marbled swordtail

{{Short description|Species of fish}}

{{Speciesbox

| image =

| status = EW

| status_system = IUCN3.1

| status_ref = {{cite iucn |author=Almada-Villela, P. |author2=Contreras-Balderas, S. |author3=Hendrickson, D. |date=2019 |title=Xiphophorus meyeri |volume=2019 |page=e.T23158A2784905 |doi=10.2305/IUCN.UK.2019-2.RLTS.T23158A2784905.en |access-date=15 November 2021}}

| taxon = Xiphophorus meyeri

| authority = Schartl & Schröder, 1987

| synonyms = Xiphophorus marmoratus Obregón-Barboza & Contreras-Balderas, 1988

| synonyms_ref = {{cite journal|title=A new species of the genus Xiphophorus Heckel 1848, endemic to northern Coahuila, Mexico (Pisces: Poeciliidae)|first2 = Johannes Horst |last2 = Schröder | first1= Manfred | last1 = Schartl | journal = Senckenbergiana Biologica| year= 1987|volume= 68|issue= 4/6| pages=311–321| url = https://opus.bibliothek.uni-wuerzburg.de/files/6936/Schartl_6936.pdf}}{{cite web|url=https://mexfish.info/species.php?id=258|title=Xiphophorus marmoratus Obregón-Barboza & Contreras-Balderas, 1988|website=The Freshwater Fishes of Mexico|date=29 November 2012|editor=Juan Miguel Artigas Azas|access-date=3 July 2023}}

}}

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.{{FishBase|genus=Xiphophorus|species=meyeri|year=2018|month=September}}{{cite book | editor1=Ceballos, G. | editor2=E.D. Pardo | editor3=L.M Estévez | editor4=H.E. Pérez | year=2016 | title=Los peces dulceacuícolas de México en peligro de extinción | page=283 | publisher=Fondo de Cultura Económic | isbn=978-607-16-4087-1 }} It was restricted to springs, connected creeks and pools in waters with a pH slightly above neutral and temperatures of {{cvt|16-26|C|F}}, with captive studies indicating that the optimum temperature is around {{cvt|24|C|F}}.{{cite web| title=Northern Platyfish Husbandry Manual | url=https://oevvoe.org/xnp-project-expanding | publisher=Österreichischen Verband für Vivaristik und Ökologie | accessdate=17 January 2022 }}

The marbled swordtail is considered extinct in the wild by the IUCN with the last wild record in 1997, meaning that it survives only in captivity. Captive populations are maintained at the Xiphophorus Genetic Stock Center, Texas State University, United States, and by XNP conservation project members, which include public aquariums, universities and private aquarists in several European countries and the United States.{{cite web| title=XNP project annual report – year 3 | url=https://oevvoe.org/xnp-project-annual-report-%E2%80%93-year-3 | publisher=Österreichischen Verband für Vivaristik und Ökologie | accessdate=17 January 2022 }}{{cite web| title=XNP project expanding | url=https://oevvoe.org/xnp-project-expanding | publisher=Österreichischen Verband für Vivaristik und Ökologie | accessdate=17 January 2022 }}{{cite web| title=Transfer of fish from Würzburg University to Ostrava ZOO | url=https://oevvoe.org/transfer-fish-w%C3%BCrzburg-university-ostrava-zoo | publisher=Österreichischen Verband für Vivaristik und Ökologie | accessdate=17 January 2022 }} The marbled swordtail shares the title as northernmost naturally distributed Xiphophorus with the closely related Monterrey platyfish (X. couchianus) and northern platyfish (X. gordoni).{{cite journal | author1=Kang, J.H. | author2=M. Schartl | author3=R.B. Walter | author4=A. Meyer | year=2013 | title=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 | journal=BMC Evolutionary Biology | volume=13 | issue=25 | pages=25 | doi=10.1186/1471-2148-13-25 | pmid=23360326 | pmc=3585855 | doi-access=free | bibcode=2013BMCEE..13...25K }} The specific name of this species honours the German ichthyologist Manfred K. Meyer.{{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 | accessdate = 9 November 2019 | publisher = Christopher Scharpf and Kenneth J. Lazara}}