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This strange-looking microbe is a Suctorian, and it’s sort of the ugly duckling of ciliates.
Not because they’re ugly, but because like the poor fabled cygnet, suctorians do not
bear a resemblance to the rest of their ciliate family.
For a eukaryote to be classified as a ciliate, it really needs to meet one important criteria:
it needs to have those short little hairs called cilia.
And with such lax requirements, it’s not surprising that ciliates can take on so many
different forms.
You’ve got the long-necked lacrymaria olor.
The trumpet-y stentor coeruleus.
The springy florals of the vorticella.
They may look very different from one another, but they’re all decorated with cilia that
help them move or eat.
Meanwhile, there’s no sign of cilia on this suctorian.
And there’s none on this one either.
They’re hairless, practically bald by microbe standards…except for a few tentacles on
their head.
And there’s some other weird traits that distinguishes suctorians from other ciliates.
So why consider them a ciliate?
Well, we’ll get to that.
First, let’s talk about the tentacles.
This isn’t our first tentacle sighting in the microcosmos.
We’ve seen them before on actinobolina, made through a similar assembly of microtubules—though
the actinobolina’s extensions look a lot spikier next to the dotted end of the suctorian’s tentacles.
Plus, unlike the spikes that radiate around the entirety of the actinobolina’s body,
many suctorian species keep their tentacles bundled together.
But physical differences aside, both organisms rely on their tentacles for the same purpose: to hunt.
Both species use their tentacles to grab ahold of their prey, and toxicysts to immobilize it.
For actinobolina, the next step is to drag their food inwards, bringing it closer and
closer towards their version of a mouth, so that they can begin eating.
But suctorians differ in one one crucial feature: the mouth.
They don’t have one.
Or rather, they don’t have the oral cavity that seems kind of mouth-like in other microbes.
But they do have a very special kind of tentacle that lets them have something even better…many
mouths, which is a trait called polystomy.
Their tentacles are like a Swiss Army knife.
When hunting, they act as a poison-tipped harpoon.
And when eating, they act like a straw.
After the suctorian latches onto its prey, the membrane of its tentacle merges with the
membrane of its food, creating a shared surface that lets the suctorian begin to consume the
inside of its food.
That rounded end begins to form a pocket that travels inwards, carrying bits of the suctorian’s
prey with it.
So suctorians eat a bit weirdly for a ciliate, and it turns out they also poop differently.
To get rid of waste, many ciliates have a cytoproct, an opening that helps transport
material out of the organism when it’s done eating.
But suctorians do not have one.
And no, we’re not about to follow this up with a reveal like the many mouths they ended up having.
Suctorians do not have one butthole, nor do they have many buttholes.
Instead, different species had to devise their own waste disposal methods.
Some of them create little waste-specific regions in their body, which then periodically
get removed.
Others get rid of waste at the base of their tentacles.
But if they don’t get rid of that waste fast enough, they can potentially feed themselves to death.
It’s just one of those reminders from the microcosmos not to take the little things,
like being able to poop, for granted.
And so between the hairlessness and the many mouths and the lack of a cytoproct, why would
we even classify suctorians with ciliates to begin with?
Alfred Kahl, the influential ciliate scholar, didn’t even include them in his most important studies.
Well, let’s just watch this suctorian for a bit—the oval with its tentacles latched
onto some unfortunate ciliate prey.
It’s eating and eating, but you can see the suctorian begin to push some round thing
out of itself.
And then…a thing so exciting it caught our master of microscopes James off guard for
a second there, but that little round thing that came out is a swarmer, a little bitty
baby suctorian that has budded off its parent.
We sadly don’t have a lot of swarmers to show you.
But that young suctorian is why they’re considered ciliates because at this stage
in life, they have bands of cilia, which help them move around.
As they grow older, the suctorians settle into a different form, like the ones we’ve
been watching for most of this video.
The maturing suctorians create stalks that attach to whatever substrate seems most appealing,
which can even include the bodies of other animals.
And that’s where they will stay, exchanging cilia for tentacles, and swarming for sessility—a
lack of mobility.
But the young swarmer stage that came before, however brief and strange it is compared to
the rest of the suctorian’s life, is still important, helping the species spread and
move beyond the stationary home their parent created for themselves.
There are, after all, many ways to be anything, including ciliates.
And to be temporarily one is a means to the suctorian’s own ends, a way of life that
has little concern for human understanding or classification, but that delights us not
in spite of its resistance to classification...but because of it.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
Patrick Olson is a composer, musician, and science publisher who just today released
his new album Music for Scientists!
Music for Scientists is a celebration of truth.
It’s made in tribute to those that have dedicated their lives to science-driven work.
And the music itself is inspired by the beauty of science and the knowable-ness of the universe.
If this sounds like something you’d enjoy listening to, you can find a link to the music
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