Electrocommunication

Electrocommunication is the communication method used by weakly electric fishes. Weakly electric fishes are a group of animals that utilize a communicating channel that is "invisible" to most other animals: electric signaling. Electric fishes communicate electrically by one fish generating an electric field and a second individual receiving that electric field with its electroreceptors. The receiving side will interpret the signal frequencies, waveforms, and 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 aquatic (or at least moist) environments due to large resistance of all other media (e.g. air). So far, communication between electric fish has been identified mainly to serve the purpose of conveying information in

Electric fish are capable of generating an external electric fields or receive electric fields (electroreception). Electric fish can be further divided into three categories: strongly discharging, weakly discharging, and fish that sense but is unable to generate electric fields. Strongly electric fish generate strong electric field up to 500 volts for predatory purposes; Strongly electric fish include both marine and fresh water fishes (two freshwater taxa- African electric catfish (Malapterurus electricus) and the Neotropical electric eel (Electrophorus electricus) and the marine torpedo rays (Torpedo)). Weakly electric fish generates electric fields mainly for communication and electrolocation purposes; weakly electric fish are found in fresh water only and includes African freshwater Mormyridae and Gymnarchus and Neotropical electric knifefishes. Lastly, fish that are only able to detect electrical signals includes sharks, rays, skates, catfishes, and a number of other groups (see Electroreception).

Electric fishes generate discharge from electric organs located near the tail region. Electric organs are mostly derived from muscle cells (myogenic); except for one gymnotiform family has electric organ derived from neurons (neurogenic organs). To detect the electric signals, electric fish has two types of receptive cells- ampullary and tuberous electroreceptors.

All organisms respond to sufficiently strong electric shocks, but only some aquatic vertebrates can detect and utilize weak electric fields such as those that occur naturally. These aquatic organisms are therefore called electroreceptive. (For an example, human-beings react to strong electric currents with a sense of pain and sometimes a mixture of other senses; however, we cannot detect weakly electric fields and therefore are not electroreceptive.) The ability to sense and utilize electric fields was found almost solely in lower, aquatic vertebrates (fishes and some amphibians). Terrestrial animals, with very few exceptions, lack this electric sensing channel due to low conductivity of air, soil, or media other than aqueous environment. Exceptions include the Australian monotremes, i.e. the echidna which eats mainly ants and termites, and the semi-aquatic platypus that hunts by utilizing electric fields generated by invertebrate prey.

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