Jamming avoidance response

Jamming avoidance response (JAR) is a behavior performed by some species of weakly electric fish. The JAR occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish will shift its discharge frequency to increase the difference between the two fish's discharge frequencies. By doing this, both fish prevent jamming of their sense of electroreception.

The behavior has been most intensively studied in the South American species Eigenmannia virescens. The behavior is also present in other Gymnotiformes such as Apteronotus, as well as in the African species Gymnarchus niloticus. The JAR was one of the first complex behavioral responses in a vertebrate to have its neural circuitry completely specified. As such, the JAR holds special significance in the field of neuroethology.

The jamming avoidance response was discovered by Akira Watanabe and Kimihisa Takeda in 1963 while working at the Tokyo Medical and Dental University. The fish they used was an unspecified species of Eigenmannia, which has a quasi-sinusoidal wave-like discharge of about 300 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 will alter its EOD frequency to increase the difference between its own frequency and the stimulus frequency. Stimuli above the fish's EOD frequency will "push" the EOD frequency downwards, while frequencies below that of the fish will push the EOD frequency upward, with a maximum change of about ±6.5 Hz.

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.

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