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Albino iguana Why are animals like this “green” iguana sometimes born colorless? (Steve Cooper / Photo Researchers, Inc.)

Life Without Color

The world is full of hidden dangers for albinos

Last summer, twin wallabies born at a zoo in Australia caused quite a stir. One was the usual brown color, but the other was completely white. That earned them the names Salt and Pepper. Salt’s pink eyes and all-white body were a sure sign that it’s an albino.

Animals usually get their distinctive coloring from pigments, or colored chemical compounds. Before birth, an organism’s genes direct its cells to produce these pigments.

But Salt—and most other albino animals, including albino humans— lacks these color-coding units of hereditary material (see Albinism in People, sidebar). The result is an unusual phenotype, or physical appearance: Albinos’ skin, eyes, and fur or hair are mostly color-free. Since Salt is well cared for, the wallaby isn’t in any danger. But for wild animals, this rare trait can spell serious trouble.

WHAT ARE THE ODDS?

The likelihood of an animal or person exhibiting albinism is extremely low. “The odds of a human being born with the characteristics of albinism are only about 1 in 20,000,” says Dr. Rick Thompson, an eye doctor and adviser to the National Organization for Albinism and Hypopigmentation. That’s because the gene that controls for pigmentation has two alleles (forms of a gene)—one for coloration and one for albinism. Humans and other animals have two copies of most genes, one copy inherited from each parent. The allele for albinism is recessive. So an organism will be born without color only if both copies of its pigment genes code for albinism.

That can happen even if neither parent shows signs of albinism. Both parents must be carriers, or have at least one copy of the albinism allele and pass it on to the offspring. If only one parent passes on the albinism allele, the offspring will have typical pigmentation, says Dr. Thompson.

The odds of a wild animal—such as a wallaby—being born with albinism are even lower than those for a human. Why? Few albinos born in the wild survive long enough to breed. For color-free animals, even everyday tasks carry hidden dangers.

LACK OF CAMOUFLAGE

For animals trying to hide from predators, albinism can be a dangerous trait. A white squirrel compared with a brown one, for instance, doesn’t stand a chance of blending in with a tree trunk.

Often, survival means spying an enemy first and making a quick getaway. Even that can be tough for albino animals: Lack of pigmentation leads to abnormal eye development and poor vision.

The good news? “Animals in the wild rely on peripheral vision to spot movement, and that remains intact,” says Thompson.

When animals aren’t hiding from danger, they’re often darting about in search of food or basking in the midday sun. But even the sun can be an enemy to albinos.

AT RISK FROM DEADLY RAYS

The sun’s hazardous ultraviolet (UV) rays constantly bombard an animal’s skin. For most creatures, these invisible energy waves signal their bodies to pump up the production of melanin. This pigment that controls color helps skin tan rather than burn.

Since albino animals can’t produce pigments, they’re unable to naturally protect their skin. Too much UV exposure can spell severe sunburn—and even cause deadly skin cancers.

Albino reptiles face a particularly serious dilemma. These cold-blooded animals depend on external heat, like that coming from the sun, to regulate their body temperature and metabolism—the process by which the body breaks down food for energy.

When wild albino reptiles bask in the sun, they’re in for trouble, says John Brueggen, a herpetologist, or reptile scientist, at the St. Augustine Alligator Farm in Florida. “They burn,” he says. “But they don’t know they’re burning. So they’ll keep burning until they blister.”

Captive albino reptiles have it a little easier. Herpetologists like Brueggen have ways to keep them warm without exposing them to UV rays. They place slabs of heated stones in the animals’ habitats. The hot rocks allow the reptiles to heat up without UV exposure.

Sunblock can also protect captive albinos’ sensitive skin. When an albino kangaroo at the San Francisco Zoo was a baby, zookeepers regularly applied sunscreen to its pigment-free pink ears and nose until thick, adult fur grew in to provide a more natural shield from the sun.

SUCCESS IN THE WILD

So what’s an albino animal without access to sunscreen or warm rocks to do? With so many dangers stacked up against wild albinos, it’s tempting to try to protect them. But park rangers prefer a hands-off approach. Charles Ooro, a wildlife official, did just that when an albino zebra was born at the Nairobi National Park in Africa. The zebra seemed to be doing fine despite how it stood out from the rest of its black-and-white herd, he says. So the park allowed it to stay in the wild to lead a natural life.

This article originally appeared in the March 5, 2012 issue of Science World. For more from Science World, click here.

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