Fig. 5. Acclimation induces electrophysiological dimorphism in males of Brachyhypopomus pinnicaudatus. (A) Normalized EOD recordings of a male captured in July before (grey line) and after (black line) acclimation (30 days at 28°C, constant photoperiod and water conductivity). (B) Electrophysiological dimorphism of the male, measured by the duration of P2/duration P1 (DP2/DP1) ratio, of males captured from the natural habitat in August/September and October (grey bars) and males captured in August/September and acclimated for 30 days at 28°C (black bar). The DP2/DP1 ratio was significantly higher after acclimation than those obtained in freshly captured fish (Mann–Whitney test, P<0.05).