Electrolocation - Scholarpedia

Figure 1: Passive vs. Active electroreception. A: Paddlefish sense electric fields emitted by zooplankton (Daphnia) B: The gymnotiform wave-type weakly electric fish Apteronotus Leptorhynchus emits an electric field, the electric organ discharge (EOD), through an electric organ located in its tail. Objects with a conductivity different than that of the surrounding water will cause distorsions of this self-generated electric field. Zooplankton has a conductivity greater than that of the surrounding water and will strengthen the electric field locally. C: For active electrolocation, distorsions caused by a metal sphere lateral to tha animal form an electric image on the skin surface. In this case, the metal sphere increases the local amplitude of the EOD. This amplitude modulation is sensed by amplitude coding tuberous electroreceptors on the skin surface.