page_title: Electrocommunication
section_title: Electric organs
hierarchical_section_title: Electrocommunication / Electric organs
caption_attribution_description: Position und Aufbau des Elektroplax am Beispiel eines Rochens
context_page_description: Electrocommunication is the communication method used by weakly-electric fish. Weakly-electric fish are a group of animals that utilize a communicating channel that is "invisible" to most other animals: electric signaling. Electric fish communicate by generating an electric field that a second individual receives with its electroreceptors. The fish interperets the message using the signal's frequencies, waveforms, delay, etc. The best studied species are two freshwater lineages- the African Mormyridae and the South American Gymnotiformes. While weakly-electric fish are the only group that have been identified to carry out both generation and reception of electric fields, other species either generate signals or receive them, but not both. Animals that either generate or receive electric fields are found only in wet or aquatic environments due to water's relatively low electrical resistance, compared to other substances. So far, communication between electric fish has been identified mainly to serve the purpose of conveying information such as:
  species
  courtship and biological sex
  motivational status
  environmental conditions
context_section_description: Weakly-electric fish generate Electric Organ Discharge (EOD) with specialized compartments called electric organ. Almost all the weakly-electric fish have electric organs derived from muscle cells (myogenic) ; the only exception is the Apteronotidae, a family under Gymnotiforms that has electric organs derived from nerve cells (neurogenic). Myogenic electrocytes are arranged into columns of small, disks-like cells called electroplate. The exceptional family, Apteronotidae, also carries myogenic electric organs in larval stages. However, as the fish matures, electrogenic organs derived from central spinal cord gradually replace the muscle cell-derived electric cells.
  Discharge of an electric organ begins with central command from a medullary pacemaker that determines the frequency and rhythm of EODs. These two characteristics (frequency and rhythm) of EODs are also referred to as SPI- sequence of pulse intervals. The command from medullary pacemaker is then passed on by spinal electromotor neurons to electrocytes forming the electric organ, which determine the waveform of the EODs based on its morphophysiological properties. As command from pacemaker reaches electric organ, it opens up all the sodium channels, causing net sodium ion flux in one direction. The direction will either be towards or away from the head, and brings simultaneous depolarization of all electroycytes on the same side of cell. The result is a positive polarity at the fish's head relative to the tail, or vice versa: a dipole system. The polarity built up by the electric organ therefore sets up an electrostatic field in the water.
  Electric organs are quite different between mormyrids and gymnotiforms and therefore will be presented separately:
caption: Electric organ
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