vacuum resistance

Tardigrade

When we look up at the stars, we wonder if there is life on other planets. Space is usually characterized as an empty void. And yet, there exist organisms on earth that can survive in the great beyond: tardigrades, also known as water bears. Found across pop culture from Marvel movies to Star Trek, these microorganisms make up the invertebrate phylum of Tardigrada, and have the unique ability to adapt to difficult environments.

How were they discovered?

Tardigrades were believed to be first identified in duckweed in stagnant water by German zoologist Johann August Ephraim Goeze outside of Quedlinburg, Germany in 1773. For their bear-like appearance, Goeze named them the “Kleiner Wasserbär” (the small waterbear).

Image: National Geographic Kids

What makes its power unique?

Although tardigrades are small, on the order of micrometers, they look similar to an animal. Their body is split up into a head and four segments with legs and claws on their feet. In addition to their visual complexity, they also have a complete digestive system fit into their microscopic body. Yet, that is not the only interesting feature of their anatomy: tardigrades also have multiple sensory organs. The organisms’ defining feature, however, is their resistance to extreme conditions.

Imagine a superhero capable of surviving in the harshest conditions, even when all water disappears. Tardigrades possess this remarkable ability to enter a state called ‘cryptobiosis’, where they can withstand extreme dehydration by essentially pausing their biological functions.

Why does it need this power?

They survive their severe environment by entering a form commonly referred to as ‘tun’ state, which allows them to cope with these conditions. Similar to an armadillo rolling up in defense, tardigrades contract their body inwards. Within thirty minutes, a tardigrade can release water from its body and reduce its volume by as much as 85% to 90%. This ‘tun’ state allows tardigrades to survive severe osmotic shock, freezing temperatures, exposure to the vacuum of space, and even cosmic radiation.

In an experiment conducted by NASA in 2007, tardigrades were observed to have survived and maintained their ability to reproduce while in outer space. This experiment demonstrated tardigrades’ ability to survive severe UV rays from the sun, which is usually deadly to cells and causes skin cancer to humans.

When conditions become favorable again and water returns, tardigrades rehydrate and spring back to life, emerging from their seemingly dormant state as if they’ve been resurrected. This ability to withstand extreme dehydration and then revive themselves is nothing short of superheroic resilience!

An animated tardigrade, seen on the show Cosmos!

What can we learn by studying this organism?

Understanding the biology of tardigrades and their remarkable survival strategy can teach us valuable lessons about adaptation and resilience. Scientists are studying these tiny creatures to learn how they manage to protect their cells and biomolecules during dehydration, which could lead to advancements in preserving biological materials and even improving our understanding of human health.