Fig. 3. Photographs and species-typical electrocommunication signals of 15 apteronotid taxa. (A) Photograph of the head, not shown to scale. (B) A 3 ms section of head-to-tail EOD waveform with peak-to-peak amplitude normalized for all taxa. (C) EOD frequency trace (top) and head-to-tail EOD waveform (voltage) trace (bottom) of characteristic chirps in each species. Amplitude reductions during chirps are apparent from the amplitude envelope of the waveform trace in some species. Axes are the same as in Fig. 1A. Axis scales are identical within column C across all panels to allow direct comparison of chirp FM and duration. Red bars show positive start and stop times, respectively. Orange bars show the negative stop time. (D) Additional examples of chirps for each species shown as in C. Note the different frequency scale in D compared with C. The frequency axis scales are identical across panels within column D, but time scales vary as indicated. (E) Scatter plot of positive FM and duration showing all EODMs recorded in each taxon. Chirps are shown as red squares, GFRs as blue circles. The chirps identified in columns C and D are colored yellow and labeled. The purple line illustrates the linear function used to distinguish chirps from GFRs when necessary (see Materials and methods for details). Note that the duration axis is logarithmic, and thus the linear functions appear curved. Axis scales are identical across all panels within column E.