Fig. 9. Examples of Knollenorgan responses to natural EOD stimuli. Results are shown for electroreceptors with relatively low best frequencies in the type I morph (A; specimen 4) and the type II morph (B; specimen 2), as well as electroreceptors tuned to higher frequencies in the type I morph (C; a different unit in specimen 4) and the type II morph (D; specimen 5). Stimuli (red) are plotted on the same time axis as compound PST histograms of spike-like receptor potentials (black). In each sub-plot, the upward histogram gives responses to the EOD polarity shown, whereas the inverted stimulus was used to generate each downward histogram. Within each panel (A-D), the same stimulus waveforms are aligned vertically and are shown from lower (top) to higher (bottom) stimulus amplitudes (dB indicated). Identical stimulus waveforms (played to each morph) are shown in A,B, and a different set of identical waveforms is shown in C,D. The type II stimulus for A,B is a female-like EOD recorded from the Ivindo River. The type II stimulus for C,D is an EOD recorded from a Mouvanga Creek male exhibiting a slight degree of waveform elongation. All type III stimuli are the same EOD of an Okano River adult (sex and breeding status undetermined). Type I stimuli are female-like EODs (recorded from different individuals in A,B versus C,D).