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An electric fish is any fish that can generate electric fields. A fish that can generate electric fields is said to be ''electrogenic'' while a fish that has the ability to detect electric fields is said to be ''electroreceptive''. Most electrogenic fish are also electroreceptive. Electric fish species can be found both in the ocean and in freshwater rivers of South America (Gymnotiformes) and Africa (Mormyridae). Many fish such as sharks, rays and catfishes can detect electric fields and are thus electroreceptive, but they are not classified as electric fish because they cannot generate electricity. Most common bony fish (teleosts), including most fish kept in aquaria or caught for food, are neither electrogenic nor electroreceptive. 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.〔 In: 〕 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). ==Strongly electric fish== Strongly electric fish are fish with an EOD that is powerful enough to stun prey. Typical examples are the electric eel, the electric catfishes, and electric rays. The amplitude of the signal can range from 10 to 600 Volts with a current of up to 1 Ampere, according to the surroundings, for example different conductances of salt and fresh water. To maximize the power delivered to the surroundings, the impedances of the electric organ and the water must be matched: * Strongly electric marine fish deliver low voltage, high current electric discharges. In salt water, a small voltage can drive a large current limited by the internal resistance of the electric organ. Hence, the electric organ consists of many electrocytes in parallel. Freshwater fish have high voltage, low current discharges. * In freshwater, the power is limited by the voltage needed to drive the current through the large resistance of the medium. Hence, these fish have numerous cells in series. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「electric fish」の詳細全文を読む スポンサード リンク
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