Tardigrades: Chubby, Misunderstood, & Not Immortal

Tardigrades: Chubby, Misunderstood, & Not Immortal


Now, we didn’t want to start this channel out
with a video about tardigrades. We wanted to share at least a bit about
some of the other mind blowing organisms of the microcosmos first. But we also knew it wasn’t going to be long
before we got to them. We are, it must be admitted, tardigrade enthusiasts. And we’ve been excited to watch as a fair
number of people have joined us in that enthusiasm. However, of course, and we’re not mad about
this, the popular narratives about tardigrades have, in their enthusiasm, gotten a few things less than correct, and also skipped over some of the most interesting facets of this celebrity of the
microcosmos. So…tardigrades. They’re chubby and they have heads and legs and butts and they look, at first glance, somewhat familiar. That’s why we sometimes call them water
bears or, even better in our opinion, moss piglets because they are often in the aquatic environments
that cling to mosses. But they are also very unlike macro-animals. For one thing, they have eight legs. For another thing they are not closely related
to anything else on earth. Though taxonomists are still fighting about this, the leading system places tardigrades inside a clade called Tactopoda that includes two
groups. There’s tardigrades and there’s something called Euarthropoda. And that other clade includes basically every bug, insects, arachnids, even crustaceans and trilobites. The organism that branched away from tardigrades has literally millions of species as its ancestor. But the branch that tardigrades sit on…just tardigrades. Though there are over 1000 described tardigrade species and there are likely many times more than that out there. But nonetheless, they do look a lot like bears with their claws and stumpy four pairs of legs. Tardigrades hover right on the edge of microscopic. They range widely in size from 50 microns long to 1200 microns but usually, they’re under 500 microns in size. Tardigrades can be found in three major
aquatic environments. Some live in marine or brackish water, others in fresh waters like ponds, lakes, and rivers, and then there are the terrestrial habitats but this isn’t exactly what it sounds like. See, tardigrades do live on what we would
consider land, but they live in films of water clinging to plants and dirt. This thin film, though nearly invisible to
us, can be a Tardigrade’s whole world. But these films can easily dry up in the daytime…which
is part of why Tardigrades are so good at surviving difficult situations, which of course we’ll be discussing shortly. They occupy almost every place on earth, from
the Arctic to the Antarctic, from soil to beach sand, rivers, lakes, streams, on mosses, lichens,
algae and plants. We know of a couple of places where we will almost certainly find them waddling around in samples we take. And we will make a whole episode about that process but that’s for later. Although they are aquatic, tardigrades don’t swim, they kind of walk. In fresh water, they live among vegetation
and mainly feed on the cell contents of plants and algae by piercing the cells with the two
stylets they have in their mouthpart but some species eat single-celled organisms or even other micro animals including rotifers and also other tardigrades Some species of tardigrades have eyes, besides helping them look super cute, they also boggle the mind because they aren’t eyes. To be an eye, you have to be an organ, and
to be an organ, you have to be composed of tissues that are themselves composed of cells. But each tardigrade eye is, in fact, a single
photoreceptive cell. That is wild. On their whole body, sometimes containing tens of thousands of cells, they have two cells, and those two cells, are there two little eyes Tardigrades are also covered in a kind of
skin, or shell, called a cuticle. Coloration is produced by the pigmentation
of the cuticle and also the content of the digestive tract. Gray, bluish, yellow brown, reddish or brown
are common colors. This cuticle always stays the same size, and
so must be shed as the tardigrade grows. Some species of tardigrades lay their eggs
into this cuticle, which expands to hold them. And then when the cuticle is shed, the eggs stay inside, giving them an extra layer of protection from roving predators. If those eggs manage to avoid being eaten, they will hatch into tiny, little tardigradelettes that, oddly enough, have the same number of cells that they will always have. But their cells, and thus their bodies, will
grow larger. Tardigrades are marveolously complex for such
tiny animals, they have digestive systems and salivary glands, even small brains. The most complex have over 40,000 cells. And yes, when they’re done extracting nutrients
from their food, they have to get rid of it just like the rest of us. Of course, tardigrades are best known for
their survival skills. Many species have the ability to survive environmental extremes, such as temperatures as low as -272 degrees Celsius and as high as 150 degrees celsius. Extreme radiation. Extreme pressures as high as 6000 atmospheres. NASA sent a bunch of tardigrades
to outer space and brought them back alive after exposing the animals to the vacuum of
space and extreme radiation from the sun. A tardigrade may have a life-span of a couple
of weeks to more than 100 years. A museum specimen of a dried moss that was in a herbarium for 120 years yielded active tardigrades when soaked in water. Tardigrades are able to survive these extremely hostile conditions by undergoing a process known as
cryptobiosis. In cryptobiosis, the metabolism of the tardigrades
can lower to less than 0.01% of normal and when conditions get better the tardigrades simply get back to life. There are actually several of kinds of cryptobiosis. In Anhydrobiosis are dealing with a lack of water, and they curl up into a ball called a tun to being all dried up A glass-like protective sugar, trehalose is
synthesized and it replaces the water in the cells of the tardigrades. This sugar prevents crucial parts of the cells from getting damaged during water loss and lets tardigrades to survive the dry period. Anoxibiosis occurs when there is insufficient
oxygen. The body of the tardigrade swells and becomes
rigid and turgid. There is no movement and the tardigrade looks
dead. This sometimes happens in our prepared slides. So when it happens, we simply blow air into the slide from the side for around 10 seconds and that is enough to increase the oxygen
concentration and “revive” the water bear. And there are some other types of cryptobiosis such as cryobiosis where tardigrades can withstand extremely low temperatures and osmobiosis where they can withstand changes in osmotic pressure. One of the misconceptions about tardigrades
is that they are immortal. They are resistant to these extreme conditions
when they are in tun state, but otherwise they are quite delicate animals and can be
hurt and killed easily. Because of their small size, tardigrades are eaten by some eve bigger single-celled organisms. In this video, we managed to record a close encounter between tardigrade and a giant eukaryote. We don’t even know what this single-celled
organism here is, let us know if you think you can identify it, but it could easily eat
the tardigrade and digest it. But this lucky little one managed to escape and even damaged the cell of the eukaryote in the process And in this clip we have a happy tardigrade
waddling on one of the most dangerous residents of the ponds, a brown hydra. Hydra’s tentacles are armed with something
called nematocysts. These are like tiny harpoons that are fired upon contact to immobilize the hydra’s prey. This water bear was either very lucky or too small to activate the nematocysts and so got away from a heartbreaking end. Tardigrades are not extremophiles, they don’t
enjoy living in extreme conditions they are just good at surviving them. In that way, maybe they are something like
us. We also sometimes live through situations
we thought would be impossible. But, all things being equal, both tardigrades
and us just want a nice place to live, plenty of yummy food, and whenever possible, to not be exposed to the vacuum of space. We are so happy that these friends share
their world with us, so often just outside of our notice, but successfully chomping their
way through the microcosmos for more than half a billion years. And just in case you wanted to see it again… (laughs) That’s good. Thank you for coming on this journey with us through the unseen world that surrounds us. If you want to see more from our Master of Microscopes, James check out Jam and Germs on Instagram. And if you want to see more from us here at Journey to the Microcosmos, I bet there’s a subscribe button somewhere nearby. We really appreciate everybody’s kind words in the comments. It really is just a joy to make this channel.

100 thoughts on “Tardigrades: Chubby, Misunderstood, & Not Immortal”

  1. Oh gosh, after having scabies I HATE anything that you can't see with the naked eye then these lil guys came along… omg I'm just shocked I've never heard of these b4… man, I want a new pet! If only they were a tad bigger 😉🤷

  2. The way they flail their arms around is so cute. I wanna take one home with me and eat it >\<⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆

  3. There's literally an alien like world that most of us have not explored. Right underneath a microscope. I absolutely love learning new things like this. I'm hooked on these microscope videos!

  4. Now I really want a microscope, and see the world through it !
    Thank you for this beautiful channel.
    As I love the music theme, could you please tell me what is/are the name you use?
    Thank you.

  5. Would a creature this tiny be self-conscious and be able to distinguish pleasure from distress?
    Might be a silly question and come over as a joke but I really mean it. Thanks!

  6. Who ever said they are immortal in the first place? Everyone knows they are resilient. Which isn't the same as being immortal.

  7. Wow I am so glad I found this channel. This is exactly the type of content I am looking for. Incredibly well edited, scripted and commentated. I've got a lot of videos to get through now and I'm looking forward to them all!

  8. video: tardigrades are easily killed

    me: oh

    video: but for the sake of our harts, just take my word for it while you look at more cute scenes of them
    because I'm not showing that on screen

    me: understandable

  9. Some wud find them disgusting and creepy while others wud call them cute and adorable and there are some who'd call Tardigrades yummy and mouthwatering. So which one are you?

  10. Why do they have 2 eye “cells” in places similar to those of us with binocular vision if their eye cells are incapable of binocular vision?

  11. LIES THESE ARE LIES THEY CAN SURVIVE SPACE AND WITHOUT WATER OR FOOD WUT YOU ST- you know what don’t make any comments about this bye

  12. I think water bears like to be in extreme conditions because other predators kills water bears but they cant survive in those conditions

  13. Is there anywahere I can find a list of what tardigrade species can survive what conditions? For example, I've read not all species can do anhydrobiosis, is there a place where I can find which ones can? Or if not all spexies can survive extreme cold, is there a list somewhere of which ones can or can't? Etc.

  14. the big green eucaryote in the video looks like Paramecium bursaria I literally googled single celled big eucaryotes and found it as a search result

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