The yellow swordtail (''Xiphophorus clemenciae'') is a species of freshwater fish in the family Poeciliidae. It is endemic to the upper

Coatzacoalcos River The Coatzacoalcos is a large river that feeds mainly the south part of the state of Veracruz; it originates in the Sierra de Niltepec and crosses the state of Oaxaca in the region of the Isthmus of Tehuantepec, flowing for toward the Gulf of M ...

basin in southern Mexico. It is typically found in brooks and streams with slow current; it is less frequent in areas with strong current. The yellow swordtail is considered a threatened species by Mexican authorities. It reaches up to 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 ...

. Unusually, the yellow swordtail appears to be the result of hybrid speciation, and its ancestors a platy species and a swordtail species. The southern mountain swordtail (''X. monticolus''), which is found further south in the Coatzacoalcos River basin than the yellow swordtail, is the result of a similar event. The fish is named in honor of Álvarez’ wife Clemencia, without whose help and advice made it possible for him to devote himself to the pursuit of his scientific research.

Sources

Xiphophorus Endemic fish of Mexico Freshwater fish of Mexico Taxa named by Jose Álvarez del Villar Fish described in 1959 Taxonomy articles created by Polbot {{Cyprinodontiformes-stub