How to Survive the Microcosmos

If you’ve watched any number of nature documentaries, you’ve probably seen some variation on this scene.

In place of ciliates, you might see a lionstalking its prey, or a shark lunging for its next meal.

The tension builds, the motion of spring loadedmuscles matched by creeping music as the predator waits for its moment to strike.

Sometimes the outcome is similar to this feedingfrenzy.

But other times, the kindly voice of an elderlynarrator assures you that the prey has escaped.

All is well.

.

.

this time.

The microcosmos is filled with its own versionsof these tales of predation and survival.

This isn’t a world built on nocturnal predatorsor camouflage that shields predator and prey alike.

These are hunters who have to resort to othermethods to find their food, like this lacrymaria’s sweeping approach to the hunt.

While this protist may look delicate, it isan incredibly successful hunter.

It can extend the tip of its neck out to seventimes the length of its body, and then retract it back in a matter of seconds, and it usesthis motion to seek out its prey.

Each time the lacrymaria sticks its head out, what it’s really doing is gambling.

It’s playing the odds that as it whips around, it’ll make contact with food, and it can play this game for minutes and minutes, usingthe dense cilia on its head to search until, like this lucky lacrymaria, an unfortunateciliate comes into contact and quickly becomes prey.

But not all threats in the microcosmos moveso quickly.

Sometimes, it's the stationary organisms youhave to look out for.

Collothecas, for example, are a type of rotiferthat are sessile, meaning they do not move around.

Instead, it attaches its foot to a surfaceand just waits, letting its exceptionally long cilia hang out like cat's whiskers todraw in food.

And from this angle, the rotifer seems tomake catching food look easy, like it just needs to sit around and wait for a flagellateto stroll into its mouth.

From the flagellate’s perspective, the situationis a little more dire.

It was just casually living its life one second, and then trapped in the belly of a rotifer the next.

Take a wrong turn in the microcosmos, andyou might find yourself facing other threats as well, not just at the hands of a predator.

This ciliate came from a lake that was nearlyfrozen, and as we prepared it for the microscope, the organism had to contend with a very rapidchange in temperature.

Unable to withstand that change in its surroundings, the ciliate died, its membrane rupturing and emptying out.

All of that order, immediately returned todisorder.

This other ciliate was able to survive theinitial temperature shock that took its neighbor.

But as it nears the spilled contents of thedying ciliate, the healthy one suddenly becomes much less healthy.

And it too bursts.

We've seen this before on our channel, andit still remains a mystery no matter how many times we watch an organism experience thisstrange, contagious death.

Perhaps there was a change in osmotic pressurearound the first dying ciliate, which would have then damaged the membrane of the healthyone wandering by.

But some threats can be anticipated.

This homalozoon is a single-celled hunter, and it is on the prowl, searching for something delicious to eat in a veritable buffet ofparamecium.

And when one potential prey comes near, thehomalozoon winds up, using structures on its ectoplasm called extrusomes that act likeharpoons to pierce their target and inject toxins into them.

But where you might expect a victorious hunter, this homalozoon recoils back.

It all happens so quickly, it’s hard forus to see exactly what’s going on.

It turns out that the homalozoon was not theonly organism coming into battle armed.

The paramecium had its own defenses too, a4 micron long structure called a trichocyst that can extend to a longer length in a matterof milliseconds in response to some kind of stimulus—like another organism trying toinjure it.

The homalozoon is able to get its attack in, stunning the paramecium.

But it is also left confused by the paramecium’sresponse, as it begins nibbling away on those protective trichocysts instead of the deliciousmicrobe itself.

And in the meantime, the paramecium is ableto recover and escape… this time.

But sometimes, these natural protections canfail you.

Testate amoebas form protection out of bitsof sand from their environment, sticking them together with an adhesive to form a shell.

It’s difficult for us to get a good imageof this shell, but it’s that dark shape moving through the frame.

And like any shell, it’s great protection–aslong as you can stay inside it.

But the amoeba has things it has to do, andthat means it needs to extend its body outwards using its pseudopodia.

And in that moment of vulnerability, the colepsstrikes.

Coleps may be tiny, but they have extrusomesthat pack quite a punch.

The toxins they inject into the amoeba dotheir work quickly, tearing the pseudopodium apart.

And like a pack of scavengers following thesmell of blood in water, these coleps can sense the dying amoeba.

They swarm around and consume the bits andpieces, the undigested amoeba visible inside their bodies while the shell sits uselesslynext to them.

But the microcosmos is remarkable in its resiliency.

And so let us end with this ciliate, whichhas dealt with some kind of damage.

There are a number of microbes that are ableto repair themselves, some of which we’ve talked about on this channel.

But we haven’t been able to show you onein action.

We don’t know what caused this ciliate’smembrane to rupture in this way, where we can see these bits and pieces almost pokingout of it.

But as it turns and turns and waves its cilia, we can see its membrane beginning to knit back together until finally at the end, italmost seems as if there was never any damage to begin with.

The ciliate has survived this day, and allis well, no matter what may happen tomorrow.

Thank you for coming on this journey with us as we explore the unseen world that surrounds us.

And if you like what we do, you should be thanking these people on the screen right now.

They are our patrons on Patreon.

I know there are some of you right now, looking at your own name.

So, thank you.

And if you want to join that wonderful group of people, you can do that at Patreon.

com/journeytomicro If you want to see more from our Master of Microscopes James, check out Jam & Germs on Instagram if you want to see more from us, you can find our channel at YouTube.

com/microcosmos.