''Xiphophorus'' 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 ...

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an e ...

and freshwater fishes in the family

Poeciliidae The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family was t ...

of order

Cyprinodontiformes Cyprinodontiformes is an order of ray-finned fish, comprising mostly small, freshwater fish. Many popular aquarium fish, such as killifish and live-bearers, are included. They are closely related to the Atheriniformes and are occasionally inc ...

, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and swordtails. Platyfish formerly were classified in another genus, ''Platypoecilia'', which is now obsolete. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''X. hellerii,'' the

green swordtail The green swordtail (''Xiphophorus hellerii'') is a species of freshwater/brackish fish in family Poeciliidae of order Cyprinodontiformes. A live-bearer, it is closely related to the southern platyfish or 'platy' (''X. maculatus'') and can cros ...

. Like most other new world Poeciliids, platies and swordtails are live-bearers that use internal fertilization and give birth to live young instead of laying eggs like the bulk of the world's fishes. The name ''Xiphophorus'' derives from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

words ξίφος (dagger) and φόρος (bearer), referring to the

gonopodium Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

on the males. All are relatively small fishes, which reach a maximum length of depending on the exact species involved.

Distribution and conservation status

The various ''Xiphophorus'' species range from the southern

Rio Grande The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico. The length of the Rio G ...

basin in Mexico, through eastern drainages in the country (river basins draining into the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

), to northern

Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...

Belize Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wate ...

and northern

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...

. Three species and their hybrids are common in the aquarium trade: the

(''X. hellerii''), the

southern platyfish The southern platyfish, common platy, or moonfish (''Xiphophorus maculatus'') is a species of freshwater fish in family (biology), family Poeciliidae of order (biology), order Cyprinodontiformes. A live-bearing aquarium fish, live-bearer, it i ...

(''X. maculatus'') and the variable platyfish (''X. variatus''). These three are the only species that have large native ranges. They have also been introduced outside their native range (both in Mexico, Central America and other continents) where they sometimes become invasive species that outcompete and endanger native species, including other, more localized members of ''Xiphophorus''. All other species of ''Xiphophorus'' are highly localized and mostly

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to Mexico. Only three of the localized species, the

Chiapas swordtail The Chiapas swordtail or upland swordtail (''Xiphophorus alvarezi'') is a species of livebearing freshwater fish of family Poeciliidae, and genus '' Xiphophorus''. It is, therefore, in the same genus as the common platy and the swordtail. The ...

(''X. alvarezi''), '' X. mayae'' and '' X. signum'', range outside Mexico and the last two are the only ''Xiphophorus'' species not found in Mexico at all. In many locations there are two

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

species, but the localized species are mostly (though not entirely) separated from each other, even when they are restricted to the same river basin. This includes three restricted species in the Rio Grande basin (all fully separated), nine restricted species in the

Pánuco River The Pánuco River ( es, Río Pánuco, ), also known as the ''Río de Canoas'', is a river in Mexico fed by several tributaries including the Moctezuma River and emptying into the Gulf of Mexico. The river is approximately long and passes throug ...

basin (mostly separated) and three restricted species in the

Coatzacoalcos River The Coatzacoalcos is a large river that feeds mainly the south part of the state of Veracruz; it originates in the Sierra de Niltepec and crosses the state of Oaxaca in the region of the Isthmus of Tehuantepec, flowing for toward the Gulf of M ...

basin (mostly separated). The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN) lists the spiketail platyfish (''X. andersi'') and

northern platyfish The northern platyfish (''Xiphophorus gordoni'') is a small, endangered species of fish in the family Poeciliidae. It is endemic to the vicinity of Cuatro Ciénegas in the Mexican state of Coahuila. It is restricted to hot-spring heated ditches ...

(''X. gordoni'') as

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

, while the

Monterrey platyfish The Monterrey platyfish (''Xiphophorus couchianus'') is a species of freshwater fish in family Poecilidae. A live-bearer, it was native to a very small section of the San Juan River system (itself part of the Rio Grande basin) in the vicinity ...

(''X. couchianus'') and

marbled swordtail The marbled swordtail (''Xiphophorus meyeri'') is a species of freshwater fish in the family Poeciliidae. It was endemic to the Rio Salado system (itself a part of the Rio Grande basin) in Coahuila, northeastern Mexico. It was restricted to spri ...

(''X. meyeri'') are listed as

Extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as known only by living members kept in captivity or as a naturalized population outside its historic range due ...

, and thus only survive in captivity. In addition to those, Mexican authorities recognize the yellow swordtail (''X. clemenciae'') and Catemaco platyfish (''Xiphophorus milleri'') as

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

. Almost all the ''Xiphophorus'', including the rare species, have captive populations that are maintained as "insurance" populations at breeding centers and by dedicated private aquarists.

Human uses

''Xiphophorus'' species are regularly used in genetic studies, and scientists have developed many interspecific hybrids, especially in melanoma research since the 1920s. The Xiphophorus

Genetic stock center Genetic stock centers are collections of pure genetic stock available for use in research. They are often housed at research universities, and include everything from single cell life to plants, fish, and small mammals such as mice and rats. Genet ...

, founded by Myron Gordon in 1939, is an important source of these fish for research. In addition, several species are commonly kept by aquarium hobbyists, especially the green swordtail (''X. helleri''), southern platyfish (''X. maculatus''), and variable platyfish (''X. variatus''). In fact, these three species comprise one of the most prominent groups of aquarium species, being part of a group of extremely hardy livebearing fish, alongside the molly and

guppy The guppy (), also known as millionfish and rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all ...

, that can adjust to a wide range of conditions within the aquarium. Unlike some species, these are almost always offered as captive bred individuals due to the ease of breeding these livebearers. In captivity, they will coexist with many other fish species, although in an aquarium with too many males and not enough females, fighting can ensue between males of the same species. They can also easily jump out of an inadequately covered aquarium.

Species and taxonomy

Xiphophorus montezumae - AquaPorteDoree 07

There are currently 28 recognized species in this genus, according to

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

. Two of these species, ''X. clemenciae'' and ''X. monticolus'', are likely the result of natural

hybrid speciation Hybrid speciation is a form of speciation where hybridization between two different species leads to a new species, reproductively isolated from the parent species. Previously, reproductive isolation between two species and their parents was thou ...

(ancestors of both are a platy species and a swordtail species). Two other proposed species, ''X. kosszanderi'' and ''X. roseni'', are recognized by FishBase, but not by all other authorities, as the first appears to be a

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...

between ''X. variatus'' and ''X. xiphidium'', and the second between ''X. variatus'' and ''X. couchianus'' (''X. kosszanderi'' and ''X. roseni'' have not undergone speciation as in ''X. clemenciae'' and ''X. monticolus''). Otherwise hybridization in the wild is uncommon in this genus and only known from three or four locations, despite the fact that many sites have two sympatric species. Although traditionally divided into swordtails and platies, this separation is not supported by

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

studies, which have shown that the swordtails are

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

compared with the platies. These studies suggest that the genus can be divided into three

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 gro ...

groups: the northern swordtails (of the

basin, marked with a star* in the list), southern swordtails (southern Mexico to Honduras) and the platies. The common names given to individual species in this genus do not always reflect their actual relationships; for example, the marbled swordtail (''X. meyeri'') is actually in the platy group based on its genetics while the short-sword platyfish (''X. continens'') is closer to the swordtails. Swordtails (''Xiphophorus'') * '' Xiphophorus alvarezi'' D. E. Rosen, 1960 (Chiapas swordtail) * '' Xiphophorus birchmanni''* Lechner & Radda, 1987 (sheepshead swordtail) * '' Xiphophorus clemenciae''

Álvarez Álvarez or Álvares may refer to: People *Álvarez (surname), Spanish surname Places *Alvares (river), a river in northern Spain * Alvares (ski resort), in Iran *Alvares, Iran * Alvares, Portugal *Álvarez, Santa Fe, a town in the province of Sa ...

, 1959 (yellow swordtail) * '' Xiphophorus continens''* Rauchengerger,

Kallman Kallman is a surname of the following people: *Brent Kallman (born 1990), American association football player *Brian Kallman (born 1984), American association football player, brother of Brent *Chester Kallman (1921–1975), American poet, libre ...

& Morizot, 1990 (short-sword platyfish) * '' Xiphophorus cortezi''* D. E. Rosen, 1960 (delicate swordtail) * ''

Xiphophorus hellerii ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and ...

'' Heckel, 1848 (green swordtail) * '' Xiphophorus kallmani'' M. K. Meyer & Schartl, 2003 * '' Xiphophorus malinche''* Rauchengerger,

& Morizot, 1990 (highland swordtail) * ''

Xiphophorus mayae ''Xiphophorus mayae'' is a fish in the family Poeciliidae. It is found in Central America: eastern Guatemala and western Honduras. This species has red lines on its body which extend on to the upper portion of the caudal fin Fins are disti ...

'' M. K. Meyer & Schartl, 2002 * '' Xiphophorus mixei''

Walter Walter may refer to: People * Walter (name), both a surname and a given name * Little Walter, American blues harmonica player Marion Walter Jacobs (1930–1968) * Gunther (wrestler), Austrian professional wrestler and trainer Walter Hahn (born 19 ...

, Morizot & Kazianis, 2004 (Mixe swordtail) * '' Xiphophorus montezumae''* D. S. Jordan & Snyder, 1899 (Montezuma swordtail) * '' Xiphophorus monticolus''

, Morizot & Kazianis, 2004 (southern mountain swordtail) * ''

Xiphophorus multilineatus ''Xiphophorus multilineatus'' is a fish in the family Poeciliidae. It is endemic to a small part of the Pánuco River The Pánuco River ( es, Río Pánuco, ), also known as the ''Río de Canoas'', is a river in Mexico fed by several tributar ...

''* Rauchengerger,

& Morizot, 1990 * ''

Xiphophorus nezahualcoyotl ''Xiphophorus nezahualcoyotl'', the mountain swordtail, is a live bearing fish in the family Poeciliidae. It is endemic to the northwestern Pánuco River The Pánuco River ( es, Río Pánuco, ), also known as the ''Río de Canoas'', is a riv ...

''* Rauchengerger,

& Morizot, 1990 (mountain swordtail) * '' Xiphophorus nigrensis''* D. E. Rosen, 1960 (Panuco swordtail) * '' Xiphophorus pygmaeus''* C. L. Hubbs &

Gordon Gordon may refer to: People * Gordon (given name), a masculine given name, including list of persons and fictional characters * Gordon (surname), the surname * Gordon (slave), escaped to a Union Army camp during the U.S. Civil War * Clan Gordon, ...

, 1943 (pygmy swordtail) * ''

Xiphophorus signum ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and ...

'' D. E. Rosen &

, 1969 Platies (''Platypoecilus'') * ''

Xiphophorus andersi ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and ...

'' M. K. Meyer & Schartl, 1980 (spiketail platyfish) * ''

Xiphophorus couchianus ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and s ...

'' ( Girard, 1859) (Monterrey platyfish) * '' Xiphophorus evelynae'' D. E. Rosen, 1960 (Puebla platyfish) * '' Xiphophorus gordoni'' R. R. Miller &

W. L. Minckley Wendell Lee Minckley (November 13, 1935 – June 22, 2001) was a college professor and leading expert on fish. He spent most of his career at Arizona State University. In 1963, he with Robert Rush Miller discovered and named the northern platy ...

, 1963 (northern platyfish) * '' Xiphophorus kosszanderi'' M. K. Meyer & Wischnath, 1981 – often not recognized as a valid species, as likely a hybrid * ''

Xiphophorus maculatus ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order (biology), order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (o ...

'' ( Günther, 1866) (southern platyfish) * '' Xiphophorus meyeri'' Schartl &

Schröder Schröder (Schroeder) is a German language, German surname often associated with the Schröder family. Notable people with the surname include: * Arthur Schröder (1892–1986), German actor * Atze Schröder, stage name of German comedian Hubertu ...

, 1988 (marbled swordtail) * ''

Xiphophorus milleri ''Xiphophorus milleri'', the Catemaco platyfish, is a poeciliid fish endemic to Mexico's Lake Catemaco and its tributaries. As it has traits of both swordtails and platies, its discovery confirmed that these two groups should be consolidated into ...

'' D. E. Rosen, 1960 (Catemaco platyfish) * '' Xiphophorus roseni'' M. K. Meyer & Wischnath, 1981 – often not recognized as a valid species, as likely a hybrid * '' Xiphophorus variatus'' (

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 ...

, 1904) (variable platyfish) * ''

Xiphophorus xiphidium The swordtail platyfish (''Xiphophorus xiphidium'') is a species of ray-finned fish within the family Poeciliidae. The species is endemic to the Soto la Marina River basin in Tamaulipas and Nuevo Leon. It lives in springs, streams, arroyos, dit ...

'' (

, 1932) (swordtail platyfish)

References

External links

xiphophorus genetic stock center

xiphophorus.org

xiphophorus.net
Chinese ver.) {{Taxonbar, from=Q132098 Ovoviviparous fish Freshwater fish genera Taxa named by Johann Jakob Heckel Ray-finned fish genera Poeciliidae