Xiphophorus birchmanni

Xiphophorus birchmanni Lechner & Radda, 1987

Affiliation: northern swordtail

IUCN status: least concern

Distribution: several rivers in Río Pánuco basin (drainages of Río Candelaria, Río Atlapexco, Río Calabozo, Río San Pedro etc.) and Río Tuxpan basin (incl. Río Vinazco); Hidalgo and Veracruz, Mexico

Known locations (existing/former): several

Type locality: Río Talol, headwater of Río San Pedro, Río Tempoal, Río Pánuco basin, Hidalgo, Mexico
(27.4.1987, P. Lechner & H. Birchmann)

Habitat description:  Inhabits fast-flowing waters, such as streams and rivers, with substrates ranging from sand to gravel and boulders.

Biotope reports:

• none yet

Description: Medium-sized swordtail with robust body; males reaching up to 6 cm and females up to 7 cm in total length. The species exhibits marked sexual dimorphism. Males display a metallic blue to violet sheen with prominent dark scale edges, creating a distinct reticulated pattern. They also have dark pattern consisting of oval vertical bars along the flanks. The dorsal fin is large, yellowish with dense black spotting, and the caudal fin is bright yellow. Males lack an extended caudal filament, sword is absent or < 1 mm long. Older males develop a distinct head bump. Females are more subdued in coloration, with a greyish-olive base color and a distinct dark lateral stripe running from the snout to the caudal peduncle.

Variability: Small variability in hues or black patterns; some individuals have deep black spots on caudal peduncle or caudal fin.

XWG status: not yet actively managed

Represented in aquaria: Rarely kept; occasionally maintained by specialized breeders and research institutions.

Known issues: Prefers cooler temperatures and pristine water.

Known collections or populations:

• Río Atlapexco, Hidalgo, Mexico
• Río Tuntitlán, Hidalgo, Mexico
• Río Calnalí, Hidalgo, Mexico

Remarks: This species is known to hybridize with X. malinche in parts of its natural habitat. X. malinche lives upstream, X. birchmanni downstream. Hybrid zones where both species overlap are subject to research.

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