Journal of Comparative Physiology A

, Volume 183, Issue 6, pp 759–768

Plasticity of the electric organ discharge waveform of the electric fish Brachyhypopomus pinnicaudatus I. Quantification of day-night changes

  • C. R. Franchina
  • P. K. Stoddard

DOI: 10.1007/s003590050299

Cite this article as:
Franchina, C. & Stoddard, P. J Comp Physiol A (1998) 183: 759. doi:10.1007/s003590050299


The electric organ discharge of the gymnotiform fish Brachyhypopomus pinnicaudatus is a biphasic waveform. The female's electric organ discharge is nearly symmetric but males produce a longer second phase than first phase. In this study, infrared-sensitive video cameras monitored the position of unrestrained fish, facilitating precise measurement of electric organ discharge duration and amplitude every 2 h for 24 h. Males (n=27) increased electric organ discharge duration by 37 ± 12% and amplitude by 24 ± 9% at night and decreased it during the day. In contrast, females (n=8) exhibited only minor electric organ discharge variation over time. Most of a male's increase occurred rapidly within the first 2–3 h of darkness. Electric organ discharge values gradually diminished during the second half of the dark period and into the next morning. Modulation of the second phase of the biphasic electric organ discharge produced most of the duration change in males, but both phases changed amplitude by similar amounts. Turning the lights off at mid-day triggered an immediate increase in electric organ discharge, suggesting modification of existing ion channels in the electric organ, rather than altered genomic expression. Exaggeration of electric organ discharge sex differences implies a social function. Daily reduction of duration and amplitude may reduce predation risk or energy expenditure.

Key words Gymnotiformes Weakly electric fish Electric organ discharge Rapid modulation Action potential plasticity 

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • C. R. Franchina
    • 1
  • P. K. Stoddard
    • 1
  1. 1.Dept of Biological Sciences, Florida International University, Miami FL 33199, USA e-mail: Fax: +1-305-348-1986US

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