{{short description|Species of fish}} {{Speciesbox | name = Green swordtail | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Daniels, A. |author2=Maiz-Tome, L. |date=2019 |title=''Xiphophorus hellerii'' |volume=2019 |article-number=e.T191780A2002911 |doi=10.2305/IUCN.UK.2019-2.RLTS.T191780A2002911.en |access-date=19 November 2021}}</ref> | status2 = G5 | status2_system = TNC | image = DSC 0690 - Edited.jpg | image_caption = Wild type male of ''Xiphophorus hellerii'' | image2 = Xiphophorus hellerii red male female 01.jpg | image2_caption = ''Xiphophorus hellerii'', captive-bred red variant, male (top) and female (below) | taxon = Xiphophorus hellerii | authority = Heckel, 1848 }} The '''green swordtail''' ('''''Xiphophorus hellerii''''') is a species of freshwater/brackish fish in family Poeciliidae of order Cyprinodontiformes.<ref>{{FishBase species | genus = Xiphophorus | species = hellerii | month = November | year = 2013}}</ref> 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.
==Description== thumb|left|A male swordtail The male green swordtail grows to a maximum overall length of {{Convert|14|cm|in}} and the female to {{Convert|16|cm|in}}. The name 'swordtail' is derived from the elongated lower lobe of the male's caudal fin (tailfin). Sexual dimorphism is moderate, with the female being larger than the male, but lacking the 'sword'. The wild form is olive green in color, with a red or brown lateral stripe and speckles on the dorsal and, sometimes, caudal fins. The male's 'sword' is yellow, edged in black below. Captive breeding has produced many color varieties, including black, red, and many patterns thereof, for the aquarium hobby. All varieties share the dark-red or brown central stripe.<ref>Axelrod, Dr. Herbert R., Wischnath, Lothar, Swordtails and Platies, Neptune, N.J., T.F.H. Publications Inc., Copyright 1991</ref>
The green swordtail prefers swift-flowing, heavily vegetated rivers and streams, but is also found in warm springs and canals. Omnivorous, its diet includes both plants and small crustaceans, insects, and annelid worms.
==Invasive species== ''X. hellerii'' has become a nuisance pest as an introduced species in a number of countries. It has caused ecological damage because of its ability to rapidly reproduce in high numbers. Feral populations have established themselves in southern Africa, including Natal and eastern Transvaal in South Africa, Chinhoyi Caves in Zimbabwe, and Otjikoto Lake in Namibia, as well as in Madagascar, Puerto Rico, and Hawaii. Significant populations have also established themselves along the east coast of Australia.<ref>{{Cite web |title=Green swordtail |url=https://www.dpi.nsw.gov.au/dpi/biosecurity/aquatic-biosecurity/aquatic-pests-and-diseases/freshwater-pests/freshwater-finfish/green-swordtail |access-date=2026-03-20 |website=NSW Government |language=en}}</ref>
==Etymology and taxonomy== The binomial of the green swordtail is made up of its generic name, ''Xiphophorus'' which means ''sword bearer'' in Greek, a reference to the extended lower part of the caudal fin which is referred to as the "sword". The specific name honours the collector of the type, the Austrian botanist Karl Bartholomaeus Heller (1824–1880), who discovered this fish while exploring México in 1845–1848.<ref name = ETYFish>{{cite web | url = http://www.etyfish.org/cyprinodontiformes4/ | work = The ETYFish Project Fish Name Etymology Database | author1 = Christopher Scharpf | author2 = Kenneth J. Lazara | date = 26 October 2019 | title= Order CYPRINODONTIFORMES: Families POECILIIDAE, ANABLEPIDAE, VALENCIIDAE, APHANIIDAE and PROCATOPODIDAE | access-date = 8 November 2019 | publisher = Christopher Scharpf and Kenneth J. Lazara}}</ref> The green swordtail was described from Heller's type by Johann Jakob Heckel in 1848 with the type locality given as Orizaba, Mexico.<ref name = Coffs>{{Cof record|spid=13936|title=''Xiphophorus helleri''|access-date=8 November 2019}}</ref> It is the type species of the genus ''Xiphophorus''.<ref name = CofFG>{{Cof record|genid=2001|title=''Xiphophorus''|access-date=8 November 2019}}</ref> ==Aquarium fish== One of the most popular tropical aquarium fish, the green swordtail has been bred into various hybrid forms for the aquarium hobby due to its hardiness and suitability for community tanks.<ref>{{cite web |last1=Edmond |first1=Adam |title=Swordtail Fish Care Guide |url=https://www.theaquariumguide.com/articles/swordtail-fish-care-guide |website=The Aquarium Guide |date=11 March 2017 |access-date=23 June 2021}}</ref>
''X. hellerii'' is a common laboratory animal and has been used as a model organism in studies involving female mate preference<ref>{{Cite journal|last=Basolo|first=Alexandra L.|date=1990-08-01|title=Female preference for male sword length in the green swordtail, Xiphophorus helleri (Pisces: Poeciliidae)|journal=Animal Behaviour|volume=40|issue=2|pages=332–338|doi=10.1016/S0003-3472(05)80928-5|s2cid=54382421}}</ref> and male conflict.<ref>{{Cite journal|last1=Beaugrand|first1=Jacques|last2=Goulet|first2=Claude|last3=Payette|first3=Daniel|date=1991-03-01|title=Outcome of dyadic conflict in male green swordtail fish, Xiphophorus helleri: Effects of body size and prior dominance|url=http://cogprints.org/1966/3/beaugrand-goulet-payette-1991.pdf|journal=Animal Behaviour|volume=41|issue=3|pages=417–424|doi=10.1016/S0003-3472(05)80842-5|s2cid=16699266}}</ref>
It is often designated ''X. helleri'' (with one 'i'), but authorities consider this an orthographic error and the spelling with two 'i's to be the valid specific epithet. It is named after Karl Bartholomaeus Heller, who collected the type specimen. Due to interbreeding with the southern platyfish or 'platy', most swordtails in aquariums are hybrids to some degree.
The males' elongated caudal fins have been found to significantly affect their chances at mating. The presence of a well-endowed male spurs the maturity of females, while it inhibits the maturity of juvenile males in the vicinity of the well-endowed male.<ref name="YNscienceattraction">{{cite news|date=2007-02-13|title=In the science of sexual attraction, size matters|work=Yahoo! Science News|publisher=Yahoo! Inc|url=https://news.yahoo.com/s/nm/20070214/sc_nm/science_size_dc_1|access-date=2007-02-14|archive-url=https://web.archive.org/web/20070216004617/http://news.yahoo.com/s/nm/20070214/sc_nm/science_size_dc_1|archive-date=2007-02-16}}</ref><ref name="LiveScience1">{{cite news|last=Choi|first=Charles Q.|date=2007-02-13|title=Male Bling Makes Female Fish Mature Faster|work=LiveScience Animaldomain|publisher=Imaginova Corp.|url=http://www.livescience.com/animalworld/070213_sight_sex.html|access-date=2007-02-14}}</ref><ref name="YNLiveScience1">{{cite news|last=Choi|first=Charles Q.|date=2007-02-13|title=Male Bling Makes Female Fish Mature Faster|work=Yahoo! Science News|publisher=Yahoo!, Inc.|url=https://news.yahoo.com/s/livescience/20070214/sc_livescience/maleblingmakesfemalefishmaturefaster}}</ref>
==Breeding== Swordtails are some of the easiest fish for amateur aquarist to breed, if the conditions of the tank are appropriate and it contains both males and females reproduction will occur without intervention. Often all female groups which have come from a mixed gender tank will be pregnant on arrival, creating a breeding population when the fry sexually mature at around three months of age.<ref>{{Cite web|date=2013-11-19|title=Swordtail Fish Breed Information and Pictures|url=https://www.petguide.com/breeds/fish/swordtail/|access-date=2020-09-12|website=PetGuide}}</ref> Later stages of pregnancy can be seen without much difficulty as a dark gravid spot will develop near the anal fin. Males can be distinguished from females by the presence of a Gonopodium, a modified anal fin used to impregnate the female during breeding. A ratio of one male to three or four females is recommended to ensure that individual females will not be overly harassed to breed.<ref>{{Cite web|date=2017-03-11|title=Swordtail Fish Care Guide|url=https://www.theaquariumguide.com/articles/swordtail-fish-care-guide|access-date=2020-09-12|website=The Aquarium Guide|language=en-US}}</ref>
Plants and other structure in the aquarium will offer fry a place to hide after birth. This is important as newborn fry will be eaten by other aquarium inhabitants if they cannot find shelter.
==Gallery== <gallery> File:Swordtail cultivar.JPG|Cultivated form of ''X. hellerii'' File:Xiphophorus hellerii fry 01.jpg| Fry File:Xiphophorus hellerii red wagtail female 01.jpg File:Xiphophorus helleri Annanasschwerttaeger Maennchen.JPG </gallery>
==References== {{Reflist|30em}}
==External links== * {{Commons category-inline|Xiphophorus hellerii|''Xiphophorus hellerii''}} * {{Wikispecies-inline|Xiphophorus hellerii|''Xiphophorus hellerii''}} * {{FishBase_species|genus=Xiphophorus|species=hellerii|year=2004|month=October}} * {{ITIS |taxon=Xiphophorus hellerii |id=647013 |access-date=9 December 2004}} *[http://www.fishesninverts.com/fish-profiles/xiphophorus-hellerii/ Xiphophorus hellerii profile with photographs of various strains on Fishes N Inverts] {{Webarchive|url=https://web.archive.org/web/20120815052008/http://www.fishesninverts.com/fish-profiles/xiphophorus-hellerii/ |date=2012-08-15 }} *[http://www.fishesninverts.com/gallery/Mohanasundaram/Xiphophorus+hellerii/ Xiphophorus hellerii gallery with photographs of various strains on Fishes N Inverts] {{Webarchive|url=https://web.archive.org/web/20201125185830/http://www.fishesninverts.com/gallery/Mohanasundaram/Xiphophorus+hellerii/ |date=2020-11-25 }} {{Taxonbar|from=Q272188}}
Category:Xiphophorus Category:Live-bearing fish Category:Ovoviviparous fish Category:Fish described in 1848 Category:Freshwater fish of Mexico Category:Taxa named by Johann Jakob Heckel Category:Freshwater fish of Central America