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Electric eels are fish capable of generating an electrical field.

An electric fish is a fish that can generate electric fields. It is said to be electrogenic; a fish that has the ability to detect electric fields is said to be electroreceptive. All fish that are electrogenic are also electroreceptive. Electric fish species can be found both in the sea and in freshwater rivers of South America and Africa. Many fish such as sharks, rays and catfishes can detect electric fields, and are thus electroreceptive, but as they cannot generate an electric field they are not classified as electric fish. Most common bony fish (teleosts), including most fish kept in aquaria or caught for food, are neither electrogenic nor electroreceptive.

Contents

Strongly and weakly electric fish

Electric fish produce their electrical fields from a specialized structure called an electric organ. This is made up of modified muscle or nerve cells, which became specialized for producing bioelectric fields stronger than those that normal nerves or muscles produce. Typically this organ is located in the tail of the electric fish. The electrical output of the organ is called the electric organ discharge (EOD).

Fish that have an EOD that is powerful enough to stun their prey are called strongly electric fish. The amplitude of the signal can range from 10 to 500 Volts with a current of up to 1 Ampere. Typical examples are the electric eel (Electrophorus electricus; not a true eel but a knifefish), the electric catfishes (family Malapteruridae), and electric rays (order Torpediniformes).

By contrast, weakly electric fish generate a discharge that is typically less than one volt in amplitude. These are too weak to stun prey, but are used for navigation, object detection (electrolocation) and communication with other electric fish (electrocommunication). Some of the best known and most studied examples are Peters' elephantnose fish (Gnathonemus petersi) and the black ghost knifefish (Apteronotus albifrons).

The EOD waveform takes two general forms depending on the species. In some species the waveform is continuous and almost sinusoidal (for example the genera Apteronotus, Eigenmannia and Gymnarchus) and these are said to have a wave-type EOD. In other species, the EOD waveform consists of brief pulses separated by longer gaps (for example Gnathonemus, Gymnotus, Raja) and these are said to have a pulse-type EOD.

Table of electric fish

Following is a table of all known electric fish species within fresh water. There are two groups of marine fishes, the electric rays (Torpediniformes: Narcinidae and Torpedinidae) and the stargazers (Perciformes: Uranoscopidae) capable of generating strong electric pulses.

References

  • Bullock, T.H., Heiligenberg, W. (eds) (1986) Electroreception. Wiley, 722 pp.
  • Heiligenberg, W. (1991) Neural nets in electric fish. MIT Press, 179 pp.
  • Moller, P. (1995) Electric Fishes: History and Behavior. Chapman & Hall, 583 pp.

External links


Simple English

s are fish capabale of generating an electrical field.]] An Electric fish is a fish that can make electric fields. Fishes that can generate such fields are said to be electrogenic, those that can detect them are called electroreceptive. Most electrogenic fish are also electroreceptive. Many fish, for example sharks, rays, and catfishes are electroreceptive. They cannot generate electric fields though, and are therefore not classified as electric fish. Most bony fish are neither electrogenic nor electroreceptive.

Strongly and weakly electric fish

Electrogenic fish have a special organ that can generate electricity. This organ is usually called electric organ. It is usually located near the tail of the fish. It is made from specialised muscle or nerve cells. When the organ produces electricity that is released this is called Electric Organ Discharge (or EOD for short).

Based on the strength of the EOD, the electrogenic fish can be classified into two types:

  • Strongly electric fish: Their discharge is so strong they can stun (and capture) prey with it. Examples for such fish are the Electric eel (which is a knifefish, not a true eel), electric catfishes, or electric rays
  • Weakly electric fish: Their discharge is not strong enough to stun prey with it; rather, they use the electricity to locate objects, to navigate, or to communicate with other electric fish. Examples for weakly electric fish are Peters' elephantnose fish or Black ghost knifefish.

In total, there are 348 known species of electric fish, in about 56 genera. The only known species that lives in salt water are the electric rays, with 23 species.








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