The Monterrey platyfish (''Xiphophorus couchianus'') is a species of

freshwater fish Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes, ponds and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many wa ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Poecilidae Poeciliidae are a family of freshwater ray-finned fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the fami ...

. A live-bearer, it was native to a very small section of the San Juan River system (itself part of the

Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...

basin) in the vicinity of the city of

Monterrey Monterrey (, , abbreviated as MtY) is the capital and largest city of the northeastern Mexican state of Nuevo León. It is the ninth-largest city and the second largest metropolitan area, after Greater Mexico City. Located at the foothills of th ...

, Mexico. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

refers to the

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...

soldier and naturalist

Darius N. Couch Darius Nash Couch (July 23, 1822 – February 12, 1897) was an American soldier, businessman, and naturalist. He served as a career United States Army, U.S. Army officer during the Mexican–American War, the Second Seminole War, and as a general ...

(1822–1897) who collected the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

on a self-financed expedition to Mexico.

Appearance

The Monterrey platyfish is a dull-colored fish, appearing not unlike a female

guppy The Greater Underwater Propulsion Power Program (GUPPY) was initiated by the United States Navy after World War II to improve the submerged speed, maneuverability, and endurance of its submarines. (The "Y" in the acronym was added for pronouncea ...

. Another form, sometimes referred to as ''X.

aff. ''Species affinis'' (commonly abbreviated to: ''sp.'', ''aff.'', or ''affin.'') is taxonomic terminology in zoology and botany. In open nomenclature it indicates that available material or evidence suggests that the proposed species is related t ...

couchianus'', was discovered in

Apodaca Apodaca () is a city and its surrounding municipality that is part of Monterrey Metropolitan area. It lies in the northeastern part of the Monterrey Metropolitan Area. It is known for becoming recently a heavy industrialized city. As of 2019, ...

, central Monterrey, in 1983. It has large black blotching, unlike the typical, unspotted form from the Huasteca Canyon. Whether the Apodaca form represents a separate species is presently unclear.

Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

is moderate, the male Monterrey platyfish growing to a maximum overall length of and the female .

Conservation

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

lists the Monterrey platyfish as "

extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as only consisting of living members kept in captivity or as a naturalized population outside its historic range ...

". Although once found more widely in the region of Monterrey, populations have been lost to

urban sprawl Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city". Urban sprawl has been described as the unrestricted ...

, with water habitats either drying up (due to land reclamation and water extraction) or being heavily polluted.

Introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived ther ...

is another threat. "Safety populations" are maintained in captivity by the Centro de Resguardo para Peces en Peligro de Extinción at

Universidad Autónoma de Nuevo León Universidad (Spanish for "university") may refer to: Places * Universidad, San Juan, Puerto Rico * Universidad (Madrid) Football clubs * Universidad SC, a Guatemalan football club that represents the Universidad de San Carlos de Guatemala ...

, Mexico (maintaining both the typical form and ''X. aff. couchianus''), ''Xiphophorus'' Genetic Stock Center at

Texas State University Texas State University (TXST) is a public university, public research university with its main campus in San Marcos, Texas, United States, and another campus in Round Rock, Texas, Round Rock. Since its establishment in 1899, the university has ...

, United States (maintaining typical form), via the American Livebearer Association that mostly includes private aquarists in the United States (maintaining typical form), and by XNP conservation project members, which include public aquariums, universities and private aquarists in several European countries and the United States (maintaining typical form). The species has proven harder to maintain in captivity than most ''Xiphophorus'' species. The Monterrey platyfish shares the title as northernmost naturally distributed ''Xiphophorus'' with the closely related

northern platyfish The northern platyfish (''Xiphophorus gordoni'') 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 ...

(''X. gordoni'') and

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. It was restricted to spri ...

(''X. meyeri''), which are two species that also are restricted to northeastern Mexico and seriously threatened.

References

* {{Taxonbar, from=Q2170401 Freshwater fish of Mexico Xiphophorus Fish described in 1859 Taxa named by Charles Frédéric Girard IUCN Red List extinct in the wild species