Electric eels can generate more than eight hundred volts of electricity
Electric eels are not true eels—they are knifefish whose bodies function as living biological batteries. Over eighty percent of their length is packed with thousands of specialized disc-shaped cells called electrocytes. When hunting or defending themselves, nervous system signals open cell membranes to discharge all electrocytes in series. In 2019, scientists identified a species, Electrophorus voltai, capable of delivering discharges reaching 860 volts, the highest voltage recorded in any living creature.
An Impostor Among True Eels
Despite their common name and elongated, serpentine bodies, electric eels are not true eels. Taxonomically, true eels belong to the order Anguilliformes, a group comprising marine and catadromous fishes such as morays, congers, and freshwater eels. Electric eels, by contrast, belong to the order Gymnotiformes, commonly known as Neotropical knifefish. They are more closely related to catfishes and carps than to any true eel. Their lack of pelvic, dorsal, and standard caudal fins, combined with an exceptionally long anal fin that runs along nearly the entire underside of their bodies, allows them to swim backward and forward with equal precision.
The internal anatomy of an electric eel reflects an unusual evolutionary bargain. Virtually all of the fish's vital organs—including the brain, heart, digestive tract, and reproductive system—are tightly packed into the front fifth of its body, situated directly behind the head. The remaining four-fifths of its long, cylindrical torso is almost completely occupied by three specialized electric organs. In addition, electric eels are obligate air-breathers. Their gills are so reduced that they would drown if held submerged; instead, they must regularly surface to gulp atmospheric air, absorbing oxygen through a heavily vascularized network of folds inside the oral cavity.
This unique body plan leaves massive spatial volume available for non-visceral tissue. Rather than dedicating internal space to typical skeletal muscle or sprawling viscera, the electric eel evolved to allocate the majority of its body mass to electrogenesis. This specialization turned an otherwise slow-moving river predator into one of the most energetically formidable hunters in freshwater ecosystems.