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 1 month free trial of  Skillshare’s Premium Membership.

For those of you afraid of spiders, the  microcosmos probably seems like a safe haven.   When you’re scanning through a microscopic  ocean full of single-celled organisms,   the likelihood of a spider crawling  across your screen feels comfortingly low.   The few times we’ve seen a spider under the  microscope, it’s because we put it there.  But safe as the microcosmos might  seem from a surprise spider attack,   it would be misleading to pretend that it’s  completely free of spider-like sightings. Because   even at this small scale, you could find yourself  subject to an ambush of the arachnid sort.  These are water mites, relatives of spiders  in that they are also members of the Arachnid   class.

And the resemblance is uncanny,  especially with the eight legs waving around.  But that detail aside, there is something about this water mite that looks   more like a cartoon spider, something  you might have doodled in a notebook.  For one, there’s the eyes, those simple dots.  Water mite species usually have two pairs,   which act mainly to detect light. It’s much  less intimidating to stare into the eyes of a   water mite than into the eight eyes of a spider. Another reason for the cartoon spider-iness of   some water mites is down to a defining aspect  of their shape.

Spiders have segmented bodies,   with an abdomen that is distinct from  the cephalothorax that holds its head.   But water mites aren’t segmented. Instead,  those different parts are all fused together.   In the case of this particular species, the  final result is round and kind of adorable.  So now we’re going to disrupt that cuteness by  bringing up a creature we’ve talked about before,   one that’s more closely related to water mites  and one that does not evoke any sense of cuteness.   We’re talking about dust mites, which are part of  the same superorder of mites called Acariformes.  If you haven’t watched our episode about  dust mites before, you should check it   out after watching this video, especially if  you’re looking for motivation to clean your   room. Because without spoiling too much, the main  thing to know about dust mites is that their poop   is, it’s not great.

I’m bringing that up now   because while water mite poop might not evoke  the same concern that dust mite poop does,   it is still fascinating. Their excretory system  is made of a large tube connected to a pore.   The tube takes in waste from the mite’s version  of blood, called hemolymph. And in the tube,   the waste is stored as yellow or white  crystals.

To clear out its storage of crystals,   the mite simply moves its muscles to push  everything out through its excretory pore.  From the studies we’ve found on other mites  with similar systems, our best guess is that   these poops are guanine crystals, produced by  the mite’s own body as it breaks down nutrients.  Now crystal poop is weird. But the weirder thing is that crystalline poop is not the   weirdest thing that water mites excrete. But before we get there, let’s talk about just how   red some of our water mites are.

They’re so red  that they seem like walking drops of blood. They are not actually chock-full of blood though; the red color is likely just some kind of carotenoid   that turns the water mite crimson. And for a time, scientists believed   that the red color was a way for  these species of water mites to flash   a warning signal to fish, a sort of “Do not eat  me” expressed solely through threatening hue.  But like why?

Why did scientists think fish would  heed this warning anyway? Why would a fish   bother to listen to a water mite  when it could be eating instead?  Well, many water mite species have an  approach to warding off predators that   is…sticky. Water mites have little globe-shaped  organs dotting their bodies called glandularia,   each with their own little opening and a little  bristle-y hair called a seta.

When something, say,   a fish, brushes up against that hair, it triggers  the glandularia into releasing a milky fluid into   the water, where it mixes into a tackier,  more viscous substance. And for predators,   the idea of having to wade through some gloppy  mess to get to your food is probably unappealing.  So when the scientists saw, in the context of their own  experiments, that fish seemed to quickly stop trying to eat water mites, they decided  that the red coloring was the water mites’   way of telling the fish, “We’re the sticky prey.” But while it’s possible the fish do learn not to   pick out these water mites for food,  the idea that the red color exists   specifically as a warning to predators does not  hold up to the basics of how these particular   species live. Red water mite species tend  to be found in transient pools of water,   places that fish don’t often find themselves.  So the likelihood that they would have evolved   this trait for the purpose of warning fish is low.  It’s more likely that the pigments are a way of   protecting them from ultraviolet light.

It just maybe happened to also protect them from fish as well.  And the sticky fluid that makes them unappealing to  fish also has another use: reproduction.   In one genus called Arrenurus, the males use it to   hold the females still during copulation. This is part of a wider spectrum of weird   reproductive behaviors. On one end, there are  the species like the ones we just mentioned,   which engage very directly and  physically with each other.  On the other end of the spectrum, there are water  mite species where the sexes don’t feel the need   to interact at all to make reproduction happen.  They don’t communicate, they don’t touch.

The   males simply deposit spermatophores somewhere for  their female counterparts to find them and pick them up.  And then, somewhere between the directly  copulating water mites and the cold shoulder   water mites, there are the dancers. They’re  sort of like the second group in that the males   drop off their spermatophores. But then they  actually stick around, mostly so they can draw   females in and help them find the spermatophores.

And this is where dancing comes in. Sometimes this   involves vibrating their legs  to mimic their favorite prey,   drawing the attention (and aggression) of a  wandering female. Other times though, this means   waltzing together as a pair, moving in circles  with careful pauses to pick up the spermatophores.  We obviously don’t have video of that or  we would be showing it to you.

But at some point,  some scientist watched this happen. Someone  watched the dance of the mating water mites,   and then they carefully documented it.  Just like someone saw the mite-averse fish,   and the crystal poops, and the many other strange  things that make up the lives of water mites. Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.  And we’d like to also say thank you again  to Skillshare for supporting this video.

Maybe you are a little overwhelmed with all of  the spider-like imagery in this video. Well,   how about spending some time  with a different kind of spider? On Skillshare you can learn everything  from How to Draw Spider-Man to How to   Transplant a Spider Plant.

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And if you’re one of the first 1,000 people  to click the link in the description   can get a 1 month free trial of  Skillshare’s Premium Membership. The names on the screen right now, these are  our Patreon patrons. They’re the people who   make it possible for us to do this thing,  and I am so grateful to you because before   this channel started I knew that I  would be interested in this stuff,   but I did not know anything about it yet and now  I know so much.

And I hope that by coming on this   journey with us, you do too. And actually  the video in the background here, of these   little mites you’re seeing, that’s actually from  my Microcosmos microscopes! I found some mites   in my local pond, like the same week that we were  making this video.

So I sent them to our editor,   and they are getting edited in. If you would like to see more   from our Master of Microscopes, James Weiss,  you can check out Jam & Germs on Instagram.  And if you wanna see more from us, there is  always a subscribe button somewhere nearby.