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Electric fish

(Redirected fromWeakly electric fish)

Anelectric fishis anyfishthat cangenerate electric fields,whether to sense things around them, for defence, or to stun prey. Most fish able to produce shocks are also electroreceptive, meaning that they can sense electric fields. The only exception is thestargazerfamily (Uranoscopidae). Electric fish, although a small minority of all fishes, include both oceanic and freshwater species, and both cartilaginous and bony fishes.

Among the electric fishes areelectric eels,knifefishcapable of generating anelectric field,both at low voltage forelectrolocationand at high voltage to stun theirprey.

Electric fish produce their electrical fields from anelectric organ.This is made up of electrocytes, modifiedmuscleornervecells, specialized for producing strong electric fields, used to locate prey, fordefence against predators,and forsignalling,such as in courtship. Electric organ discharges are two types, pulse and wave, and vary both by species and by function.

Electric fish have evolved many specialised behaviours. The predatoryAfrican sharptooth catfisheavesdrops on its weakly electricmormyridprey to locate it when hunting, driving the prey fish to develop electric signals that are harder to detect.Bluntnose knifefishesproduce an electric discharge pattern similar to theelectrolocationpattern of the dangerous electric eel, probably a form ofBatesian mimicryto dissuade predators.Glass knifefishthat are using similar frequencies move their frequencies up or down in ajamming avoidance response;African knifefishhaveconvergently evolveda nearly identical mechanism.

Evolution and phylogeny

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Further information:Electroreception and electrogenesis

All fish, indeed allvertebrates,useelectrical signalsin their nerves and muscles.[1]Cartilaginous fishes and some other basal groups use passive electrolocation with sensors that detect electric fields;[2]the platypus and echidna have separately evolved this ability. The knifefishes and elephantfishes actively electrolocate, generating weak electric fields to find prey. Finally, fish in several groups have the ability to deliver electric shocks powerful enough to stun their prey or repelpredators.Among these, only the stargazers, a group of marine bony fish, do not also use electrolocation.[3][4]

Invertebrates,electroreception is anancestral trait,meaning that it was present in their last common ancestor.[2]This form of ancestral electroreception is called ampullary electroreception, from the name of the receptive organs involved,ampullae of Lorenzini.These evolved from the mechanical sensors of thelateral line,and exist incartilaginous fishes(sharks,rays,andchimaeras),lungfishes,bichirs,coelacanths,sturgeons,paddlefish,aquaticsalamanders,andcaecilians.Ampullae of Lorenzini were lost early in theevolutionof bony fishes andtetrapods.Where electroreception does occur in these groups, it has secondarily been acquired in evolution, using organs other than and nothomologouswith ampullae of Lorenzini.[2][5]Most commonbony fishare non-electric. There are some 350 species of electric fish.[6]

Electric organshave evolved eight times, four of these being organs powerful enough to deliver an electric shock. Each such group is aclade.[7][2]Most electric organs evolved from myogenic tissue (which forms muscle), however, one group ofGymnotiformes,theApteronotidae,derived their electric organ from neurogenic tissue (which forms nerves).[8]InGymnarchus niloticus(the African knifefish), the tail, trunk, hypobranchial, and eye muscles are incorporated into the organ, most likely to provide rigid fixation for the electrodes while swimming. In some other species, the tail fin is lost or reduced. This may reduce lateral bending while swimming, allowing the electric field to remain stable for electrolocation. There has beenconvergent evolutionin these features among the mormyrids and gymnotids. Electric fish species that live in habitats with few obstructions, such as some bottom-living fish, display these features less prominently. This implies that convergence for electrolocation is indeed what has driven the evolution of the electric organs in the two groups.[9][10]

Actively electrolocating fish are marked on thephylogenetic treewith a small yellow lightning flash.Fish able to deliver electric shocks are marked with a red lightning flash.Non-electric and purelypassively electrolocating speciesare not shown.[2][11][10]

Vertebrates
Chondrichthyes

Torpediniformes(electric rays) (69 spp)

Rajiformes(skates) (~200 spp)

430mya
Bony fishes
Osteogloss.
110 mya

Gymnotiformes
S. Amer.

(>100 spp)

knifefishes
Electric eels

(3 spp)

119 mya
amp. recept.
Siluriformes

Uranoscopidae

Stargazers(50 spp)

no electro‑
location
425mya
Amp. of Lorenzini

Weakly electric fish

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Theelephantnose fishis a weakly electric fish which generates an electric field with its electric organ, detects small variations in the field with itselectroreceptors,and processes the detected signals in the brain to locate nearby objects.[12]

Weakly electric fish generate a discharge that is typically less than one volt. These are too weak to stun prey and instead are used fornavigation,electrolocationin conjunction with electroreceptors in their skin, andelectrocommunicationwith other electric fish. The major groups of weakly electric fish are theOsteoglossiformes,which include theMormyridae(elephantfishes) and the African knifefishGymnarchus,and theGymnotiformes(South American knifefishes). These two groups haveevolved convergently,with similar behaviour and abilities but different types of electroreceptors and differently sited electric organs.[2][11]

Strongly electric fish

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Impedance matchingin strongly electric fishes. Since seawater conducts far better than freshwater, marine fish operate at much higher currents but lower voltages.[13]
Further information:History of bioelectricity

Strongly electric fish, namely theelectric eels,theelectric catfishes,theelectric rays,and thestargazers,have an electric organ discharge powerful enoughto stun preyor be usedfor defence,[14]andnavigation.[15][9][16]The electric eel, even when very small in size, can deliver substantial electric power, and enough current to exceed many species'pain threshold.[17]Electric eels sometimes leap out of the water to electrify possible predators directly, as has been tested with a human arm.[17]

Theamplitudeof the electrical output from these fish can range from 10 to 860voltswith a current of up to 1ampere,according to the surroundings, for example different conductances of salt and freshwater. To maximize the power delivered to the surroundings, theimpedancesof theelectric organand the water must bematched:[13]

  • Strongly electric marine fish give low voltage, high current electric discharges. In salt water, a small voltage can drive a large current limited by the internal resistance of the electric organ. Hence, the electric organ consists of many electrocytes in parallel.
  • Freshwater fish have high voltage, low current discharges. In freshwater, the power is limited by the voltage needed to drive the current through the large resistance of the medium. Hence, these fish have numerous cells in series.[13]

Electric organ

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Main article:Electric organ (fish)

Anatomy

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Anatomy of a strongly electric freshwater fish: the electric eel's threeelectric organs.The main organ is long, with a stack of many electrocytes in series to provide a high voltage, matching the high impedance of freshwater.

Electric organsvary widely among electric fish groups. They evolved from excitable, electrically active tissues that make use of action potentials for their function: most derive from muscle tissue, but in some groups the organ derives from nerve tissue.[18]The organ may lie along the body's axis, as in the electric eel andGymnarchus;it may be in the tail, as in the elephantfishes; or it may be in the head, as in the electric rays and the stargazers.[3][8][19]

Physiology

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Anelectric ray(Torpediniformes) showing paired electric organs in the head, and electrocytes stacked vertically within it

Electric organs are made up of electrocytes, large, flat cells that create and store electrical energy, awaiting discharge. The anterior ends of these cells react to stimuli from the nervous system and containsodium channels.The posterior ends containsodium–potassium pumps.Electrocytes become polar when triggered by a signal from the nervous system. Neurons release the neurotransmitteracetylcholine;this triggersacetylcholine receptorsto open andsodium ionsto flow into the electrocytes.[15]The influx of positively charged sodium ions causes thecell membraneto depolarize slightly. This in turn causes the gated sodium channels at the anterior end of the cell to open, and a flood of sodium ions enters the cell. Consequently, the anterior end of the electrocyte becomes highly positive, while the posterior end, which continues to pump out sodium ions, remains negative. This sets up a potential difference (avoltage) between the ends of the cell. After the voltage is released, the cell membranes go back to theirresting potentialsuntil they are triggered again.[15]

Discharge patterns

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Electric organ discharges(EODs) need to vary with time forelectrolocation,whether with pulses, as in the Mormyridae, or with waves, as in the Torpediniformes andGymnarchus,the African knifefish.[19][20][21]Many electric fishes also use EODs for communication, while strongly electric species use them for hunting or defence.[20]Their electric signals are often simple and stereotyped, the same on every occasion.[19]

Electrocommunication

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Weakly electric fish can communicate by modulating the electricalwaveformthey generate. They may use this to attract mates and in territorial displays.[22]

Sexual behaviour

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Insexually dimorphicsignalling, as in thebrown ghost knifefish(Apteronotus leptorhynchus), the electric organ produces distinct signals to be received by individuals of the same or other species.[23]The electric organ fires to produce a discharge with a certainfrequency,along with short modulations termed "chirps" and "gradual frequency rises", both varying widely between species and differing between the sexes.[24][20]For example, in theglass knifefishgenusEigenmannia,females produce a nearly puresine wavewith few harmonics, males produce a far sharper non-sinusoidal waveform with strongharmonics.[25]

Malebluntnose knifefishes(Brachyhypopomus) produce a continuous electric "hum" to attract females; this consumes 11–22% of their total energy budget, whereas female electrocommunication consumes only 3%. Large males produced signals of larger amplitude, and these are preferred by the females. The cost to males is reduced by acircadian rhythm,with more activity coinciding withnight-timecourtship and spawning, and less at other times.[26]

Antipredator behaviour

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Further information:Antipredator adaptation

Electric catfish (Malapteruridae) frequently use their electric discharges to ward off other species from their shelter sites, whereas with their own species they have ritualized fights with open-mouth displays and sometimes bites, but rarely use electric organ discharges.[27]

The electric discharge pattern of bluntnose knifefishes is similar to the low voltage electrolocative discharge of theelectric eel.This is thought to be a form of bluffingBatesian mimicryof the powerfully protected electric eel.[28]

Fish that prey on electrolocating fish may "eavesdrop"[29]on the discharges of their prey to detect them. The electroreceptive African sharptooth catfish (Clarias gariepinus) may hunt the weakly electric mormyrid,Marcuseniusmacrolepidotusin this way.[30]This has driven the prey, in anevolutionary arms race,to develop more complex or higher frequency signals that are harder to detect.[31]

Jamming avoidance response

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When aglass knifefishencounters a neighbour with a closely similar frequency, one fish shifts its frequency upward and the other downward in thejamming avoidance response.
Main article:Jamming avoidance response

It had been theorized as early as the 1950s that electric fish near each other might experience some type of interference. In 1963, Akira Watanabe and Kimihisa Takeda discovered thejamming avoidance responseinEigenmannia.[32]When two fish are approaching one another, their electric fields interfere.[33]This sets up abeatwith a frequency equal to the difference between the discharge frequencies of the two fish.[33]The jamming avoidance response comes into play when fish are exposed to a slow beat. If the neighbour's frequency is higher, the fish lowers its frequency, and vice versa.[32][25]A similar jamming avoidance response was discovered in the distantly relatedGymnarchus niloticus,the African knifefish, byWalter Heiligenbergin 1975, in a further example of convergent evolution between the electric fishes of Africa and South America.[34]Both the neural computational mechanisms and the behavioural responses are nearly identical in the two groups.[35]

See also

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References

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  1. ^Belanger, J. H. (1 August 2005)."Contrasting Tactics in Motor Control by Vertebrates and Arthropods".Integrative and Comparative Biology.45(4): 672–678.doi:10.1093/icb/45.4.672.PMID21676816.
  2. ^abcdefBullock, Theodore H.;Bodznick, D. A.; Northcutt, R. G. (1983)."The phylogenetic distribution of electroreception: Evidence for convergent evolution of a primitive vertebrate sense modality"(PDF).Brain Research Reviews.6(1): 25–46.doi:10.1016/0165-0173(83)90003-6.hdl:2027.42/25137.PMID6616267.S2CID15603518.
  3. ^abAlves-Gomes, J. (2001). "The evolution of electroreception and bioelectrogenesis in teleost fish: a phylogenietic perspective".Journal of Fish Biology.58(6): 1489–1511.Bibcode:2001JFBio..58.1489A.doi:10.1111/j.1095-8649.2001.tb02307.x.
  4. ^Berry, Frederick H.; Anderson, William W. (1961)."Stargazer fishes from the western north Atlantic (Family Uranoscopidae)"(PDF).Proceedings of the United States National Museum.1961.
  5. ^King, Benedict; Hu, Yuzhi; Long, John A. (11 February 2018)."Electroreception in early vertebrates: survey, evidence and new information".Palaeontology.61(3): 325–358.Bibcode:2018Palgy..61..325K.doi:10.1111/pala.12346.
  6. ^Rubega, Margaret (December 1999)."Vertebrate Life. F. Harvey Pough, Christine M. Janis, John B. Heiser".The Quarterly Review of Biology.74(4): 478–479.doi:10.1086/394168.
  7. ^Kirschbaum, Frank (2019). "Structure and Function of Electric Organs".The Histology of Fishes.Boca Raton, Florida:CRC Press.pp. 75–87.doi:10.1201/9780429113581-5.ISBN9780429113581.S2CID216572032.
  8. ^abBullock, Theodore H.;Hopkins, Carl D.; Popper, Arthur N.; Fay, Richard R., eds. (2005)."Electroreception".Springer Handbook of Auditory Research.21.doi:10.1007/0-387-28275-0.ISBN978-0-387-23192-1.
  9. ^abLissmann, H. W. (1958-03-01)."On the Function and Evolution of Electric Organs in Fish".Journal of Experimental Biology.35(1): 156–191.doi:10.1242/jeb.35.1.156.
  10. ^abLavoué, Sébastien; Miya, Masaki; Arnegard, Matthew E.; Sullivan, John P.; Hopkins, Carl D.; Nishida, Mutsumi (14 May 2012)."Comparable Ages for the Independent Origins of Electrogenesis in African and South American Weakly Electric Fishes".PLOS One.7(5): e36287.Bibcode:2012PLoSO...736287L.doi:10.1371/journal.pone.0036287.PMC3351409.PMID22606250.
  11. ^abLavoué, Sébastien; Miya, Masaki; Arnegard, Matthew E.; Sullivan, John P.; Hopkins, Carl D.; Nishida, Mutsumi (2012-05-14). Murphy, William J. (ed.)."Comparable Ages for the Independent Origins of Electrogenesis in African and South American Weakly Electric Fishes".PLOS ONE.7(5): e36287.Bibcode:2012PLoSO...736287L.doi:10.1371/journal.pone.0036287.PMC3351409.PMID22606250.
  12. ^Von der Emde, G. (1999). "Active electrolocation of objects in weakly electric fish".Journal of Experimental Biology,202(10): 1205–1215.Full text
  13. ^abcKramer, Bernd (2008)."Electric Organ Discharge".In Marc D. Binder; Nobutaka Hirokawa; Uwe Windhorst (eds.).Encyclopedia of Neuroscience.Berlin, Heidelberg: Springer. pp. 1050–1056.ISBN978-3-540-23735-8.Retrieved2012-03-25.
  14. ^Macesic, Laura J.; Kajiura, Stephen M. (November 2009)."Electric organ morphology and function in the lesser electric ray, Narcine brasiliensis".Zoology.112(6): 442–450.Bibcode:2009Zool..112..442M.doi:10.1016/j.zool.2009.02.002.PMID19651501.
  15. ^abcTraeger, Lindsay L.; Sabat, Grzegorz; Barrett-Wilt, Gregory A.; Wells, Gregg B.; Sussman, Michael R. (July 2017)."A tail of two voltages: Proteomic comparison of the three electric organs of the electric eel".Science Advances.3(7): e1700523.Bibcode:2017SciA....3E0523T.doi:10.1126/sciadv.1700523.PMC5498108.PMID28695212.
  16. ^Nelson, Mark."What IS an electric fish?".Retrieved10 August2014.
  17. ^abCatania, Kenneth C. (2017-09-25)."Power Transfer to a Human during an Electric Eel's Shocking Leap".Current Biology.27(18): 2887–2891.e2.Bibcode:2017CBio...27E2887C.doi:10.1016/j.cub.2017.08.034.PMID28918950.S2CID13359966.
  18. ^Albert, J. S.; Crampton, William G. R. (2006). "Electroreception and electrogenesis". In Evans, David H.; Claiborne, James B. (eds.).The Physiology of Fishes(3rd ed.). CRC Press. pp. 431–472.ISBN978-0-8493-2022-4.
  19. ^abcCrampton, William G. R. (2019-02-05)."Electroreception, electrogenesis and electric signal evolution".Journal of Fish Biology.95(1): 92–134.Bibcode:2019JFBio..95...92C.doi:10.1111/jfb.13922.PMID30729523.S2CID73442571.
  20. ^abcNagel, Rebecca; Kirschbaum, Frank; Hofmann, Volker; Engelmann, Jacob; Tiedemann, Ralph (December 2018)."Electric pulse characteristics can enable species recognition in African weakly electric fish species".Scientific Reports.8(1): 10799.Bibcode:2018NatSR...810799N.doi:10.1038/s41598-018-29132-z.PMC6050243.PMID30018286.
  21. ^Kawasaki, M. (2011). "Detection and generation of electric signals".Encyclopedia of Fish Physiology.Elsevier.pp. 398–408.doi:10.1016/b978-0-12-374553-8.00136-2.
  22. ^Hopkins, C. D. (1999). "Design features for electric communication".Journal of Experimental Biology.202(Pt 10): 1217–1228.doi:10.1242/jeb.202.10.1217.PMID10210663.
  23. ^Fukutomi, Matasaburo; Carlson, Bruce A. (2020-08-12)."Signal Diversification Is Associated with Corollary Discharge Evolution in Weakly Electric Fish".The Journal of Neuroscience.40(33): 6345–6356.doi:10.1523/JNEUROSCI.0875-20.2020.PMC7424872.PMID32661026.
  24. ^Ho, Winnie W.; Fernandes, Cristina Cox; Alves-Gomes, José A.; Smith, G. Troy (2010-07-11)."Sex Differences in the Electrocommunication Signals of the Electric Fish Apteronotus bonapartii".Ethology.116(11): 1050–1064.Bibcode:2010Ethol.116.1050H.doi:10.1111/j.1439-0310.2010.01823.x.PMC2953865.PMID20953311.
  25. ^abKramer, Berndt (15 May 1999). "Waveform discrimination, phase sensitivity and jamming avoidance in a wave-type electric fish".Journal of Experimental Biology.202(10): 1387–1398.doi:10.1242/jeb.202.10.1387.PMID10210679.
  26. ^Salazar, Vielka L.; Stoddard, Philip K. (15 March 2008). "Sex differences in energetic costs explain sexual dimorphism in the circadian rhythm modulation of the electrocommunication signal of the gymnotiform fishBrachyhypopomus pinnicaudatus".Journal of Experimental Biology.211(6): 1012–1020.doi:10.1242/jeb.014795.PMID18310126.S2CID14310938.
  27. ^Rankin, Catharine H.; Moller, Peter (26 April 2010). "Social Behavior of the African Electric Catfish, Malapterurus electricus, during Intra- and Interspecific Encounters".Ethology.73(3). Wiley: 177–190.doi:10.1111/j.1439-0310.1986.tb00909.x.
  28. ^Stoddard, P. K. (1999). "Predation enhances complexity in the evolution of electric fish signals".Nature.400(6741): 254–256.Bibcode:1999Natur.400..254S.doi:10.1038/22301.PMID10421365.S2CID204994529.
  29. ^Falk, Jay J.; ter Hofstede, Hannah M.; Jones, Patricia L.; et al. (7 June 2015)."Sensory-based niche partitioning in a multiple predator–multiple prey community".Proceedings of the Royal Society B: Biological Sciences.282(1808).doi:10.1098/rspb.2015.0520.PMC4455811.PMID25994677.
  30. ^Merron, G. S. (1993)."Pack-hunting in two species of catfish, Clavias gariepinus and C. ngamensis, in the Okavango Delta, Botswana".Journal of Fish Biology.43(4): 575–584.Bibcode:1993JFBio..43..575M.doi:10.1111/j.1095-8649.1993.tb00440.x.
  31. ^Stoddard, P. K. (2002). "The evolutionary origins of electric signal complexity".Journal of Physiology - Paris.96(5–6): 485–491.doi:10.1016/S0928-4257(03)00004-4.PMID14692496.S2CID6240530.
  32. ^abBullock, Theodore H.;Hamstra, R. Jr.; Scheich, H. (1972). "The jamming avoidance response of high frequency electric fish".Journal of Comparative Physiology(77): 1–22.
  33. ^abShifman, Aaron R.; Lewis, John E. (2018-01-04)."The complexity of high-frequency electric fields degrades electrosensory inputs: implications for the jamming avoidance response in weakly electric fish".Journal of the Royal Society Interface.15(138): 20170633.doi:10.1098/rsif.2017.0633.PMC5805966.PMID29367237.
  34. ^Heiligenberg, Walter(1975). "Electrolocation and jamming avoidance in the electric fishGymnarchus niloticus (Gymnarchidae, Mormyriformes)".Journal of Comparative Physiology A.103(1): 55–67.doi:10.1007/bf01380044.S2CID42982465.
  35. ^Kawasaki, M. (1975). "Independently evolved jamming avoidance responses in Gymnotid and Gymnarchid electric fish: a case of convergent evolution of behavior and its sensory basis".Journal of Comparative Physiology(103): 97–121.
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