''Gymnotus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeogra ...

freshwater fish in the family Gymnotidae found widely in South America, Central America and southern Mexico ( 36th parallel south to 18th parallel north). The greatest species richness is found in the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

. They are sometimes referred to by the English name banded knifefish, although this typically is reserved for the most widespread species, '' G. carapo''. Overall ''Gymnotus'' is the most widespread genus in the order

Gymnotiformes The Gymnotiformes are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water (the ...

. They are the only members of the subfamily Gymnotinae. Although not commonly eaten by humans, some members of this genus are used locally as

fishing bait Fishing bait is any bait (luring substance), luring substance used specifically to attract and fishing, catch fish, typically when angling with a fish hook, hook and fishing line, line. There are generally two types of baits used in angling: '' ...

, and occasionally kept in aquariums.

Habitat

''Gymnotus'' occur in most freshwater habitats within their geographic range, with the exception of large and deep river channels, and can tolerate little oxygen (survives by breathing air directly from the water surface) and areas affected by pollution,. One species, ''G. curupira'' can survive in moist leaf litter if their aquatic habitat dries out. Large species tend to live near floating vegetation along the edges of large rivers or floodplains, while smaller tend to live among leaf-litter or near banks of small streams. The genus includes both widespread and common species that occur in many different habitat types, and more restricted and rare species that occur in fewer habitats. There are species that remain in the same habitat throughout their lives, while others breed in specific habitats and spend the rest of their time elsewhere. At least as many as five species of ''Gymnotus'' may occur together in the same region and habitat.

Behavior

''Gymnotus'' species are

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

and mainly feed on aquatic

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, small fish and other small animals, but may also take plant material. Being

electric fish An electric fish is any fish that can Bioelectrogenesis, generate 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 ...

, they generate weak

electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...

s used for navigation, finding prey and communicating with other individuals of their species. At least some species are highly

territorial A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...

and will react aggressively if detecting the electric field of another individual of their species, especially between conspecific males. The electric signal is species specific, and tends to differ between males and females. However, ''Gymnotus'' are not able to generate a strong electric field that can be used for incapacitating prey or enemies, like the related

electric eel The electric eels are a genus, ''Electrophorus'', of neotropical freshwater fish from South America in the family Gymnotidae, of which they are the only members of the subfamily Electrophorinae. They are known for their electric fish, ability ...

. Nothing is known about the breeding behavior of most members of this genus, but in two species, ''G. carapo'' and ''G. mamiraua'', males make a "nest" (a depression in the bottom in the former species and within vegetation in floating meadows in the latter) and guard the young. Additionally, males of at least ''G. carapo'' will mouthbrood.

Appearance

''Gymnotus'' are generally brownish with a banded pattern, but this can also be more mottled or spotted in some species. Small scales are always present on these fish. The mouth is superior, meaning it is turned upwards. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

terminates at a point near the tip of the tail. Like other

Neotropical knifefish The Gymnotiformes are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water (the ...

, they often lose their tail due to attacks by predators or aggressive encounters with conspecifics, but they are able to regenerate it. The largest ''Gymnotus'' are up to in total length. Most species reach less than one-third that size and the smallest only around long.

Species

''Gymnotus'' contains the following recognized species. These have been proposed to be divided into six subgenera: However, these genera were published without a ZooBank registration and so are unavailable. * '' Gymnotus anguillaris'' Hoedeman, 1962 * '' Gymnotus arapaima'' Albert & Crampton, 2001 * '' Gymnotus arapiuns'' Kim, Crampton & Albert, 2020 * '' Gymnotus ardilai'' Maldonado-Ocampo & Albert, 2004 * '' Gymnotus aripuana'' Kim, Crampton & Albert, 2020 * '' Gymnotus bahianus'' Campos-da-Paz & W. J. E. M. Costa, 1996 * * '' Gymnotus capanema'' Milhomem, Crampton, Pieczarka, Shetka, D. S. Silva & Nagamachi, 2012 * '' Gymnotus capitimaculatus'' Rangel-Pereira, 2014 * '' Gymnotus carapo''

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of ''Systema Naturae'', the starting point of modern zoologic ...

(Banded knifefish) * '' Gymnotus cataniapo'' Mago-Leccia ,1994 * '' Gymnotus chaviro'' Maxime & Albert, 2009 * '' Gymnotus chimarrao'' Cognato, Richer-de-Forges, Albert & Crampton, 2008 * '' Gymnotus choco'' Albert, Crampton & Maldonado-Ocampo, 2003 * '' Gymnotus coatesi'' La Monte, 1935 * '' Gymnotus coropinae'' Hoedeman, 1962 * '' Gymnotus cuia'' Craig, Malabarba, Crampton & Albert ,2018 * '' Gymnotus curupira'' Crampton, Thorsen & Albert, 2005 * '' Gymnotus cylindricus'' LaMonte, 1935 * '' Gymnotus darwini'' Campos-da-Paz & de Santana, 2019 * '' Gymnotus diamantinensis'' Campos-da-Paz, 2002 * '' Gymnotus esmeraldas'' Albert & Crampton, 2003 * '' Gymnotus eyra'' Craig, Correa-Roldán, Ortega, Crampton & Albert, 2018 * '' Gymnotus henni'' Albert, Crampton & Maldonado-Ocampo, 2003 * '' Gymnotus inaequilabiatus'' (

Valenciennes Valenciennes (, also , , ; ; or ; ) is a communes of France, commune in the Nord (French department), Nord Departments of France, department, Hauts-de-France, France. It lies on the Scheldt () river. Although the city and region experienced ...

, 1839) * '' Gymnotus interruptus'' Rangel-Pereira, 2012 * '' Gymnotus javari'' Albert, Crampton & Hagedorn, 2003 * '' Gymnotus jonasi'' Albert & Crampton, 2001 * '' Gymnotus maculosus'' Albert & R. R. Miller, 1995 * '' Gymnotus mamiraua'' Albert & Crampton, 2001 * '' Gymnotus melanopleura'' Albert & Crampton, 2001 * '' Gymnotus obscurus'' Crampton, Thorsen & Albert, 2005 * '' Gymnotus occidentalis'' Craig, Crampton & Albert, 2017 * '' Gymnotus omarorum'' Richer-de-Forges, Crampton & Albert, 2009 * '' Gymnotus onca'' Albert & Crampton, 2001 * '' Gymnotus panamensis'' Albert & Crampton, 2003 * '' Gymnotus pantanal'' Fernandes, Albert, Daniel-Silva, C. E. Lopes, Crampton & Almeida-Toledo, 2005 * '' Gymnotus pantherinus'' ( Steindachner, 1908) * '' Gymnotus paraguensis'' Albert & Crampton, 2003 * '' Gymnotus pedanopterus'' Mago-Leccia, 1994 * '' Gymnotus refugio'' Giora & Malabarba, 2016 * '' Gymnotus riberalta'' Craig, Correa-Roldán, Ortega, Crampton & Albert, 2018 * '' Gymnotus stenoleucus'' Mago-Leccia, 1994 * '' Gymnotus sylvius'' Albert & Fernandes-Matioli, 1999 * '' Gymnotus tigre'' Albert & Crampton, 2003 * '' Gymnotus tiquie'' Maxime, F. C. T. Lima & Albert, 2011 * '' Gymnotus ucamara'' Crampton,

Lovejoy ''Lovejoy'' is a British television comedy-drama mystery fiction, mystery series, based on the Lovejoy (novel series), novels by John Grant (Lovejoy), John Grant under the pen name Jonathan Gash. The show, which ran to 71 episodes over six ser ...

& Albert, 2003 * '' Gymnotus varzea'' Crampton, Thorsen & Albert, 2005

References

{{Taxonbar, from=Q13033659 Gymnotidae Fish of South America Freshwater fish genera Taxa named by Carl Linnaeus