Albinism facts for kids
Albinism is a condition some people and animals are born with. This condition is caused by a lack of pigment (colour) in their hair, eyes, and skin. A person or animal with albinism is called an albino. Many albino people prefer to be called a "person with albinism". There are ten different types of albinism.
People with albinism can have white or light blonde hair. They can have very pale skin. Their eyes are blue, or rarely pink-ish. People with albinism can have problems such as bad vision and getting sunburnt easily. This is because people with albinism have less pigments in their eyes, skin and hair.
Albinism is rare in the United States. One out of every 20,000 people in the United States has albinism. There are about 15,945 people in the United States who have albinism.
Vision problems in albinism include nystagmus (irregular fast movements of the eyes), strabismus (where the eyes fail to balance) and refractory errors (like being near-sighted or far-sighted).
In most environments, Albino animals are more easily seen and so may be attacked by predators. They lack the camouflage that the non-albino members of their species have. Also, where colour is a factor in mate selection, they may be at a disadvantage there, too.
Genetics of albinism
Albinism is a hereditary condition. It is usually inherited in a recessive pattern; it means, both parents have to give the albinism gene to a child to cause albinism. Parents pass on pairs of genes to their children. One of the pairs of genes is in charge of making melanin. If both of these genes are flawed, then little or no pigment is made. If only one gene if flawed then pigment can still be made.
Mechanism and frequency
Melanin is an organic pigment that produces most of the colour seen in mammals. Depending on how it is created, melanin comes in two colour ranges, eumelanin (producing dark browns and blacks) and pheomelanin (producing light reddish tans and blondes). The dark and light melanins have their influence either alone or in conjunction, making either plain or multi-coloured coats. Sometimes, in a condition called agouti, they make multi-coloured individual hairs. The production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase. Mammals have a gene that codes for the presence of tyrosinase in cells - called the TYR gene. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal will become an albino. Besides the TYR gene, several other genes can cause albinism. This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. 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. At least 300 species in North America have had at least one reported instance of albinism. Albinism occurs once in every 10,000 mammal births, however, albinism is much more common in birds, occurring once in every 1,764 births. Albinism in animals is most commonly seen in birds, reptiles and amphibians. It is more rarely seen in mammals and other species. It is often difficult to explain these occasional occurences, especially when only one documented incidence has occured such as only one albino gorilla and one albino koala bear.
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.
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 eyes of albino animals appear red because the colour of the red blood cells in the retina can be seen through the iris, which has no pigment to obscure this. Some albino animals may have pale-blue eyes due to other colour generating processes.
Reduced protection from sunlight
Many animals with albinism lack their protective camouflage and are therefore less able to conceal themselves from their predators or prey: The survival rate of animals with albinism in the wild can be low, however, it has been stated that in studies where animals had many places to hide, predators captured albino and normally coloured animals at the same rate. Furthermore, albino animals may be excluded from families or other groups, or rejected as mates. The novelty of albino animals has occasionally led to their protection by groups such as the Albino Squirrel Preservation Society.
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 and albino laboratory rabbits.
Albino dolphins were first sighted in the Gulf of Mexico in 1962. Since 1994, three further individuals have been seen. These tend to be pink in colour due to blood vessels showing through the blubber and unpigmented skin.
Famous albino mammals
Famous albino mammals include Migaloo, a humpback whale living off the coast of Australia; Pinky, a bottlenose dolphin living in and around in Calcasieu Lake, Louisiana; Snowflake, a Barcelona Zoo gorilla, and Mahpiya Ska (Sioux for "White Cloud"), a buffalo in Jamestown, North Dakota. The inspiration for Herman Melville's novel Moby-Dick was a sperm whale known as Mocha Dick.
In other vertebrates
Some animals may have a single or several patches of skin that lack melanin - this is called partial albinism. In albinistic birds and reptiles, ruddy and yellow hues or other colors may be present on the entire body or in patches (as is common among pigeons), because of the presence of other pigments unaffected by albinism such as porphyrins, pteridines and psittacins, as well as carotenoid pigments derived from the diet.
The most important pigments that determine plumage coloration in birds are melanines and carotenoids. These are ingested in food and transformed into colour pigments by enzymes. Aberrations in this pigmentation are mostly caused by food defficiencies and usually do not have a genetic basis. Well-known examples are flamingos which owe their distinct pink colour to the presence of red carotenoids in their natural food. When these carotenoids are in short supply, these birds appear white after the next moult. Mutations causing changes in carotenoid-based colour pigments are rare; melanine mutations occur much more frequently. Two types of melanin, eumelanin and phaeomelanin, are present in birds. In the skin and eyes, only eumelanin is present. In some bird species, the colour is completely caused by eumelanin, however, both types of melanin are found in most species. In birds, albinism is defined as "a total lack of both melanins in feathers, eyes and skin as a result of an inherited absence of tyrosinase".
Tyrosinase does not affect the formation of carotenoids. In an albino of a bird species with carotenoids as additional colour, these pigments remain present. These birds will remain completely or partially yellow or red, dependening on the natural location of the carotenoids in the bird's plumage. These birds have red eyes and a colourless skin. Contrary to popular belief, albino birds are therefore not necessarily all-white.
Albinism is only seen in about 1 of every 1,800 birds. A true albino bird has a white beak, white plumage, non-coloured skin, white talons and pink or red eyes. The two most common species of albino birds are the common house swallow and the American robin. Partial albinism is more common than complete albinism in birds. Famous albino birds include "Snowdrop", a Bristol Zoo penguin.
It has been argued that the definition of albanism precludes the possibility of "partial albinism" in which a mostly white bird shows some form of melanin pigmentation. "It is simply impossible, just like being ‘partially pregnant’.
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).
Albinism is also found in reptiles. The California Academy of Science, in the Steinhart Aquarium, as of 2015, has on display an albino American alligator named "Claude". The alligator is blind because of lack of pigment in its eyes. The albino alligator hatched from the egg in 1995 in Florida, and was brought to the Academy in 2008. This alligator would not have survived in the wild because its whiteness would have made it too easy a prey object. The only known albino alligators are in captivity.
In snakes, partial albinism is more common than absolute albinism. For snakes that are usually patterned in colours, they appear as a faint blue, peach or yellowish. In these cases, there has been a genetic mutation in the melanin and pigment delivery. The appearance comes from the inability for full colours to be present, such as black, red, brown and others. The eyes of an albino or partial albino snake are typically red or pink. Albino snakes can remain in the sunlight for several hours with minimal harm. Corn snakes and snakes of larger types, such as a boa or diamondback, are the most commonly affected by albinism often appearing to be a pinkish or yellowish colour.
Albino turtles are uncommon. Sulcata Tortoises are the most likely type of turtle to express albinism. The shells have an almost yellow colouration and they have pink eyes. For turtles, a pure white colour is nearly impossible, even with albinism. Albino turtles can have a longer lifespan than many other albino animals; their hard shells help to prevent predation and other environmental challanges. Vision and sensory organs are slightly affected.
Albinism in mollusks has been recognized to be a hereditary phenomenon at least since 1900. Albinism in mollusks can exist to a variable degree: sometimes an individual snail will have a normally pigmented body, but the shell will be completely without the normal pigmentation because of a defect in the cells of the mantle. Shells of certain mollusk species can be translucent when they lack the normal pigmentation.
An exhibit showing albino and normal specimens of numerous local species of marine mollusks, both gastropods and bivalves (The Bailey-Matthews National Shell Museum in Sanibel, Florida).
Albino freshwater snail Biomphalaria glabrata showing the red oxygen-transport pigment haemoglobin. Without its normal pigment, the shell of this species is translucent.
The yellow mutation in fruit flies is a mutation causing a congenital lack of normal pigment; it is a similar phenomenon to albinism in other organisms.
Plants that are pale due to a mutation that eliminates chlorophyll production are sometimes termed albinos, whereas plants that are pale simply from being in the dark are instead termed etiolated. An albino redwood is a rare examples of an albino tree with white needles; despite its lack of chlorophyll it may grow to substantial size as a parasite, usually on the base of the Redwood tree from which it first grew. Only about sixty examples of albino redwoods are known.
In human culture
The Albino Squirrel Preservation Society was founded at the University of Texas at Austin in 2001. Members of the society at the University of North Texas petitioned for an election to name their albino squirrel as the university’s secondary mascot. The University of Louisville in Kentucky also has a documented population of albino squirrels.
Famous people with albinism
Albinism Facts for Kids. Kiddle Encyclopedia.