Image of a tardigrade taken at microscopic level.

Tardigrades are eight-legged, microscopic, water-dwelling critters that were first discovered in 1773 by a German zoologist and are celebrities among the protist world. Allegedly “immortal,” and inherently “indestructible,” there is much controversy about these creatures. So, let’s clear the haze and establish some facts. What are tardigrades, and why are they so unique?

Abnormally cute for a protist, the tardigrade is also commonly known as a moss piglet or a water bear. As their nicknames suggest, they thrive mostly in mossy waters. However, tardigrades have also been found in the most unusual of places. They have been documented to live in often dehydrated areas, such as temporary, thin films of water which can evaporate. As such, their nicknames might not be exactly astute.

“I would call them baby hippopotamuses. They look like microscopic hippopotamuses,” said biology teacher Mrs. Blankenship when asked to give tardigrades a funny name like ‘Water Bears’ or ‘Moss Piglets.’

Their presence in inconsistent water sources is not the only factor that makes them differ from other protists. In fact, they are not like any other protist at all.

The genus Tardigrada includes around 1200 species. However, this family is believed to have evolved separately from all other life on Earth. A long going debate between taxonomists has placed them in the group Tactopoda. Tactopoda is composed of two clades: Tardigrades, and a group known as Euarthapoda. The clade Euarthapoda consists of every arthropod. Insects, arachnids, and crustaceans are the closest relatives to these microscopic oddballs, and even that is broken by several, several million years.

“Some give us oxygen, some photosynthesize. They’re also the bottom of the food chain, so other organisms eat them. They’re plant-like, animal-like, and there are so many types of protists that fill so many niches,” Mrs. Reedy, an AP biology teacher here at Hidden Valley, states about the versatility of protists.

Now to speak of their most profound trait: the ability to perform a process called “Cryptobiosis”. When a tardigrade goes into a condition of cryptobiosis, it becomes invulnerable to dangers that would be lethal to any living thing.

This is where the myth of their invincibility and immortality comes from. Cryptobiosis is a reversible death-like state, where the tardigrade sacrifices metabolism and conscience to focus all-in on one extreme condition. A tardigrade can maintain this state in some cases for more than a century, which is impressive, but they are still mortal. As their time in an extreme environment increases, they have a much higher chance of perishing.

“They must have evolved similar to cockroaches, where you had the ones who had the ability to survive certain conditions that survived with those traits, and then passed those genetics on to their offspring,” Blankenship says on the topic of cryptobiosis.