The photo is of a male Redtail Black Variatus, a commercial (domestic, if you prefer) strain of Xiphophorus variatus. Like most commercial xiphophorines (swordtails, platies, and variatus), this fish is likely to be of hybrid origin, although the strain clearly is primarily X. variatus based on its fins and shape.
We acquired our first variatus and the ancestors of all most of our variatus strains in 2003 from a Florida fish farm when we bought breeders to restock after Hurricane Claudette. We ordered a box lot (about 300 fish) of Tuxedo Variatus with the intent of selecting the best to retain as breeders and selling the rest. After inspection, we set aside as breeders 6 males and about 40 females, selecting fish with yellow dorsals, red tails, and as much black on the body as possible. It only took a couple of generations of selection to yield fish like the male pictured from some relatively ugly Tuxedo Variatus.
From those early fish we have developed of range of colors (subject of future blogs) and hifin and plumetail fin types. We’ll soon add lyretail to our suite of fin types. This will be done by crossing male variatus to lyretail swordtails the backcrossing the resulting lyretail hybrids to the variatus. After about three generations of backcrossing we should have variatus type lyretails.