Abstract
In this study, a first comparative investigation of all four species of Petrocephalus ( P. bovei , P. bane , P. soudanensis and P. cf. pallidomaculatus ) present in the Upper Volta system and their electric organ discharges (EOD) was conducted. It was found that P. bovei was the most widespread (in terms of habitat use), but in several places P. bovei , P. soudanensis and P. cf. pallidomaculatus occurred syntopically. All species emitted a triphasic signal, and with very few exceptions, the Petrocephalus species of the Upper Volta system could clearly be identified on the basis of their EOD waveforms. The most obvious differences between species in EOD waveforms were in amplitude of the last phase, total duration and fast Fourier transformation (FFT) peak frequency. No sexual dimorphism was present in the EOD of any species although external dimorphism, i.e. an indentation at the base of the anal fin of mature males, was common. The EOD waveform diversity in the Upper Volta principally resembled that found in four sympatric Petrocephalus species from the Ogooué system (Gabon) and might play a role in species recognition and speciation processes.