The electric eel (Electrophorus electricus) is a most unusual species of fish. It is capable of generating powerful electrical shocks, up to 600 volts, which it uses for both hunting and self-defense. In fact, it is a top predator in its South American range, no other animal being willing to endure electrocution to try to eat one.
The electric eel may be found in the basins of both the Amazon River and Orinoco River, as well as the surrounding areas. It can grow up to 2.5 m in length and 20 kg in weight, although 1-m specimens are more common. It is rather an ugly species, with an elongated cylindrical body bearing only a few scales, a flattened head, and an overall dark grayish green color, yellowish on the bottom.
They prefer to live on muddy bottoms in calm water, and are obligate air-breathers. Rising to the surface every 10 minutes or so, the animal will gulp air, and return to the bottom.
The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. In the electric eel, stacked electroplaques (some 5,000 to 6,000 of them) are capable of producing a shock at up to 500 volts, and 1 ampere of current. There are reports of animals producing larger voltages, but this seems relatively unimportant as this much current is sufficient to stun or deter virtually any other animal. Juveniles produce smaller voltages (about 100 volts). Electric eels are capable of varying the intensity of the electrical discharge, using lower discharges for "hunting," and higher intensities are used for stunning prey, or defending themselves.
The species is of some interest to researchers, who make use of its acetylcholinesterase and ATP. As it is capable of producing strong intermittent electrical shocks over a long period of time (at least an hour) when agitated without signs of tiring, there is some desire to figure out precisely how it is capable of doing so.
Similar species are the electric catfish (Malapterurus electricus) and the electric ray (Torpedo mamorata, T. californica).
Although the eels are common in their range, and popular draws for public aquaria, the eel's habit of delivering shocks, even when gently handled, means that they are too dangerous for most amateurs to try to keep at home. Moreover, animals grow very large, and are impossible to maintain for all but the most dedicated of keepers. Countries such as Australia strictly forbid the keeping electric eels, for fear that they could escape into the wild and become a public hazard.
The species is so unusual that it has been reclassified several times. Originally a species in Gymnotus, it was later given its own family Electrophoridae, and only demoted to a genus of Gymnotidae alongside Gymnotus.
The handling of electric eels was featured as a stunt on the TV program Fear Factor. Even the eels were relatively small (< 30 cm), their shocks caused considerable pain to the contestants.