Albinism in biology

Albinism in biology is the "Congenital absence of any pigmentation or coloration in a person, animal or plant, resulting in white hair and pink eyes in mammals." 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 hours due to the lack of protection from UV and their lack of camouflage to avoid predators. Albino animals have characteristic pink or red eyes because the lack of pigment in the iris allows the blood vessels of the retina to be visible. Familiar albino animals include in-bred strains of laboratory animals (rats, mice, guinea-pigs 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. It has been claimed by some, e.g. that "albinism" can occur for a number of reasons aside from inheritance including genetic mutations, diet, living conditions, age, disease, or injury, however, this is contrary to definitions where the condition is inherited.

In plants, albinism is characterised by partial or complete loss of chlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes with photosynthesis, which can reduce survivability. Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".

Biological pigments are substances produced by living organisms that have a colour resulting from selective colour absorption. What we perceive as "colour" are the wavelengths of light that are not absorbed by the pigment, but instead are reflected. Biological pigments include plant pigments and flower pigments.

Animals can appear coloured due to two mechanisms, pigments and structural colours. Animals may have both biological pigments and structural colours, for example, some butterflies.

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