Species-specific spatiotemporal pattern

There are 176 different subopulations of gymnotiforms that vary based on morphology and anatomy. (Kischbamm 2008) Only one species has both a weak and a strong electric organ, namely the Electrophorus electricus. All other subspecies possess either a neurogenic, or extended organ of the nervous system, electric organ or an organ on top of the hypaxial muscle. Each species has a unique average frequency of electric organ discharge (EOD), but there is individual variance within species. (Stoddard, ). Electric fish rely on electrolocation to sense the layout of their surroundings so that, when they send out an electric current, they receive back modulations in amplitude and phase of their discharge. Electroreceptors lie all over their outer body surface for feeling feedback currents. Other electric fish as a rivalry behavior can "jam" their discharges by releasing discharges at a similar frequency, which causes an interference in the return signal. If this occurs the fish that is getting 'jamed' will send out a staggered discharge frequency which will alleviate the effects of the interference.

Gymnotiforms can be categorized into wave-type and pulse-type fish, which emit EODs either a) at a constant frequency or b) in irregular intervals with the ability to increase or decrease the frequency. Pulse-type fish tend towards better reproductive fitness because of the ability to control their signaling to avoid interception by electrosensitive predators. (Markham 2009). EODs become costly to gymnotiforms because they take energy to produce (imagine singing for several hours at the same pitch while moving and interacting) and because of unwanted signal interception. Pulse-type gymnotiforms like Sternopygus macrurus, modulate signal amplitude at night and during social encouters by actively stimulating or inhibiting voltage-gated sodium channels which change the membrane potential difference of electrogenic cells. Electrogenic cells then develop an electrochemical gradient that spurs potassium ion efflux and action potentials in response to melanocortin (especially ACTH) reception. Melanocortin acts to control the diurnal rhythms and action potentials of pacemaker neurons in the torus semicircularis and also acts online in social situations to increase signaling  via pituitary hormones.

 

A video of electric fish at different wavelengths and frequencies jamming each other's signals. The tank lights have been programmed to respond to frequency and amplitude changes employed by the fish to compensate for jamming. The sound of the electric signals has been transformed into a human range.