March 28, 2008


Stupid Question ™
June 19, 2003
By John Ruch
© 2003

Q: Does every species have an albino variation?

A: Albinism generally refers to an abnormal lack of pigmentation in the skin, fur, feathers, eyes, etc. So obviously it does not occur in species, including myriad bacteria, that have no pigmentation whatsoever.

There are also a few uncommon species, such as the cavefish, that are essentially albino and thus have no albino variation.

Albinism is a function of abnormal pigmentation cells. Therefore, it doesn’t affect creatures whose dominant coloration comes at least in part from other sources. Albino insects are virtually unknown, apparently because their coloration often depends on the natural color of their shells, not from pigmentation cells within it.

As a final caveat, it is of course impossible to determine whether every single species on Earth has an albino variant (it being hard to define “species” anyhow).

All that being said, albinism of some type has certainly been seen in virtually all well-known vertebrates—gorillas, peacocks, giraffes, moose, lemurs, zebras, carp, alligators, tree frogs, whales, raccoons and penguins among them.

Albinism is also seen in plants, including wheat and barley and a variety of trees: spruce, buckeye, birch and aspen. These are much more rare than albino animals because plants rely on their pigmentation—chlorophyll—to produce food in a reaction with sunlight, and die rapidly without it. (It can occur non-fatally in specific areas, such as flower petals.)

Plants are genetically bizarre and can pull off the trick of being an albino/pigmented hybrid—for example, an albino stem giving off pigmented shoots. The reddish and yellowish cacti commonly sold across the country are a lab-created hybrid of normal and albino plants.

“Albinism” is a dangerously generic term and can lead to the mistake of thinking that all albino animals look the same, for the same reasons. In fact, albino snakes and frogs are usually yellowish, and most “white tigers” still have light brown stripes.

Only human albinism has been thoroughly studied. There are two main types, one involving an overall lack of the pigment melanin, and the other only a lack of eye melanin. (Albinism can also be a symptom of larger syndromes.)

The actual level of pigmentation can vary widely. (Most people with albinism have blue eyes, not reddish as is commonly believed.) In fact, the only definitive post-natal test for albinism is an eye test—the lack of pigmentation causes a birth defect in the formation of the eye, for reasons still unknown.

Things get even more complex in non-mammalian species. Reptiles, for example, have three types of pigments. One or more can be abnormal. Herpetologists use “albinism” to refer specifically to a lack of melanin, which may not affect a reptile’s overall coloration much at all.

In extremely rare cases, reptiles may have low levels of all three pigments and appear totally white, which you and I would call “albinism” but is known academically as “leucism.”

No comments: