Introduction

For most of its 250-year scientific history, the electric eel was considered a single species — a remarkable but reasonably well-understood animal that generated electricity to stun prey and deter predators. Researchers had measured its voltage, mapped its electric organs, and described its behaviour in considerable detail.

Then, in 2019, a team of scientists re-examined the electric eel using modern genetic analysis and discovered that what had been classified as a single species was actually three distinct species — and that one of them, Electrophorus voltai, could generate electric discharges of up to 860 volts, making it the most powerful bioelectric generator of any known animal on earth.

The electric eel, it turned out, was more extraordinary than anyone had realised. And the more closely researchers looked, the stranger it became.

What Is an Electric Eel?

The electric eel is not an eel. Despite its name, its appearance, and its lifestyle, it belongs to the order Gymnotiformes — the knife fishes — and is more closely related to catfish and carp than to true eels. It is the only member of its family, Electrophoridae, and the only species in its genus capable of generating high-voltage electric discharges.

There are now three recognised species: Electrophorus electricus, the original described species; Electrophorus varii, named for ichthyologist Richard Vari; and Electrophorus voltai, named for Alessandro Volta, the inventor of the battery — an appropriate tribute given that Volta’s invention was itself inspired by the electric eel’s anatomy.

All three species are found in the freshwater rivers and streams of the Amazon and Orinoco basins in South America — murky, oxygen-poor waters where visibility is near zero and most other sensory systems are of limited use. They are large animals — regularly reaching 2 metres in length and weighing up to 20 kilograms — with long, cylindrical bodies, no scales, and a small head at one end of a body that is, in cross-section, almost entirely composed of electric organ tissue.

The Electricity

Approximately 80% of the electric eel’s body is composed of three specialised electric organs — the main organ, the Hunter’s organ, and the Sach’s organ — each serving a different function and generating electricity through a different mechanism.

The electric organs are composed of electrocytes — modified muscle cells that have lost their ability to contract and instead generate electrical potential across their membranes. Each electrocyte generates a small voltage — approximately 0.15 volts — but thousands of electrocytes are stacked in series, like batteries in a torch, so that their voltages add together. The result, in Electrophorus voltai, is a discharge of up to 860 volts — the highest voltage produced by any living organism.

But voltage alone does not tell the full story. The electric eel uses its electricity in three distinct ways, each serving a different purpose.

The first is active electrolocation — a low-voltage, continuous electric field generated by the Sach’s organ that the eel uses to navigate and detect objects in the murky water. This is analogous to the echolocation of bats, but electrical rather than acoustic — the eel detects distortions in its own electric field caused by objects in the environment, building a three-dimensional map of its surroundings without using its eyes.

The second is communication — modulated electric signals used to communicate with other electric eels, conveying information about species identity, sex, and individual identity. Electric eels can recognise each other’s electric signatures, and researchers have documented complex interactions between individuals mediated entirely through electrical signals.

The third — and most dramatic — is the high-voltage discharge used for hunting and defence. This is the 860-volt shock that can knock a horse unconscious, and it is deployed with a precision and sophistication that researchers only recently began to appreciate.

The Hunt

For most of its history, the electric eel was thought to hunt by generating a high-voltage discharge that stunned prey in the surrounding water. This is partially correct — but the reality is considerably more sophisticated.

Research published in 2014 revealed that electric eels use their high-voltage discharges to remotely control the muscles of hidden prey. When an eel detects a fish hiding in vegetation or buried in sediment, it generates a rapid series of high-voltage pulses — not a single shock, but a precise volley that causes the prey’s muscles to contract involuntarily, revealing its location through the movement. The eel then generates a sustained high-voltage discharge that immobilises the prey, and consumes it.

More remarkably, a 2016 study documented electric eels leaping partially out of the water to press their chins against the bodies of large animals — including humans — and delivering high-voltage shocks directly through direct contact. This behaviour, first described by Alexander von Humboldt in 1800 but dismissed by subsequent researchers as exaggeration, was confirmed using laboratory experiments and high-speed video. The direct-contact discharge is significantly more effective than a discharge delivered through water, and the leaping behaviour appears to be a defensive response to large animals that cannot be deterred by a standard discharge.

Biology and Ecology

The electric eel is an obligate air breather — it must surface to breathe atmospheric oxygen every few minutes, a necessity in the oxygen-poor waters it inhabits. It has a highly vascularised mouth lining that functions as a primitive lung, absorbing oxygen directly from air held in the mouth. This adaptation allows it to survive in water conditions that would be lethal to most fish.

It is largely nocturnal and solitary, spending the day in sheltered locations and hunting at night. Despite its size and its formidable electrical capabilities, it is not an apex predator — it is preyed upon by caimans and large river dolphins, which appear to be resistant to its electric discharges.

Reproduction involves the male constructing a nest from his own saliva, into which the female deposits eggs. The male guards the nest and the larvae, which feed initially on unfertilised eggs provided by the female. A single nest can contain up to 3,000 larvae — an extraordinary reproductive output for a large vertebrate.

Conservation

The electric eel is not currently assessed as threatened. It is widespread across the Amazon and Orinoco basins, adaptable to a range of freshwater environments, and not significantly targeted by commercial fishing. The primary long-term threat is the degradation of Amazonian freshwater ecosystems through deforestation, pollution, and dam construction — pressures that affect the entire freshwater biodiversity of the region.

Conclusion

The electric eel spent 250 years being understood — or so scientists thought. Then genetic analysis revealed it was three species, high-speed video revealed it was leaping out of the water to shock large animals, and laboratory experiments revealed it was remotely controlling the muscles of hidden prey with precisely targeted electrical volleys.

It is not an eel. It generates more voltage than any other living organism. It navigates by electricity, communicates by electricity, hunts by electricity, and defends itself by electricity — using three different electrical systems for three different purposes, with a precision that engineers building bioelectric devices are actively studying.

The Amazon is full of extraordinary animals. The electric eel — whatever it actually is — is among the most extraordinary of all.