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Electric Organ Discharge Activity of Resting and Stimulated Gnathonemus Petersii (Mormyridae)

1974; Brill; Volume: 50; Issue: 3-4 Linguagem: Inglês

10.1163/156853974x00507

1568-539X

Richard Bauer,

Fish Biology and Ecology Studies

1. The electric organ discharge (EOD) activity of 12 isolated Gnathonemus petersii was analyzed by means of interpulse interval histograms (IIH), joint interval histograms (JIIH) as well as by measurements of the instanaeous frequency of consecutive intervals. 2. The IIH of 10 resting fish was characterized by three modes and in two fish by two modes. The higher frequency mode (25-62 Hz) corresponds to burst-like frequency increases (BA) of the EOD, the lower are due to inter-burst activity (IBA). 3. Frequency ranges of modes are remarkably constant during following days and even months. Because of the individual specific position of modes, the IIH renders it possible to distinguish individuals from one another. 4. JIIH computation of the EOD of resting G. petersii reveals that besides a random activity, two types of correlation exist between consecutive intervals (regularization). The first, type I regularization, is characterized by consecutive intervals of nearly equal duration. It occurs in the BA of trimodal and bimodal fish, and also in the IBA range of bimodal fish. The second, type 2 regularization, is characterized by alternating long and short intervals, corresponding to the second and third mode, which are displayed during the IBA of trimodal fish. 5. The transition from IBA to BA and vice versa is brief and distinct. The analyses of long periods of activity reveal that the resting G. petersii displays its entire activity spectrum (BA and IBA) in a sequence of about 200 intervals. 6. When stimulated by the discharges of a conspecific or another mormyrid, the EOD activity of G. petersii becomes more regular. Trains of up to 330 equal intervals (type I regularization) were observed. The preferred frequency range for this emission is individual specific and is situated in the minimum between BA and IBA. Its appearence is also characteristic for mechanically stimulated G. petersii. 7. The results described here give evidence that G. petersii emits at least at 6 preferred ranges of frequency.