electric eel

 

Electric eel
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Gymnotiformes Family: Gymnotidae Genus: Electrophorus Species: E. electricus
Binomial name
Electrophorus electricus (Linnaeus, 1766)

The electric eel, Electrophorus electricus, is a species of fish. It is capable of generating powerful electric shocks, which it uses for both hunting and self-defense. It is an apex predator in its South American range. Despite its name it is not an eel at all but rather a knifefish.

Anatomy

A typical electric eel has an elongated square body, a flattened head, and an overall dark grayish green color shifting to yellowish on the bottom.^[1] They have almost no scales. The mouth is square, placed right at the end of the snout. The anal fin continues down the length of the body to the tip of their tail.^[2] It can grow up to 2.5 m (about 8.2 feet) in length and 20 kg (about 44 pounds) in weight, making them the largest Gymnotiform.^[1][2] 1 m specimens are more common.^{[citation needed]}

They have a vascularized respiratory organ in their oral cavity.^[2] These fish are obligate air-breathers; rising to the surface every 10 minutes or so, the animal will gulp air before returning to the bottom. Nearly 80% of the oxygen used by the fish is taken in this way.^{[citation needed]}

Scientists have been able to determine through experimental information that E. electricus has a well developed sense of hearing. They have a Weberian apparatus that connects the ear to the swim bladder which greatly enhances their hearing capability.^{[citation needed]}

Physiology

Electrical generation

Electric eel have three abdominal pairs of organs that produce electricity. They are the Main Organ, the Hunter's Organ, and the Sachs’ Organ. These organs take up 4/5 of its body. Only the front 1/5 contains the vital organs.[1] These organs are made of electrocytes lined up in series. The electrocytes are lined up so the current flows through them and produces an electrical charge. When the eel locates its prey, the brain sends a signal through the nervous system to the electric cells. This opens the ion channel, allowing positively-charged sodium to flow through, reversing the charges momentarily. By doing that it creates electricity, and fires it at its prey. 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, some 5,000 to 6,000 stacked electroplaques are capable of producing a shock at up to 500 volts and 1 ampere of current (500 watts). The organs give the electric eel the ability to generate two types of electric organ discharges (EODs), low voltage and high voltage. The shock could be harmful for an adult human.

The Sachs organ is associated with electrolocation.^[1] It is also the primary source of communication among E. electricus. This organ transmits a signal about 10V in amplitude at up to 25 Hz. These signals are used in communication as well as orientation, useful not only to find prey but also thought to play an important role in finding and choosing a mate. The Sachs' organ is capable of only producing low voltage pulses. Its purpose is electro communication and navigation. Inside the organs are many muscle-like electronic cells, which are called electrocytes. Each one of them can only produce 0.15V.

High-voltage EODs are emitted by the main organ and the Hunter's organ that can be emitted at rates of several hundred Hz. ^[1] These high voltage EODs may reach up to 600 volts. The electric eel is unique among the gymnotiforms in having large electric organs capable of producing lethal discharges that allows them to stun prey.^[2] There are reports of animals producing larger voltages, but the typical output 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. When agitated, it is capable of producing these intermittent electrical shocks over a period of at least an hour without signs of tiring. The species can stun or kill their prey just by touching them. The species is of some interest to researchers, who make use of its acetylcholinesterase and ATP.^{[citation needed]}

The electric eel also possesses high-frequency sensitive tuberous receptors patchily distributed over the body that seem useful for hunting other gymnotiforms.^[1]

Distribution

The electric eel may be found in northern South America, primarily in the basins of both the Amazon River and Orinoco River, as well as the surrounding areas.^[2]

Ecology and life history

Habitat

They tend to live on muddy bottoms in calm water. They are also found in swamps, coastal plains, and creeks.^[1]

Feeding ecology

Juvenile eels feed on invertebrates, while adult eels feed on fish and small mammals. First-born hatchlings will even prey on other eggs and embryos from later batches.^[1]

Taxonomic history

The species is so unusual that it has been reclassified several times. Originally it was given its own family Electrophoridae, and then placed in a genus of Gymnotidae alongside Gymnotus.^[2]

Importance to humans

In captivity

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, the animals grow very large, and are impossible to maintain for all but the most dedicated of keepers. It is necessary to wear rubber gloves when handling them. Countries such as Australia strictly forbid the keeping of electric eels, for fear that they could escape into the wild and become a public hazard.

See also

• Electric fish
• Electric catfish
• Electric ray

Bibliography

• Valasco, T. (2003). "Electrophorus electricus" (On-line). Animal Diversity Web. Retrieved on 2007-04-01.

References

External links

• 1954 educational film about the electric eel from the Moody Institute of Science
• Electrophorus electricus (TSN 163322). Integrated Taxonomic Information System. Accessed on 11 March 2006.
• Interview with Fear Factor contestant

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