Electric 'eels' are knifefish split into three species
South America's electric eels stun prey with shocks of up to 860 volts, yet they are knifefish, not true eels. Linnaeus described one species in 1766, and for over two centuries the genus was thought to hold just that one—until a 2019 study split it into three.
Their name, Electrophorus, means electricity bearer, from the Greek for amber, which holds static charge. Theodore Gill gave them that genus in 1864 and their own family in 1872, though later workers folded them back into Gymnotidae. Most of their knifefish relatives are only weakly electric, sensing surroundings without delivering shocks, and the electric eel lineage split from its closest cousins sometime in the Cretaceous. Studies of their power began in 1775 and fed into the invention of the electric battery in 1800.
In 2019 C. David de Santana and colleagues used DNA, anatomy, habitat and electrical output to recognise E. electricus, E. voltai and E. varii, although some biologists treat E. varii as a synonym of a species named from Peru in 1941. E. voltai, the strongest living generator of electricity, ranges north from the Brazilian shield; E. electricus is confined to the Guiana Shield; E. varii lives in the lowlands between. E. varii seems to have diverged about 7.1 million years ago, the other two about 3.6 million years ago.
They are nocturnal and see poorly, finding prey by electrolocation, and they mainly eat fish such as armoured catfish. E. voltai has been seen hunting in packs, herding tetras into a tight shoal before striking together, and one had a toxic-skinned caecilian in its stomach.
E. electricus can reach 2 metres and 20 kilograms. An eel keeps growing throughout life by adding vertebrae, up to about 300 in all, and swims by rippling a long anal fin with over 400 rays. Roughly every two minutes it gulps air into a blood-rich mouth lining, which lets it survive oxygen-poor water and even hours on land if its skin stays wet.
Source: Electric eel
