Tardigrade, also known as water bears or moss piglets, are the most famous and well-studied of the microscopic animals known as “extremophiles”. Tardigrades are found in every type of environment on Earth, from the coldest polar regions to the hottest deserts and even beyond, living on top of mountaintops or at the bottom of oceans. They can survive being frozen for hundreds of years, boiled alive, exposed to intense ultraviolet or X-ray radiation, and crushed by pressures more than six times that found in the deepest ocean trenches. In 2007, tardigrades were even sent into space aboard a NASA rocket and subjected to the vacuum and extreme cold of outer space for 10 days—and they survived!
Despite their ability to withstand such extreme conditions, tardigrades are very delicate creatures that require specialized care when being studied in laboratories. When scientists first began studying tardigrades in the 17th century using microscopes, they quickly realized that these animals were unlike any other creature they had ever seen before. Tardigrades have four pairs of legs (unlike most other invertebrates) and their bodies are segmented (unlike most other worms). But it wasn’t until late in the 19th century that scientists realized just how unique tardigrades really are.
It was then that German zoologist Anton Dohrn first described tardigrada as a new phylum—a grouping of animals with similar body plans but no close relatives. Since then, only a handful of new phyla have been added to the animal kingdom while many others have been lost to extinction. This makes tardigrada one of only 30 or so “living phyla” on Earth today!
While we may not know exactly how many species of tardigrade there are (estimates range from 1,000 to over 2 million), we do know that these tiny creatures come in a staggering variety of shapes and sizes. Some species measure less than 0.5 millimeters long while others can reach up to 1 centimeter—that’s about as big as your thumbnail! And although most tardigrades look fairly similar (they all have four pairs of legs and segmented bodies), some species sport unusual features like extra appendages or colorful markings.
But regardless of their appearance, all tardigrades share a few key characteristics: they all have eight legs (bear-like paws) with claws; they lack eyesight but have sensory organs on their head; their mouths contain sharp teeth; and females lay eggs whereas males produce spermatozoa for fertilization. Most importantly, all tardigards possess a special protein called “trevorin” which allows them to enter into a state of suspended animation when faced with extreme conditions like dehydration or starvation—essentially putting their lives on hold until conditions improve! Trevorin works by protecting cells from damage caused by oxidative stress (damage caused by reactive oxygen molecules). This means that when faced with an unsuitable environment, tARDIGRADE CAN GO WITHOUT FOOD OR WATER FOR EXTENDED PERIODS OF TIME without suffering any ill effects! It is this amazing ability that has made them one Of THE MOST FASCINATING CREATURES ON EARTH AND HAS LED TO THEIR BEING STUDIED IN EXTREME ENVIRONMENTS LIKE SPACE!