Eye of Science/Photo Researchers Inc.

Ecologists refer to the large animals people go to zoos to see as “charismatic megafauna.” The microscopic tardigrade—which is about the size of the period at the end of this sentence—surely qualifies as charismatic microfauna. It trundles about its moss, lichen, or leaf-litter habitat on stubby limbs like an eight-legged panda. The tardigrade (whose name means “slow walker”) may be the only invertebrate universally regarded as “cute.”

Tardigrades also may be the toughest creatures on the planet. When the habitat they favor dries up, so do they, through a process of cryptobiosis, into dustlike specks called tuns. In a desiccated state of suspended animation, they can be blown by the wind until they encounter a moist, hospitable location, whereupon they rehydrate and resume their active lives.

During their dehydrated period, tardigrades can tolerate nearly anything. They’ve been exposed to temperatures of minus 272.95 degrees Celsius (functional absolute zero) and 150 degrees Celsius (302 degrees Fahrenheit) and survived, none the worse for wear. They’ve even been exposed to solar heat and radiation in the vacuum of space and returned home to Earth to move, eat, grow, and reproduce. The latter isn’t hard, since many are also parthenogenetic (i.e., they can give birth without the bother of sex). –William R. Miller

Published in Sierra Club on line:

http://www.sierraclub.org/sierra/201203/grapple-charismatic-microfauna-tarigrade-127.aspx