Life of a tardigrade on the slide of an optical microscope
The titular tardigrade was floating through the unending water in which he had lived his small, long life when, one day, out of the blue, the tardigrade was taken out of the blue and the world became a whole lot smaller. Yes, even for a half a millimeter long tardigrade.
Just moments ago, the tardigrade had lazily lumbered across his favorite moss pillow and feeding ground to go for a swim in the lake that was full of possibilities and adventures. Spring was coming, and he could sense the warmth of the water tingling the tips of his sensory bristles. Reaching a claw of his stubby leg into the roller coaster current, the tardigrade prepared for take-off. Placing all his four sets of legs on the very edge of the moss, the tardigrade prepared to let go and propel himself forward in an epic dive. Well, an epic dive for a tardigrade, at least: a micrometers-high plop sideways into the increasingly agitated flow. At first, the little tardigrade was convinced nothing was wrong. Of all the countless hardships the animal had endured, a few odd vibrations in the great current of the lake couldn’t possibly mean anything permanent. No sooner had he plopped, however, did the Great Calamity happen.
The moss pillow trembled due to thunderous vibrations in the nearby ground. A shadow blocked the midday sun. Had the tardigrade had ears, he could not have missed the squawking of the disturbed goose (whose flippers had been solely responsible for the great lake current the tardigrade was surfing) as it took to the skies. In the moment the current was about to take hold, it formed an eddy instead, and the most awful, terrible thing happened. And there was no time whatsoever to say goodbye.
In times like these, the little animal would like to remind himself that he could survive almost anything he set his mind to. After all, he’d thought(and tardigrades do think, I assure you, I translated it painstakingly from the tardigrade-ese, plus otherwise we wouldn’t have a story) I have lived for over 500 bright lights in the sky, withstood the hot times, and slept well during the cold times. I lived through the change of the taste of the water that killed some of the mosses; I lived through the pesky worm migration and the lack of food on one side of the big blue by swimming to the other. My children will live through what I cannot. I am one of the most resilient creatures I know, and I know I will just keep going, in some form or another. It is funny, however, how we forget the things we know by heart when a truly shocking and calamitous event supplants all we have learned before. This particular tardigrade, in fact, was curiously only able to remember his troubles in perfect detail and forget that he had ever earned any success. So, unfortunately, in this crisis it did not even occur to the tardigrade to think any of these helpful thoughts (and it wasn’t just because he was an unthinking tardigrade that didn’t have a heart).
Thrown off balance, all the little tardigrade could do was swim-waddle up to the inner edge of the clear cylinder that had scooped him up, cling to the walls with his sticky little claws, and stare out the glass. Or at least, he tried to look as far as his eye spots would reach, but he did not have very good eyes at all. This is what he never saw: his whole universe, the big beautiful lake, fading to a pinpoint as the distance grew.
Now, after some time, looking out from his jar in despair, the tardigrade slowly detached his claws and surveyed the new world around him. Although still large compared to himself, the jar had clear edges, so the water did not go on in seemingly infinite directions, like the lake. The tardigrade could cross it in only half an hour—a longer feeling for the tardigrade than you or me, sure, but when all you have is an uncertain future within the same half a liter of water ahead, swimming in all possible directions quickly becomes quite dull. So much for the day’s planned adventures of the current.
While the jar was still in transit, a discovery was made. The walls of the jar were quite curious, a strange material the tardigrade had barely encountered before. Shapes moved beyond the walls, light creating an enthralling dance before his tiny eye spots. As he grew bored of circling the edge, he just stopped and stared and saw something even more curious. Transfixed, he became aware that as his segments moved, the glass also reflected it, and he stared at it in wonderment for hours, forgetting for a while his terrible plight. He shouldn’t have to remember anyway. What good would his suffering do when he could just watch the newfound delight of himself in a mirror and the moving world passing him by.
“Ahem,” a deep strange voice (that somehow travels through water) rang out at the edge of the tardigrades’ attention. “Ahem, friend, are you also alone from your kind in this strange place?”
The tardigrade turned slowly, and his eyes, which would have been glassy and tired if human, instantly cleared, and his eye spots popped up in amazement. A giant monster was arrayed before him; ten times as long as him, her magnificent tentacles extended towards him in a friendly touch of welcome that was instantly interpreted as one of threat.
Now, it is important to note that in a great big lake, not every microorganism is intimately familiar with all his neighbors, as they are very tiny and usually far apart from the other strange creatures. When organisms got close, they could poison another, or suck an unsuspecting animal into their eating vacuoles, guaranteeing either a fight for its life or the end of it. Even as old as the tardigrade was for the lake creatures, he did not have great defensive abilities and had learned to avoid that which was not food or his own species. And it had been a very long time since he had set his eye spots on a hydra.
And it is also extremely important to note that the hydra is generally a microbial predator.
The tardigrade flailed his little feet and tried to muster the energy to escape, but the hydra gracefully maneuvered her tentacles to pause his motion without killing him. “Wait,” she pleaded. “My photoreceptors are not strong enough to see what you must be seeing outside the strange smooth edge. You are a noble Tardigrada, almost as long lasting as the undying hydra—please, let me know what you can see.”
The tardigrade stopped struggling. His tiny eye was only a cup of light, but it was infinitely more than she had.
“I lived in a symbiotic relationship with some algae on the other side of your moss.” She hissed softly. “I get nourishment from the sun, not always from eating my neighbors.”
The tardigrade stopped reluctantly. He could think of nothing else he could do from within her grasp. He kept one eye on the hydra, another on the window, and described for them both the fast-shifting shapes that danced both right before them and unfathomable distances beyond their combined sight.
The hydra had awakened the tardigrade to a whole new world beyond himself and his despair. With her gentle nudge (and a fear of God put into him by her terrifying presence) he realized the dull jar that had trapped him in his doom was actually teeming with life. Why just in his formerly solitary corner alone there were hundreds of microplankton that he had ignored, but which the hydra casually munched on as they conversed. A sight to behold, she extended her tentacles to their full length and felt the liquid around her for prey, snapping back to coil around a tiny crustacean. Still attached to a small piece of her leaf covered in the algae she protected, she moved along it in slow tumbling somersaults across the surface. Eventually, the tardigrade, who had barely eaten in what felt like forever, felt his sharp mouth stylets twitching in hunger, and he found some even tinier bacteria nearby to keep him going. Watching the crowd together, the tardigrade and the hydra passed protozoa and arthropods, a lost little nematode native to the soil, a whale of an amoeba, and a fast colony of Euglena that zipped past. Each Euglena was ten times smaller than the tardigrade, but together big enough to surround him, they made annoying little whooshes as the colony ran right into him. Were they nervous too, about the animalcules’ plight? Or were they even aware, to the extent the tardigrade was, of how life had suddenly changed? He had never really gotten to know his neighbors at home, and now he realized he probably never would, except for the few left here. Even some windswept algae and lichens had made it into the jar, and most poignantly for the tardigrade, a single scrap of his favorite type of moss from his nest, which he clutched to him like a blanket.
The hydra was very old for a creature of the lake, and very wise. As they remained trapped in the jar, they communicated however you’d like to imagine, for it obviously actually couldn’t have been speech. It doesn’t need to have been a complicated language to console the tardigrade, however; nor to resonate throughout his whole little hemocoel. The tardigrade lamented their fate; it was no use, he thought, of going on doing the same old thing in the monotony of the jar that could never support life as long as the lake had. The hydra waited through his cries patiently perched on her leaf.
In our words, this is how the hydra replied: “It is a different place, sure enough, but really nothing has changed. I don’t know how long I have lived. I am in some sense no different than my mother, who was a clone of hers. I know I shall not grow old, so I have already forgotten yesterday. Was I the mother who gave birth to a daughter then? Or am I the newborn, mature already, ready to repeat the cycle of rebirth that gives me purpose until the end of days? Being immortal, my memory works only in broad themes and long earned wisdom. Since I do not age, there is nothing to mark the time. There is no point in recording your feelings from day to day; they don’t matter when it comes to the great task of survival. Be grateful there is at least food aplenty here and this time will pass soon enough for you as well, my resilient little water bear.”
The tardigrade was intrigued but unconvinced. Well, my feelings matter an awful lot to me, he thought. But surely it wasn’t all just the same. Surely here were new delights to be found that made life worth living, surely all of this could be undone, and he could return to his patch of moss once more… His claw snagged the moss too tightly and it cleaved in two.
“It’s really gone forever, isn’t it?” He whispered softly.
The hydra inclined her tentacles in a nod. “But we will outlive it, child. The environment around us is always the same in that it always changes, but we are the constant in our own lives, and we continue on just the same as we were forever. I am resolute in one thing: this strange chamber shall not change who I am.” She caught another plankton between her tentacles and snapped her coils around it.
He let go of the last piece of moss.
Once the jar made it to the lab, the shapes beyond the jar stopped moving for a time, and the light beyond was cold and dark. The tardigrade considered the hydra’s words again. Some of it rang true as he began to remember what he was. After all, I am a tardigrade. I have lived through all sorts of calamity before and survived. I am one of the most resilient creatures I know, and I know I will just keep going. That was enough for now. Just that little bit of resolve was very brave indeed for a creature so small. The tardigrade plunged himself headlong into just eating and surviving, feasting on the bacteria and algae around him. The hydra bade him drive the plankton that were too far for her to sense closer, and together they formed a partnership like the hydra had with her lost algae.
When light came again, the water trembled, and not just because the jar was being moved, but because something was being inserted inside the jar, another strange rectangular smooth surface. Dragged through the water to create a current, the poor Euglena colony went first, struggling to detach themselves from the new surface the water adhered to and failing. “The end is coming!” their little wooshes seemed to say in the mind of the tardigrade, but he turned his eye spots away and concentrated on his new tasks. Again, the despair was there in his mind, but at least now he was doing something productive, something for the noble cause of survival the hydra had spoken so eloquently about. What will the hydra do if she is taken? he wanted to know. He asked her. She continued her business in the same placid way, as if to simply say “Survive. I know I will anyway.” Daily, the disturbance returned. Together, all the inhabitants waited for their turn to come.
A few days later, awaiting the harvest time, the smooth slide caught hold of the edge of the hydra’s leaf. The tardigrade swam to help, getting caught up himself in the middle of the rectangle while the leaf was caught on the edge. The forces of the water and the changing pressure were too quick; he could easily survive them, but he couldn’t do anything to help her detach her huge millimeters long leaf.
Above the jar, a human spotted the tiny leaf fragment on the edge of his microscope’s slide and simply flicked it off the edge. It was useless there.
As the hydra fell four feet to the ground, losing water, food and structural integrity, she still insisted that she was immortal, that she had survived everything and could do so without compromise forever. And it could be said of her today that she had indeed never compromised forever.
The tardigrade stared downward through the glass of the slide he was securely held to by a droplet of water. It seemed he was always staring out through glass.
He was in a nice bright sunny spot of focused light again at least. He stared up through the glass at the cruel “sun,” with as withering a glare as his little eyes could muster. Unfazed by the brightness, he tried to continue on as nobly and unchangingly as the hydra had, but eventually he could feel a new change all around him. For it is inevitable that when working with a wet mount microscope slide, it will eventually dry out. There was one last trick the tardigrade knew how to do instinctively. He had done it in the dry cool winters that he had lived through so well before. He took one last meal of algae and settled in the last drop of water to evaporate from the slide. With a metaphorical sigh, he pulled in his legs and reduced his surface area, clenching his little muscles close to him. There was nothing guaranteed by this, he knew, no certain promise of life like the one the hydra had offered. He would lose something, too, his ability to observe, that wonderful ability that his hydrated state had given him (at least in this story). He would need to trust that a better day would come, that water would revive him in only a moment, like suddenly falling then waking up from a deep sleep. With that he prepared himself meticulously to enter the tun state, that amazing adaptation of tardigrade that gives them their resilient reputation and can let them live in stasis for years longer than they’ve lived before.
I am one of the most resilient creatures I know, and I know I will just keep going, in some form or another. In some form or another, be it the same old comfortable one, or a brand new and better one. Yes, that was his philosophy. He had remembered it again despite it all. It would be on the front of his mind when he woke up again.
Now, it’s important to remember, children, that this story is only about a tardigrade. And a metaphorical one too. Real tardigrades don’t have feelings, I promise.