Xiphophorus pygmaeus (Hubbs and Gordon 1943)

Etymology:

Xiphophorus: Greek, xiphos = sword + Greek, pherein = to carry

pygmaeus: due to it diminutive size

First description:

C.L. Hubbs and M Gordon (1943)

‘Studies of cyprindonont fishes. 19. Xiphophorus pygmaeus, new species from Mexico’ Copeia 1943(1):31-3

Synonyms:

Xiphophorus pygmaeus pygmaeus Rosen 1960

Common name:

Slender Pygmy Swordtail

History:

Collected by Myron Gordon and Salvador Coronado, April 14th 1939

Group:

Xiphophorus pygmeaus is one of the nine northern swordtails and belongs to the Pygmaeus clade consisting of consisting of X. pygmaeus, X. nigrensis and X. multilineatus.

Type locality:

 Río Axtla of Río Panuco system, at Axtla, San Luis Potosí, Mexico.

Distribution:

Rio Axtla system, Rio Panuco drainage, SLP: abundant in Rio Huichihuayan, less common in lower 9 km of Rio Tancuilin and upper 5 km of Rio Axtla.

Populations:

Rio Axtla

Rio Huichihuayan

Habitat:

X. pygmaeus is most commonly found in rivers or pools which have dense vegetation with overhanging banks.

Size:

Males 25mm – 30mm females 40mm

Distinguishing characteristics:

A very small slender form of swordtail with a very short sword. There are two male size variations. Ranging from 25mm to 30mm standard length.

Colour/Pattern Variability:

Males

A single bold lateral line runs from the eye. The colouration below the lateral line is white with a bluish tint, a pale blue stripe sits above the lateral line and the rest of the back is brown with the edges of the scales being darker giving a net like appearance.

A short sword of generally less than 2mm but never more than 8mm, the sword does not have black edging.

The dorsal fin in this species is short, both in height and base length, the fin is clear with a faint black edge and faint black band one third of the way up the fin.

As with all of the Pygmaeus clade a yellow form can be found. This Yellow form has been fixed within the hobby and can easily be acquired.

Females

A single bold lateral line runs from the eye. The colouration below the lateral line is white with a bluish tint, a pale blue stripe sits above the lateral line and the rest of the back is brown with the edges of the scales being darker giving a net like appearance. The females show a gravid spot

The dorsal fin is clear with an extremely faint black edge and an extremely faint black band one third of the way up the fin.

Behaviour:

A shy species that likes plenty of plant cover to feel secure.

Husbandry:

A small aquarium well planted with an air driven sponge filter or no filter but regular water changes. Plenty of Java moss should be on the bottom of the aquarium

Breeding Notes:

Broods are born on a monthly cycle and number about 5 – 10, fry are and normally left alone by the parents.

References:

Middle-American poeciliid fishes of the genus Xiphophorus.

Bull. Fla. St. Mus. Biol. Sci 5 (4): p 57-242.                Donn E. Rosen

American Museum Novitates Number 2975, June 27, 1990.

Monophyly and Geography of the Rio P’anuco Basin Swordtails (Genus Xiphophorus) with

Descriptions of Four New Species                             Rauchenberger, Kallman & Morizot

Platies and swordtails                                              Derek and Pat Lambert

Fishbase

Wikipedia

Photograph courtesy of Dave Macallister

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