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A tank of black hifin swordtails.
A pair of albino marigold swordtails.
Sunset and black marigold swordtails. These fish are colorful, but more work needs to be done to increase the intensity of the red pigmentation.

























Two varieties of birchmanni hybrid swordtails. The fish on the left have yellow dorsals and bright orange swordtails. While not as colorful nor as full-bodied as X. birchmanni, the fish on the right more closely resembles its wild ancestor. Its body is also more reflective of light.
















This black-orange swordtail has a wide and relatively long hifin.








Veiltail Genetics

It has been suggested that two doses of the dominant lyretail gene (L) produces a veiltail (Glenn Takeshita TFH February 2008 and others). In my 4/20/13 posting I suggested that this may not be the case. I have subsequently used artificial insemination to breed a tuxedo veiltail male to a non-lyretail marigold swordtail female that has never been in a tank with black pigmented males. The only way that a baby from this cross could inherit the tuxedo pattern is from the tuxedo veiltail male. Of the 51 tuxedo babies that I examined, 27 (54%) are lyretails and 24 (46%) are non-lyretails. These percentages approximate the 50:50 ratio expected if the tuxedo veiltail male is heterozygous (Ll) for the lyretail gene. The birth of tuxedo non-lyretail babies therefore confirms that veiltails are not necessarily homozygous (LL) for the lyretail gene. Joanne Norton described the veiltail in "Enjoy Your Modern Swordtails and Platys" and her crossing of veiltails with non-lyretails also produced many non-lyretails. The most likely explanation is that one dose of L is sufficient to produce a lyretail and another gene or genes are necessary for all of the rays of the caudal fin to grow out and fill in the lyretail, resulting in a veiltail. Some of the lyretail babies are veiltails, but it is too early to tell what percentage are partial or full veiltails.


While it is presumed that the expression of the lyretail gene is required to produce a veiltail, this has not been formally proven. It may be possible to obtain a veiltail that does not express the lyretail gene. We cannot truly understand the genetics of the lyretail and veiltail traits until we know how these genes control the growth of the caudal fin rays at the molecular level.

The veiltail swordtail that was obtained from crossing a normal lyretail swordtail and X. birchmanni and from which all of my veiltails are derived. 













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There are several different styles of hifin, two of which are shown here. The dorsal rays of the hifin on the left have continued to grow and are extensively branched. This gives the hifin a long, flowing appearance, but also a lot of bulk. The dorsal rays of the hifin on the right also exhibit significant branching, but they have not grown as long. Consequently, the fish on the right is more likely to fully extend ("fan") its dorsal fin during mating and male dominance displays than the fish on the left. A judge might find the hifin on the left more desirable, but a well proportioned shorter hifin can also be very attractive.




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This birchmnni hybrid contains splotches of color resembling the koi phenotype. I have never had fish with the koi pattern before and this pattern may have resulted from a spontaneous mutation.

A Word About Names


When fish on this website are described, I usually refer to the hybrid nature of the fish in the name. For example, the "koi-like" fish shown above is described as a birchmanni hybrid. I include that information when I believe the ancestry of a fish may in part be responsible for its appearance. Commercially available swordtails and platies are all hybrids to some extent, but they are not referred to as hybrids, just as swordtails and platies. This "koi-like" fish could therefore be called a koi swordtail.