Figure 1.

Inter-species comparison of EOD regularity. Log of the minimum observed SD of the EOD period decreases with EOD frequency. Individuals from each species are represented as follows: ◊, S. dariensis; □, E. virescens; ◃, A. leptorhynchus; ○, A. albifrons; and ▵, A. bonapartii. Individuals fall within the species-specific frequency range. E. virescens also differs significantly in SD from all species of Apteronotus. The SD of the EOD differs significantly between A. leptorhynchus and A. albifrons. (Inset) CV decreases with increasing species frequency (same data). Each point is the average CV over 5 s. Significance of the slope of the CV is calculated from successive CV values from nonoverlapping windows, so N is ca. 25 times more than plotted.