title: Electroreception in Gymnotus carapo: differences between self-generated and conspecific-generated signal carriers.
abstract: Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish ('local self-generated fields') and on the skin of a conspecific ('local conspecific-generated fields') using a specially designed probe. Local self-generated fields showed a constant pattern along the body of the fish. At the head, these fields were collimated, much stronger than elsewhere on the fish, and had a time waveform that was site-independent. This waveform consisted of a slow head-negative wave followed by a faster head-positive wave. In contrast, time waveforms in the trunk and tail regions were site-specific, with field vectors that changed direction over time. Local conspecific-generated fields were similar to the head-to-tail field, but their spatio-temporal pattern at the skin depended on the relative orientation between the receiving fish and the emitting fish. Because self-generated fields had a slow early component at the head region, they displayed a low-frequency peak in their power spectral density histograms. In contrast, the conspecific-generated fields had time waveforms with a sharper phase reversal, resulting in a peak at higher frequency than in the self-generated field. Lesions in emitting fish demonstrated that waveform components generated by the trunk and tail regions of the electric organ predominate in conspecific-generated fields, whereas waveform components generated by the abdominal region prevail in self-generated fields. Similar results were obtained from Brachyhypopomus pinnicaudatus. These results suggest that, in pulse-emitting gymnotids, electrolocation and electrocommunication signals may be carried by different field components generated by different regions of the electric organ.
authors.affiliation: Laboratorio de Neurofisiología Comparada, Departamento de Neuroanatomía Comparada, Unidad Asociada a Facultad de Ciencias, Instituto de Investigaciones Biológicas Clemente Estable, Av. Italia 3318, Montevideo, Uruguay.
authors.forename: P A
authors.initials: PA
authors.lastname: Aguilera
authors.forename: M E
authors.initials: ME
authors.lastname: Castelló
authors.forename: A A
authors.initials: AA
authors.lastname: Caputi
mesh_terms: D000819:Animal Communication; D000818:Animals; D004555:Electric Fish / Q000502:physiology*; D004557:Electric Organ / Q000502:physiology*; D004594:Electrophysiology; D008297:Male