The electric organ of a mormyrid as a current and voltage source.

We have examined how the electric organ discharge (EOD) of a mormyrid ( Gnathonemus petersii) is affected by changes in resistive load (Figs. 3, 4, 5). We have also shown how this load depends on resistivity and distance to non-conducting boundaries (Figs. 10, 11). When resistive load was varied, voltage and current were related in a linear, battery-like manner for the initial, head positive phase of the EOD (Figs. 4, 5). This linear relation made it possible to estimate first phase e.m.f. and source resistance. For the second, head negative phase, however, voltage rose to a peak and then fell as resistance increased. Furthermore, the waveform of the second but not the first phase was strongly affected by load changes. These second phase features were shown to reflect a dependence of second phase e.m.f. on first phase current. A linear and battery-like relation between second phase voltage and current was seen when first phase load was held constant while varying second phase load (Fig. 6). These results on the behavior of the whole electric organ can be understood in terms of the underlying properties of the cellular generators, the electrocytes. [ABSTRACT FROM AUTHOR]