Xiphophorus туқымдасы: Плати және қылышша балықтар туралы ақпарат

Genus of fishes
the fish genus

Xiphophorus is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many Xiphophorus species are all known as platyfish (or platies) and swordtails. Platyfish formerly were classified in another genus, Platypoecilia, which is now obsolete. The type species is X. hellerii, the green swordtail. Like most other new world Poeciliids, platies and swordtails are live bearers that use internal fertilization and give birth to live young instead of laying eggs like the bulk of the world's fishes. The name Xiphophorus derives from the Greek words ξίφος (dagger) and φόρος (bearer), referring to the gonopodium on the males. All are relatively small fishes, which reach a maximum length of depending on the exact species involved. Three species and their hybrids are common in the aquarium trade: the green swordtail (X. hellerii), the southern platyfish (X. maculatus) and the variable platyfish (X. variatus). These three are the only species that have large native ranges. All other species of Xiphophorus are highly localized and mostly endemic to Mexico. Only three of the localized species, the Chiapas swordtail (X. alvarezi), X. mayae and X. signum, range outside Mexico and the last two are the only Xiphophorus species not found in Mexico at all.

Xiphophorus species are regularly used in genetic studies, and scientists have developed many interspecific hybrids, especially in melanoma research since the 1920s. The Xiphophorus Genetic stock center, founded by Myron Gordon in 1939, is an important source of these fish for research.

There are currently 28 recognized species in this genus, according to FishBase. Two of these species, X. clemenciae and X. monticolus, are likely the result of natural hybrid speciation (ancestors of both are a platy species and a swordtail species). Otherwise hybridization in the wild is uncommon in this genus and only known from three or four locations, despite the fact that many sites have two sympatric species. Although traditionally divided into swordtails and platies, this separation is not supported by phylogenetic studies, which have shown that the swordtails are paraphyletic compared with the platies. These studies suggest that the genus can be divided into three monophyletic groups: the northern swordtails (of the Pánuco River basin, marked with a star* in the list), southern swordtails (southern Mexico to Honduras) and the platies. The pigment melanin in the fish epidermis partially protected against the induction of pyrimidine dimers.