Albino Animal

• Leucism differs from albinism in that the melanin is, at least, partially absent but the eyes retain their usual color. Some leucistic animals are white or pale because of chromatophore (pigment cell) defects, and do not lack melanin.
• Melanism is the direct opposite of albinism. An unusually high level of melanin pigmentation (and sometimes absence of other types of pigment in species that have more than one) results in an appearance darker than non-melanistic specimens from the same genepool.
Intentionally bred albinistic strains of some animal species are commonly used as model organisms in biomedical study and experimentation, although some researchers have argued that they are not always the best choice. Examples include the BALB/c mouse and Wistar and Sprague Dawley rat strains, while albino rabbits were historically used for Draize toxicity testing. The yellow mutation in fruit flies is their version of albinism.
The incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals (arsenic, cadmium, copper, mercury, selenium, zinc).