Field studies in West Africa show that Mormyrid Electric Fishes have evolved an impressive diversity of electric organ discharges (EODs) which are used in electrolocation, and social communication. Field playback experiments indicate that males of at least one species can recognize the EODs of their own species, and will electrically court females but not males. Species recognition, thus, depends on waveform or rhythmic qualities of the EOD, and tests with artificial stimuli strongly implicate the EOD waveform. Compared to other communication modalities, Mormyrids employ relatively simple electrical signals for encoding species-specificity. Because the modality is used by so few species, electric communication is an ideal model system for studying signal co-evolution and ecological determinants of signal quality. Electrophysiological studies of electroreceptors in these fish have focused on neural coding of species-specific EOD stimuli, on stimulus filtering (Fig. 11), and on potential mechanisms for discriminating among electrical stimuli. With field background, the electrophysiological work hopes to delimit the requirements of a stimulus filter that could recognize species-specific EODs. The continuing research outlines further behavioral and electrophysiological experiments designed to examine the role of different features of EOD signals used in species and/or sex recognition. A digital computer would be needed to synthesize artificial EODs, and analyze nerve spike data. Synthesized signals will be distortions and modifications of EOD stimuli. These artificial stimuli will be used both in the field playback experiments, and in extensive electrophysiological experiments, to test a variety of independently-variable features of stimuli. Electrophysiological studies will also use computer analysis of nerve spike data for characterizing neural coding by electroreceptors.
Showing the most recent 10 out of 25 publications
