Albinos: Animals without pigmentation

StoryImage( ‘/Images/Story//Auto-img-11460873832558.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘An albino ferret makes a nice pet and can occasionally be found in pet stores.’);

Albinos have always been objects of superstition and wonder because of their unusual appearance and rarity. For example, to the Indian tribes of the Great Plains, a rare white buffalo was a sacred animal and regarded as a special messenger of the Sun God. When one was found and killed, the hide was always carefully tanned, made into a robe, and at the next major religious festival, it was hung high as an offering to the Sun God. The robe was never worn or traded but allowed to hang until it deteriorated and fell to pieces; the scraps then being used by the medicine man to wrap his sacred pipes or to make a head band that was worn on special occasions.

Being originally applied to “white” natives Portuguese explorers occasionally encountered in West Africa, the term albino has come to mean an individual of any species that lacks the pigments in its body that other members of its type normally possess.

Albinos occur in approximately equal numbers in all races of humans, almost all species of domestic animals, and a wide variety of wild species. Sometimes we also see the opposite of albinism; an intense pigmentation of the body called melanism such as the black squirrels and dark cottontails we frequently see around the Rock River Valley.

The substance melanin is responsible for coloration in living things and is synthesized from the amino acid Tyrosine. An enzyme (organic catalyst) is required for the body to manufacture melanin, and, when this enzyme is absent, no pigment is produced. Whether the conversion enzyme is present or not is a matter of heredity. The gene for albinism is recessive, so when two of these recessives occur together, the individual will be an albino. The gene for normal pigmentation is dominant, and an individual may have a single recessive albinistic gene but have normal pigmentation due to the presence of a single dominate. Such an individual is termed a “carrier.”

True albinos show an almost total lack of pigmentation in the skin, hair and eyes. The eyes, however, appear pink or red because the blood vessels in the iris and retina reflect light. In normally-pigmented individuals, the blood vessels are masked by the pigment in the iris. Albinos of all species have defective vision with the eyes being extremely sensitive to light. An albino’s skin is white and never tans, so sunburns are much more serious than in ordinary blonds.

Among humans and other animals, most albinos spring from parents with normal pigmentation, but both of which are carriers of the recessive gene for albinism. On the average, one-fourth of their progeny will be albinos. Of course, the mating of two albinos will result in 100 percent of their offspring being albinos.

Albino rats, mice, gerbils, guinea pigs and rabbits are reared on a large scale for use in laboratories or for pets. In general, these animals are preferred because they thrive in captivity and are tamer than their wild, normally-pigmented relatives.

Newspapers and magazines frequently print reports of the finding or sighting of some type of albino. For some reason, albinism is extremely rare in the great animal phylum Arthropoda, which includes the insects, spiders, crustaceans and similar creatures. Therefore, it was quite interesting to recently read of the discovery of an albino blue crab taken from the Chesapeake Bay. When I lived in Maryland, I literally came in contact with thousands of blue crabs but never encountered a white one. But, I have seen in nature an albino rattlesnake, deer (an entire herd at the Argonne National Laboratory west of Chicago), squirrels, and, once in Alaska, I caught an albino Dolly Varden trout.

The albino in the wild has a difficult time surviving, and they usually fall prey to predators because they are so conspicuous and their eyesight so poor. I believe that is one reason we encounter so few of them in nature.

Though Herman Melville does not mention it, I wonder if “Moby Dick” was an albino.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

From the April 26-May 2, 2006, issue

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