Silent signals in the dark: Electric communication in fishes

Electrocommunication has evolved in six fish orders. It involves the generation of an electric field, which is detected by conspecifics using electroreceptors. Electrocommunication is highly developed in two tropical freshwater fish groups, the Mormyroidea and Gymnotiformes. These two groups generate either intermittent pulse-type or continuous wave-type discharges from specialized electric organs, which are detected by an array of tuberous electroreceptors. The electrocommunication signals of mormyroids and gymnotiforms facilitate various sexual and territorial social interactions, permit recognition of sex, species, and individuals, and aid in group cohesion. More rudimentary forms of electrocommunication are exhibited by skates, certain catfishes, and stingrays, which use simple electric organs or discharges from transmembrane potentials. The signals produced by skates, catfishes, and stingrays are detected using ampullary electroreceptors, the class of receptors used by many aquatic craniates for passive electrolocation.