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.^[4][5] 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).^[1][5][6]

Marbled swordtail
Conservation status
Extinct in the Wild  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Cyprinodontiformes
Family:	Poeciliidae
Genus:	Xiphophorus
Species:	X. meyeri
Binomial name
Xiphophorus meyeri Schartl & Schröder, 1987
Synonyms[2][3]
Xiphophorus marmoratus Obregón-Barboza & Contreras-Balderas, 1988

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.^[1] Captive populations are maintained at the Xiphophorus Genetic Stock Center, Texas State University, United States,^[1] and by XNP conservation project members, which include public aquariums, universities and private aquarists in several European countries and the United States.^[7][8][9] The marbled swordtail shares the title as northernmost naturally distributed Xiphophorus with the closely related Monterrey platyfish (X. couchianus) and northern platyfish (X. gordoni).^[5][10] The specific name of this species honours the German ichthyologist Manfred K. Meyer.^[11]