The EOD sound response in weakly electric fish

A spontaneous EOD response to sound is described in two gymnotoids of the pulse Electric Organ Discharge (EOD) type, Hypopomus and Gymnotus , and in onemormyrid, Brienomyrus . In all these species, the EOD response to the sound onset was a transient EOD rate increase. In the low EOD rate Hypopmus (3-6 EODs/s at rest) the first, second, or third EOD interval following sound onset was significantly shorter than the average EOD interval before stimulation. The shortest latency found was 100 ms, the longest ca. 1.2s. Gumnotus (around 50 EODs/s at rest) responded similarly, but the third interval after sound onset was the first to be affected even at highest intensities (shortest latencies approx. 60 ms; latencies >0.5 s at low sound intensities). In Brienomyrus (4-8 EODs/s at rest) the response occurred already at the first EOD interval after sound onset. It is concluded that the EOD response to sound is similar to EOD response to other kinds of stimulation (light, touch, vibration, food and even electrical). The possible biological function is discussed.