Tardigrades? They're truly everywhere

December 19, 2011 

"A lifetime can be spent in a Magellanic voyage around the trunk of a single tree."

Edward O. Wilson, insect biologist at Harvard University

It sounds like a horror movie - billions of miniature, bear-like creatures crawling through the lawns and shrubbery in Raleigh, Charlotte and Durham. Neither drought nor flood nor extreme temperature will kill them. During a heat wave, they curl into a ball and wait for better conditions to "come back to life." They dominate their miniature kingdom of soil, leaf surfaces and water droplets. These invincible, microscopic beasts are... tardigrades.

Tardigrade means "slow walker." They're also called water bears, bears of the moss or moss piglets. They thrive in water, coral islands, moist tropical forests, and even the extremes from deserts to Antarctic slopes. Dispersed on all seven continents, tardigrades may be the most common organism of N.C.

Fortunately, they are quite harmless. But it's good to know and appreciate who lives in your neighborhood.

The scientific classification of water bears is between roundworms (nematodes) and arthropods (crustaceans, insects, ticks and mites). Like higher animals, they have digestive, excretory, musculatory and nervous systems. But similar to lower animals, tardigrades lack respiratory and circulatory systems: They breathe through their skin. The nickname "water bears" stems from their association with water and from their physique. Smaller than the point of a pencil, they eat bacteria, algae, tiny soil organisms such as nematodes and sometimes each other.

One unique characteristic of tardigrades is that they can endure extreme conditions. During droughts, they shrivel into a suspended state called cryptobiosis. As tiny cryptobiotic balls, they are frequently blown by the wind (called "tardigrade rain"), accounting for their global distribution. Tardigrades can hibernate for more than 100 years, and reactivate when environmental conditions improve.

They are important components of the food chain, feeding on other small creatures, and in turn, becoming food for insect larvae and microarthropods. Tardigrades are also inadvertently eaten by grazers, because they cling to leaf surfaces. You could devour dozens in a fresh salad!

Their unique habit of survival in a suspended state may someday prove important for medical research or for space travel.

So the next time you have a chance to speak with authority and pride about the unique features of North Carolina, be sure and mention our designation as a world center for tardigrades.

And suddenly you will become a noted expert on your local biodiversity.

Meg Lowman is an N.C. State University professor and forest canopy expert who directs the Nature Research Center, N.C. Museum of Natural Sciences. Online: www.canopymeg.com.

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