Electric organ discharge (EOD) and prey capture behaviour in the electric eel, Electrophorus electricus

Summary

• 1. The prey capture behaviour and the pattern of the associated electric organ discharge (EOD) were studied in the electric eel, Electrophorus electricus.

• 2. The resting fish emits only low-voltage EODs at a rate of about 1 Hz; the rate of this emission increases during swimming, reaching values of 10 Hz.

• 3. The strong electric discharge is emitted during prey capture as well as while hunting prey. Prey capture discharge trains comprise between 50 and several thousand impulses. In the case of prey capture failure, the number of impulses is significantly lower (Fig. 3). A hunting discharge is composed of high-voltage pulses at 500 Hz, the first one being preceded by a single low-voltage pulse.

• 4. Prey capture discharge trains occur any time during an ongoing low-voltage pulse train. The first pulse of the train is generally of low amplitude, preceding by 2 ms the strong electric pulses. Depending on the time relationship to the low-voltage EOD, this first impulse may show variable amplitude (Fig. 5).

• 5. In all the fish studied, the frequency of the Sach's electric organ discharge increased before the onset of the strong pulse train. However, this increase was only significant for the last pulse (Fig. 4). No evidence was found that the prey was detected by the low-voltage EOD.

• 6. The prey capture discharge may be easily elicited by water displacement directed towards the head of the electric eel.