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Electric Eeels
This nOde last updated June 1st, 2001 and is permanently morphing...
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Electric Fish

Electric Fish, common name for several unrelated fishes that emit electrical discharges. The organs adapted for this purpose consist of groups of highly compact nerve endings concentrated in the tail. Discharges are emitted by electric fish to stun their prey while hunting; they are also emitted in self-defense, in the detection of prey and obstacles, and in navigation. Electric fish must rest after making numerous discharges in a short interval in order to replenish their organs.
The most important electric fishes are the electric eels (Electrophorus electricus), the electric catfish (Malapterus electricus), and the electric rays, of which there are several. The most powerful discharge is emitted by the electric eel found in certain South American rivers. This electric eel can stun large animals with its shock.

Scientific classification: The electric eel makes up the family Electrophoridae of the order Gymnotiformes. Electric catfishes make up the family Malapteruridae of the order Siluriformes. Electric rays make up the family Torpedinidae of the order Rajiformes.

• The adult Electric Eel has enough electrical power in them that could power a house of about twelve hundred square feet.
• Adult electric eels 5ft to 7ft long produce enough electricity -- 600 volts -- to stun a horse.

To understand the answer to the electric fish puzzle, we must restrict the discussion to those fish with active electric sensing systems. This group includes electric eels, South American knife fish, and African elephant snout fish. All of these have evolved, in a remarkable instance of parallel evolution, the capability of generating pulses of electricity. These pulses (up to 1,000 per second) radiate through the surrounding water. Prey and other nearby objects distort these oscillating electric fields. Electroreceptors on the fish and a sophisticated data processing system convert the field distortions into an "image" of the surroundings. M. and S.J. Lannoo, of Ball State University, have watched the black ghost knife fish, which plies murky Amazon waters, approach likely prey tail first. Swimming backward using an elongated belly fin, the knife fish slowly cruises past its potential victim. If the electrical image looks appetizing, the knife fish grabs its dinner with a forward lunge as it appears in front of it.

"The researchers suggest that the fish swims past objects in order to scan them with its electroreceptors. This is the only way the fish can identify prey because an electric sense cannot be focussed like an eye. But if the fish carried out its scan by swimming forwards, the prey would end up at its tail. The fish must swim backwards to be in a posi- tion to eat the food."

(Day, Stephen; "Why Do Electric Fish Swim Backwards?" New Scientist, p. 13, April 17, 1993.)

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