Xiphophorus xiphidium

Xiphophorus xiphidium (Gordon, 1932)

Affiliation: southern platyfish

IUCN status: least concern (see Remarks)

Distribution: endemic to Río Soto la Marina drainage in Tamaulipas, Mexico

Known locations (existing/former): many

Habitat description: Inhabits mostly quiet zones of water courses with slow to medium current, including large rivers and small streams, ditches, spring areas, marshes. Water clear to slightly turbid. Prefers environments with abundant aquatic vegetation and substrates ranging from mud to gravel.

Biotope reports:

• none yet

Description: Males typically reaching up to 4 cm and females up to 5 cm in total length. This species is characterized by rather high, laterally compressed body. Males have a relatively short sword-like extension on the lower margin of the caudal fin. Individuals exhibit variability in colouration and patterning; base colouration ranges from olive to brownish tones, with patterns including bright blue hues, vertical stripes, large side patches or black spots (colour accents can change depending on mood). Sexual dimorphism is pronounced, with males displaying the caudal extension and a more slender body, while females are larger and more robust. Dark spot on the abdomen present in both sexes.

Variability: Some populatios differ in their characteristic marking at the base of the caudal fin, appearing as a single spot, a pair of spots, or a crescent-shaped mark.

XWG status: not yet actively managed

Represented in aquaria: moderately

Known issues:

• Susceptible to common aquarium diseases, including parasitic infestations such as Ichthyophthirius multifiliis (“ich”) and bacterial infections (Mycobacterium spp.). Generally hardy under proper care conditions.
• There may be a significant male predominance in the offspring.

Known collections or populations:

• Río Soto La Marina, Tamaulipas, Mexico
• Río Purificación, Tamaulipas, Mexico (also spelled as Purification)
• Santa Engracia, Tamaulipas, Mexico
• Río Corona, Tamaulipas, Mexico
• “twin-spot”
• “half-moon”

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

Remarks:

• Although the species is classified as “Least Concern” due to its “relatively wide distribution” and the fact that “there is no evidence of major population decline” [IUCN], it is in significant decline in its native range (Rejlková, unpublished). Many of the originally documented localities are virtually devoid of small fish due to the presence of the non-native largemouth bass (Micropterus salmoides), a voracious predator, and the increasing pollution of streams. In addition, hybridisation with X. variatus may occur.