Xiphophorus

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Xiphophorus
Xiphophorus helleri Annanasschwerttaeger Maennchen.JPG
Green swordtail, Xiphophorus hellerii
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Tribe: Poeciliini
Genus: Xiphophorus
Heckel, 1848
Type species
Xiphophorus hellerii
Heckel, 1848 [1]
Species

See text

Synonyms [2]

Xiphophorus is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. Xiphophorus species can be divided into 3 groups based on their evolutionary relationships: platyfish (or platies), northern swordtails, and southern swordtails. Platyfish formerly were classified in another genus, Platypoecilus, which is now obsolete. The type species is X. hellerii, the green swordtail. 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 words ξίφος (dagger) and φόρος (bearer), referring to the gonopodium on the males. All are relatively small fishes, which reach a maximum length of 3.5–16 cm (1.4–6.3 in) depending on the exact species involved. [3]

Contents

Distribution and conservation status

The Monterrey platyfish is one of three Xiphophorus species that is restricted to the southern Rio Grande basin and threatened 016776F000199W000002.jpg
The Monterrey platyfish is one of three Xiphophorus species that is restricted to the southern Rio Grande basin and threatened

The various Xiphophorus species range from the southern Rio Grande basin in Mexico, through eastern drainages in the country (river basins draining into the Gulf of Mexico), to northern Guatemala, Belize and northern Honduras. [4] [5]

Three species and their hybrids are common in the aquarium trade: the green swordtail (X. hellerii), the southern platyfish (X. maculatus) and the variable platyfish (X. variatus). These three are the only species that have large native ranges. [4] They have also been introduced outside their native range (in Mexico, Central America, and other continents) where they sometimes become invasive and outcompete and endanger native species, including other, more localized members of Xiphophorus. [6]

All other species of Xiphophorus are highly localized and mostly endemic to Mexico. Only three of the localized species, the Chiapas swordtail (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. [4] [5] In many locations there are two or more sympatric species, [5] but the localized species are mostly (though not entirely) separated from each other, even when they are restricted to the same river basin. [4] This includes three restricted species in the Rio Grande basin (all fully separated), nine restricted species in the Pánuco River basin (mostly separated) and three restricted species in the Coatzacoalcos River basin (mostly separated). [4]

The International Union for Conservation of Nature (IUCN) lists the spiketail platyfish (X. andersi) and northern platyfish (X. gordoni) as Endangered, while the Monterrey platyfish (X. couchianus) and marbled swordtail (X. meyeri) are listed as Extinct in the wild, 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. [6] 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. [6] [7] [8]

Human uses

Red tuxedo platy.JPG
Poissons 02.jpg
Two southern platyfish showing some of the extreme variations achieved through selective breeding in captivity

Xiphophorus species are regularly used in genetic studies, and scientists have developed many interspecific hybrids,. [9] Xiphophorus have proved a useful model to understand the consequences of hybridization, especially in the context of melanoma research since the 1920s. [10] The Xiphophorus Genetic stock center, founded by Myron Gordon in 1939, is an important source of these fish for research. [7]

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, 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. [11]

Species and taxonomy

Males of the Montezuma swordtail have the proportionally longest tail "sword" among the swordtails, but as in all species the females lack it Xiphophorus montezumae - AquaPorteDoree 07.JPG
Males of the Montezuma swordtail have the proportionally longest tail "sword" among the swordtails, but as in all species the females lack it
One of the typical captive forms of the variable platyfish Xipho variatus maschio.jpg
One of the typical captive forms of the variable platyfish

There are currently 28 recognized species in this genus, according to FishBase. [3] Two of these species, X. clemenciae and X. monticolus, are likely the result of natural hybrid speciation (ancestors of both are a platy species and a swordtail species). [4] [5] Two other proposed species, X. kosszanderi and X. roseni, are recognized by FishBase, [3] but not by all other authorities, as the first appears to be a hybrid 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). [4] [12] Contemporary hybridization in the wild was thought to be uncommon in this genus [13] until recently. [14] [15]

Although traditionally divided into swordtails and platies, this separation is not supported by phylogenetic studies, which have shown that the swordtails are paraphyletic compared with the platies. These studies suggest that the genus can be divided into three monophyletic groups: the northern swordtails (of the Pánuco River basin, marked with a star* in the list), southern swordtails (southern Mexico to Honduras) and the platies. [4] 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. [4]

Swordtails (Xiphophorus)

Platies (Platypoecilus)

Research

Hybridization:Xiphophorus is a leading animal model systems in the study of hybridization between species. In particular, studies in Xiphophorus provided some early evidence that recombination controlled patterns of ancestry in hybrid genomes. [16] An interesting consequence of hybridization is the origin of spontaneous melanoma in hybrids. [17] For example, in the well-studied Gordon-Kosswig cross between X. maculatus and X. hellerii, hybrids develop spontaneous melanoma due to an interaction between the oncogene xmrk and a repressor locus on a distinct chromosome. [18]

Pigmentation:Xiphophorus pigmentation has been investigated since the 1920s using classical genetics techniques such as crosses. [19] As a result, inheritance patterns of many traits have been described. More recently, researchers have identified specific genes and even mutations causing pigment pattern variation (for instance, a spot allowing males to mimic females [20] ) and investigated selective mechanisms on these traits.

Sexual selection: Researchers since Darwin have studied Xiphophorus species for their sexually selected ornaments (e.g. caudal fin "swords"). [21] More recent studies have focused on male ornamentation, courtship strategies, and female mate choice. [22]

Related Research Articles

<span class="mw-page-title-main">Southern platyfish</span> Species of fish

The southern platyfish, common platy, or moonfish is a species of freshwater fish in family Poeciliidae of order Cyprinodontiformes. A live-bearer, it is closely related to the green swordtail and can interbreed with it. It is native to an area of North and Central America stretching from Veracruz, Mexico, to northern Belize.

<span class="mw-page-title-main">Monterrey platyfish</span> Species of fish

The Monterrey platyfish 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 in the vicinity of the city of Monterrey, Mexico. The specific name refers to the American soldier and naturalist Darius N. Couch (1822–1897) who collected the type on a self financed expedition to Mexico.

<span class="mw-page-title-main">Variable platyfish</span> Species of fish

The variable platyfish, also known as variatus platy or variegated platy, is a species of freshwater fish in family Poecilidae of order Cyprinodontiformes. A livebearer, it is native to southern Tamaulipas and northern Veracruz states in northeastern Mexico. It is a popular fish in the aquarium trade due to its prolific breeding, as are hybrids with other members of its genus, most notably the southern platyfish.

Myron Gordon was an American biologist and geneticist and became an expert on platy fish Xiphophorus while using them for his pioneering cancer research, starting in the late 1920s. Early papers were published while still a graduate student at Cornell University, but he is best known for his research at New York University and the New York Zoological Society.

The yellow swordtail is a species of freshwater fish in the family Poeciliidae. It is endemic to the upper Coatzacoalcos River basin in southern Mexico. It is typically found in brooks and streams with slow current; it is less frequent in areas with strong current. The yellow swordtail is considered a threatened species by Mexican authorities. It reaches up to 5.1 cm (2.0 in) in standard length.

The northern platyfish 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 and marshes of the Laguna Santa Tecla. Its native water is shallow and vegetation-choked, with very stable temperatures that generally are around 27–30 °C (81–86 °F), although captive studies show the species also can live in slightly colder water.

The marbled swordtail is a species of freshwater fish in the family Poeciliidae. It was endemic to the Rio Salado system in Coahuila, northeastern Mexico. It was restricted to springs, connected creeks and pools in waters with a pH slightly above neutral and temperatures of 16–26 °C (61–79 °F), with captive studies indicating that the optimum temperature is around 24 °C (75 °F).

The Chiapas swordtail or upland swordtail 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 Chiapas swordtail was discovered and first described by Donn E. Rosen in 1960, along with four other species of Xiphophorus.

<span class="mw-page-title-main">Green swordtail</span> Species of fish

The green swordtail 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 crossbreed with it. It is native to an area of North and Central America stretching from Veracruz, Mexico, to northwestern Honduras.

<span class="mw-page-title-main">Platy (fish)</span> Defunct genus of freshwater fish

Platy is a common name of freshwater fish in the genus Xiphophorus that lack a "sword" at the bottom of their tails. Both species are livebearers, similar to other fish of the family Poeciliidae, such as the guppy and molly. Platies are native to the east coast of Central America and southern Mexico.

Xiphophorus kosszanderi, the speckled platy, is a fish in the family Poeciliidae. It is found in Mexico. Although Fishbase lists this species as valid other authorities regard this taxon as a hybrid between Xiphophorus variatus and X. xiphidium.

<i>Xiphophorus nigrensis</i> Species of fish

Xiphophorus nigrensis, the Panuco swordtail, is a species of fish in the family Poeciliidae that is endemic to a small part of the Pánuco River basin in Mexico.

Xiphophorus multilineatus is a fish in the family Poeciliidae. It is endemic to a small part of the Pánuco River basin in Mexican.

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, males have the lower part of the caudal fin extended into a "sword".

<i>Xiphophorus nezahualcoyotl</i> Species of fish

Xiphophorus nezahualcoyotl, the mountain swordtail, is a live bearing fish in the family Poeciliidae. It is endemic to the northwestern Pánuco River basin in Mexico. The specific name of this fish refers to the poet, philosopher and emperor of Texcoco, Nezahualcoyotl (1402-1472).

<i>Xiphophorus continens</i> Species of fish

Xiphophorus continens, also known as El Quince swordtail or short-sword platyfish, is a live-bearing freshwater fish in the family Poeciliidae. It is endemic to the Pánuco River basin in east-central Mexico. Its name comes from the Greek conto, meaning short, and Latin ensis, meaning "sword". due to the species' sword size in males.

Xiphophorus malinche, also known as highland swordtail, is a live bearing fish in the family Poeciliidae. It is endemic to the Pánuco River basin in east-central Mexico. This species is named after La Malinche, an Indian slave who played a role in the Spanish conquest as the interpreter, secretary, and mistress of Hernán Cortés.

<i>Xiphophorus pygmaeus</i> Species of fish

Xiphophorus pygmaeus, the pygmy swordtail, is a poeciliid fish from northeastern Mexico. It is the smallest of the swordtails. The male's sword is barely visible and the species is often called the swordless swordtail. It is sometimes kept in home aquaria, but is a rather delicate species.

<i>Xiphophorus milleri</i> Species of fish

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 a single genus, Xiphophorus.

<i>Xiphophorus signum</i> Species of fish

Xiphophorus signum is a poeciliid fish endemic to Guatemala. It occurs in only one creek and adjacent pools, making it a vulnerable species.

References

  1. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Xiphophorus". Catalog of Fishes . California Academy of Sciences . Retrieved 7 November 2019.
  2. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Genera in the family Poeciliidae". Catalog of Fishes . California Academy of Sciences . Retrieved 7 November 2019.
  3. 1 2 3 Froese, Rainer; Pauly, Daniel (eds.). "Species in genus Xiphophorus". FishBase . September 2018 version.
  4. 1 2 3 4 5 6 7 8 9 10 11 Kang, J.H.; M. Schartl; R.B. Walter; A. Meyer (2013). "Comprehensive phylogenetic analysis of all species of swordtails and platies (Pisces: Genus Xiphophorus) uncovers a hybrid origin of a swordtail fish, Xiphophorus monticolus, and demonstrates that the sexually selected sword originated in the ancestral lineage of the genus, but was lost again secondarily". BMC Evolutionary Biology. 13 (25): 25. Bibcode:2013BMCEE..13...25K. doi: 10.1186/1471-2148-13-25 . PMC   3585855 . PMID   23360326.
  5. 1 2 3 4 Meyer, A.; W. Salzburger; M. Schartl (2006). "Hybrid origin of a swordtail species (Teleostei: Xiphophorus clemenciae) driven by sexual selection". Molecular Ecology. 15 (3): 721–730. Bibcode:2006MolEc..15..721M. doi:10.1111/j.1365-294X.2006.02810.x. PMID   16499697. S2CID   128413.
  6. 1 2 3 Ceballos, G.; E.D. Pardo; L.M Estévez; H.E. Pérez, eds. (2016). Los peces dulceacuícolas de México en peligro de extinción. Fondo de Cultura Económic. pp. 48, 279–284. ISBN   978-607-16-4087-1.
  7. 1 2 "Xiphophorus Genetic Stock Center". Texas State University. Retrieved 23 September 2018.
  8. ↑ Coletti, T. (December 2007). "Preserving Xiphophorus couchianus in the Home Aquarium, Part I: Sad History & Unanswered Questions". tfhmagazine.com. Retrieved 23 September 2018.
  9. ↑ "Hybrid Crosses : Xiphophorus Genetic Stock Center : Texas State University". Archived from the original on October 23, 2014. Retrieved October 22, 2014.
  10. ↑ Patton, E Elizabeth; Mitchell, David L; Nairn, Rodney S (2010). "Genetic and environmental melanoma models in fish". Pigment Cell & Melanoma Research. 23 (3): 314–337. doi:10.1111/j.1755-148X.2010.00693.x. PMC   2881310 . PMID   20230482.
  11. ↑ Edmond, Adam (11 March 2017). "Swordtail Fish Care Guide". The Aquarium Guide. Retrieved 23 June 2021.
  12. 1 2 3 Meyer M (1983). "Xiphophorus-Hybriden aus Nord-Mexiko, mit einer Revision der Taxa X. kosszanderi und IIIX. roseni". Zoologische Abhendlungen Steatliche Naturhistorische Sommlungen Dresden. 38: 258–291.
  13. ↑ Kallman, K.D.; S. Kazianis (2006). "The genus Xiphophorus in Mexico and Central America". Zebrafish. 3 (3): 271–285. doi:10.1089/zeb.2006.3.271. PMID   18377209.
  14. ↑ Powell, Daniel (2021). "Two new hybrid populations expand the swordtail hybridization model system". Evolution. 75 (10): 2524–2539. doi:10.1111/evo.14337. PMC   8659863 . PMID   34460102.
  15. ↑ Banerjee, Shreya M; Powell, Daniel L; Moran, Benjamin M; Ramírez-Duarte, Wilson F; Langdon, Quinn K; Gunn, Theresa R; Vazquez, Gaby; Rochman, Chelsea; Schumer, Molly (2023-02-08). "Complex hybridization between deeply diverged fish species in a disturbed ecosystem". Evolution. 77 (4): 995–1005. doi:10.1093/evolut/qpad019. ISSN   0014-3820. PMID   36753531.
  16. ↑ Schumer, Molly; Xu, Chenling; Powell, Daniel L.; Durvasula, Arun; Skov, Laurits; Holland, Chris; Blazier, John C.; Sankararaman, Sriram; Andolfatto, Peter; Rosenthal, Gil G.; Przeworski, Molly (2018-05-11). "Natural selection interacts with recombination to shape the evolution of hybrid genomes". Science. 360 (6389): 656–660. Bibcode:2018Sci...360..656S. doi:10.1126/science.aar3684. ISSN   0036-8075. PMC   6069607 . PMID   29674434.
  17. ↑ Powell, Daniel L.; García-Olazábal, Mateo; Keegan, Mackenzie; Reilly, Patrick; Du, Kang; Díaz-Loyo, Alejandra P.; Banerjee, Shreya; Blakkan, Danielle; Reich, David; Andolfatto, Peter; Rosenthal, Gil G.; Schartl, Manfred; Schumer, Molly (2020-05-15). "Natural hybridization reveals incompatible alleles that cause melanoma in swordtail fish". Science. 368 (6492): 731–736. Bibcode:2020Sci...368..731P. doi:10.1126/science.aba5216. ISSN   0036-8075. PMC   8074799 . PMID   32409469.
  18. ↑ Schartl, Angelika; Dimitrijevic, Nicola; Schartl, Manfred (December 1994). "Evolutionary Origin and Molecular Biology of the Melanoma-Inducing Oncogene of Xiphophorus". Pigment Cell Research. 7 (6): 428–432. doi:10.1111/j.1600-0749.1994.tb00072.x. ISSN   0893-5785. PMID   7761351.
  19. ↑ Gordon, Myron (1927-05-01). "The Genetics of a Viviparous Top-Minnow Platypoecilus; the Inheritance of Two Kinds of Melanophores". Genetics. 12 (3): 253–283. doi:10.1093/genetics/12.3.253. ISSN   1943-2631. PMC   1200943 . PMID   17246524.
  20. ↑ Dodge, Tristram O.; Kim, Bernard Y.; Baczenas, John J.; Banerjee, Shreya M.; Gunn, Theresa R.; Donny, Alex E.; Given, Lyle A.; Rice, Andreas R.; Cox, Sophia K. Haase (2024-05-14), Complex structural variation and behavioral interactions underpin a balanced sexual mimicry polymorphism, doi:10.1101/2024.05.13.594052 , retrieved 2024-05-30
  21. ↑ Darwin, Charles (1871). THE DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. London: William Clowes and Sons.
  22. ↑ Rosenthal, Gil G.; De León, Francisco J. García (March 2006). "Sexual Behavior, Genes, and Evolution in Xiphophorus". Zebrafish. 3 (1): 85–90. doi:10.1089/zeb.2006.3.85. ISSN   1545-8547. PMID   18248248.
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