ZoOLogy > What's this? Life at the Limits

It might be hard to believe these creatures are found anywhere on Earth, but tardigrades live almost everywhere. These tiny, eight-legged creatures live in places few other organisms could survive – from bubbling hot springs to Antarctic ice to the ocean floor . Tardigrades can endure the most extreme conditions: freezing, boiling, extreme pressure, and even the intense radiation and vacuum of outer space.

A tardigrade can even survive without water . How? It shrinks into a dried-out ball and its body systems almost completely shut down. It can live like this for decades, then spring back to action with a drop of water!

The wood frog has an amazing trait to survive bitterly cold winters. When the weather turns freezing, it freezes too!

During hibernation, most of the water in its body turns to solid ice. The blood freezes first, pulling water out of the cells . Then water freezes between the cells, so the cells aren't destroyed by ice inside them. As the weather warms, ice in the frog melts and its body returns to normal.

How does the fennec fox survive the scorching heat of the Sahara Desert? Believe it or not, it has a lot to do with those gigantic ears! A fox's ears do more than hear. They also give off heat to keep the animal cool. So the bigger the ears, the more heat they give off. (This also explains why the arctic fox has tiny ears.)

The thick fur on its body protects it from the blazing Sun , and the fur on its feet help it walk across hot desert sand. The fennec fox also stays cool is by hunting at night, when the desert cools down.

Salt is an important nutrient for many organisms. But could you imagine drinking nothing but salt water? It wouldn't just taste bad – it would be deadly. Too much salt is actually poisonous!

But some species, like the Galápagos marine iguana, are adapted to salty environments. This iguana swallows seawater, and sneezes out the excess salt. A lot of this salty mucus lands on its head, leaving a white "cap" of dried, crusty salt.

Most trees cannot survive in saltwater. But mangrove trees grow right out of the ocean! These trees take root in the sandy bottoms of warm, coastal waters while their leaves stay above water.

Like all plants, mangroves need fresh water to survive. So they have ways to filter out the salt. Some species [like this grey mangrove] "sweat out" the salt through glands in their leaves, leaving behind dried salt crystals. Others use their roots to filter salt from the seawater. And in some mangroves, the salt collects in the bark. When the bark sheds, the stored salt goes with it.

Few organisms can survive the darkness and crushing pressure of the deepest parts of the ocean. But for giant tube worms , this is home. Miles below sea level, these creatures live along hydrothermal vents – cracks in the seafloor that spew superheated water.

But without sunlight or plants, how do tube worms get their energy ? From chemicals flowing out of the vent! The tube worms absorb chemicals through their red, feathery tips. Then microbes living inside their bodies convert the chemicals to nutrients.