The electric organ discharge (EOD) of most species of the freshwater knifefishes (Gymnotiformes) of South America is of the wave, not the pulse, type. Wave EODs are usually of constant frequency and amplitude, and show a bewildering multitude of species-characteristic waveforms. The EOD of Eigenmannia is sexually dimorphic in waveform and in the intensity of its higher harmonics. In a go/no go paradigm, trained food-rewarded fish discriminated between these waveforms, and naive (untrained) fish showed a significant preference. To determine whether spectral or waveform (time) cues are used by the fish, artificial stimuli of identical amplitude spectrum were synthesized that differed only in phase relationship between their harmonics, i.e. waveform, and the fish discriminated even among these stimulus waveforms (i.e. spectral cues are not required). Our sensory model predicts that, for successful waveform detection, a minimum frequency difference is required between the stimulus and the EOD. As expected, trained fish confused test stimuli of different waveform that were frequency-clamped and phase-locked to the EOD (frequency difference 0 Hz). Opening the electronic feedback loop immediately restored discrimination performance on an on/off basis, and a strong jamming avoidance response (JAR; a frequency shift away from the stimulus) accompanied every behavioural decision (to go for a food reward). The strong habituation of the JAR that occurs in response to stimuli of no behavioural consequence (the usual test situation) was not seen in the present experiments. The proposed sensory model (which is based on time-marking T electroreceptors) is supported by these experiments, and a biological function for the JAR - subserving EOD waveform discrimination is shown to be useful in a social context.
Skip Nav Destination
JOURNAL ARTICLE| 15 May 1999
Waveform discrimination, phase sensitivity and jamming avoidance in a wave-type electric fish
Online Issn: 1477-9145
Print Issn: 0022-0949
© 1999 by Company of Biologists
J Exp Biol (1999) 202 (10): 1387–1398.
- Views Icon Views
- PDF LinkPDF
- Share Icon Share
- Search Site
B. Kramer; Waveform discrimination, phase sensitivity and jamming avoidance in a wave-type electric fish. J Exp Biol 15 May 1999; 202 (10): 1387–1398. doi: https://doi.org/10.1242/jeb.202.10.1387
Download citation file: