Spontaneous modulations of the electric organ discharge in the weakly electric fish, Apteronotus leptorhynchus: a biophysical and behavioral analysis

• Published in: Journal of Comparative Physiology Vol. 186; no. 7-8; pp. 645 - 660
• Main Authors: Engler, G, Fogarty, C.M, Banks, J.R, Zupanc, G.K.H
• Format: Journal Article
• Language: English
• Published: Germany Springer-Verlag 01.08.2000; Springer Nature B.V
• Subjects: Animals; Apteronotus leptorhynchus; Behavior, Animal - physiology; Biophysical Phenomena; Biophysics; Discharge frequency; Electric discharges; electric field; Electric Fish - physiology; Electric instruments; Electric Organ - physiology; Electric Stimulation; electrical treatment; Electrophysiology; Firing pattern; Fish; Fourier Analysis; Freshwater; Ghosts; Mimicry; Stimulation
• ISSN: 0340-7594; 1432-1351
• DOI: 10.1007/s003590000118

Brown ghosts, Apteronotus leptorhynchus, are weakly electric gymnotiform fish whose wave-like electric organ discharges are distinguished by their enormous degree of regularity. Despite this constancy, two major types of transient electric organ discharge modulations occur: gradual frequency rises, which are characterized by a relatively fast increase in electric organ discharge frequency and a slow return to baseline frequency; and chirps, brief and complex frequency and amplitude modulations. Although in spontaneously generated gradual frequency rises both duration and amount of the frequency increase are highly variable, no distinct subtypes appear to exist. This contrasts with spontaneously generated chirps which could be divided into four "natural" subtypes based on duration, amount of frequency increase and amplitude reduction, and time-course of the frequency change. Under non-evoked conditions, gradual frequency rises and chirps occur rather rarely. External stimulation with an electrical sine wave mimicking the electric field of a neighboring fish leads to a dramatic increase in the rate of chirping not only during the 30 s of stimulation, but also in the period immediately following the stimulation. The rate of occurrence of gradual frequency rises is, however, unaffected by such a stimulation regime.