Patterns of the electric organ discharge during courtship and spawning in the mormyrid fish, Pollimyrus isidori

Summary. Pollimyrus isidori's electric organ dis-charge (EOD) is of the pulse type. Patterns of EOD intervals were investigated prior to, during and fol-lowing spawning behaviors as related with overt behaviors, and with the sound production by the nestbuilding male. Prior to the time of reproduc-tion, isolated and socially interacting fish (n = 15) showed characteristic discharge interval patterns for resting, swimming, probing, hovering and hid-ing activities. Males (n = 8) and females (n = 6) did not differ in their mean EOD repetition rates dur-ing resting (11.6+2.5 Hz), nor Short Bursts/rain (less than 20 intervals of 8-13 ms). In interacting fish Long Bursts (greater than 20 intervals of 8-13 ms, lasting for more than 300 ms) were ob-served only during the attack and bite sequence. A pursuing fish displayed a rapid alternation of Long Bursts with Discharge Breaks (300-1000 ms silence) during the chase behavior. Avoidance be-havior which followed from several attacks was correlated with a Medium Uniform Rate (8-12 Hz) normally lasting for 20 to 60 s, or a Discharge Ar-rest (silence greater than 1 s) in the submissive fish. The nocturnal courtship behavior began soon after dark (1900 h). Spawning typically started 2 to 5 h after dark, continuing for 2 to 6 h until about 0200 h. During courtship and spawning the fe-male's brief visits (15-25 s) to the male's territory recurred every 30-60 s. At all other times the fe-male was aggressively excluded from the nest re-gion. Courtship and spawning behaviors are de-scribed along with the electrical displays identified from 19 spawnings in three fish pairs (from a total of 37 spawnings in 4 males and 4 females). Jus