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 lion stalking its prey, or a shark lunging for
its next meal.
The tension builds, the motion of spring loaded muscles matched by creeping music as the predator
waits for its moment to strike.
Sometimes the outcome is similar to this feeding frenzy.
But other times, the kindly voice of an elderly narrator assures you that the prey has escaped.
All is well...this time.
The microcosmos is filled with its own versions of these tales of predation and survival.
This isn’t a world built on nocturnal predators or camouflage that shields predator and prey alike.
These are hunters who have to resort to other methods to find their food, like this lacrymaria’s
sweeping approach to the hunt.
While this protist may look delicate, it is an incredibly successful hunter.
It can extend the tip of its neck out to seven times the length of its body, and then retract
it back in a matter of seconds, and it uses this 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, using the dense cilia on its head to search until,
like this lucky lacrymaria, an unfortunate ciliate comes into contact and quickly becomes prey.
But not all threats in the microcosmos move so quickly.
Sometimes, it's the stationary organisms you have to look out for.
Collothecas, for example, are a type of rotifer that are sessile, meaning they do not move around.
Instead, it attaches its foot to a surface and just waits, letting its exceptionally
long cilia hang out like cat's whiskers to draw in food.
And from this angle, the rotifer seems to make catching food look easy, like it just
needs to sit around and wait for a flagellate to stroll into its mouth.
From the flagellate’s perspective, the situation is 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, and you might find yourself facing other threats
as well, not just at the hands of a predator.
This ciliate came from a lake that was nearly frozen, and as we prepared it for the microscope,
the organism had to contend with a very rapid change 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 to disorder.
This other ciliate was able to survive the initial temperature shock that took its neighbor.
But as it nears the spilled contents of the dying ciliate, the healthy one suddenly becomes
much less healthy.
And it too bursts.
We've seen this before on our channel, and it still remains a mystery no matter how many
times we watch an organism experience this strange, contagious death.
Perhaps there was a change in osmotic pressure around the first dying ciliate, which would
have then damaged the membrane of the healthy one 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 of paramecium.
And when one potential prey comes near, the homalozoon winds up, using structures on its
ectoplasm called extrusomes that act like harpoons 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 for us to see exactly what’s going on.
It turns out that the homalozoon was not the only organism coming into battle armed.
The paramecium had its own defenses too, a 4 micron long structure called a trichocyst
that can extend to a longer length in a matter of milliseconds in response to some kind of
stimulus---like another organism trying to injure it.
The homalozoon is able to get its attack in, stunning the paramecium.
But it is also left confused by the paramecium’s response, as it begins nibbling away on those
protective trichocysts instead of the delicious microbe itself.
And in the meantime, the paramecium is able to recover and escape… this time.
But sometimes, these natural protections can fail you.
Testate amoebas form protection out of bits of sand from their environment, sticking them
together with an adhesive to form a shell.
It’s difficult for us to get a good image of this shell, but it’s that dark shape
moving through the frame.
And like any shell, it’s great protection--as long as you can stay inside it.
But the amoeba has things it has to do, and that means it needs to extend its body outwards
using its pseudopodia.
And in that moment of vulnerability, the coleps strikes.
Coleps may be tiny, but they have extrusomes that pack quite a punch.
The toxins they inject into the amoeba do their work quickly, tearing the pseudopodium apart.
And like a pack of scavengers following the smell of blood in water, these coleps can
sense the dying amoeba.
They swarm around and consume the bits and pieces, the undigested amoeba visible inside
their bodies while the shell sits uselessly next to them.
But the microcosmos is remarkable in its resiliency.
And so let us end with this ciliate, which has dealt with some kind of damage.
There are a number of microbes that are able to repair themselves, some of which we’ve
talked about on this channel.
But we haven’t been able to show you one in action.
We don’t know what caused this ciliate’s membrane to rupture in this way, where we
can see these bits and pieces almost poking out 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, it almost seems as if there was never any damage
to begin with.
The ciliate has survived this day, and all is 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