Le schede dei pesci

XIPHOPHORUS NEZAHUALCOYOTL (Rauchenberger, Kallmann and Morizot,1990)

by Paul McFarlane
From the Monthly Bulletin of the Hamilton and District Aquarium Society, February 2002 Aquarticles
Taken from the website : http://www.aquarticles.com

Xiphophorus nezahualcoyotl is sometimes called the "Northern Mountain Swordtail". Originally imported in 1964 into Germany, it was first named "X. montezumae Hamburg 64". In 1990 it was described under the current name by Rauchenberger, Kallmann and Morizot.

The fish is named after a famous philosopher king of the Texcocan people in Mexico, Nezahualcoyotl, (1403-1473), whose name means "hungry fox". After the death of his father, the king, in a war, he was forced to flee his country. But some years later, after many adventures, he returned to overthrow the conqueror and reclaim the throne. His reign was apparently one that encouraged the arts and he died believing he had founded a dynasty. He was unaware that 47 years after his death, the Spaniards under Cortez would destroy his civilization. It seems fitting that a Mexican swordtail should be named after such a man.



Pics of a male and a female of X.nezahualcoyotl

The area in which X. nezahualcoyotl is found is the Rio Tamasi drainage in the Mexican state of San Luis Potosi. In its natural state the fish is found mostly in fast-flowing waters and would probably appreciate power filtration in the aquarium.

This is the kind of fish that is rarely or never found offered for sale in a pet shop. The only way one is likely to obtain them is by belonging to a club or attending one of the club auctions that take place in various areas during the year. Sally and I got our original pair at an auction in Kitchener. The sellers were Brian and Susan Glazier and they later generously gave us the remaining three or four females from their stock.

The characteristic that I find most appealing about these fish is their size. They are decidedly a dwarf swordtail when compared to X. helleri which can grow to more than 15 cm TL. X. nezahualcoyotl females will grow to 6cm TL while males make only 5. This smaller size makes it quite possible to keep a pair or two very comfortably in a five or ten gallon tank and still be assured that with proper food and care they will attain full size.

My original pair were given a ten gallon tank to themselves and a large clump of Java Moss was added in anticipation of fry. The female did regularly (about once a month) produce babies but, whether she only threw a few or whether they ate some of them, there were only two or three each time. And then of course the male died.

By this time, a few of the fry had grown to about an inch in length. One of them looked "different" and very shortly after 'daddy's' death, he started to grow a swordtail and took his place. The sequence of events may have just been coincidence but on the other hand the male characteristics definitely developed immediately upon the demise of the adult male.

This fellow grew into a nice looking adult and was obviously functional since several females have now produced batches of fry. On top of this the number of fry has increased to a dozen or so per batch. Strangely enough though, he appears to be the only male in the tank although several of the inhabitants are the size at which he began to develop male traits.

At the time of writing this article, the original female, one of her older daughters and the male have been moved to another tank. I hope that they will continue to reproduce here and that at least one of the fish in the original tank will turn out to be a male.

If no more males turn up it may be necessary to play games with pH or temperature to see if the sex ratio can be made more equal. I would rather it were just a matter of removing males as they develop!

Note (D.Montanari) Next spring I’ll probably receive some specimens of X.nezahualcoytl “Ocampo”. I will let you know my experience with them

Picture of  X.nezahualcoyotl “Ocampo”. From the Xiphophorus Stock Center

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