In mice, a total of 100 genes are known to affect albinism.All the genetic traits for albinism are recessive traits. This means that their influence is hidden when paired with stronger traits. For the recessive albino trait to be expressed in a mammal, the offspring must inherit a recessive gene from both parents.Albinism occurs throughout the animal kingdom. The condition is most commonly seen in birds, reptiles and amphibians, but more rarely seen in mammals and other taxa. It is often difficult to explain occasional occurrences, especially when only one documented incidence has occurred, such as only one albino gorilla and one albino koala. In mammals, albinism occurs once in every 10,000 births, but in birds, the rate is once in every 1,764 births.Some species, such as white peacocks, swans and geese, are not believed to be true albinos, as they do not have red eyes, rather, their colouration is suggested to be the expression of a white fur or feather gene, not a lack of melanin. Consequences
Melanin has several functions in most mammals and other animals; these are disrupted by albinism. Abnormal eye development and appearance
Melanin functions in the normal development of various parts of the eye, including the iris, retina, eye muscles, and optic nerve. The absence of melanin results in abnormal development of eyes and leads to problems with focusing, and depth perception.
The gross eye morphology, feeding and swimming behaviours between wild-type and albino zebrafish were indistinguishable, except under dim or bright light or low contrast. In mammals, albinism is occasionally associated with hearing impairments. However, when tested, there was no differences in responses between wild-type and albinistic European wels catfish (Silurus glanis) and South American bronze catfish (Corydoras aeneus). Similarly, Mexican blind cave fish (Astyanax mexicanus) do not differ in hearing sensitivity from the normally pigmented and eyed surface-dwelling populations. Fish lack melanin in the inner ear, meaning that hearing in fishes is less likely to be affected by albinism than in mammals. Naturally occurring
There are several reports of total albinism in both freshwater and marine fish, however, frequently captured albino fish are only reported in aquarium magazines and local newspapers.The incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals (e.g. arsenic, cadmium, copper, mercury, selenium, zinc).In the wild, albinism is reasonably common in the teleosts, especially the Pleuronectiformes (flatfish), however, it is rarely reported in the elasmobranchs. Albinism has been reported in hagfish, lampreys, sharks, rays and numerous teleost fishes, e.g. catfishes, grunts or cyprinids. In Actinopterygii
Albino and normally pigmented channel catfish (Ictalurus punctatus) differ in their characteristics. Normal individuals of this species are superior to albinos in body weight and total length. Albinos crossed with other albinos require 11 days longer to spawn and produce smaller egg masses. These masses contain eggs of lighter weight with poorer hatchability than crosses of normal fish.