Jamming avoidance response

The jamming avoidance response is a behavior of some species of weakly electric fish. 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. 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. It is also present in other Gymnotiformes such as Apteronotus, as well as in the African species Gymnarchus niloticus. The jamming avoidance response was one of the first complex behavioral responses in a vertebrate to have its neural circuitry completely specified. As such, it holds special significance in the field of neuroethology. The jamming avoidance response (JAR) was discovered by Akira Watanabe and Kimihisa Takeda in 1963. The fish they used was an unspecified species of Eigenmannia, which has a quasi-sinusoidal wave 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 alters its EOD frequency to increase the difference between its own frequency and the stimulus frequency. 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 ±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. In 1975, Walter Heiligenberg discovered a JAR in the distantly-related Gymnarchus niloticus, the African knifefish, showing that the behavior had convergently evolved in two separate lineages. Eigenmannia 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.