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Thanks to Skillshare for supporting this  episode of Journey to the Microcosmos.   The first 1,000 people to click the  link in the description can get a   free trial of Skillshare’s Premium Membership.

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 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   you can learn how to make your own! Among the many many helpful courses you   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.  Skillshare is an online learning community that  offers membership with meaning. With so much to   explore, real world projects to create, and the  support of fellow-creatives, Skillshare empowers   you to accomplish real growth. It’s curated  specifically for learning, meaning there are no   ads to distract you, and they’re always launching  new premium classes, so you can stay focused   and follow wherever your creativity takes you. And an annual premium subscription to Skillshare   is less than $10 a month.

If you’re one  of the first 1,000 people to click the   link in the description, you can get a free  trial of Skillshare’s Premium Membership.  The people who are on the screen  right now, that’s a bunch of names,   and those people are the reason that we can  make weird videos about microbes and feet.  We are very happy to be able to do  it. It’s one of the joys of our life,   and you are the reason that that’s possible. If you’d like to help us reach more people and   find more cool things in the microcosmos, you can  support this show at  If you want to see more from our  master of microscopes James weiss,   you can check out jam and germs on Instagram,   and if you want to see more from us, there’s  always a subscribe button somewhere nearby.