Modulations in electrocommunication behaviour and non-invasively measured 11-ketotestosterone during cue-induced seasonal breeding in the weakly electric fish, Apteronotus leptorhynchus

Androgens are correlated with reproductive behaviours including courtship and aggression. In the weakly electric fish, Apteronotus leptorhynchus , 11-ketotestosterone (11-KT) has been previously implicated in the regulation of electrocommunication behaviours that are believed to have roles in both aggression and courtship. In this thesis a method for performing repeated, non-invasive measurements of androgens released into the water was validated and applied for the first time in A. leptorhynchus. Changes in 11-KT levels and electrocommunication behaviour were observed in males following environmental cues that simulated the onset of the breeding season. Males showed an increase in mean electric organ discharge frequency (EODf), which is consistent with earlier results showing a female preference for high EODf. A subset of males with high EODfs showed increases in both 11-KT and EODf which provides support for an EODf-based dominance hierarchy in this species. No direct correlation was seen between 11-KT and EODf, however, which suggests that other factors are involved in regulating male EODf. Electrocommunication signals produced during inter-male aggression were confirmed to serve in deterring attacks, and their pattern of production further suggested the formation of a dominance hierarchy. Evidence is presented that another type of electrocommunication signal previously implicated in courtship may be an inter-male signal of submission. The method for non-invasive hormone sampling first applied here will form the basis for future investigations of the hormonal control of communication behaviour.