Jump to content

Xiphophorus

From Wikipedia, the free encyclopedia
This article is about the fish genus. For the free software foundation, seeXiph.Org Foundation.
"Swordtail" redirects here. For the butterfly, seeGraphium (butterfly).

Xiphophorus
Green swordtail,Xiphophorus hellerii
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Tribe: Poeciliini
Genus: Xiphophorus
Heckel,1848
Type species
Xiphophorus hellerii
Species

See text

Synonyms[2]

Xiphophorusis agenusofeuryhalineand freshwater fishes in the familyPoeciliidaeoforderCyprinodontiformes,native to Mexico and northern Central America.Xiphophorusspecies 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. Thetype speciesisX. hellerii,thegreen swordtail.Like most other new world Poeciliids, platies and swordtails arelive-bearersthat use internal fertilization and give birth to live young instead of laying eggs like the bulk of the world's fishes. The nameXiphophorusderives from theGreekwords ξίφος (dagger) and φόρος (bearer), referring to thegonopodiumon 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]

Distribution and conservation status

[edit]
TheMonterrey platyfishis one of threeXiphophorusspecies that is restricted to the southernRio Grandebasin and threatened

The variousXiphophorusspecies range from the southernRio Grandebasin in Mexico, through eastern drainages in the country (river basins draining into theGulf of Mexico), to northernGuatemala,Belizeand northernHonduras.[4][5]

Three species and their hybrids are common in the aquarium trade: thegreen swordtail(X. hellerii), thesouthern platyfish(X. maculatus) and thevariable platyfish(X. variatus). These three are the only species that have large native ranges.[4]They have also beenintroducedoutside 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 ofXiphophorus.[6]

All other species ofXiphophorusare highly localized and mostlyendemicto Mexico. Only three of the localized species, theChiapas swordtail(X. alvarezi),X. mayaeandX. signum,range outside Mexico and the last two are the onlyXiphophorusspecies not found in Mexico at all.[4][5]In many locations there are two or moresympatricspecies,[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 thePánuco Riverbasin (mostly separated) and three restricted species in theCoatzacoalcos Riverbasin (mostly separated).[4]

TheInternational Union for Conservation of Nature(IUCN) lists thespiketail platyfish(X. andersi) andnorthern platyfish(X. gordoni) asEndangered,while theMonterrey platyfish(X. couchianus) andmarbled swordtail(X. meyeri) are listed asExtinct in the wild,and thus only survive in captivity. In addition to those, Mexican authorities recognize theyellow swordtail(X. clemenciae) andCatemaco platyfish(Xiphophorus milleri) asthreatened.[6]Almost all theXiphophorus,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

[edit]
Twosouthern platyfishshowing some of the extreme variations achieved throughselective breedingin captivity

Xiphophorusspecies are regularly used ingeneticstudies, and scientists have developed many interspecifichybrids,.[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 XiphophorusGenetic stock center,founded byMyron Gordonin 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 hardylivebearingfish, alongside themollyandguppy,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

[edit]
Males of theMontezuma swordtailhave the proportionally longest tail "sword" among the swordtails, but as in all species the females lack it
One of the typical captive forms of thevariable platyfish

There are currently 28 recognized species in this genus, according toFishBase.[3]Two of these species,X. clemenciaeandX. monticolus,are likely the result of naturalhybrid speciation(ancestors of both are a platy species and a swordtail species).[4][5]Two other proposed species,X. kosszanderiandX. roseni,are recognized by FishBase,[3]but not by all other authorities, as the first appears to be ahybridbetweenX. variatusandX. xiphidium,and the second betweenX. variatusandX. couchianus(X. kosszanderiandX. rosenihave not undergone speciation as inX. clemenciaeandX. 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 byphylogeneticstudies, which have shown that the swordtails areparaphyleticcompared with the platies. These studies suggest that the genus can be divided into threemonophyleticgroups: the northern swordtails (of thePánuco Riverbasin, 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

[edit]

Hybridization:Xiphophorusis a leading animal model systems in the study ofhybridizationbetween species. In particular, studies inXiphophorusprovided 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 betweenX. maculatusandX. hellerii,hybrids develop spontaneous melanoma due to an interaction between theoncogenexmrk and a repressor locus on a distinct chromosome.[18]

Pigmentation:Xiphophoruspigmentation 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 sinceDarwinhave studiedXiphophorusspecies 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]

References

[edit]
  • "Xiphophorus".Integrated Taxonomic Information System.Retrieved9 December2004.
  1. ^Eschmeyer, William N.;Fricke, Ron & van der Laan, Richard (eds.)."Xiphophorus".Catalog of Fishes.California Academy of Sciences.Retrieved7 November2019.
  2. ^Eschmeyer, William N.;Fricke, Ron & van der Laan, Richard (eds.)."Genera in the family Poeciliidae".Catalog of Fishes.California Academy of Sciences.Retrieved7 November2019.
  3. ^abcFroese, Rainer;Pauly, Daniel (eds.)."Species in genusXiphophorus".FishBase.September 2018 version.
  4. ^abcdefghijkKang, 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.PMC3585855.PMID23360326.
  5. ^abcdMeyer, 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.PMID16499697.S2CID128413.
  6. ^abcCeballos, 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.ISBN978-607-16-4087-1.
  7. ^ab"Xiphophorus Genetic Stock Center".Texas State University.Retrieved23 September2018.
  8. ^Coletti, T. (December 2007)."Preserving Xiphophorus couchianus in the Home Aquarium, Part I: Sad History & Unanswered Questions".tfhmagazine.com.Retrieved23 September2018.
  9. ^"Hybrid Crosses: Xiphophorus Genetic Stock Center: Texas State University".Archived fromthe originalon October 23, 2014.RetrievedOctober 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.PMC2881310.PMID20230482.
  11. ^Edmond, Adam (11 March 2017)."Swordtail Fish Care Guide".The Aquarium Guide.Retrieved23 June2021.
  12. ^abcMeyer 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.PMID18377209.
  14. ^Powell, Daniel (2021)."Two new hybrid populations expand the swordtail hybridization model system".Evolution.75(10): 2524–2539.doi:10.1111/evo.14337.PMC8659863.PMID34460102.
  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.ISSN0014-3820.PMID36753531.
  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.ISSN0036-8075.PMC6069607.PMID29674434.
  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.ISSN0036-8075.PMC8074799.PMID32409469.
  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.ISSN0893-5785.PMID7761351.
  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.ISSN1943-2631.PMC1200943.PMID17246524.
  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,retrieved2024-05-30
  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.ISSN1545-8547.PMID18248248.
[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=Xiphophorus&oldid=1262439800"