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Mermaids are, apparently, not real. But depending on how loose you are with your
definitions of fantastical creatures, we could be convinced that rotifers are a little like
microscopic mermaids. Yeah, they don’t have any particularly human resemblance. But like sailors
of old might have confused sea creatures that they saw with the fantastical creatures in their heads,
there’s something kind of fun about imagining the rotifer as our own little mermaids.
But rotifers do have something that the famous little mermaid didn’t have and so desperately
wanted. What’s the word? Oh right, a foot. It’s that long thing on the end, which on any other
animal we might call a tail, or on a mermaid, a fin. And at the end of the foot is a toe, through
which the rotifer produces a cement-like substance so that it can glue itself to other surfaces.
Of course, the foot of the rotifer is not actually a foot in the way we think about
feet. Nor is the toe a toe in the way we think about toes. But it’s hard not to peer
into the microcosmos and see the structure of things familiar, even if not exactly the same.
Take, for example, the ciliate. As we have seen often throughout our journey to the microcosmos,
ciliates may just be composed of one cell, but they can put that one cell to
great use, taking on many shapes and forms that act in magnificent ways.
The defining feature of ciliates are the hairy cilia that covers them. For some,
that’s a general fuzziness that covers their whole unicellular body. But for other ciliates,
those cilia bundle together to form a structure called cirri.
With all those hairs working together, the cirri is more like a limb that helps the organism
move around. The effect for some species is that the ciliate looks almost like a weird,
misshapen centipede as it creeps along the slide. Of course, there are organisms whose legs and feet
are actual limbs, like our favorite tardigrades, whose bumbling bodies include four pairs of legs:
three along the trunk, and another right towards the butt end of the tardigrade.
At the end of those legs are claws, and that means that yes,
depending on the angle, sometimes it looks like tardigrades do have little butt claws.
And oh what a variety of claws they have. Describing just one singular shape of claws for
tardigrades would be tough because there are just so many different ones out there, so much so that
claws are one of the features used to distinguish between different species, whether that’s by
assessing the size of them, the number of them, or how they are attached to the tardigrade’s legs.
Because tardigrades live in many different environments, whether that’s
water or moss or soil, their legs and claws are adapted to suit their home. Those that live in
soil tend to have shorter legs and shorter claws than those living in freshwater or on mosses,
possibly to help them fit better in the small spaces available underground. And some tardigrades
have lost those hind claws entirely, which sounds a bit sad when you think about how
cool it would be to have butt claws. But that’s a small price to pay for comfort and survival.
Feet and legs have a purpose, they help organisms move around, but feet can also
play a different role altogether, if we switch up the scale we’re looking at.
They can serve as a home. If you’ve ever gotten a whiff of a smelly foot, well, you’re probably
smelling the leavings of bacteria. You’ll notice this particularly when you’ve been wearing shoes
that aren’t well ventilated, which makes your feet sweaty and converts them into a nutritious,
watery world for microbes. And as the microbes metabolize the nutrients that your
feet have expelled, the bacteria produce compounds that just aren’t that great to sniff.
And then, of course, there are the more nefarious means of foot life. This is a mite,
and it is beautiful in that creepy, unsettling way when it is still. But watching it crawl
across the screen kind of makes it…cute? Well, cute until you remember that there
are species of mites, like the scabies mite, that use their front legs to dig into the outer layer
of your skin and lay their eggs. And yes, that includes the skin of people’s feet.
Mites aren’t the only parasite that finds their way into a host through feet.
If you want to continue to be unsettled, you can look into parasitic worms that
have taken advantage of the proximity of feet to find their way into human bodies.
Now, we could end on that unsettling note, but instead let us revisit our microscopic mermaids
from the beginning of the episode, the rotifer. As we said, the rotifer technically has a foot,
but it’s not actually a foot. In some ways, it’s kind of the opposite of a foot,
it keeps the rotifer anchored to one place instead of helping it move around.
But rotifers are also happy to take advantage of other animal’s feet for transportation. A few
years ago, a group of scientists obtained some ducks’ feet from a local butcher
and then pressed them into samples of sediment to see how well they could be a vector
for rotifer dispersal. Well it turns out they can, though they’re probably not as effective at
spreading rotifers around the world as something much more simple, and less animate, the wind.
There are so many of these invisible mechanisms for transporting microbes around the world,
whether that is through the feet that trod on ground or fly through the air.
If you look up in the sky, what you’re seeing there, maybe a bird.
Or invisibly, it may be a rotifer, with its foot attached to a foot attached to some wings.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
If you’d like to add some additional microbes to your feet, you can get
a pair of paramecium socks over at DFTBA.com And we’d also like to also say thank you again
to Skillshare for supporting this video. Even if you’ve already picked up a pair of
your paramecium socks, you know one pair of socks is never enough. And with Skillshare
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can find on Skillshare, there is “Cozy House Socks: An introduction to Sock Knitting”,
hosted by Whitney Hayward, where you’ll learn how to take your knitting game to
the next level by making a pair of cozy, thick socks to keep your toes warm around the house.
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We are very happy to be able to do it. It’s one of the joys of our life,
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find more cool things in the microcosmos, you can support this show at patreon.com/journeytomicro.
If you want to see more from our master of microscopes James weiss,
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