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

poeciliid 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 fam ...

fish from Mexico. Named after the Spanish ''

conquistador Conquistadors (, ) or conquistadores (; ; ) were Spanish Empire, Spanish and Portuguese Empire, Portuguese colonizers who explored, traded with and colonized parts of the Americas, Africa, Oceania and Asia during the Age of Discovery. Sailing ...

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

, ''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 Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

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

scientific description A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it diffe ...

. 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 fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

. 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 system in northeastern Mexico. Two congeners, '' X. pygmaeus'' and '' X. variatus'', are found in the same section of

Rio Axtla Rio or Río is the Portuguese and Spanish word for "river". The word also exists in Italian, but is largely obsolete and used in a poetical or literary context to mean "stream". Rio, RIO or Río may also refer to: Places United States * Rio, Flo ...

, 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 Resource (biology), resources an ...

References

{{Taxonbar, from=Q3764497

pygmaeus In Greek mythology, Pygmaeus () was the ancestor of the Pygmies, a tribe of diminutive men living at the southernmost shores of the great earth-encircling river Okeanos. He was the son of Dorus, son of King Epaphus of Egypt. Otherwise, the Pygmies ...

Freshwater fish of Mexico Endemic fish of Mexico Taxa named by Donn Eric Rosen Fish described in 1960