Eels are elongated aquatic creatures, long a subject of human curiosity. Their snake-like appearance and elusive nature often lead to questions about their ability to generate electricity.
The Electric Few
Despite their common name, electric eels are not true eels; they belong to the order Gymnotiformes. True eels are members of the order Anguilliformes, which includes species like moray eels or conger eels. The vast majority of true eel species do not produce electric discharges.
The genus Electrophorus, commonly known as electric eels, contains three recognized species: Electrophorus electricus, Electrophorus voltai, and Electrophorus varii. These South American freshwater fish are unique in their capacity to generate substantial electrical outputs. Electrophorus voltai is known to produce the highest voltage of any animal, reaching up to 860 volts.
Generating Biological Current
Electric eels generate electrical discharges using specialized cells called electrocytes, or electroplaques. These disc-shaped cells are modified muscle cells that make up a significant portion of the eel’s body. They are arranged in columns, similar to a series of batteries, with each cell contributing a small voltage of approximately 0.1 to 0.15 volts.
When the eel decides to discharge electricity, its brain sends a signal to these electrocytes. This signal triggers ion channels to open, allowing positively charged sodium ions to rapidly flow into the cells. This sudden ion movement creates a temporary electrical potential difference across each cell. The simultaneous discharge of thousands of these stacked cells produces a cumulative high-voltage shock.
Why Eels Zap
Electric eels employ their electrical capabilities for various purposes, including predation, defense, and navigation. For hunting, they emit powerful high-voltage pulses to stun or incapacitate prey. These strong shocks can cause involuntary muscle contractions in their targets, making escape difficult. An eel can even deliver concentrated discharges by curling its body, bringing its head and tail closer to the prey, to increase the effectiveness of the shock.
Beyond stunning prey, electric eels also use their high-voltage discharges as a defense mechanism against predators. They can even leap partially out of the water to deliver a direct, concentrated shock to a threat. For navigating their murky freshwater habitats, where visibility is poor, electric eels emit weaker, low-voltage electrical pulses. This lower voltage creates an electric field around them, which functions like a biological sonar, allowing them to detect objects, other animals, and even prey hidden in the mud by sensing distortions in the field.
Safety and Encounters
While the electrical discharge from an electric eel can be powerful, it is rarely fatal to humans. A single shock typically causes intense pain, muscle spasms, and temporary numbness or paralysis. The amperage, or current, is relatively low, which contributes to the non-lethal nature of most shocks.
Repeated shocks or prolonged exposure can be more dangerous, potentially leading to respiratory or heart failure. A more common risk for humans interacting with electric eels is secondary injury, such as drowning, if the shock causes disorientation or incapacitation in water. Caution and respect are advised when in environments where electric eels are present.