Monster Week—It Lurks in Puddles!
September 7, 2015
Monster Week begins—a week in which World Book features animals that look scary enough to be monsters.
What kind of “bear” has eight legs tipped with razor-sharp claws and can survive in outer space? It is not the latest blockbuster movie monster, but a real life animal called the water bear, or tardigrade (TAHR duh grayd). And millions could be lurking in puddles nearby!
If you ever meet such a fearsome creature, you will be glad to know that the water bear is microscopic in size. Adults typically range from about 1/250 to 1/50 inch (0.1 to 0.5 millimeter) in length. That means they are just a little too small for people to see—smaller than a grain of salt. So, you have little to fear unless you are a defenseless bacteria or a delicious bit of microscopic plant matter. Water bears also dine on algae and on such small animals as rotifers, roundworms, and even other water bears.
The tiny tardigrade is not really a bear at all. Rather, it was named for its fearsome appearance and lumbering gait. Water bears are commonly found in puddles or thin films of water. They also sometimes live on moss, and some people have called them “moss piglets” because of their piglike snout.
Perhaps the most amazing thing about this microscopic monster is its ability to survive in nearly any kind of environment. Scientists have found tardigrades just about everywhere they have looked for them, from the frigid wastes of Antarctica to the simmering heat of hot springs. In a scientific experiment, water bears even survived exposure to the vacuum of space.
Many kinds of water bear are especially resistant to a more mundane menace—dehydration. To avoid drying out when water is scarce, a water bear can curl up into a ball and enter an inactive state. Water bears in this state are known as tuns. Water bears can survive as tuns for many years, becoming active again in minutes when the water returns.