Electroreception and electrogenesis
Most bony fishes have secondarily lost their ampullae of Lorenzini, but other non-homologous electroreceptors have repeatedly evolved, including in two groups of mammals, the monotremes (platypus and echidnas) and the cetaceans (Guiana dolphin).[4][5] In 1921, the German anatomist Viktor Franz described the knollenorgans (tuberous organs) in the skin of the elephantfishes, again without knowledge of their function as electroreceptors.In 1949, the Ukrainian-British zoologist Hans Lissmann noticed that the African knife fish (Gymnarchus niloticus) was able to swim backwards at the same speed and with the same dexterity around obstacles as when it swam forwards, avoiding collisions.[10][11] Passive electroreception usually relies upon ampullary receptors such as ampullae of Lorenzini which are sensitive to low frequency stimuli, below 50 Hz.Active electroreception typically has a range of about one body length, though objects with an electrical impedance similar to that of the surrounding water are nearly undetectable.[22] When two glass knifefishes (Sternopygidae) come close together, both individuals shift their discharge frequencies in a jamming avoidance response.The electroreceptive African sharptooth catfish (Clarias gariepinus) may hunt the weakly electric mormyrid, Marcusenius macrolepidotus in this way.[25] This has driven the prey, in an evolutionary arms race, to develop more complex or higher frequency signals that are harder to detect.These evolved from the mechanical sensors of the lateral line, and exist in cartilaginous fishes (sharks, rays, and chimaeras), lungfishes, bichirs, coelacanths, sturgeons, paddlefishes, aquatic salamanders, and caecilians.Ampullae of Lorenzini appear to have been lost early in the evolution of bony fishes and tetrapods, though the evidence for absence in many groups is incomplete and unsatisfactory.Stargazers Sharks and rays (Elasmobranchii) rely on electrolocation using their ampullae of Lorenzini in the final stages of their attacks, as can be demonstrated by the robust feeding response elicited by electric fields similar to those of their prey.[30][31][32][33] Two groups of teleost fishes are weakly electric and actively electroreceptive: the Neotropical knifefishes (Gymnotiformes) and the African elephantfishes (Notopteroidei), enabling them to navigate and find food in turbid water.While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves.Western long-beaked echidnas feed on earthworms in leaf litter in tropical forests, wet enough to conduct electrical signals well.The hairless vibrissal crypts on the rostrum of the Guiana dolphin (Sotalia guianensis), originally associated with mammalian whiskers, are capable of electroreception as low as 4.8 μV/cm, sufficient to detect small fish.
elephantnose fishmormyridelectric fieldelectric organknollenorganselectricalelectric fieldselectric eelknifefishconductorelectric fishGymnotiformesMormyridaeGymnarchusmodifiedelectric raystargazersampullae of Lorenzinicartilaginous fishessharksbony fishescoelacanthssturgeonshomologousmammalsmonotremesplatypusechidnascetaceansGuiana dolphinHistory of bioelectricityHans LissmannGymnarchus niloticusStefano LorenzinielephantfishesAfrican knife fish (Gymnarchus niloticus)lateral lineelectrical potentialecological nichesbioelectric fieldsion pumposmoregulationElectric organ (biology)knollenorganweakly electric fishsinusoidalApteronotusDaphniaresistancecapacitanceelectrical impedanceepithelialcapacitivelyElephantfishCapacitativeresistiveglass knifefishgymnotidelectric organsElectric eelsmusclesBatesian mimicrywaveformjamming avoidance responseBrachyhypopomuscircadian rhythmAfrican sharptooth catfishMarcuseniusevolutionary arms racevertebratesancestral traitchimaeraslungfishesbichirspaddlefishessalamanderscaeciliansevolutiontetrapodsFish able to deliver electric shocksLampreysJawed fishesCartilaginous fishesSelachimorphaBatoideaTorpediniformesRajidaeBony fishesLobe-finned fishesAmphibiansRay-finned fishesreedfishesMormyroideaGymnarchidaeAfrican knifefishelectric organElectric eelsSiluriformesElectric catfishesUranoscopidaeAmp. of Lorenz.Elasmobranchiidirect currentteleostNotopteroideiin seriesmonotremetrigeminal nervesmucous glandssaccadespressure sensorsechidnaLong-beaked echidnasshort-beaked echidnasWestern long-beaked echidnasearthwormstermitesDolphinsvibrissalrostrumActive sensory systemsFeature detection (nervous system)MagnetoreceptionJournal of Experimental BiologyAlexander, R. McNeillLorenzini, Stefano