![]() Eigenmannia typically are within the electric field range of three to five other fish of the same species at any time. If a neighboring sinusoidal electric field is discharging close to the fish's EOD frequency, it causes interference which results in sensory confusion in the fish and sufficient jamming to prevent it from electrolocating effectively. The EOD frequency is very steady, typically with less than 0.3% variation over a 10-minute time span. For the genus Eigenmannia, frequencies range from 240 to 600 Hz. All fish with the JAR are wave-discharging fish that emit steady quasi-sinusoidal discharges. Electric fish use their electric organ to create electric fields, and they detect small distortions of these fields using special electroreceptive organs in the skin. Įigenmannia and other weakly electric fish use active electrolocation – they can locate objects by generating an electric field and detecting distortions in the field caused by interference from those objects. This behavior was given the name "jamming avoidance response" several years later in 1972, in a paper by Theodore Bullock, Robert Hamstra Jr., and Henning Scheich. Stimuli above the fish's EOD frequency push the EOD frequency downwards, while frequencies below that of the fish push the EOD frequency upwards, with a maximum change of about ☖.5 Hz. They found that when a sinusoidal electrical stimulus is emitted from an electrode near the fish, if the stimulus frequency is within 5 Hz of the fish's electric organ discharge (EOD) frequency, the fish alters its EOD frequency to increase the difference between its own frequency and the stimulus frequency. The fish they used was an unspecified species of Eigenmannia, which has a quasi- sinusoidal wave discharge of about 300 Hz. The jamming avoidance response (JAR) was discovered by Akira Watanabe and Kimihisa Takeda in 1963. As such, it holds special significance in the field of neuroethology. The jamming avoidance response was one of the first complex behavioral responses in a vertebrate to have its neural circuitry completely specified. It is also present in other Gymnotiformes such as Apteronotus, as well as in the African species Gymnarchus niloticus. The behavior has been most intensively studied in the South American species Eigenmannia virescens. By doing this, both fish prevent jamming of their sense of electroreception. It occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish shifts its discharge frequency to increase the difference between the two. The jamming avoidance response is a behavior of some species of weakly electric fish. Two neighboring Eigenmannia perform the jamming avoidance response: When two fish with around the same frequency meet, one fish shifts its frequency upward and the other shifts its frequency downward. ![]()
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