Figure 2.

AP cost at the whole-animal level depends on baseline frequency. A, Incremental cost: whole-animal oxygen consumption (ṀO₂) measured with respirometry during manipulation of EODf, expressed as incremental change on a log-linear scale. The exponential curve fit (solid black line) is given by ΔṀO₂[μmol g⁻¹ h⁻¹/Hz] = 0.003 · exp(0.009 · EODf); R² = 0.88, p = 0.006, n = 6 fish. B, Baseline cost: Resting ṀO₂ as a function of baseline EODf on a log-linear scale; ṀO₂ = 0.15 · exp(0.009 · EODf); R² = 0.90, p < 0.001, n = 9 fish. Note that the fitted line has the same exponential rate in both A and B. C, Energetic costs in ATP molecules per 1 Hz increase in frequency for different baseline frequencies on a log-linear scale: single cortical neuron (red; based on Hallermann et al., 2012), single electrocyte (green; see text), and entire electric organ (EO, blue; see text) that are assumed to be constant with baseline frequency; whole-animal EOD data from A (open symbols, curve fit in black) are reproduced for comparison.