Characiformes is an order of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known

piranha A piranha or piraña (, , or ; or , ) is one of a number of freshwater fish in the family Serrasalmidae, or the subfamily Serrasalminae within the tetra family, Characidae in order Characiformes. These fish inhabit South American rivers, f ...

and tetras.; Buckup P.A.: "Relationships of the Characidiinae and phylogeny of characiform fishes (Teleostei: Ostariophysi)", ''Phylogeny and Classification of Neotropical Fishes'', L.R. Malabarba, R.E. Reis, R.P. Vari, Z.M. Lucena, eds. (Porto Alegre: Edipucr) 1998:123-144.

Taxonomy

The Characiformes form part of a series called the Otophysi within the superorder Ostariophysi. The Otophysi contain three other orders,

Cypriniformes Cypriniformes is an order of ray-finned fish, including the carps, minnows, loaches, and relatives. Cypriniformes is an Order within the Superorder Ostariophysi consisting of " Carp-like" Ostariophysins. This order contains 11-12 famil ...

, Siluriformes, and

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 (t ...

. The Characiformes form a group known as the Characiphysi with the Siluriformes and Gymnotiformes. The order Characiformes is the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the orders Siluriformes and Gymnotiformes, though this has been debated in light of recent molecular evidence. Originally, the characins were all grouped within a single family, the

Characidae Characidae, the characids or characins is a family of freshwater subtropical and tropical fish, belonging to the order Characiformes. The name "characins" is the historical one, but scientists today tend to prefer "characids" to reflect their ...

. Since then, and also 18 different families have been separated out. However, classification varies somewhat, and the most recent (2011) study confirms the circumscribed Characidae as

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

.Claudio Oliveira, Gleisy S Avelino, Kelly T Abe, Tatiane C Mariguela, Ricardo C Benine, Guillermo Ortí, Richard P Vari and Ricardo M Corrêa e Castro,"Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling", ''BMC Evolutionary Biology'' 2011, 11:275)
Currently, 18 families, about 270

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

, and at least 1674

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

are known. The suborder Citharinoidei, which contains the families Distichodontidae and Citharinidae, is considered the sister group to the rest of the characins, suborder

Characoidei Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationsh ...

Evolution

The oldest characiform is '' Santanichthys'' of the early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

(

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...

stage) of

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. While all extant species are of fresh water, this species was probably either brackish or marine. Many other fossils are also known. The Characiformes likely first diversified during the Cretaceous period, though fossils are poorly known. During the Cretaceous period, the rift between South America and Africa would be forming; this may explain the contrast in diversity between the two continents. Their low diversity in Africa may explain why some primitive fish families and the Cypriniformes coexist with them while they are absent in South America, where these fish may have been driven extinct. The characiforms had not spread into Africa soon enough to also reach the land bridge between Africa and Asia. The earliest they could have spread into Central America was the late

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Phylogeny

Below is a phylogeny of living Characiformes based on Betancur-Rodriguez ''et al.'' 2017 and Nelson, Grande & Wilson 2016.

Description

Characins possess a

Weberian apparatus The Weberian apparatus is an anatomical structure that connects the swim bladder to the auditory system in fishes belonging to the superorder Ostariophysi. When it is fully developed in adult fish, the elements of the apparatus are sometimes co ...

, a series of bony parts connecting the

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their current water depth wit ...

and

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in th ...

. Superficially, the Characiformes somewhat resemble their relatives of the order

, but have a small, fleshy adipose fin between the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

and

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammal ...

. Most species have teeth within the mouth, since they are often

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

. The body is almost always covered in well-defined scales. The mouth is also usually not truly protractile. The largest characins are ''

Hydrocynus goliath ''Hydrocynus goliath'', also known as the goliath tigerfish, giant tigerfish, or mbenga, is a very large African predatory freshwater fish of the family Alestidae. Distribution ''Hydrocynus goliath'' is found in the Congo River Basin (including ...

'' and ''

Salminus franciscanus ''Salminus'', popularly known as dorado or dourado, is a genus of relatively large (up to long), predatory freshwater fish from the family Characidae. They are native to large tropical and subtropical rivers in South America, and undertake mi ...

'' and ''

Hoplias aimara ''Hoplias aimara'', also known as anjumara, traíra, trahira, ''manjuma'', ''anjoemara'' and wolf fish, is a species of freshwater fish found in the rivers of South America. In Amazonia, the native populations are concerned by high levels of mer ...

'',http://www.fishing-worldrecords.com/scientificname/Salminus%20franciscanus/show both of which are up to . The smallest in size is about in the Bolivian pygmy blue characin, '' Xenurobrycon polyancistrus''. Many members are under .

Distribution and habitat

Characins are most diverse in the

Neotropics 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 bioge ...

, where they are found in lakes and rivers throughout most of

South South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþa ...

and

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

. The

red-bellied piranha The red-bellied piranha, also known as the red piranha (''Pygocentrus nattereri''), is a type of piranha native to South America, found in the Amazon, Paraguay, Paraná and Essequibo basins, as well as coastal rivers of northeastern Brazil. ...

, a member of the family

Serrasalmidae The Serrasalmidae (serrasalmids) are a family of characiform fishes, recently elevated to family status. It includes more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the belly of the ...

within the Characiformes, is endemic to the Neotropical realm. At least 209 species of characins are found in Africa, including the distichodontids, citharinids, alestiids, and hepsetids. The rest of the characins originate from the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...

Relationship to humans

A few characins become quite large, and are important as food or game. Most, however, are small shoaling fish. Many species known as tetras are popular in aquaria due to their bright colors, general hardiness, and tolerance towards other fish in community tanks.

References

{{Taxonbar, from=Q217458 Ostariophysi Ray-finned fish orders Fish of Africa Fish of South America Fish of Central America Extant Albian first appearances