Electric signals and species recognition in the wave-type gymnotiform fishApteronotus leptorhynchus

Abstract

SUMMARYGymnotiformes are South American weakly electric fish that produce weak electric organ discharges (EOD) for orientation, foraging and communication purposes. It has been shown that EOD properties vary widely across species and could thus be used as species recognition signals. We measured and quantified the electric signals of various species using a landmark-based approach. Using discriminant function analysis to verify whether these signals are species specific based on different signal parameters, we found that the EOD waveform is a more specific cue than EOD frequency, which shows large overlap across species. Using Apteronotus leptorhynchus as a focal species, we then performed a series of playback experiments using stimuli of different species (varying in frequency, waveform, or both). In an experiment with restrained fish, we found, in contrast to what we predicted, that the choice of stimulus waveform did not affect the production of communication signals. In an experiment with free-swimming fish, the animals spent more time near the playback electrodes and produced more communication signals when the stimuli were within their conspecific frequency range. Waveform again had no measurable effect. The production of communication signals correlated with the frequency difference between the stimulus and the fish's own EOD, but approach behavior did not.

Evolution and hormonal regulation of sex differences in the electrocommunication behavior of ghost knifefishes (Apteronotidae)

“…Thus, fish discriminated between different EOD waveforms, but signals with conspecific waveforms were less effective at evoking chirps than pure sine waves. Male A. leptorhynchus approached and chirped more towards playback stimuli with conspecific versus heterospecific EOD frequencies, but did not behave differently towards playbacks with conspecific versus heterospecific EOD waveforms (Fugère and Krahe, 2010). These results suggest that at least for chirping and approach, male A. leptorhynchus do not prefer conspecific EOD waveforms.…”

Co-adaptation of electric organ discharges and chirps in South American ghost knifefishes (Apteronotidae)

“…Additionally, free-swimming A. leptorhynchus males chirped more robustly to playbacks of A. leptorhynchus EODs compared to sine waves of the same frequency, indicating that waveform may contain social information (Dunlap & Larkins-Ford, 2003b). However, free-swimming A. leptorhynchus did not preferentially approach conspecific (quasi-sinusoidal) waveforms relative to heterospecific (complex) waveforms and did not chirp more toward the conspecific waveforms in a chirp chamber (Fugère & Krahe, 2010). …”

“…However, it is currently unclear whether weakly electric fish perceive or attend to waveform information (Fig. 3; Dunlap & Larkins-Ford, 2003b; Fugère & Krahe, 2010; Kramer & Otto, 1991). Additionally, the relationship between EOD frequency and beat frequency is well understood, but little is known about how EOD waveform affects beat structure (Bullock et al, 1972; Heiligenberg et al, 1978; Scheich, 1977a).…”

Differential serotonergic modulation of two types of aggression in weakly electric fish

“…It is striking that the differences in agonistic electric communication in gymnotiforms lie not in the diversity of signals but in the different meaning the signal conveys in each species (Black-Cleworth, 1970; Westby, 1975a,b; Hagedorn and Zelick, 1989; Hupé et al, 2008; Triefenbach and Zakon, 2008; Perrone et al, 2009; Fugère and Krahe, 2010; Batista et al, 2012). Further, the role of communicative electric displays should be coherent with the type of aggression displayed and the social structure of each species.…”