Albinism in animals is caused by a lack of melanin, or pigmentation, in the body. Melanin is responsible for the coloration of various parts of the body. If an animal is born with an inability to produce this pigmentation, it is classified as an albino. Albinism in animals is hereditary and occurs in a variety of forms, ranging from complete albinism to partial or patchy albinism. The condition is caused when a recessive gene from each parent is passed on to the offspring.
True albinos completely lack melanin and exhibit completely white or pinkish colored skin or scales with no markings. Animals with this condition have eyes that appear pink or red in color, though the irises of the eye are not really pink, but rather lacking in color. This absence of melanin in the iris causes the blood vessels in the eyes to show through. True albinism in animals also causes other parts of the body to appear a pinkish color, such as the nails, skin or scales.
Partial albinism in animals results when the animal possesses slight pigmentation. Animals that are partially albino often exhibit light blue eyes. They may also show slight color on various parts of the body, though white or pink is the primary color that is present. Albinism in animals can also be dependent upon temperature. The animal may exhibit some color pigmentation on cooler parts of the body, but not on the warmer areas.
Various forms of patchy albinism also occur in animals. This type of albinism is often the result of a lack of certain color pigmentations, but the presence of others. For example, anerythristic albino animals lack red pigmentation. These albino animals often appear bluish-grey in color. Axanthic albinism in animals is the result of a lack of yellow pigmentation.
Tyrosinase is an enzyme in the body that produces melanin. Animals that lack this enzyme are referred to as Tyrosinase-negative albinos, and they usually have cream or pale yellow skin and pink eyes. In contrast, Tyrosinase-positive albinism in animals means the cells in the body are unable to create melanin, but can synthesize tyrosinase. This generally produces a muted lavender color in the animal’s skin and eyes.
Not all animals that are white are truly albinos. The easiest way to determine if an animal with white skin is an albino is to look carefully at the eyes. If the eyes are pink or light blue, the animal is an albino. Leusistic animals are often mistaken for albinos because their skin is mostly white, but they have dark pigmentation present in their eyes and nails.