Electric eels use high-voltage pulses to make their prey's muscles tighten so it cannot move. They can even send short pulses toward hidden fish, which makes the fish twitch and reveals where they are. A 2021 report also described one species hunting in groups.

Despite its name, the electric eel is not a true eel but a South American knifefish. Most of its body consists of an electric organ in which thousands of muscle-derived cells, arranged in series like batteries, discharge simultaneously to generate high voltage. In 2019, a team from the Smithsonian re-examined specimens across the Amazon basin using genetic, anatomical and environmental data and found that what had been considered a single species for over 250 years is actually three. One of them, Electrophorus voltai, produced a discharge of 860 volts, surpassing the previous record of 650 volts.

Research by Catania showed how this power is used: high-voltage pulses directly stimulate the prey's motor neurons, causing involuntary muscle contractions that freeze it in place, while brief pulses aimed at hidden prey make it twitch and give away its location. Catania also supported an account of an event in 1800 by the explorer Humboldt, who described eels pressing against horses to shock them. A 2021 report even described wild E. voltai hunting in groups, although field observations of such behavior are still scarce.