XFins

X. montezumaare large, beautiful swordtails. They are particularly remarkable because they have the longest caudal fin. F1 lyretail hybrids also have impressive caudal fins. X. montezuma express modifier genes that favorably affect the appearance of the dorsal fin. These modifiers specifically enhance the length of the anterior rays of the dorsal fin which are short in many strains of hifin swordtails.

Many Xiphophorus hybrids have been developed over the years by researchers to study specific genetic traits and as model systems to study cancer, specifically melanoma. Some of the many hybrids can be seen on the Images Page of the Xiphophorus.org website. Hobbyists and commercial breeders have also utilized interspecies hybridization to develop new varieties of swordtails and platies. X. maculatus and X. variatus are the sources of many of the genes that have produced the colorful varieties of livebearers that are available today. The hi-fin and lyretail genes, first discovered in X. helleri-derived swordtails, have been transferred to several species of Xiphophorus, including X. variatus and X. maculatus.

X. birchmanni are majestic fish. The full body and the manner in which the male extends its large, beautiful dorsal fin makes it the Xiphophorus version of the sailfin molly. F1 hifin hybrids often have long, flowing dorsal fins, primarily because the hifin continues to grow as the fish matures and ages. Although X. birchmanni do not have swordtails many of the hybrids do have short swords. Note the characteristic "birchmanni bump" on the heads of many of the hybrids.

X. malinche are attractive fish and have a short swordtail. Hybrids between X. malinche and X. birchmanni are frequently found in the wild. F1 hifin hybrids are also attractive, but I have not seen any evidence that X. malinche contain modifier genes that might improve hifin appearance. I have crossed a F1 hifin hybrid back to a wild X. malinche, but the hifin of the one F2 obtained was of poor quality (see below).

The X. malinche hybrids shown above were born to a brick colored swordtail female. The young hybrid shown on the right was born to a X. malinche female using a red wag swordtail father. This cross produced a more bronze colored body. Note how the dorsal fin has grown as the fish matures.

This X. birchmanni F1 hybrid, born to a birchmanni female, has a nice lyretail considering that X. birchmanni do not have swordtails. The dorsal fin contains some of the spotted markings found in the wild fish.