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| Species specificity in electrical signaling has been clearly documented. Frequency, amplitude and morphology of the signals can differ greatly among across species (Westby, 1988). Species recognition based on signaling becomes increasingly important during breeding season. It is also crucial when species form protective social groups. Eigenmannia virescens can be aggressive toward conspecifics, and will only display this aggression when they encounter signals from the same species (Hopkins, 1974). | In many species electrical signaling can be used to distinguish sex, although within-species variation of signals is much less common than intra-species variation. In Hypopomus beebei, males produce an asymmetrical signal, while females produce a symmetrical signal. This signal dimorphism is evident in several species. In other species morphological dimorphism is not detectable, but, as in Gymnotus carapo, there are differences between males and females in the amplitudes of different phases of the signal (Westby, 1988). Other species, such as Eigenmannia virescens, there are differences between sexes in the duration and frequency of signals (Hagendorn & Heiligenberg, 1985). | Identification of age class has not been studied as much as other aspects of identification by signals, though there are a few examples of diversity of signals across age class. In Gymnotus carapo, signals reflect the size of the signal and, therefore, generally reflects the age of the signaler as well. Hopkins (1974) also observed that the frequency of postlarval G. carapo signals is lower than that of adults. In contrast, juvenile Hypopomus brevirostris discharge at a much higher frequency than adults. Apteronotus albifrons, on the other hand, discharge at the same frequency as adults, but the juvenile signal is monophasic, while the adult signal is biphasic (Hopkins, 1974). |
species uses
signals production
courtship predator/prey
identification
hormonal control