Xiphophorus alvarezi

Xiphophorus alvarezi   Rosen, 1960

Affiliation: southern swordtail

IUCN status: least concern

Distribution: southern Mexico (Chiapas: Río Chacamax, Río Palenque, Río Dolores; Tabasco: Río Usumacinta; Campeche: Río Candelaria) and Guatemala (Alta Verapaz, Huehuetenango, Quiché)

Known locations (existing/former): many

Threats in the wild: Deforestation, water pollution, and habitat fragmentation due to agricultural expansion and infrastructure development. Hybridization with introduced Xiphophorus hellerii poses a potential genetic threat in some areas.

Habitat description: larger and smaller streams with clear, cool, well-oxygenated water; moderate to fast current; rocky pools or mixed substrate, often interspersed with aquatic vegetation or submerged root systems; shaded environments with dense riparian cover are typical

Biotope reports:

• none yet

Description: A striking livebearer, Xiphophorus alvarezi is notable for its bright coloration and elongated sword in mature males. Males can reach up to 8 cm in total length, with females slightly larger at 9–10 cm. Males exhibit a vibrant base coloration ranging from greenish-gold to reddish-orange, with a prominent iridescent blue-green sheen and distinct vertical barring along the flanks. The caudal sword is long and vivid, typically orange with a black edge. The dorsal fin is large and often brightly marked. Females are more subdued in coloration, with a robust body and faint patterning.

Variability: Wild populations may show variation in sword length, body coloration, and fin patterning, especially in males. Environmental conditions and population isolation may influence phenotypic diversity.

XWG status: not yet actively managed

Represented in aquaria: Occasionally represented in the hobby, particularly among livebearer enthusiasts and breeders with interest in wild-type swordtails. Often maintained in species-dedicated setups due to specific environmental needs.

Known issues: Sensitive to poor water quality and abrupt temperature changes; requires well-filtered, oxygen-rich water.

Known collections or populations: (incomplete)

• Palenque, Chiapas, Mexico
• Río Dolores, Guatemala
• Río Candelaria Yalicar, Guatemala
• Alta Verapaz, Guatemala (? both rivers systems above are in Alta Verpaz department)

(If you have more information, please contact us at info@xipho.org – thanks!)