Ecology

More nature oddities: Tardigrades

Anne Gageby
Strawberry Hill Nature Preserve

(12/2024) I was scrolling through Instagram recently and a suggested video popped up on my feed. Normally, I’d keep scrolling without giving it a second thought. This time, something caught my eye. The video was of a creature I’d never heard of before: a tardigrade. It wiggled and danced to ABBA’s Dancing Queen. I sat, mesmerized, by this microscopic creature moving along to a fun beat. What was this thing I was watching and why was it so fascinating?

I immediately went to Google to find out all I could. It turns out tardigrades are even cooler than I imagined. First, they have two nicknames, and both are as cute as can be: water bear and moss piglet. Water bear is an appropriate moniker for a creature that truly resembles a microscopic bear and looks almost huggable. The nickname Wasserbär was first used by Protestant pastor, Johann August Ephraim Goeze in 1773. The word Wasserbär means "water bear" in German. The nickname moss piglet comes from the fact that these miraculous creatures can be found clinging to droplets of water within mosses and lichens.

But what are they exactly? Tardigrades are small invertebrate animals that live in a variety of habitats including freshwater, terrestrial, and marine environments. Invertebrates are creatures that lack spinal columns. Invertebrates make up more than 90 percent of all living things and include earthworms, crabs, insects, spiders, jellyfish, and more. Interestingly, tardigrades appear plump and squishy under a microscope. But they are covered in a tough exoskeleton made of chitin similar to the exoskeletons of insects. Like their insect cousins, tardigrades shed their exoskeletons to grow.

The name tardigrade comes from Latin for "slow walker", and they’re known for having a bear-like gait, hence the name. Their bodies are made up of five sections including a defined head and four body segments. Each segment has a pair of legs with four to six claws on each foot. Depending on the species, the claws can be anything from truly bear-like to more akin to paddles. With about 1,300 known species in the world, there is a lot of room for variation. One of the strangest adaptations, however, is the tardigrade’s hindmost legs’ configuration. These legs are attached backwards and drag behind the tardigrade unless used specifically for grasping or switching direction.

Another adaptation that’s quite odd is their mouth structure. Yes, water bears have mouths. They’re round and miniscule and are connected to muscles inside the head that act like cheeks, creating a suction action to pull food into the body. Unlike many other creatures, they don’t have teeth. Instead, they have spear-like pinchers called stylets, which pierce cell walls and allow tardigrades to suck out the nutrients of whatever meal they find. Not all tardigrades share the same diet, however. Some are plant-eaters that consume algae while others feast on smaller creatures and single-celled organisms. Some species of tardigrades are cannibalistic and will consume other tardigrades. Cute, adorable, and sometimes blood thirsty. Nature is odd.

These tiny powerhouses also have a secret weapon: they are nearly indestructible. Terrestrial tardigrades need only the smallest amount of water to stay alive. Without water they go into a protective mode called a tun state which allows them to stay dormant for extended periods of time. In this tun state they pull their arms and legs into themselves and curl into a ball. They essentially shrivel up but don’t die. Water is essential to life on earth, but tardigrades can exist without water for years at a time. But how?

It’s believed that tardigrades synthesize special molecules that replace lost water within their cells. These molecules create a matrix which protects things like DNA and other sensitive pieces of their complex puzzle. This protection allows their bodies to completely dry out without harming their metabolic system. When they’re reintroduced to water, these special molecules dissolve and leave behind undamaged cells. It’s an incredible adaptation that not only protects tardigrades but allows them to thrive no matter the condition.

Tardigrades can tolerate more extreme conditions than just desiccation. They can survive cold as low as -328 EF and heat all the way up to 304 EF. They have survived in the vacuum of space, extreme pressure, radiation a thousand times stronger than humans can handle, and chemical treatments. Water bears are the definition of beauty and brawn. They’re adorable and built to last.

Tardigrades are considered microfauna, complex multi-cellular animals just like any we see in our backyards, only tinier. Much, much tinier. Tardigrades clock in at between .002 and 0.06 inches when fully grown. Big enough to be seen with the naked eye but just barely. The easiest way to spot them is with a low-powered microscope. Or, if you have a keen eye, a decent magnifying glass will suffice.

But where should you look to find them? You can find water bears just about anywhere - leaf litter, soil, creeks and streams, and of course moss and lichen. These cuties need only a small amount of water to survive so if there’s water, there’s tardigrades. Searching for water bears could be a fun weekend activity especially if you’re looking for something science-y to do with your kids or grandkids. Head out back to a tree covered in lichen or moss. Gather a few samples in a paper bag to allow them to dry out a bit. Soak the moss or lichen in distilled water overnight to give the tardigrades a chance to rehydrate. Squeeze out the water into a petri dish or another flat-bottomed glass dish under a microscope and start looking.

It might take a few samples from different areas of your property to find some tardigrades. They are abundant but elusive. Don’t let that stop you from searching. Or, look for videos online of our littlest friends. There are wonderful resources out there with videos of live water bears in action. Try to spot different species and make a note of which ones live in your area. Either way, when you spot one, put on Dancing Queen and enjoy the party.

Anne Gageby is the Environmental Education Manager of the Strawberry Hill Foundation. Strawberry Hill inspires stewardship of our natural world by
connecting the community with educational opportunities.
 Learn more by visiting StrawberryHill.org.