''Apteronotus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of weakly electric knifefish in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Apteronotidae The ghost knifefishes are a family, Apteronotidae, of ray-finned fishes in the order Gymnotiformes. These fish are native to Panama and South America. They inhabit a wide range of freshwater habitats, but more than half the species in the family ...

, distinguished by the presence of a tiny tail fin. This genus is restricted to tropical and subtropical

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

(

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technology c ...

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...

Río de la Plata The Río de la Plata (, "river of silver"), also called the River Plate or La Plata River in English, is the estuary formed by the confluence of the Uruguay River and the Paraná River at Punta Gorda. It empties into the Atlantic Ocean and fo ...

and Magdalena basins, as well as rivers in western

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

and the

Guianas The Guianas, sometimes called by the Spanish loan-word ''Guayanas'' (''Las Guayanas''), is a region in north-eastern South America which includes the following three territories: * French Guiana, an overseas department and region of France * ...

) and

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

where found in a wide range of freshwater habitats. They feed on small animals. Depending on the exact species, they reach a total length of up to about . Although it has been claimed that ''A. magdalenensis'' is up to long, this is not supported by recent studies and likely the result of confusion with '' Sternopygus aequilabiatus''. Members of ''Apteronotus'' fall into three

species group In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

s based on their

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

: the ''A. albifrons'' group have a rounded snout and are black or dark brown with a contrasting light stripe on the top of the head, and bands on the tail and at its base, the ''A. leptorhynchus'' group have an elongate, slender snout (especially in males) and are brown with a light stripe along the head and back, and a band on the tail, and the ''A. bonapartii'' group have an elongate (males) or rounded (females) snout and are brown or gray (capable of some color change) with a light band on the tail. The last group is not closely related to the first two and will likely need to be moved to another genus. A genetic study published in 2019 found that the genus is strongly

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

with several groups that are quite distantly related.

Species

There are currently 27 recognized species in this genus: * '' Apteronotus acidops'' Triques, 2011Triques, M.L. (2011): Apteronotus acidops, ''new species of long snouted electric fish (Teleostei: Gymnotiformes: Apteronotidae) from the upper rio Paraná basin in Brazil, with a key to the apteronotid species from the area.'' Vertebrate Zoology, 61 (3): 299–306. * '' Apteronotus albifrons'' (

Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

, 1766) (Black ghost knifefish) * '' Apteronotus anu'' de Santana &

Vari Vari ( el, Βάρη) is a southern suburb of Athens and former municipality in East Attica, Greece along the Athens coast. Since the 2011 local government reform it is part of the municipality Vari-Voula-Vouliagmeni, of which it is a municipal un ...

, 2013de Santana, C.D. & Vari, R.P. (2013): Brown ghost electric fishes of the ''Apteronotus leptorhynchus'' species-group (Ostariophysi, Gymnotiformes); monophyly, major clades, and revision. ''Zoological Journal of the Linnean Society, 168 (3): 564–596.'' * '' Apteronotus apurensis'' Fernández-Yépez, 1968 * '' Apteronotus baniwa'' de Santana &

, 2013 * '' Apteronotus bonapartii'' ( Castelnau, 1855) * '' Apteronotus brasiliensis'' ( J. T. Reinhardt, 1852) * '' Apteronotus camposdapazi'' de Santana & Lehmann-A., 2006 * '' Apteronotus caudimaculosus'' de Santana, 2003 * '' Apteronotus cuchillejo'' ( L. P. Schultz, 1949) * '' Apteronotus cuchillo'' L. P. Schultz, 1949 * '' Apteronotus ellisi'' ( Alonso de Arámburu, 1957) * '' Apteronotus eschmeyeri'' de Santana, Maldenado-Ocampo, Severi & G. N. Mendes, 2004 * '' Apteronotus ferrarisi'' de Santana &

, 2013 * '' Apteronotus galvisi'' de Santana, Maldenado-Ocampo & Crampton, 2007 * '' Apteronotus jurubidae'' ( Fowler, 1944) * '' Apteronotus leptorhynchus'' ( M. M. Ellis, 1912) (Brown ghost knifefish) * '' Apteronotus lindalvae'' de Santana & Cox Fernandes, 2012de Santana, C.D. & Cox Fernandes, C. (2012): A New Species of Sexually Dimorphic Electric Knifefish from the Amazon Basin, Brazil (Gymnotiformes: Apteronotidae). ''Copeia, 2012 (2): 283-292.'' * '' Apteronotus macrolepis'' (

Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachner describ ...

, 1881) * '' Apteronotus macrostomus'' ( Fowler, 1943) * ''

Apteronotus magdalenensis ''Apteronotus'' is a genus of weakly electric knifefish in the family Apteronotidae, distinguished by the presence of a tiny tail fin. This genus is restricted to tropical and subtropical South America (Amazon, Orinoco, Río de la Plata and ...

'' (

Miles The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English ...

, 1945) * '' Apteronotus magoi'' de Santana, Castillo G. & Taphorn, 2006 * '' Apteronotus mariae'' ( C. H. Eigenmann &

Fisher Fisher is an archaic term for a fisherman, revived as gender-neutral. Fisher, Fishers or The Fisher may also refer to: Places Australia *Division of Fisher, an electoral district in the Australian House of Representatives, in Queensland *Elect ...

, 1914) * '' Apteronotus milesi'' de Santana & Maldenado-Ocampo, 2005 * '' Apteronotus pemon'' de Santana &

, 2013 * '' Apteronotus rostratus'' (

Meek Meekness is an attribute of human nature and behavior that has been defined as an amalgam of righteousness, inner humility, and patience. Meekness has been contrasted with humility alone insomuch as humility simply refers to an attitude towards o ...

Hildebrand Hildebrand is a character from Germanic heroic legend. ''Hildebrand'' is the modern German form of the name: in Old High German it is ''Hiltibrant'' and in Old Norse ''Hildibrandr''. The word ''hild'' means "battle" and ''brand'' means "sword". ...

, 1913) * '' Apteronotus spurrellii'' (

Regan The family name Regan, along with its cognates O'Regan, O Regan, Reagan, and O'Reagan, is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to have originated in ancient Gaelic ''ri'' ...

, 1914)

References

{{Taxonbar, from=Q2859065 Apteronotidae Freshwater fish of South America Taxa named by Bernard Germain de Lacépède Freshwater fish genera