Xiphophorus cortezi (Rosen 1960)

Etymology:

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

cortezi after Hernando Cortes (1485 – 1547) the Spanish conquistador who conquered most of the Aztec Empire between 1519 – 1524.

First description:

Donn E. Rosen 1960:  Middle-American poeciliid fishes of the genus Xiphophorus.

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

Synonyms:

Xiphophorus montezumae cortezi Rosen, 1960

Common name:

Cortes Swordtail

Group:

Xiphophorus cortezi is one of nine northern swordtails and belongs to the Cortezi clade consisting of consisting of X. cortezi, X. birchmanni and X. malinche.

History:

Collected by Myron. Gordon, S. Coronad and H. F. Gandy on 14-15th April 1939.

Described by Donn E. Rosen 1960 as a subspecies of X. montezumae.

Type Locality:

Arroyo Matlapa at Comoca, 3·2 km north of Axtla in the Rio Panuco Basin, state of San Luis Potosi, Mexico.

Distribution:

Distributed south of the Rio Tampaon. This sp. has been collected in the Rio Choy, Moctezuma, Axtla, San Pedro and Candelaria.

Populations:

Rio Axtla, Vinasco

Habitat:

Streams with good current flowing over rocky bases. Hides under these rocks.

Derek Lambert reported that in the headwaters of the Rio Tancuilin at Rio Verdito (state of Queretaro) the sp. was found in water with a temperature of 13°C.

Size:

Male 50mm     Female 50mm.

Distinguishing characteristics:

All members of the cortezi clade have a single zigzag horizontal/lateral stripe which runs from the eye to the caudal peduncle.

Unlike X. birchmanni and X. malinche the males do not develop a hump on their foreheads.

Colour/Pattern Variability:

Males

The colouration of the body above the lateral line is a pale golden brown with the edges of the scales edged in dark brown to black to give a mesh appearance, below the lateral line the colour is much paler. A series of narrow vertical bars are often visible on their flanks and black melanistic blotches can form to any part of the body to form random patterns.

The dorsal fin is yellow with black spotting, however the dorsal fin does not have distinct mid dorsal rows of spots found with the other members of the clade

The caudal fin can vary from a pale yellow to bright yellow caudal fin without spotting and generally have a caudal blotch which can vary in shape. The sword is yellow with a black edge and is distinctly upturned. The sword although relatively short for a swordtail is the longest within the clade.

Females

The colouration of the body is similar in females to males. The flanks can but rarely show the same narrow vertical barring that appear on males but is not so distinct. Black melanistic blotches can form to any part of the body to form random patterns.

The fins are generally clear but may show a very pale yellow tint.

Behaviour:

This species shows typical behaviour for swordtails of the montezumae or cortezi groups. The males of these species are generally found darting among and underneath large rocks.

In the aquarium the cortezi sword is a peaceful fish and will happily live within a community set up.

Husbandry:

A Biotope would be a good setting for this fish with a strong current and a rocky substrate, will do well in a planted aquarium in a species set up or community set up. This species is tolerant of a wide temperature, the optimum temperature specified is 22º C.

Breeding Notes:

In Derek Lambert’s ‘platies and Swordtails’ Derek states that brood intervals vary, with warmer temperature coupled to longer periods of daylight shortening the gestation period.

Brood sizes also can also vary with the size and age of the female as well as available food supply, generally expect brood sizes to be around 30.

Remarks:

Two size morphs have been identified according to Lambert in ‘Platies & Swordtails’ which apparently only becomes evident when raising in a mass culture. Under these conditions the smaller morph is 10 mm smaller than the larger morph.

The three species of the cortezi clade were thought to be ‘allopatric’ this means that these species although closely related evolved in geographically separate areas and therefore could not hybridize.

There are reports that now show areas where the species overlap and in some cases have produced natural hybrid populations.

References: Donn E. Rosen: Middle-American poeciliid fishes of the genus Xiphophorus.Bull. Fla. St. Mus. Biol. Sci 5 (4): p 57-242.        

Rauchenberger, Kallman and Morizot:

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

Kallman and Kazianis: Zebrafish. Volume 3, Number 3, 2006 – The Genus Xiphophorus in Mexico and Central America                     

Derek and Pat Lambert: Platies and swordtails                                                                              

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