Jamming avoidance response

The jamming avoidance response (JAR) was discovered by Akira Watanabe and Kimihisa Takeda in 1963.

[1] 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.

[2] 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.

[7] Most of the JAR pathway in the South American Gymnotiformes has been worked out using Eigenmannia virescens as a model system.

Ampullary receptors respond to low-frequency stimulation less than 40 Hz and their role in the JAR is currently unknown.

Under conditions of jamming, the P-unit fires on the amplitude peaks of the beat cycle where the two waves constructively interfere.

[7] The time-coding T-units converge onto neurons called spherical cells in the electrosensory lateral line lobe.

Neurons selective for a positive difference (stimulus greater than EOD) stimulate the prepacemaker nucleus, while neurons selective for a negative difference (stimulus less than EOD) inhibit the sublemniscal prepacemaker nucleus.

Both prepacemaker nuclei send projections to the pacemaker nucleus, which ultimately controls the frequency of the EOD.

In Gymnarchus, phase differences between EOD and stimulus are calculated in the electrosensory lateral line lobe rather than in the torus semicircularis.

[11] There are two main orders of weakly electric fish, Gymnotiformes from South America and Osteoglossiformes from Africa.

diagram showing change in waves emitted by two electric fish to avoid each other's frequency
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.
photo of an electric fish
The African knifefish also has a jamming avoidance response, evolved convergently .
diagram showing firing of receptor cells, one in time with basic wave and one firing more as beat wave increases in size
Eigenmannia sensory coding for jamming avoidance response. The fish avoids interference with its electrolocation signal by changing its frequency when a jamming signal is detected. This is mediated by a T-unit tuberous receptor which fires at the signal frequency, and a P-unit tuberous receptor which fires fastest near the peak of the beat cycle caused by the interference of two signals with similar frequencies.