In 1773 a German Pastor by the name of August Ephraim Goeze discovered these tiny animals the size of a sentence period on a newspaper. Goeze called them "little water bears," a nickname that has stuck with them until today. Italian biologist Lazzaro Spallanzani later gave them their scientific name, tardigrades, which means "slow stepper" or "slow walker." Tardigrades have been found everywhere and have very unique characteristics. There are around 1,000 species, and more are being discovered all the time. They are most famous for their resiliency and ability to withstand extreme conditions. Tardigrade fossils have been found as far back as 520 million years ago.
August Ephraim Goeze had described them as little water bears because they walk like bears. They are also known as moss piglets. When they are born, they are very tiny at 50 micrometers in length, but they can grow up to 1,500 micrometers and average about 500 micrometers. Tardigrades are nearly see-through but you can see them under the right light with the naked eye. However, most researchers observe them through microscopes at a 20-30 power magnification.
Researchers view them as miniature animals. They are barrel-shaped and have an alimentary canal where food is transported through to be absorbed. They have a brain and an open body cavity called a hemocoel. This body cavity is filled with fluids and nutrients that reach every part of their body. They have a well-defined head and four body sections. Each section has its own pair of legs, for a total of eight legs. Three of the pairs of legs are for walking and the last pair is for grasping and maneuvering.
Like most animals, tardigrades have both male and female sexes. However, some tardigrades can self-fertilize, and some can reproduce without fertilization. Tardigrades grow eggs inside their body or they attach them to nearby surfaces. Their eggs take no more than 14 days to grow and are born with fully adult cells. Their cells will not divide for the rest of their lives but will grow in size.
You can find them anywhere from the Arctic to the equator. They can live in water, sand, moss, and flowers. Their ubiquitous presence is a testament to their ability to adapt to its surroundings. They can survive extreme pressures, temperatures, heavy radiation exposure, high salinity environments, and even low oxygen conditions. They can go without food for up to 30 years.
Although it may be possible to see tardigrades with the naked eye, a microscope is best. One way you can find them is collecting some moss or lichen. Place it into a shallow dish like a petri dish and soak it in rainwater or distilled water for three or more hours. Squeeze the water out into another petri dish to collect it. Use the microscope to examine the contents of the dish. Once you have confirmed that your sample contains tardigrades you could further transfer the tardigrades into a slide to view under a higher power microscope.
As tiny animals with only six slow-moving legs, you would think getting around must be a hassle. However, tardigrades do not have to walk everywhere. One of the reasons we find them everywhere is that they get carried by the wind and water currents easily just like pollen, spores, or seeds. They go wherever the wind blows them, but most environments are not ideal for tardigrades. In those cases, a discontent tardigrade just needs to wait until the next gust of wind takes them to another tree or flower.
Tardigrades do not exist in one state at all times. The ability to resist harsh conditions is a result of their ability to change morphology. In addition to its active state, tardigrades are capable of five other states called anoxybiosis, encystment, cryobiosis, anhydrobiosis, and osmobiosis. Anoxybiosis and encystment are states for low oxygen and unfavorable conditions without losing water, respectively. Cryobiosis, anhydrobiosis, and osmobiosis are states for freezing temperatures, extremely dry conditions, or high salinity conditions. In these states, they can survive almost anything.
Because it is unlike any other animal, we do not yet fully understand its contributions to the local ecosystem. However, tardigrades are great for studies and scientific research. Understanding their ability to survive could lead to a multitude of applications in society. For instance, their ability to survive high amounts of radiation suggests that they have a good process for repairing their DNA, which might one day be helpful to those undergoing cancer treatments.
In 2007, tardigrades were exposed to lethal outer space conditions. European researchers took a sample of water bears on a mission to expose them directly to solar radiation and the vacuum of space. When the tardigrades returned to earth and were given water, they reactivated out of their cryptobiotic state and behaved as if nothing had happened.
We are finding tardigrades everywhere and that they are remarkably resilient. Researchers continue to study them to figure out its mysteries. Understanding how a tardigrade can survive such extremes can have a multitude of applications in human medicine, engineering, biology, and chemistry. To this day, we are still finding new species of tardigrades all the time. Are they found just on earth? Even though no human has been to other planets in our solar system, it would not be surprising to find them on other planetary bodies. Tardigrades are the ultimate survivors.