By Donna M. Recktenwalt
From time to time an unusual fish occurs in a killikeeper’s tanks. Among a normally colored batch of fry one will occur with a different color or pattern, or lacking dark pigment altogether, an albino. These “sports” are normal occurrences in nature, the result of minor mutations in the normal patterns of inheritance that determine color, fin shape, etc.
Occurring most often in long-established aquarium strains, such sports have resulted in a number of fish we take for granted in the hobby today – wagtail platys and swordtails, long-fin danios, balloon mollys, discus, veiltail angels, the many varieties of fancy guppies.
Most sports that occur in the wild, especially albinos, are weeded out by natural selection, but some sports thrive. Consider the yellow and red strains of Nothobranchius korthause, for example, which occur together in the same pools, or the yellow and blue forms of Fundulopanchax gardneri nigerianum, which also occur together in the wild.
Color variants are due to recessive mutations in the production of pigment, usually allowing the underlying colors to show through more clearly.
In albinos, perhaps the most commonly occurring sports, this results in a base color that is pale cream or yellow-white, against which the colored spotting patterns stand out clearly. The eyes are always pink, or red. Albinism is hardly uncommon in the killifish world. It has been observed – and some strains maintained for long periods of time – in a number of species. Because albinism is a recessive gene, it takes two parents with that gene to produce an albino. Any two albinos bred together will produce only albino offspring. An albino bred to a normal individual will produce normal colored fry that carry the recessive albino gene. When these offspring are bred together, they will (in theory) produce 25% albino, 25% normal (without the recessive albino gene), and 50% normal colored (with the albino gene).
There is no known way to determine whether an isolated normal colored individual carries the gene for albinism. However, by breeding a normal colored individual to an albino and then breeding the normal colored offspring back to their albino parent, you can quickly establish a “strain” of albinos.
“Fixing” other sport characteristics is also possible, but can require considerably more effort and time. By breeding the “sport” parent to a normal individual, and then line breeding the offspring (brother to sister, daughter to father, son to mother and so on), you can usually, over several generations, establish a strain that will breed true.
Among aquarium strains of killifish, selective breeding of sports has led to the development of the gold form of Aplocheilus lineatus, the gold and red-orange forms of Aphyosemion australe, and the blushing and pink-tail forms of Nothobranchius guentheri, among others. Albino forms of Aphyosemion gardneri and Cynolebias whitei are common. New sports continue to occur in various species from time to time.
— G.C.K.A. Newsletter, March 1997