Hormonal Influences on Social Behavior in South American Weakly Electric Fishes
This chapter highlights the contributions of four iconic Gymnotiform model species to the understanding of the neuroendocrine control of social behavior. In weakly electric fish, social behavior includes electric signaling in addition to locomotor displays. The central circuitry commanding the electric organ discharge (EOD) is well-known, and thus electrocommunication displays can be easily linked to the structures responsible for their modulation. Sexually dimorphic frequency (central) and waveform (peripheral) modulations are reviewed. In Sternopygus macrurus, androgens decrease the EOD frequency and broaden the pulse duration, whereas estrogens induce opposite effects. Long-term steroid hormone effects, acting directly on the ion-channel kinetic properties of electrocytes, combine with short-term peptide EOD waveform modulations to adapt electric signaling to environmental and social demands. Closely related species of the family Apteronotidae exhibit diverse sexual dimorphisms in EOD frequency, indicating that the actions of steroids may change their valence and sensitivity across species. The electric signal plasticity of Brachyhypopomus gauderio in response to seasonal, daily, and social changes of the environment is outstanding. The interplay of steroids and peptidergic hormones explain long- and short-term modulation of EOD amplitude, duration, and rate. In Gymnotus omarorum, gonadal-independent hormonal mechanisms are involved in the regulation of territorial aggression and in the emergence of the dominant subordinate status.
KeywordsApteronotus Brachyhypopomus Gymnotus Melanocortins Sexual dimorphism Signal plasticity Sternopygus Steroid hormone actions Territorial aggression Vasotocin
A preliminary version of this chapter was reviewed and edited by Kent Dunlap and Laura Quintana. The figures have been organized with the help of Laura Nozar.
Compliance with Ethics Statement
Ana C. Silva declares that she has no conflict of interest.
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