Albinism

Albinism is the congenital absence of pigmentation (in mammals, melanin) in an animal or plant resulting in "hair being white, red, or yellow", "feathers, scales, and skin being yellow", "eyes being red, pink, purple, violet, or blue", and "leaves or stems being white or yellow", if applicable. Individuals with the condition are referred to as albinos.

Varied use and interpretation of the terms mean that written reports of albinistic animals can be difficult to verify. Albinism can reduce the survivability of an animal; for example, it has been suggested that albino alligators have an average survival span of only 24 years due to the lack of protection from UV radiation and their lack of camouflage to avoid predators. It is a common misconception that all albino animals have characteristic pink or red or purple or violet eyes (resulting from the lack of pigment in the iris allowing the blood vessels of the retina to be visible); this is not the case for some forms of albinism. Familiar albino animals include in-bred strains of laboratory animals (rats, mice and rabbits), but populations of naturally occurring albino animals exist in the wild, e.g., Mexican cave tetra. Albinism is a well-recognized phenomenon in molluscs, both in the shell and in the soft parts. By definition albinism is a genetic condition, however a similar coloration could be caused by diet, living conditions, age, disease, or injury.

Oculocutaneous albinism (OCA) is a clearly defined set of seven types of genetic mutations which reduce or completely prevent the synthesis of eumelanin or pheomelanin, resulting in reduced pigmentation. Type I oculocutaneous albinism (OCA1a) is the form most commonly recognised as 'albino' as this results in a complete absence of melanin in the skin, hair/fur/feathers, and pink pupils, however this has led many to assume that all albinos are pure white with pink pupils, which is not the case.