Southern Platyfish, Xiphophorus maculatus
Southern Platyfish, Xiphophorus maculatus. Fish caught from a small creek in the Jemez Mountains, New Mexico, July 2019. Length: 9.5 cm (3.7 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Southern Platyfish, Xiphophorus maculatus, is a member of the Livebearer or Poeciliidae Family, that is also known as the Moonfish and the Platy and in Mexico as espada sureña. Globally, there are twenty-eight species in the genus Xiphophorus, the majority of which are found in Mexican waters, all within the freshwater drainage systems that drain into both the Atlantic and the Pacific Oceans. The Southern Platyfish is closely related to the Green Swordtail, Xiphophorus helleri, with which it cross breeds.
The Southern Platyfish is moderate in size and is sturdy with an elongated body that is about twice as long as it is deep. They vary in color but are typically an olive-brown with black spots or blotches or a dark black and brown with a blue spot above the anal fin. They are sexually dimorphic with females being larger in size having a maximum length of 6 cm (2.4 inches) versus 4 cm (1.6 inches) for males. The males have a more pointed caudal fin than the females and their anal fin has evolved into a gonopodium absent, that fall short of the caudal fin base, in the females. The females caudal fin is fan shaped. Their anal fin has third ray with a strong hook; their dorsal fin has 8 to 10 rays.
The Southern Platyfish is non-migratory and found in slow-moving waters of canals, ditches, and warm springs in waters that have temperature ranges between 18oC (64oF) and 25oC (77oF). They are omnivores that consume plant materials and annelid worms, small crustaceans, and insects. They are preyed upon by various pelagic and surface predatory fish as well as numerous seabirds, including herons. Reproduction is ovoviviparous with maturity reached within 3 months and gestation periods of 24 to 30 days with 20 to 80 young born alive.
The Southern Platyfish lack the distinctive lateral line found in the majority of Xiphophorus species and the sword-shaped tail found in swordtails.
The Southern Platyfish is a resident of Mexico’s freshwater systems of the Atlantic Slope from the Rio Nautla basin south and eastwards to Campeche, Chiapas, Oaxaca, Quintana Roo, Tabasco, and Veracruz.
From a conservation perspective the Southern Platyfish is currently considered to be Data Deficient. With very limited documentation about their biology and behavioral patterns. They are widely utilized by the aquarium trade and easily bred in captivity. Breeders have developed a multitude of color varieties. Where introduced, they reproduce rapidly, and have been implicated in the decline of native fishes.