''Xiphophorus cortezi'', the delicate swordtail, is a species of

poeciliid The Poeciliidae are a family of freshwater 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 family was t ...

fish from Mexico. Named after the Spanish ''

conquistador Conquistadors (, ) or conquistadores (, ; meaning 'conquerors') were the explorer-soldiers of the Spanish and Portuguese Empires of the 15th and 16th centuries. During the Age of Discovery, conquistadors sailed beyond Europe to the Americas, O ...

Hernán Cortés Hernán Cortés de Monroy y Pizarro Altamirano, 1st Marquess of the Valley of Oaxaca (; ; 1485 – December 2, 1547) was a Spanish ''conquistador'' who led an expedition that caused the fall of the Aztec Empire and brought large portions of w ...

, ''Xiphophorus cortezi'' was originally described in 1960 by

Donn Eric Rosen Donn Eric Rosen (1929-1986) was a member of the staff of the American Museum of Natural History. He was a Distinguished Fellow of the American Society of Ichthyologists and Herpetologists. Family Born to immigrants Irwin Rosen (b. 1885) and Ani ...

as a

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of '' X. montezumae''. It was well known in literature prior to the formal

scientific description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

. The smaller males of ''X. cortezi'' are similar to the larger males of '' X. nigrensis'', pointing to a close evolutionary relationship with this species too. Adult size is variable and averages about 30 mm in

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

. The color of the male, especially the midlateral stripe, depends on the excitement of the fish and background shade of its environment. Some specimens kept in the laboratory for years have shown such silvery coloring that black markings became absent. Different patterns of black spots on the tail exist. ''Xiphophorus cortezi'' is found in the upper

Rio Panuco Rio or Río is the Portuguese, Spanish, Italian, and Maltese word for "river". When spoken on its own, the word often means Rio de Janeiro, a major city in Brazil. Rio or Río may also refer to: Geography Brazil * Rio de Janeiro * Rio do Sul, a ...

system in northeastern Mexico. Two congeners, '' X. pygmaeus'' and '' X. variatus'', are found in the same section of Rio Axtla, a tributary of Rio Panuco, but the species are nearly always separated into different

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

References

{{Taxonbar, from=Q3764497 pygmaeus Freshwater fish of Mexico Endemic fish of Mexico Taxa named by Donn Eric Rosen Fish described in 1960