This episode is sponsored by 80,000 Hours. 80,000 Hours is a nonprofit that aims to help people have
a positive impact with their career. Head to 80000hours.org/microcosmos to start planning
a career that could potentially help solve one of the world’s most pressing problems.
From our vantage point, as relatively large organisms, it can be easy to overlook the
microcosmos, because it is simply too small to see. It floats in front of our eyes at
all times, and yet we cannot make out any of the details until we turn to other tools.
And then, even when we do turn to those tools, it can be easy to overlook the
parts of the microcosmos that seem relatively understated compared to all of the wondrous,
dramatic events that can take place. After all, if you’ve just come from, say, watching a tardigrade
wandering through a maze of moss…you might find something like this a bit underwhelming.
There’s just some squishy dots, floating around, not doing anything particularly noteworthy except
for a few brief flashes of movement. The movement is so quick that you might see it and just move
on to something else, like when you glimpse a bird flying out of the corner of your eye.
It captures your attention for a second, and perhaps releases it just as quickly.
But for today, because we are us, we're gonna linger on that moment and let it capture our
attention a little longer. Because the organism you’re looking at now is a ciliate called Cyclidium,
which is known for its ability to dart straight through the microcosmos like an arrow. It’s
only a few micrometers in length, but packed in its small body is the ability to detect
threats and quickly jump out of their reach. This is not the first time we’ve seen a very,
very fast-moving ciliate on this channel before. Early on, we watched as bundles of
the bell-shaped Vorticella extended their long stalks and then rapidly
contracted those stalks into tightly-packed spirals when other organisms got too close.
We’ve also watched a Spirostomum quickly evade unwanted contact, pulling back and shrinking down
to get itself out of reach as quickly as possible. We can think of the vorticella and spirostomum as
doing something that’s more like flinching, a rapid contraction that moves them away from a
potential threat, but that doesn’t necessarily transport them to a whole new location.
It’s remarkable and requires both tremendous force and speed. But ciliates like the cyclidium
we were watching earlier or these Halteria are performing a very different sort of athleticism,
something, more like a long jump. Not that they look like they should be
setting any records. Halteria are only around 20 microns in length, and most of
the time they just kind of spin, like a kid on a teacup ride with no concept of dizziness.
And charmingly, the halteria is edged in cilia that swirls with it,
unfurling as it moves, and then wrapping back inward as the organism winds down.
Halteria like to feed on bacteria, and they reproduce quickly. So sometimes,
James, our master of microscopes, will find thousands of them in a single drop,
another set of squishy dots that move in and out of focus,
sometimes even obscuring the other interesting bits that James is trying to look at.
But let’s zoom out, past the point where we can see the defined lines of the Halteria’s cilia,
where it really is just one dot navigating a field of debris. And see if you can keep up with it.
Most of the time, it’s not really a challenge. It looks like a floater in your vision,
a clear blob that just idles away. But then, seemingly out of nowhere,
it leaps across the screen and out of view, potentially traveling as far as 100 times
its own body length in a single second. That would be like if I, a 6 foot human being,
could leap 600 feet in a second. In response, you might say something like,
“Okay, yeah, sure Hank, but you’re a human being. Things are different
in the microcosmos.” And yes, this is true. Things really are different in the microcosmos.
In fact, things are a lot more challenging. Organisms like halteria are living in water, but because of
their small size, that water feels thick like molasses. So, they have to rely on structures
like cilia to help them swim and move quickly. But even then, most organisms only travel around
10 times their body length in a single second. The fact that halteria and a select group of other
leaping ciliates are able to jump 100 times their body length in that same second is incredible.
And we don’t know exactly what it is that makes these impressive hops possible. But it does require
a lot of energy, so it makes sense that in its off moments,
the halteria prefers to be a little more static. And there are a few other members of this elite
jumping ciliate group, like the Strombidium you see here leaping around. It is very impressive
that James can even keep up with them. And that of course is the point.
Not to avoid James, the ciliates are not aware of him. But the goal of this movement
is to help the ciliate be overlooked, to ensure that predators can’t find them.
And it works. The slightest brush of a predator’s presence sends these ciliates
into escape mode. In one experiment, researchers set some rotifers upon a population of Halteria
and found that only around 12% of them ended up as rotifer food. Another leaping ciliate called
Strobilidium was even more successful at evading capture, with only 3% of them getting eaten.
There is however one notable exception to this predator evasion. While Halteria might be able to
escape rotifers, they have a dedicated predator called the Actinobolina, which we’ve talked about
before. This tentacled, toxin-loaded ciliate could go after anything it wanted. But for some reason,
it dines exclusively on Halteria. Why? And how?
No clue. Maybe they just got lucky to live in an environment that was rich enough in Halteria that
through evolution, the Actinobolina was able to learn how to sneak up on their cagey prey.
So perhaps it is not possible for them to always be overlooked. Eventually,
someone will take a moment to appreciate them. If they are unfortunate, it is the one predator
that has managed to find a way around their tricks. But sometimes it’s just us, slowing down
just enough to catch a glimpse of something so much faster… and so much smaller… than we are.
Thanks for coming on this journey with us as we explore the unseen world that surrounds us.
And thanks again to 80,000 Hours for sponsoring today’s episode.
80,000 Hours is a nonprofit that aims to help people have a positive impact with their career.
The direction of your career path is a big life decision and 80,000 hours
has a lot of free resources to help you plan and research what options might be best for you.
They’ve got fantastic, free resources including decision-making tools, a constantly updated job
board, and even a podcast where they have in-depth conversations with experts in the world’s most
pressing problems, and discuss what you can do to help solve them. In one of their recent
episodes they discussed what’s being done on the cutting edge of malaria control and treatment,
and the state of the art efforts that are going towards trying to create a malaria-free world
80,000 Hours wants to help you find a career that does
good in the world and all of their provided resources are free! They’re a non-profit,
and their only aim is to help you find a fulfilling, high-impact career.
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