True Facts: Sea Stars

this episode is sponsored by brilliant a better way to learn millions of years ago the ancestor of sea stars and the other echinoderms thought screw it I want to be a circle the problem was it wasn't a circle and even today its descendants most often start their lives out as two-sided bilateral babies but evolution can do magical things if you get it drunk enough and as these larvae grow a second baby a round baby starts to grow inside them the second baby kind of eats the original baby and then bursts out into the world that's one way to do it this new body plan of echinoderms has radial symmetry and is a Marvel of engineering first off the skeletons of echinod terms are made out of this crap it looks like a bag of evidence from when they finally arrest the Tooth Fairy these pieces are called ossicles and they're made by cells that are almost like little 3D printers they come in all sorts of shapes and sizes and often look like something you might find on a tray at Satan's dentist up close you can see that these ossicles are made out of a porous honeycomb mesh of magnesium calcite all those little holes allow tissue to grow inside them and to connect them to other ossicles in a kind of 3D jigsaw puzzle it's a little like Evolution got a model airplane kit but where the pieces weren't labeled so there was nothing left to do but sniff the glue and get creative the resulting skeletons can be quite flexible like those in the arms of the brittle star for example or when they're fused together they can form the solid Dome or test of a sea urchin but these parts aren't just internal you can see them on the surface of the sea star as well in the form of spines or these little crazy things called pedicellari they might not look like much but you'll see in the sea Star the skeleton forms a body cavity as you can see with this one who's had a bit of a rough day this cavity is filled with organs in what is essentially seawater but listen this isn't just some star-shaped water balloon hidden in there is one of the most advanced hydraulic systems found in nature look here on the top of sea stars you'll find a little nipply thing it looks like where you'd put the pin in to blow up a ball of sport this is called the madraporite Too Close Jennings looks naughty this one's better it's like a yearbook glamor shot the madroporite is essentially a valve that leads to a series of canals the canals are connected to rows of these little tube-like nubbins the top Parts sit inside of the sea star and the bottom Parts stick out here you can see where the little Canal runs down the length of the arm and he's here on the little sticky outfits two groups of muscles control the flow of water Within These Little tubes one group pushes water down and elongates them the other shortens them by pushing water back up to the top these cubed feed as they're called run down the length of each arm in a Groove these grooves are often protected by spines and sometimes they can even close up it's like a dream that a dentist would bring to therapy in sea stars one of the functions of these tube feet is walking sometimes the tips of the feet are pointing and up close they can look like an old man in a cold pool this style of tip is especially good for digging around and burying yourself in the sand okay this one is doing it all fancy in other species these tubed feet end in these sort of disc shapes looks a bit like an elephant that tried to snort a frisbee these dicks discs sorry can secrete a kind of a glue as well as an anti-glue this allows the sea star to navigate rough terrain or to hold on in a strong current science hippies believe that these feet operate more or less independently following a set of simple rules hold on until you're stretched too far and then let go then swing forward and reattach these Simple Rules can lead to two styles of walking in crawling the tube feet are all kind of doing their own thing it's slow but it gets the job done but they also have it get me the hell out of here sort of walk in the right conditions cluster of feet start moving at the same time and it creates a faster bouncing style of movement in the world of sea stars this is a bit like a Gallop now relatives of the sea stars the brittle Stars felt like this way of walking didn't quite have enough pep instead of using tubed feet to move brittle Stars use their arms in a sort of breaststroke with a leading erection and they're good at it too when they get going they're pretty quick to change direction they don't turn they just lead with a different arm I mean they're not facing in any particular direction because they don't have a face and that's what happens when you forget to evolve a head and they can be quite cute especially when they're little look at this one he's adorable but look at this right here I know what you're thinking why does that fish look so freaked out it's just a harmless little brittle star well just wait till you hear what happened to Marjorie but first a message about our sponsor if you like learning as much as I do and I do you'll want to do it your whole life and today's sponsored brilliant is an excellent partner on that Journey brilliant is an Interactive stem learning platform that helps you deeply understand Concepts in science math and computer science their course in everyday math is a great example of how they approach teaching the fundamentals and let's face it we can all use some brushing up on our fundamentals interactive and visual exercises give you different approaches to understanding things like fractions or how you might go about finding the area of a weird shape you can tackle these in bite-sized pieces when your brain's up for it but trust me these are Concepts that you will return to again and again regardless of what you're interested in to get started for free visit brilliant.org z-e-f-r-a-n-k or click on the link in the description the first 200 people will get 20 off brilliant's annual premium subscription I'm a fan and happy to have them as a sponsor where were we all right so Marjorie this squid was out there minding her own business got a little distracted and wound up in the wrong neighborhood and look a brittle star just reaches up and grabs her she gets away from that one but the problem is she's surrounded they're freaking everywhere bad day for Marjorie that's what you get if you don't pay attention don't worry she gets away just kidding she dies I'm telling you Bittle stars are quite aggressive one finds dead fish and suddenly it's a full-on rumble look that one's getting away run away I digress now brittle stars do have tubed feet they just don't use them for walking instead it turns out the tube feet can be used to do all sorts of things for one they can absorb oxygen and be used for breathing your foot can't do that your foot's boring and it's not just breathing either on the tips of their arms sea stars have a cluster of thin wispy modified duped feet these seem to have chemoreceptive abilities that can sense concentrations of different molecules in the water around them now they don't have a central brain but sorry Central brain but instead they have a distributed nervous system the arms and even individual parts of the arms can sense and react to stimuli on their own bigger decision things like which way to move are made by integrating signals across all of the arms and it's not just touch and chemical signals you see that little orange thing you know what that is it's a freaking eye each arm has a freaking eye on the end how crazy is that you can't tell them not to point and stare that's just how the sea star do if they ever evolve faces like a people this is what you'd be looking at right before you got a tube foot up your well this compound eye sits on you'll never guess this a modified tubed foot up close you can see that it's a cluster of photoreceptive cells which look a bit like something you might see a urologist for see see stars C but they're not crazy good at the seeing thing you know you wouldn't want their help with a jigsaw puzzle but it's probably good enough to help the sea star get its bearings an eye on each arm means that sea stars can have a near 360 Degrees simultaneous field of vision can't sneak up on sea star sea stars sneak up on you some species have even fancier bits the sea star Lincoln navigata is an eye that is grounded by darkened really again all right tube feet I really feel like we could make a case for dropping the word feet these darken but see-through tubes seem to act like sunglasses and look at that they can close their eye all the way they can freaking wink with the help of their sensory tubes and little eyes sea stars can search around for things to eat different species are looking for different things preferably something they can catch which thus limited a bit some of them just sort of sift through crap that they find in the great litter box of the ocean floor mud Stars full on bury themselves and eat mouthfuls of it their mouths already pointed that way and they don't have to move that far so that's good downside is they're eating mud other species prefer Coral which sometimes comes on a stick it's like if you found a shish kebab the size of a palm tree just climb on and start eating your way to the top these sea stars don't really have teeth or the kind of mouth you can chew with so instead they ever their stomach which is a fancy science where word for saying turns the inside the outsy the stomach then just starts digesting on the outside sucks for the coral horrible way to die and it can take months if a sea star has a taste for a stupid clam it can use its little suction cup feet to pry apart the shell wide enough so that it can stick its stomach in there and go to work I know what you're thinking my stomach can't do that well not with that attitude I have a bowl of chili in a bottle of Southern Comfort I bet you could barf your stomach into a clam deep seas he stars in the order by zyngida have a different technique they suspension feed curling their arms up into the water column and trapping things that float by with the help of their pedestal Larry all right I still have to tell you about the pedestalari as if they weren't crazy enough sea stars are often covered in hundreds if not thousands of little Pinchy Pinchers sometimes they surround spines in clusters that can almost look like little pom-poms of death up close you can see they're no joke like little bear traps and they actually work they come in different shapes and sizes some look like little tweezers others can almost look like clam shells the thinking is that they're mainly used to stump parasites from getting too cozy on the surface of the sea star however some species figured out how to use them to catch prey in some cases even small fish now the sea urchins went next level with all this they have three-sided penicillary that are often on the end of long stalks up close they can sometimes look like forceps in the flower sea urchin these little Jaws are covered in a membrane which when open make them look like tiny round flowers but when they're Disturbed they snap shut into a little star shape and deliver a toxin it's crazy right it just gets weirder and weirder they're probably gonna evolve to shoot them out like little drones well that already happened when the collector urchin senses a predator is about it ejects a whole bunch of its pedest Larry into the water and they just float around chomping and injecting Venom into anything they touch it's like a little cloud of pain anyway use penicillary to suspension feed another relative of sea stars the crinoids figured out a different way to do it their arms have evolved into what basically can look like feathers these arms are lined with tubed feet and mucus covered cilia little particles get trapped and then move to the center of the arms where tube feet sort of snuck roll them into little balls and transport them down towards the mouth they just sort of sit there and let the food come to holy it turns out that even though they can look like clumps of starving Agave some feather star crinoids can get quite fidgety look at this one walking around on his fingertips one group in the order Comet tuladek even figured out how to swim don't know who taught them can't exactly throw them in the deep end can you Dad joke not the most elegant stroke looks a bit like a drowning burlesque dancer in any case these feather star cranoids figured it out and they float or Swim until they find a new place to grab on with those well the science hippies call them Siri but come on those are witch fingers and if you know anything about witch fingers you know how good they are at grabbing go ahead and clench your ass on a broom all you want but you need that support up front don't you do that in Science school do they yes science hippies another group of crinoids the sea lilies decided to go more like full-on plant with roots and all they have a long stalk that attaches quite firmly to the sea floor this hold fast keeps them anchored and in place even when they're pummeled by strong currents and it looks like an idyllic life doesn't it beachfront property palm tree well I guess you are the palm trees but overall a good setup to suspension feed in peace if it weren't for these little bastards these are cideroids sea urchins and they look a bit like the ball they use in sucker for masochists but the spiky bits aren't the problem it's what's underneath these sea urchins have a mouth that comes with five teeth-like things that can self-sharpen as they rub against each other it's terrifying this mouth part Contraption is called Aristotle's Lantern which explains why no one ever wanted to sleep over at Old aristotles most regular urchins use this to scrape stuff like algae off rocks but these sidroid urchins developed a taste for flesh crinoid flesh so this right here is a straight up scene from a crinoid horror film it's uh well the pacing is a bit slower than you might be used to but let me tell you if you speed things up a bit you can see that an urchin will seriously up a crinoid look at that he totally ripped it apart so here's the crazy thing some of these sea lilies have evolved a daring Escape Plan at the base of their stock there are segments that they can weaken using a special kind of connective tissue under threats some sea lilies will fall down and break their stalks on purpose and then freaking crawl away look at that it runs away like a mop that finally had enough of your it's amazing and that's the problem with living in the ocean there's lots of things that want to eat you down there look at this crab treating that brittle star like it's a pull apart dinner roll and that's what happens when you have all those sticking out bits it's dangerous it's why they don't have dog parks in nudist colonies you're thinking about it aren't you now if you aren't good at running away which I think we've established is the case with sea stars you need other ways to protect yourself you can cover yourself with sharp spines like this one in the genus zoroaster or the goat of spines the crown of thorn sea star but there's always an animal that figures out how to get around things like that this specific Triton here doesn't give a crap about your thorny Thorns now the cushion star Terra Aster tesylatus got a little more creative it evolved a way to create and expel toxic slime from a little hole on the top of its body not a little bit of slime either like a lot of slime you should see what it does when it likes you but sea stars have a legit magic trick they have this special collagenous tissue throughout their body that they can Harden or soften fairly quickly so for example they can crawl into a crack when they're sort of limp and then stiffen up so they're wedged in there and you can't pull them out but they can also use this collagenous tissue in the way that that sea Lily did they can weaken segments in their arms so that an arm can be pulled off easily a treat for the predator and the starfish doesn't die win-win and it isn't just when they're attacked if they have sea star wasting disease like these ones do they will pull their own arm off in order to save the rest you can see how the tissue immediately closes around the open wound that leads to the body cavity the arms that are detached are still alive and will sometimes keep on searching for food and passing it back to a mouth that doesn't exist now of course the second part of this magic trick is that they can grow their arm back they start by recreating the outer tip of the arm the part that has the sensory bits and then they start to fill in the little here's how the trick works animals start out as little undifferentiated clumps of cells these cells stem cells can become any sort of tissue a nipple an eye but in humans for example once they become that thing they can't go back to being undifferentiated your nipple cannot turn into an eye thank God sea star sales that are one thing can go back and become something else and that's how the sea star can regrow an entire arm using the cells from its body what's even more amazing is that in some species an arm that is broken off of the right segment can grow a whole rest of a starfish back I know what you're thinking if they can do that it's a hell of a lot simpler way of making babies than using dating apps there are a few species of sea Star like this one Aleister Caster in cygnus that make more of themselves simply by splitting in two the tiny little sea star part of Alaska the para can also do its solo but not by ripping itself apart instead it is a hermaphrodite fertilizes its own eggs inside of itself the babies are cannibals and eat each other inside the parents body as they grow until the lucky ones burst out of holes on its parents back sometimes killing them in the process there's a baby photo for you leptus sterious Polaris on the other hand gets into a little sex pile I know what it looks like but there's no bits going into other bits in there the males release their sperm and the females release their eggs and when they're fertilized the females curl up in a swirl and sit on their eggs like a beard Mite but most species don't put in nearly that level of effort males and females just release their baby making bits into the water cross their little tube feed and hope for the best think of it like if human sperm looked like the seeds of a dandelion and the eggs sort of came out like soap bubbles a couple times a year everyone just goes out on their balconies maybe wearing a t-shirt and socks a glass of Rose maybe then you just sort of Let It Go try not to get caught in a back Breeze and that is how the sea star do no you can't reverse it Jerry it's not the same thing well because I think it's reasonable to think that someone might want a dog park in a nudist colony but then think better of it because the dogs would right but I'm saying that no reasonable person would put a nudist colony inside of a dog park where for one the infrastructure where would the nudist shower Jerry in the drinky Fountain well yes dogs are technically nude alright fine Jenny dog parks are nudist colonies for dogs foreign we talked about this well I don't care if it feels good you don't do it in public [Music]

Channel: Ze Frank

Views: 4,123,207

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Id: dZ20KsgVeu0

Length: 18min 37sec (1117 seconds)

Published: Fri Apr 08 2022