Introduction to Echinoderms Overview

Hello, my name is Susan Keen and I am currently the Associate Dean for Undergraduate Academic Programs in the College of Biological Sciences. You will be seeing me at Freshman Orientation this summer and I'm very much looking forward to talking to you then. I have a few things that I suggest you might think about before you come to orientation. Selecting fall courses is one of the things that will happen at orientation. Before you select the courses for areas like chemistry, math, or English, there will be placement exams. or other analysis of your preparation. Depending on your readiness, you may end up taking a pre-class or you may go into the mainstream introductory class. The goal of the placement exams is to make sure that you're ready to do well in classes at UC Davis. Sometimes there will be a need for extra preparation classes, and these are sometimes called workload classes. You should see these classes as a chance to make sure that you're going to do well by filling in any holes in your background. It could be that your background wasn't correct when you took classes before you came here. And so the point of this is to find a way to fill it in to make sure you excel when you actually take the mainstream science classes or the writing class. To help you imagine yourself as a university student before you come to campus, I have embedded a video of a standard 50-minute biology class. The class will be on sea stars and their relatives and it will be part of the introductory biology series. Take a minute to read this size to read some information about the size of the class here and then I'll give you some more tips for absorbing the material in the lecture. As you watch this video imagine yourself sitting in the class. How fast will you absorb the material? How will you learn best in this environment? As you're listening to the lecture, take notes. Imagine yourself discussing the material with other students, answering the clicker questions, and trying to absorb the material. You may go over this lecture as many times as you wish. In classes at UC Davis, many times there are audio podcasts of the class available, along with PDFs of the slides, and this allows students to review before the next class. Good morning. Morning, I'm Dr. Keene. Does anybody remember me from orientation? Yay, okay. Did I tell the truth? Yes. Okay, welcome. I'm going to do today's lecture on echinoderms. And echinoderms are really fun because they're totally different than what you expect. You're thinking that they're deuterostome animals and you're looking for all the normal features and they're all in strange places or accomplished in strange ways. So that makes them quite fun. So, let's see here. So in the past you did the arthropods. We're going to do echinoderms today and then Professor Ledford is going to do chordates next and that's probably oftentimes the group people are waiting for most. So we have our learning goals here for the echinoderms. Define the deuterostomes. We're going to start a little bit with that. We'll do the general body plan and diversity in echinodermata. We'll do the synapomorphies, pentaradial symmetry, which you've seen already in lab, calcareous endoskeleton in the water vascular system. We'll talk a little bit about feeding, and then we'll go through a bit about the main lineages and how the body symmetry has changed. So here we are starting on the tree to figure out where we are. So this is where bilateral symmetry evolved a long time ago. And within that group, you've already finished talking about the protostomes. And we're going to start talking about the deuterostomes. So they already... had tripleoblastic body plans and bilateral symmetry and then when we're looking in here we have a developmental character the fate of the blastopore and then when you get to chord H you're going to do the notochord but we're going to go in here and look at a little bit at penta radial symmetry in this group so we're going to start with our clicker question Okay, and I know you've already had this topic, so I'm going to start polling. And it's which of the following are characteristic of the Deuterostomes? You can, as always, talk to your neighbors and discuss the answer. Okay, we'll go another five seconds. Okay, let's stop. Let's do show results. Okay, the vast majority of people picked C, and I would say C is right. Can you tell me how you got there? Do you know how you got there? I know A, B, and D are not right. Okay, so she said, I know A, B, and D are not right. Right? Is that how a lot of people got there? Okay, so what is monozygotic twins? Single zygote, which means the twins are identical, which means that the zygote split. Okay? If a zygote splits in half and both halves keep going, what kind of cleavage did you have to have? Regulative, exactly, right? So that's how you got to that answer. All right? Even if you got there by the elimination way, this is actually how you had to think about it to get there. Okay, so because you had regulative cleavage, you get to an eight-cell embryo, you can split into two four-cell embryos, both of them keep going. Would that have happened in a protostome? No. Excellent. Okay. Okay, so here's the characters that we've been talking about the blastopore develops into the anus in these instead of the mouth They have radial regulative cleavage, and it's pretty clear you guys figured out what that meant so that was excellent So within the deuterostomes we have three groups. Basically, the echinoderms and the hemichordates, and hemichordates aren't going to really be covered in here, and then the chordates, there's three groups, lancelets, tunicates and vertebrates. We belong in here in the vertebrae. vertebrates but today we're going to spend some time in this branch one of the characters is ciliated larvae penta radial or radial symmetry is adults and we'll see that that gets modified calcified internal plates and loss of pharyngeal gill slits and pharyngeal gill slits were a deuterostome characteristic that's been lost here and is present in these other character other groups so we assume it's ancestral for the clade so if we start thinking about echinoderms you're familiar with echinoderms you've all seen sea stars you've seen sea urchins maybe you've seen brittle stars sea cucumbers you saw those probably in the lab so you've had some familiarity with the basics of the group here's a it's a little dark in here so they don't show super well the characters we just mentioned already penta radial symmetry is adults an endoskeleton which is where we're going to start and then the water vascular system in the the epidermis they have spines or pedicel area our little three jawed pinchers two or three jawed pinchers did you see those in the lab on the skin of them at all anybody see them no if you if you take a sea star and put it under a dissecting scope and come in close you can see tiny little two jawed pinchers that are all over the surface and those are what the pedicel area are and their function is to clean the surface so if you if you look at it under a dissecting scope and then pull out a stiff hair find somebody like me with stiff curly hair and then poke at it the little pinchers will actually grab that hair and move it off of the surface okay they also collect larvae and debris that are all over the surface and move them off so that's what pedestal area are there's no header there's no brain but I will mention that they have some fairly complicated behaviors in spite of that they're dioecious there's external fertilization and we'll talk a little bit more about their lifespan in a sec So has anybody got a question before we go on? It's kind of, you got the basics of the group? Okay. So we're going to start talking about the endoskeleton. And this is a sea urchin that is dead, and you're just looking at the shell or the test, it's called. And you can see that it's all made out of hard calcium plates. And again, this is sand dollar I think pretty much everybody's seen a sand dollar skeleton and you know that it's very hard and if you looked at it closely you would see that there are lots of little tiny plates that are joined together or pressed together to make that skeleton and it's an endoskeleton it's covered by epidermis it's inside the skin and then The plates themselves are actually stitched together. What's really cool is that if you look at the plates, they're full of little tiny holes and there's collagen fibers that stitch them together. And so you have a skeleton that appears really rigid, but actually has these flexible collagen sewing lines that sew each plate together around the edges. And then this collagen, which is a special type called catch collagen, Can be stiff or flexible, but it's not controlled by muscles. It's controlled by the nervous system. Okay, so you have this unusual collagen form that allows them to be stitched together and that can be softened or Tightened and catch collagen as I said here is the special type of connective tissue It changes the rigidity of the body quickly and it's under control by the nervous system. Now the really cool thing is, and if you think about this, imagine you're a sea urchin and your body is hard because all your little plates are stitched together. How are you going to grow, right? If you're globular, how do you have to grow? How do you think you grow? If you're going to get bigger in your globular, imagine you're shaped like an orange, which way do you think you have to grow? Out, right? People are doing this with their hands, that's right. You have to do this. So how are you going to do that when your plates are stitched together? Well, if you loosen the control of the stitching and make a little bit of tiny space between each plate, then you can grow around the edges. So they grow out like an orange, getting bigger and bigger a little at a time. And they can, and there are actually kinds of urchins that are what's called floppy urchins, where their plates are always relatively loosely stitched together. And so the other ones only loosen their plates when they're going to grow around the edges. So already we're seeing something really complicated, right? A special kind of collagen that's under neuronal control that can be adjusted. So that's a really cool thing about them. Okay, so here's our next clicker question. A calcareous endoskeleton connected by collagen also occurs in Let's go another five seconds. Alright, let's see what people got. ooh okay so let's run it through cnidarians do they make calcium yes where what do you think where they don't have shells but do they secrete calcium have you ever gone to the Great Barrier Reef or read about it or watched a video what's on the Great Barrier Reef corals what are corals C. Nidarians, and do they secrete a calcium underneath of themselves and grow slowly up? Yes. So, Nidarians do calcium, but it's not, it's an exoskeleton, so you're right. Analyze. Anybody know that anilines can secrete calcium? That's a harder one unless you saw the tube-dwelling worms with the calcareous tubes. Okay, I don't know if you would have seen that one. So you could have eliminated that one just because you didn't know it. Mollusks, do they secrete calcium? Yes, and they make shells, but they're exoskeletons, right? They're outside the body. Vertebrates, do we secrete calcium? We make bones, and how are our bones held together? Muscles and? Tendon collagen tendons, right? Right ligaments and tendons so we have collagen so that's why that's the right answer and then our Arthropods do use calcium, but it's definitely an exoskeleton. Okay, are we good? These are more fun questions. At least I think they're fun. Okay. All right, so we've got a calcareous endoskeleton connected together by collagen. So that's the first thing that's unusual. But in a way, they're similar, right? They're similar to us in some ways and not in others. The next thing is the water vascular system. And water vascular system is a hydraulic system, which means it uses water to do work. Okay. And it's used for locomotion through the tube feet. It's for feeding, and we'll talk about how you can use it for feeding. You can... do waste transportation and respiration because the tube feet are very thin and they're filled with water on the inside and there's water on the outside so things can diffuse across the membranes of the tube feet and pass things in and out okay and there's an external sieve plate on the top did anybody you didn't look enough to see the pedestal area but maybe you will if you get a chance in a lab or during the practical if you're really bored you can use the scope and see the surface of the sea star Joel says no, no one's bored during the practical. Okay, all right. But anyway, if you have a chance to look closely at another sea star, and you can even see this on a dead or dried one. On the top surface somewhere usually right about here, and they show it right there, there's a little plate. And if you look at it, it's full of lots and lots of tiny little holes. And that's called the madriporite or the mother porpoit. And then it goes through a system of canals that we're gonna talk about in more detail in a minute. in a second and then it ends in the tube feet and the tube feet are all the little things that the sea stars used to walk on. You saw those, right? And sometimes they have suckers and sometimes they don't. If you were a sea star that lived on sand, would suckers do you any good? No, because you'd be sucking on to things that move. So the ones that are living on sand have no suckers, but most of them do have suckers. So here's the tube foot system. And this is the, so we're looking. here at the body of an echinoderm. This is the skin. If we went inside the skin, we'd see the calcareous plate stitched together by collagen. If we see here that also on the top surface is an anus, and then there's a digestive system which we can come back to, and then the mouth is on the bottom. Okay? So, and then also sticking out along the bottom are all of these tube feet. So if we just strip it down and look just at the water vascular system, and we know that we can imagine that each of these systems here are extended out into the five arms, this is just the water vascular system alone, okay? there's the madraporite that would be on the top surface or the aboral surface okay and that extends down into a stone canal and that's just a tube that runs from the top surface down towards the bottom surface and it's called the stone canal because if you ever do a dissection of this, it's really, really hard. It's a very stiff canal. It feels like it's made out of stone. So you go to the stone canal and you get down through the body. So we move down through the body to this ring canal and the mouth is in the center here. So does anyone have a question about where you're oriented? Are we in the right place sort of thinking about the body? Yeah. Okay. So we've dropped down from the top surface through the stone canal into a ring. canal that wraps around the mouth and the mouth is here. Coming off the ring canal are all of these what's called lateral canals. So this big canal down the center here, those are lateral canals. Okay and fluid flows in them. Now the madriporite connects the water vascular system to the outside through the top but it's only really used when the water vascular system is set up. So biologists tend to do what's called loss of function experiments right. If we want to know what something does, we break it and then we see how the animal does. So if you wanted to know whether the water vascular system was essential for the two feet to keep working, what would you do? What would you do? You could remove the madriporite or in this case they just puttied over it. They got like putty and they puttied over it and the sea star went, oh that's a drag but it kept walking and living and fine. So from that we learned that if you putty over the madriporite it can still function. It probably has other ways of bringing fluid into the tube feed. Okay, but it is if you do that early in development it doesn't work so it's important for setting up the water vascular system. Okay. So we've got fluid comes down here and fluid goes down all here into these lateral canals. And off of every lateral canal is a little thing here called a radial canal. Here they all are. And then this is the tube foot. Are we good? Okay. So I made a model of a tube foot out of a turkey baster. There's many thousands of things you can do with turkey basters. Okay. And we got the bulb up here. And this is a balloon. You can use anything that's stretchy at the bottom. And the way the tube foot works is that you've got this canal coming here, right? The lateral canal. And if the lateral... there's a valve in the lateral canal. And when that valve is open, fluid can go in here, okay? But if I need to stiffen this, what do I have to do? If I need water to be in a closed space, what do I have to do with the valve? Close it, exactly. So... If we want to use the tube foot, we close the valve and then we have to stiffen it. So this is called an ampulla. It's just a reservoir. So we've got this reservoir at the top. We've got our canal here. We close the valve. Now to stiffen the tube foot, we have to do this, right? Okay? So and then it becomes stiff and I can walk on it. Or I could if I was an echinoderm. Going along. Okay? So what kind of muscles are in here? Longitudinal muscles run long ways, circular muscles run around the body. What kind are these? Circular muscles, exactly. So you close the valve, you contract the circular muscles, you force the fluid individually down in each tube foot, and you can walk along on it, okay? So again, you've got to be thinking about the amount of neuronal control that has to go on here, because you're controlling every single tube foot, and you're telling them, let's start walking. So again, we're not talking about neuronally unsophisticated organisms. Anybody got a question about the water vascular system? Cool. And that brings us to our next clicker question. Sorry, we're doing a lot of clickers today. So if you wanted to turn the end of a tube foot into a suction cup, which of these three changes would you have to make? Okay, so what I'm asking is, if I want this to not just be like this, but to be a suction cup right here, What do I have to add to the body to do that? Okay, talk about it with your neighbors. Think about what a suction cup looks like. What shape does a suction cup have? Okay, let's go another five seconds. Okay, four, five. All right, stop. All right, let's see what we got. Oops. Okay, a little bit of uncertainty, but the majority is correct. Take that away. All right, so let's talk about it. So what shape does a suction cup have? It's lifted in the center, right? So what they do is they add a longitudinal muscle that runs from the top here to the bottom in the middle of the tube foot. So you add a longitudinal muscle that runs from here to here and then when muscle contracts the second the center of the tube foot lifts up and becomes a suction cup so they can hang on to stuff okay again sophisticated control because you have to contract you have to close the valve squeeze the circular muscles contract the longitudinal muscles and lift the center of that tube foot up to make a suction cup and In fact the other thing they have is a calcareous ring That's right around the outside edge of that tube foot to stiffen it because if you think about the mechanical structure of a suction cup Again, it's stiff around that outer edge. Okay, and then it's lifted up in the center. Are we good questions great? Okay Okay, so back to the body plan There's no head or brain as I said, but we've already there's a nerve ring and a very complicated diffuse nerve net But already you're getting the picture I think from the things I've talked about that these are not just little boys of tissue wandering around the ocean. They are capable of very active processes, and I'll talk a little bit more about their behavior eventually. So we talked about respiration by diffusion. You can diffuse across the tube feet. There's also these dermal outpocketings. It's called skin gills. Again, if you took a dissecting scope and looked close at the surface of a sea star, you'd see little clear sacs sticking up between every plate. And those are for respiration, right? So between the plates, they run little out pocketings of very thin skin. It looks like clear blisters. And they're all over the surface, and that's how they do gas exchange. See, there's a lot to look at if you get that dissecting scope on those sea stars. OK. And then we talked before there's an oral side. That's the mouth side That's on the bottom the top side is the aboral side and the aboral side has the anus So basically you're eating on the bottom you're taking your food in you're running it into the gut and then out into these Digestive tracts in each arms and that gives us a complete gut because it's mouth and anus with regional specialization Okay, anybody got questions about the guts But the sea stars have really fancy guts. They can do something else extra. It would be disgusting if we could do this thing. Okay, but it's not for them. Okay, so they have the digestive tract here, and then when they're done with the waste, they come out the top. Now, you notice here in this picture that there's a stomach here, and I know it's not super hard to see, super easy to see, and there's a tract that comes out into arms, but there's also a part of the stomach that's below that. So they have a two-part stomach, okay? So there's the mouth part one of the stomach behind that is part two of the stomach and then at the top of that is the Anus are we good all right? And so this is a video of a sea star this will be a video of a sea star eating shortly And this is a sea star right here, and it's eating this which is a muscle you remember muscles bivalves, okay, so What's happened here is that the sea star? has humped down over the muscle, which has two shells. What's holding those two shells together? Adductor muscles, exactly. So the adductor muscles are holding those two shells together, and the muscle, the bivalve, wants to keep its two shells together to stay alive, right? The C-star wants to open those two shells to get to the soft gummy bits inside and eat them all, okay? So the first thing that's happening in this picture If there's a little mini war going on and the mini war that's going on is between all those two feet Which are on the outside of the two shells and they're trying to pull pull pull pull the adductor muscles trying to Stay closed right so the first thing that's happening is the combined Suction force of all those two feet with their little suckers are trying to pull that shell open the adductor muscles are staying closed But the echinoderms have catch collagen So it's under neuronal control, but it also has a ratchet-like structure, so it can pull to a certain point and hold without spending more energy. So that allows it an edge, right, because it can pull and hold, whereas the adductor muscles constantly have to spend energy to try and stay closed. So we know who's going to win, right? But the next thing that happens, there's one more sort of fancy piece that these guys have, and that's that two-part stomach. And the two-part stomach can come right out the mouth. Now imagine if we did this, right? We'd all be sitting at the table, we'd go into a restaurant, we'd get our plate of food and then we'd blob our stomach right out on our dinner. It would be gross, right? We'd probably all be eating in closets. Okay, so, but they don't have that problem. So imagine what's going on here is they're pulling the shell open a tiny bit and then out comes the two-part stomach and it starts to go in. What's the stomach secreting? Digestive juices, yes. And so they are helping to break down the muscle. So we're going to see in the next slide, this should just play we hope, is a video showing this process. Like an advancing army, the Sea Stars move into position, slowly but surely working their way up toward their victims. The muscles cannot run or fight. All they can do is hide within their shells as their killers crawl over their bodies. Sensory tube feet sweep over the tightly packed mass of shells, searching for any gap in the mussel's defenses. Settling on its victim, the sea star hunkers down and begins its attack. The miniature camera tucked within the mussel's shell gives us the first look ever at the carnage that unfolds here every day. Once the tube feet have physically breached the mussel's defensive line, the sea star's translucent stomach begins the final assault. The animal actually pushes its stomach inside the mussel's shell, unfolding like a fatal flower. The stomach unleashes a volley of chemical weapons, digestive juices that dissolve the muscle's soft pink flesh. All that's left is a nutrient-rich soup, a broth that's quickly absorbed by the sea star. Having assimilated the muscle, the sea star's stomach pulls away. The animal moves on, leaving behind an empty shell. Without the benefit of speed, brains, or brawn, sea stars are amazingly successful predators. Okay, anybody got questions? So that was pretty good, right? You get the very much sense of what it would be like to be a muscle helplessly sitting there waiting for a sea star to finish chowing down on you. Okay, when we get to this, to the echinoderms, I'll talk a little bit more about their... too. So reproduction, they're mostly dioecious, so that means they have one sex in one body or two sexes in one body. One sex in one body and two different sexed animals, males and females, okay. They have external fertilization for the most part, which means that they release their sperm and eggs into the water around them. That's what's called spawning behavior. So you can see here is a cloud of gametes being released. Here also is a cloud of gametes being released. This one is sperm and this one is eggs. Okay, and again here's in a sea star they're tenting up to release the clouds of gametes Okay, so basically they release that so the key thing is if you're going to do external fertilization What do you have to do? To make it work Would it work just on a random day to start spewing your sperm out into the ocean? No. You have to what? You have to meet up and you have to be synchronized in time, right? So you have behaviors, oftentimes you have... have cues. In corals, for example, when they free spawn, they often use the first full moon in summer. And so there's always, or some animals, there are jellyfish, sea jellies that use the bright rays of sunlight that first hit the water about 7 a.m. in a certain season. So in a reproductive period, everyone sort of gets ready, their hormones turn on, they start producing eggs and sperm, but they have to aggregate, and then they have to have to respond to a cue because if you don't respond to a cue there's your sperm and they diffuse out into the ocean and in 30 seconds no fertilization has happened okay so again there has to be a fairly complicated set of behaviors in order to make free spawning work so again all this stuff that sounds like oh yeah just spew them out there in the water you do that you're not going to be successfully fertilizing anything okay the other thing they're capable of for some of the groups especially the sea stars is asexual reproduction by regeneration and what you can see here is one arm of a blue sea star and what you see here is what does this look like what do you think it is The rest of the sea star regrowing, okay? So the key thing in order to regrow is that they have to have a full piece of an arm and at least some of that central ring, okay? The ring that has the... water vascular system in it, the ring that has the mouth and some of the digestive tissues, they have to have those present. So if you just chop off an arm tip it won't regrow, but if you cut it so that there's a piece of the central disc present, then they can regrow the rest of the body. It's not super fast, but it's very, very sophisticated and comes back just the same way it needs to as a fully functional organism. Okay? So they're capable of pretty good regeneration. Fertilization and cleavage, if we talk about that, you saw this in the lab. Did you guys see fertilization in the sea stars? Yes? Sea urchin, okay. Okay, and it... was look the way it was supposed to yes excellent okay so you have cleavage then you get a fertilization membrane what is the fertilization membrane do does anybody know it what Right, he said, prevents further sperm from entering the egg. So it lifts the other sperm away from the surface of the membrane, and they can't penetrate, okay? It's a physical barrier, okay? So we get one sperm penetrates. the eggs fuses with the nucleus and then you start going through cleavage so uncleaved cleave to the two cell stage cleave to what looks like the four or the eight cell stage here you can see clearly it's the eight cell stage and then it goes on to form what's the name of the ball of cells early in development exactly you get a blastula then the next process to get a stomach is gastrulation lovely excellent okay so We got that. Here's another clicker question. Which deuterostome feature is clearly visible in this picture? So here what we're looking at is uncleaved egg, 2-cell, 8-cell, blastula, gastrulation, development of mesoderm, and up to the small larvae, and we'll talk about the rest of that. So which stage can you clearly, if you had to show somebody in a picture that it was happening, which stage could you see here? Which of these processes are visible? Okay, let's go five more seconds. okay let's see what people thought whoops okay we can well let's let's talk about them and see before we select an answer take that away for a second okay so radial cleavage what is radial cleavage yeah Okay, you can see it in the eight cell stage, and why don't you see if we can make this work. Okay, I don't know if you could hear that the newer cells But the student said is that the newer cells are stacked right on top of the other cells right so you can see in Radial cleavage here if it was what's the other kind of cleavage? Spiral and where that where's the top quartet of cells in spiral? cleavage offset right it's step to the side so I would say that the answer is a you can see radial cleavage can you see regulative cleavage no it's not it's a cellular process it's not visible so that's not right enterocilia would anyone want to try to defend that they've seen enterocilia here Okay, I if you wanted to try it you could maybe say that there's outpouching here Right, but I wouldn't say that I would say that the answer is a radial cleavage Okay, we can You want to give everybody the points on this one, okay? Since we've decided it's a hard question We're going to make sure that everybody will get the points no matter what you answered. As long as you know now what the answer is, right? Okay, so everyone will get the full points on that one. We'll select all of them. There, happiness. Oh, there is no E. Okay, if you picked E, you don't get points. Okay, all right, are we good with that? So let's talk a little bit about more where development goes. So we see here, we can see radial cleavage. with the eight cells stacked. We go to a blastula. We gastrolate. We form the mesoderm. Now, in enterocilia, the mesoderm and the coelom form at the same time. And we pouch out and we form a fluid-filled cavity around the gut. In echinoderms, this development at this stage keeps going till you get these larval forms. And the larval forms are really interesting for a bunch of different reasons that'll come up later through this lecture. But basically, first they start out as little sort of ball-like structures with cilia all over the surface. But then in the developing larva, the skeleton starts to form. And so what you have is a ball-like larvae with cilia, and then cilia. calcium plates start to form inside the body. So those calcium plates push the skeleton out in interesting ways that are predictable. So depending on what the larva looks like, you can identify what it's going to turn into. And basically this general form here is going to turn into a sea urchin. Basically you have this skeletal part here. The skeleton forms these stiff rods and pushes it out in strange ways. And then this larva swims around the ocean feeding for quite a long time Okay Yeah, okay, it swims around feeding then it goes through metamorphosis, and then it turns into an adult urchin So that's the body plan okay, that's the developmental plan okay, so what does that look like well? This is one here. This is a sea star larva and You can see here that it's pushed out into all these interesting patterns and And you don't have to know any of the rest of this, but how it gets into a sea star is really strange. Because at the back end here, this starts to turn into a sea star, and all this fancy stuff is just shed. So it's a really unusual development. And so you go from a bilaterally symmetrical larva. Can you guys see that that's bilaterally symmetrical? So you go from a bilaterally symmetrical to forming the back end of that larva into a pentagonal larva. Penta-radial sea star and then you just jettison all the bilateral tissue Really weird right all right, so that's the development And then we'll talk as we get to the groups about how some of them go back to bilateral symmetry So you started as a bilateral larva? most of them turn into penta-radial adults But then evolution takes some of those penta-radial adult lineages and brings them back to bilateral And that's what you can see here in this sea cucumber it's bilateral and in this one a sand dollar you probably never thought of a sand dollar is bilateral but if you look right here there's a plane of symmetry right through the middle that gives you two identical halves okay so that's why it's called secondary bilateral symmetry because you come back to it evolutionarily after being penta radial okay very strange okay so there's the bilateral symmetry part so now I'm going to go briefly through the classes and then we're going to end with a little bit of ecology so the classes are the crinoids or the sea lilies asteroids are the sea stars ophieroids are brittle stars Kinoids are the urchins and hollow thyroids are the cucumbers. So we'll do, and we're going to do this morphology using the rubber sea star, which is cut out of a yoga mat. Whoops, I'm trying to get more light. I don't think these work super well. Okay, there we go. This is a rubber cut out of a yoga mat meant to represent the sea star. There's the mouth. Here's the five arms, right? Why is this useful? It's useful because it helps us understand how this basic body plan occurs in different groups. So in the crinoids or the sea lilies, most of which are present in fossil form, but there are a few left, the body plan is as if all the arms come out from the center and face up, and there's a stalk or little feet down here. So they're stuck down in, if they have a stalk, they stick themselves down, then they sit with their tube feet up and they collect particles. Okay, that's the basic body plan of the crinoid. If we go to the next one. In the sea star, you already know that, that basic body plan is to face the mouth down, have the tube feet face down, and crawl along surfaces. Yeah, we good with that? just ask a question if you have anything that's not clear as we go through these body plans in the brittle stars which is this is a brittle star right here the key characteristic is that the central disc is set off from the arms so if you want to know am I looking at a sea star or brittle star their bodies are brittle first that's the thing the plates are very heavy and hard but right here you can see this central disk clearly ends and the arms clearly begin you can't see that in a sea star okay if their arms branch more you get a basket star and some of them are bioluminescent this is one that's glowing okay does anybody got a lot of the baskets a lot of the brittle stars are predators they actually have little jaws inside that they use to chew things if you had an aquarium and you want to feed them you can give them a hard-boiled egg and they'll just chow right through it something else you might not need in life case you're going to grow those okay and then the sea urchins and the sand dollars how are they made well they are made as if you took this yoga mat again we've got our five arms we take it and we put it's as if the five arms are connected together at the top to create an orange like shape right now if we do that the mouth down anus is at the top there's five rows of tube feet all around the outside of the orange okay and it can crawl along like this Do we get that? So that's the body plan. And then in the center here there's a mouth, the gut coils around inside, and the anus is still back at the top. So we have this basic five-part body plan that we modify in a whole bunch of different directions. Are we good so far? Questions? Okay, suppose we want to make this into a sand dollar. Then we flatten it like this, and it crawls along this way. If you crawl along with one edge at the front, what kind of symmetry gets selected for? bilateral right because you're moving forward with one edge at the front so we get bilateral symmetry in this in the sand dollars now the cucumbers take the same body plan as the orange okay and then they tip it sideways And then they go like this. So now they got a mouth out here at one end, an anus at the other end. The two feet run long ways down the body. And they're crawling along kind of like this. Right, they don't make any noise. But they go along like this. okay there they go and their two feet run this way so what kind of symmetry gets selected for once you start doing that bilateral right so we see how evolution takes the body plan and keeps turning it in really strange and unpredictable directions and that's how you get so in them they've got a mouth here an anus here gut goes basically linearly two feet run along are the two feet on the top of the body going to be doing much no so mostly in the in the more evolved forms the ones that have changed that the two feet all migrate to the bottom and basically become a foot so we get these amazing changes in body plan Okay, and that gets us to these guys, the cucumbers. Okay. So I'm going to skip this question and go to a little bit of their ecology. So in the urchins, so the urchins that we've just been talking about... They feed on kelp, which is a brown alga. The kelp forests are very rich in number of species, but the urchins, with their little chewing jaws, can chew huge numbers of things, right? So if they become extremely abundant, they can wipe out the kelp forest. And when they do that, they change the ecosystem. As they wipe out the kelp forest, then all of the things that used to live in, on, and around the kelp become what's called an urchin barren. okay so you're and that makes them a keystone ecological species in this to be you learned about the very top of this system does anybody remember what the top predator is orcas right killer whales so there's there is sea otters you're right so there's urchins and they're eaten by otters and so the otters can knock the urchins down but the top predator is killer whales and the killer whales do what to the otters Eat them, right? So what does that mean for the urchins if the otters get eaten? Urchins are up, right? So this was an example you covered in an ecological food web in 2B. And then the other thing is that in BIS 2C, we're just going to mention this disease that the sea stars and some urchins get. You read a paper about this? Can you summarize the paper? Who is willing to summarize the paper? One sentence or less. Can you summarize the paper? Anybody summarize the paper? Uh oh. Okay. Well basically, the paper, maybe you're just being shy. Can you summarize the paper? Okay, well basically the paper says that there's a virus, densovirus, that attacks them and turns them into soft white blobs, where they disintegrate, their arms fall off. It sounds like a horrendous disease, okay? Basically they disintegrate, so that brings us to our last clicker question. Go. What community changes might result from an outbreak of the wasting virus? Okay. Since we just did food webs, you should be able to figure this out. Okay, I think we're there. Let's stop. Yes, I would say that the majority are correct. And the answer is survivorship and increased competition. Okay, thanks. Now that the lecture is finished, you should be able to describe the key features of echinoderms. You should also ask yourself the questions that are posed on the screen. In particular, you should wonder how many times you would need to watch the video or listen to the audio podcast to grasp everything. Watch this as many times as you need, and then we will offer you a practice test. The practice test will help you figure out how much you've assessed, and the key thing is not to be able to look at your notes, but just try the test. We're now going to do the post-lecture sample test. Please take out a piece of paper so that you can record your answers. The first question is, if developing embryos of protostome animals are cut in half, neither half can develop properly. If the developing embryos of deuterostome animals split into two halves at an early stage, both halves can continue to develop. Which of the following choices are deuterostomes? I'll now give you about 20 seconds to read the choices and select the answer you think is best. Let's do the second question. The second question says the echinoderm water vascular system, colon, and gives you five choices, some of which would accurately describe the water vascular system. Please read the choices and select your preferred answer. Question 3 asks about vertebrates. It says, the vertebrates and most other deuterostomes exhibit bilateral symmetry and can be divided into two identical halves. How would you describe the pattern of symmetry in echinoderms? Again, there are five choices, so select your best answer. Question 4 asks, what morphological feature is shared by echinoderms and vertebrates but not present in corals and crabs? Check your answers and make your best choice, please. We're coming up to question five on our practice test. Sea cucumbers are very soft echinoderms. Which of the following are likely to be found in a sea cucumber but not present in a sea urchin? Check your choices. We're now halfway through the practice test. Question 6 asks, which of the following best describes how sea stars feed? So recall what you saw in the video and make your selection. Question 7 asks, for many animals, the anterior-posterior axis is typically seen from the head to the tail. Why do we have to use the oral-aboral axis in echinoderms? Choose one. Question 8 asks about the water vascular system and in particular the echinoderm tube foot. You have five choices to correctly describe a tube foot. Question 9 is the following. Which of the following pairs are most closely related to each other? And you have five groups of taxa to choose from. We are now at the final question of our post-lecture sample test. Question 10 asks, sea urchins are globular echinoderms with skeletons made from hard plates that press together tightly. How can they grow? You'll have to recall material from the lecture to answer this question. Now that you've finished the sample test, you should think about your scores and the questions that were on the tests. One of the things to notice is that each question was paired with one of the learning goals that was on the first slide in the lecture. The learning goals are what you see here. ways that you can figure out what is considered to be important and you should be able to answer learning goals and discuss them without looking at your notes. Another key point is the grading scale in your classes. Some classes will be curve graded but many will not. not. Introductory biology is graded on a straight scale, and you see that I have written here the percentages roughly associated with each of the letter grades. The key thing to notice is that students at Davis must maintain a C average, which on a straight scale is about 73% to be in good standing. Anything below this, including the C-grade, means that you are not in good standing. Students must be in good standing to stay on the campus, and this means that you have to be in good standing. to get a C-. So it's very important that you keep track of your grades and performance in classes to make sure that you always stay in good standing throughout your time at Davis. As you can see in this slide, I've posted the answers to the 10 practice questions. You should now mark yourself and then ask what percentage of the questions did you get right? Are you satisfied with your score? As you think back, you can ask about an efficient learning strategy. If you go and visit the BASC website, which stands for Bias and Biology Academic Success Center, we do have study tips posted from other students. But my hope with this video is that it gave you a chance to figure out how you would perform in class and to give you some time to think about study strategies that are going to work for you when you come to Davis. I'm looking forward to seeing you at orientation, and thanks for listening to this and watching it.

Before you select the courses for areas like chemistry, math, or English, there will be placement exams. or other analysis of your preparation. Depending on your readiness, you may end up taking a pre-class or you may go into the mainstream introductory class.

The goal of the placement exams is to make sure that you're ready to do well in classes at UC Davis. Sometimes there will be a need for extra preparation classes, and these are sometimes called workload classes. You should see these classes as a chance to make sure that you're going to do well by filling in any holes in your background.

It could be that your background wasn't correct when you took classes before you came here. And so the point of this is to find a way to fill it in to make sure you excel when you actually take the mainstream science classes or the writing class. To help you imagine yourself as a university student before you come to campus, I have embedded a video of a standard 50-minute biology class.

The class will be on sea stars and their relatives and it will be part of the introductory biology series. Take a minute to read this size to read some information about the size of the class here and then I'll give you some more tips for absorbing the material in the lecture. As you watch this video imagine yourself sitting in the class. How fast will you absorb the material? How will you learn best in this environment?

As you're listening to the lecture, take notes. Imagine yourself discussing the material with other students, answering the clicker questions, and trying to absorb the material. You may go over this lecture as many times as you wish. In classes at UC Davis, many times there are audio podcasts of the class available, along with PDFs of the slides, and this allows students to review before the next class.

Good morning. Morning, I'm Dr. Keene. Does anybody remember me from orientation? Yay, okay.

Did I tell the truth? Yes. Okay, welcome. I'm going to do today's lecture on echinoderms.

And echinoderms are really fun because they're totally different than what you expect. You're thinking that they're deuterostome animals and you're looking for all the normal features and they're all in strange places or accomplished in strange ways. So that makes them quite fun. So, let's see here. So in the past you did the arthropods.

We're going to do echinoderms today and then Professor Ledford is going to do chordates next and that's probably oftentimes the group people are waiting for most. So we have our learning goals here for the echinoderms. Define the deuterostomes.

We're going to start a little bit with that. We'll do the general body plan and diversity in echinodermata. We'll do the synapomorphies, pentaradial symmetry, which you've seen already in lab, calcareous endoskeleton in the water vascular system. We'll talk a little bit about feeding, and then we'll go through a bit about the main lineages and how the body symmetry has changed. So here we are starting on the tree to figure out where we are.

So this is where bilateral symmetry evolved a long time ago. And within that group, you've already finished talking about the protostomes. And we're going to start talking about the deuterostomes.

So they already... had tripleoblastic body plans and bilateral symmetry and then when we're looking in here we have a developmental character the fate of the blastopore and then when you get to chord H you're going to do the notochord but we're going to go in here and look at a little bit at penta radial symmetry in this group so we're going to start with our clicker question Okay, and I know you've already had this topic, so I'm going to start polling. And it's which of the following are characteristic of the Deuterostomes? You can, as always, talk to your neighbors and discuss the answer.

Okay, we'll go another five seconds. Okay, let's stop. Let's do show results.

Okay, the vast majority of people picked C, and I would say C is right. Can you tell me how you got there? Do you know how you got there?

I know A, B, and D are not right. Okay, so she said, I know A, B, and D are not right. Right? Is that how a lot of people got there? Okay, so what is monozygotic twins?

Single zygote, which means the twins are identical, which means that the zygote split. Okay? If a zygote splits in half and both halves keep going, what kind of cleavage did you have to have?

Regulative, exactly, right? So that's how you got to that answer. All right? Even if you got there by the elimination way, this is actually how you had to think about it to get there. Okay, so because you had regulative cleavage, you get to an eight-cell embryo, you can split into two four-cell embryos, both of them keep going.

Would that have happened in a protostome? No. Excellent. Okay. Okay, so here's the characters that we've been talking about the blastopore develops into the anus in these instead of the mouth They have radial regulative cleavage, and it's pretty clear you guys figured out what that meant so that was excellent So within the deuterostomes we have three groups.

Basically, the echinoderms and the hemichordates, and hemichordates aren't going to really be covered in here, and then the chordates, there's three groups, lancelets, tunicates and vertebrates. We belong in here in the vertebrae. vertebrates but today we're going to spend some time in this branch one of the characters is ciliated larvae penta radial or radial symmetry is adults and we'll see that that gets modified calcified internal plates and loss of pharyngeal gill slits and pharyngeal gill slits were a deuterostome characteristic that's been lost here and is present in these other character other groups so we assume it's ancestral for the clade so if we start thinking about echinoderms you're familiar with echinoderms you've all seen sea stars you've seen sea urchins maybe you've seen brittle stars sea cucumbers you saw those probably in the lab so you've had some familiarity with the basics of the group here's a it's a little dark in here so they don't show super well the characters we just mentioned already penta radial symmetry is adults an endoskeleton which is where we're going to start and then the water vascular system in the the epidermis they have spines or pedicel area our little three jawed pinchers two or three jawed pinchers did you see those in the lab on the skin of them at all anybody see them no if you if you take a sea star and put it under a dissecting scope and come in close you can see tiny little two jawed pinchers that are all over the surface and those are what the pedicel area are and their function is to clean the surface so if you if you look at it under a dissecting scope and then pull out a stiff hair find somebody like me with stiff curly hair and then poke at it the little pinchers will actually grab that hair and move it off of the surface okay they also collect larvae and debris that are all over the surface and move them off so that's what pedestal area are there's no header there's no brain but I will mention that they have some fairly complicated behaviors in spite of that they're dioecious there's external fertilization and we'll talk a little bit more about their lifespan in a sec So has anybody got a question before we go on?

It's kind of, you got the basics of the group? Okay. So we're going to start talking about the endoskeleton.

And this is a sea urchin that is dead, and you're just looking at the shell or the test, it's called. And you can see that it's all made out of hard calcium plates. And again, this is sand dollar I think pretty much everybody's seen a sand dollar skeleton and you know that it's very hard and if you looked at it closely you would see that there are lots of little tiny plates that are joined together or pressed together to make that skeleton and it's an endoskeleton it's covered by epidermis it's inside the skin and then The plates themselves are actually stitched together. What's really cool is that if you look at the plates, they're full of little tiny holes and there's collagen fibers that stitch them together. And so you have a skeleton that appears really rigid, but actually has these flexible collagen sewing lines that sew each plate together around the edges.

And then this collagen, which is a special type called catch collagen, Can be stiff or flexible, but it's not controlled by muscles. It's controlled by the nervous system. Okay, so you have this unusual collagen form that allows them to be stitched together and that can be softened or Tightened and catch collagen as I said here is the special type of connective tissue It changes the rigidity of the body quickly and it's under control by the nervous system. Now the really cool thing is, and if you think about this, imagine you're a sea urchin and your body is hard because all your little plates are stitched together.

How are you going to grow, right? If you're globular, how do you have to grow? How do you think you grow? If you're going to get bigger in your globular, imagine you're shaped like an orange, which way do you think you have to grow?

Out, right? People are doing this with their hands, that's right. You have to do this. So how are you going to do that when your plates are stitched together?

Well, if you loosen the control of the stitching and make a little bit of tiny space between each plate, then you can grow around the edges. So they grow out like an orange, getting bigger and bigger a little at a time. And they can, and there are actually kinds of urchins that are what's called floppy urchins, where their plates are always relatively loosely stitched together.

And so the other ones only loosen their plates when they're going to grow around the edges. So already we're seeing something really complicated, right? A special kind of collagen that's under neuronal control that can be adjusted.

So that's a really cool thing about them. Okay, so here's our next clicker question. A calcareous endoskeleton connected by collagen also occurs in Let's go another five seconds.

Alright, let's see what people got. ooh okay so let's run it through cnidarians do they make calcium yes where what do you think where they don't have shells but do they secrete calcium have you ever gone to the Great Barrier Reef or read about it or watched a video what's on the Great Barrier Reef corals what are corals C. Nidarians, and do they secrete a calcium underneath of themselves and grow slowly up? Yes.

So, Nidarians do calcium, but it's not, it's an exoskeleton, so you're right. Analyze. Anybody know that anilines can secrete calcium? That's a harder one unless you saw the tube-dwelling worms with the calcareous tubes.

Okay, I don't know if you would have seen that one. So you could have eliminated that one just because you didn't know it. Mollusks, do they secrete calcium?

Yes, and they make shells, but they're exoskeletons, right? They're outside the body. Vertebrates, do we secrete calcium?

We make bones, and how are our bones held together? Muscles and? Tendon collagen tendons, right? Right ligaments and tendons so we have collagen so that's why that's the right answer and then our Arthropods do use calcium, but it's definitely an exoskeleton. Okay, are we good?

These are more fun questions. At least I think they're fun. Okay. All right, so we've got a calcareous endoskeleton connected together by collagen.

So that's the first thing that's unusual. But in a way, they're similar, right? They're similar to us in some ways and not in others. The next thing is the water vascular system.

And water vascular system is a hydraulic system, which means it uses water to do work. Okay. And it's used for locomotion through the tube feet. It's for feeding, and we'll talk about how you can use it for feeding.

You can... do waste transportation and respiration because the tube feet are very thin and they're filled with water on the inside and there's water on the outside so things can diffuse across the membranes of the tube feet and pass things in and out okay and there's an external sieve plate on the top did anybody you didn't look enough to see the pedestal area but maybe you will if you get a chance in a lab or during the practical if you're really bored you can use the scope and see the surface of the sea star Joel says no, no one's bored during the practical. Okay, all right. But anyway, if you have a chance to look closely at another sea star, and you can even see this on a dead or dried one. On the top surface somewhere usually right about here, and they show it right there, there's a little plate.

And if you look at it, it's full of lots and lots of tiny little holes. And that's called the madriporite or the mother porpoit. And then it goes through a system of canals that we're gonna talk about in more detail in a minute.

in a second and then it ends in the tube feet and the tube feet are all the little things that the sea stars used to walk on. You saw those, right? And sometimes they have suckers and sometimes they don't. If you were a sea star that lived on sand, would suckers do you any good? No, because you'd be sucking on to things that move.

So the ones that are living on sand have no suckers, but most of them do have suckers. So here's the tube foot system. And this is the, so we're looking.

here at the body of an echinoderm. This is the skin. If we went inside the skin, we'd see the calcareous plate stitched together by collagen. If we see here that also on the top surface is an anus, and then there's a digestive system which we can come back to, and then the mouth is on the bottom.

Okay? So, and then also sticking out along the bottom are all of these tube feet. So if we just strip it down and look just at the water vascular system, and we know that we can imagine that each of these systems here are extended out into the five arms, this is just the water vascular system alone, okay? there's the madraporite that would be on the top surface or the aboral surface okay and that extends down into a stone canal and that's just a tube that runs from the top surface down towards the bottom surface and it's called the stone canal because if you ever do a dissection of this, it's really, really hard. It's a very stiff canal.

It feels like it's made out of stone. So you go to the stone canal and you get down through the body. So we move down through the body to this ring canal and the mouth is in the center here.

So does anyone have a question about where you're oriented? Are we in the right place sort of thinking about the body? Yeah. Okay. So we've dropped down from the top surface through the stone canal into a ring.

canal that wraps around the mouth and the mouth is here. Coming off the ring canal are all of these what's called lateral canals. So this big canal down the center here, those are lateral canals.

Okay and fluid flows in them. Now the madriporite connects the water vascular system to the outside through the top but it's only really used when the water vascular system is set up. So biologists tend to do what's called loss of function experiments right. If we want to know what something does, we break it and then we see how the animal does. So if you wanted to know whether the water vascular system was essential for the two feet to keep working, what would you do?

What would you do? You could remove the madriporite or in this case they just puttied over it. They got like putty and they puttied over it and the sea star went, oh that's a drag but it kept walking and living and fine. So from that we learned that if you putty over the madriporite it can still function. It probably has other ways of bringing fluid into the tube feed.

Okay, but it is if you do that early in development it doesn't work so it's important for setting up the water vascular system. Okay. So we've got fluid comes down here and fluid goes down all here into these lateral canals.

And off of every lateral canal is a little thing here called a radial canal. Here they all are. And then this is the tube foot. Are we good?

Okay. So I made a model of a tube foot out of a turkey baster. There's many thousands of things you can do with turkey basters. Okay.

And we got the bulb up here. And this is a balloon. You can use anything that's stretchy at the bottom.

And the way the tube foot works is that you've got this canal coming here, right? The lateral canal. And if the lateral...

there's a valve in the lateral canal. And when that valve is open, fluid can go in here, okay? But if I need to stiffen this, what do I have to do? If I need water to be in a closed space, what do I have to do with the valve? Close it, exactly.

So... If we want to use the tube foot, we close the valve and then we have to stiffen it. So this is called an ampulla. It's just a reservoir.

So we've got this reservoir at the top. We've got our canal here. We close the valve. Now to stiffen the tube foot, we have to do this, right?

Okay? So and then it becomes stiff and I can walk on it. Or I could if I was an echinoderm.

Going along. Okay? So what kind of muscles are in here? Longitudinal muscles run long ways, circular muscles run around the body.

What kind are these? Circular muscles, exactly. So you close the valve, you contract the circular muscles, you force the fluid individually down in each tube foot, and you can walk along on it, okay?

So again, you've got to be thinking about the amount of neuronal control that has to go on here, because you're controlling every single tube foot, and you're telling them, let's start walking. So again, we're not talking about neuronally unsophisticated organisms. Anybody got a question about the water vascular system?

Cool. And that brings us to our next clicker question. Sorry, we're doing a lot of clickers today. So if you wanted to turn the end of a tube foot into a suction cup, which of these three changes would you have to make?

Okay, so what I'm asking is, if I want this to not just be like this, but to be a suction cup right here, What do I have to add to the body to do that? Okay, talk about it with your neighbors. Think about what a suction cup looks like. What shape does a suction cup have?

Okay, let's go another five seconds. Okay, four, five. All right, stop.

All right, let's see what we got. Oops. Okay, a little bit of uncertainty, but the majority is correct.

Take that away. All right, so let's talk about it. So what shape does a suction cup have? It's lifted in the center, right?

So what they do is they add a longitudinal muscle that runs from the top here to the bottom in the middle of the tube foot. So you add a longitudinal muscle that runs from here to here and then when muscle contracts the second the center of the tube foot lifts up and becomes a suction cup so they can hang on to stuff okay again sophisticated control because you have to contract you have to close the valve squeeze the circular muscles contract the longitudinal muscles and lift the center of that tube foot up to make a suction cup and In fact the other thing they have is a calcareous ring That's right around the outside edge of that tube foot to stiffen it because if you think about the mechanical structure of a suction cup Again, it's stiff around that outer edge. Okay, and then it's lifted up in the center. Are we good questions great?

Okay Okay, so back to the body plan There's no head or brain as I said, but we've already there's a nerve ring and a very complicated diffuse nerve net But already you're getting the picture I think from the things I've talked about that these are not just little boys of tissue wandering around the ocean. They are capable of very active processes, and I'll talk a little bit more about their behavior eventually. So we talked about respiration by diffusion.

You can diffuse across the tube feet. There's also these dermal outpocketings. It's called skin gills.

Again, if you took a dissecting scope and looked close at the surface of a sea star, you'd see little clear sacs sticking up between every plate. And those are for respiration, right? So between the plates, they run little out pocketings of very thin skin. It looks like clear blisters. And they're all over the surface, and that's how they do gas exchange.

See, there's a lot to look at if you get that dissecting scope on those sea stars. OK. And then we talked before there's an oral side. That's the mouth side That's on the bottom the top side is the aboral side and the aboral side has the anus So basically you're eating on the bottom you're taking your food in you're running it into the gut and then out into these Digestive tracts in each arms and that gives us a complete gut because it's mouth and anus with regional specialization Okay, anybody got questions about the guts But the sea stars have really fancy guts.

They can do something else extra. It would be disgusting if we could do this thing. Okay, but it's not for them. Okay, so they have the digestive tract here, and then when they're done with the waste, they come out the top.

Now, you notice here in this picture that there's a stomach here, and I know it's not super hard to see, super easy to see, and there's a tract that comes out into arms, but there's also a part of the stomach that's below that. So they have a two-part stomach, okay? So there's the mouth part one of the stomach behind that is part two of the stomach and then at the top of that is the Anus are we good all right? And so this is a video of a sea star this will be a video of a sea star eating shortly And this is a sea star right here, and it's eating this which is a muscle you remember muscles bivalves, okay, so What's happened here is that the sea star? has humped down over the muscle, which has two shells.

What's holding those two shells together? Adductor muscles, exactly. So the adductor muscles are holding those two shells together, and the muscle, the bivalve, wants to keep its two shells together to stay alive, right? The C-star wants to open those two shells to get to the soft gummy bits inside and eat them all, okay? So the first thing that's happening in this picture If there's a little mini war going on and the mini war that's going on is between all those two feet Which are on the outside of the two shells and they're trying to pull pull pull pull the adductor muscles trying to Stay closed right so the first thing that's happening is the combined Suction force of all those two feet with their little suckers are trying to pull that shell open the adductor muscles are staying closed But the echinoderms have catch collagen So it's under neuronal control, but it also has a ratchet-like structure, so it can pull to a certain point and hold without spending more energy.

So that allows it an edge, right, because it can pull and hold, whereas the adductor muscles constantly have to spend energy to try and stay closed. So we know who's going to win, right? But the next thing that happens, there's one more sort of fancy piece that these guys have, and that's that two-part stomach. And the two-part stomach can come right out the mouth. Now imagine if we did this, right?

We'd all be sitting at the table, we'd go into a restaurant, we'd get our plate of food and then we'd blob our stomach right out on our dinner. It would be gross, right? We'd probably all be eating in closets. Okay, so, but they don't have that problem. So imagine what's going on here is they're pulling the shell open a tiny bit and then out comes the two-part stomach and it starts to go in.

What's the stomach secreting? Digestive juices, yes. And so they are helping to break down the muscle. So we're going to see in the next slide, this should just play we hope, is a video showing this process.

Like an advancing army, the Sea Stars move into position, slowly but surely working their way up toward their victims. The muscles cannot run or fight. All they can do is hide within their shells as their killers crawl over their bodies. Sensory tube feet sweep over the tightly packed mass of shells, searching for any gap in the mussel's defenses. Settling on its victim, the sea star hunkers down and begins its attack.

The miniature camera tucked within the mussel's shell gives us the first look ever at the carnage that unfolds here every day. Once the tube feet have physically breached the mussel's defensive line, the sea star's translucent stomach begins the final assault. The animal actually pushes its stomach inside the mussel's shell, unfolding like a fatal flower. The stomach unleashes a volley of chemical weapons, digestive juices that dissolve the muscle's soft pink flesh. All that's left is a nutrient-rich soup, a broth that's quickly absorbed by the sea star.

Having assimilated the muscle, the sea star's stomach pulls away. The animal moves on, leaving behind an empty shell. Without the benefit of speed, brains, or brawn, sea stars are amazingly successful predators. Okay, anybody got questions?

So that was pretty good, right? You get the very much sense of what it would be like to be a muscle helplessly sitting there waiting for a sea star to finish chowing down on you. Okay, when we get to this, to the echinoderms, I'll talk a little bit more about their... too.

So reproduction, they're mostly dioecious, so that means they have one sex in one body or two sexes in one body. One sex in one body and two different sexed animals, males and females, okay. They have external fertilization for the most part, which means that they release their sperm and eggs into the water around them.

That's what's called spawning behavior. So you can see here is a cloud of gametes being released. Here also is a cloud of gametes being released. This one is sperm and this one is eggs. Okay, and again here's in a sea star they're tenting up to release the clouds of gametes Okay, so basically they release that so the key thing is if you're going to do external fertilization What do you have to do?

To make it work Would it work just on a random day to start spewing your sperm out into the ocean? No. You have to what? You have to meet up and you have to be synchronized in time, right? So you have behaviors, oftentimes you have...

have cues. In corals, for example, when they free spawn, they often use the first full moon in summer. And so there's always, or some animals, there are jellyfish, sea jellies that use the bright rays of sunlight that first hit the water about 7 a.m.

in a certain season. So in a reproductive period, everyone sort of gets ready, their hormones turn on, they start producing eggs and sperm, but they have to aggregate, and then they have to have to respond to a cue because if you don't respond to a cue there's your sperm and they diffuse out into the ocean and in 30 seconds no fertilization has happened okay so again there has to be a fairly complicated set of behaviors in order to make free spawning work so again all this stuff that sounds like oh yeah just spew them out there in the water you do that you're not going to be successfully fertilizing anything okay the other thing they're capable of for some of the groups especially the sea stars is asexual reproduction by regeneration and what you can see here is one arm of a blue sea star and what you see here is what does this look like what do you think it is The rest of the sea star regrowing, okay? So the key thing in order to regrow is that they have to have a full piece of an arm and at least some of that central ring, okay? The ring that has the... water vascular system in it, the ring that has the mouth and some of the digestive tissues, they have to have those present.

So if you just chop off an arm tip it won't regrow, but if you cut it so that there's a piece of the central disc present, then they can regrow the rest of the body. It's not super fast, but it's very, very sophisticated and comes back just the same way it needs to as a fully functional organism. Okay? So they're capable of pretty good regeneration.

Fertilization and cleavage, if we talk about that, you saw this in the lab. Did you guys see fertilization in the sea stars? Yes?

Sea urchin, okay. Okay, and it... was look the way it was supposed to yes excellent okay so you have cleavage then you get a fertilization membrane what is the fertilization membrane do does anybody know it what Right, he said, prevents further sperm from entering the egg.

So it lifts the other sperm away from the surface of the membrane, and they can't penetrate, okay? It's a physical barrier, okay? So we get one sperm penetrates. the eggs fuses with the nucleus and then you start going through cleavage so uncleaved cleave to the two cell stage cleave to what looks like the four or the eight cell stage here you can see clearly it's the eight cell stage and then it goes on to form what's the name of the ball of cells early in development exactly you get a blastula then the next process to get a stomach is gastrulation lovely excellent okay so We got that.

Here's another clicker question. Which deuterostome feature is clearly visible in this picture? So here what we're looking at is uncleaved egg, 2-cell, 8-cell, blastula, gastrulation, development of mesoderm, and up to the small larvae, and we'll talk about the rest of that. So which stage can you clearly, if you had to show somebody in a picture that it was happening, which stage could you see here? Which of these processes are visible?

Okay, let's go five more seconds. okay let's see what people thought whoops okay we can well let's let's talk about them and see before we select an answer take that away for a second okay so radial cleavage what is radial cleavage yeah Okay, you can see it in the eight cell stage, and why don't you see if we can make this work. Okay, I don't know if you could hear that the newer cells But the student said is that the newer cells are stacked right on top of the other cells right so you can see in Radial cleavage here if it was what's the other kind of cleavage?

Spiral and where that where's the top quartet of cells in spiral? cleavage offset right it's step to the side so I would say that the answer is a you can see radial cleavage can you see regulative cleavage no it's not it's a cellular process it's not visible so that's not right enterocilia would anyone want to try to defend that they've seen enterocilia here Okay, I if you wanted to try it you could maybe say that there's outpouching here Right, but I wouldn't say that I would say that the answer is a radial cleavage Okay, we can You want to give everybody the points on this one, okay? Since we've decided it's a hard question We're going to make sure that everybody will get the points no matter what you answered.

As long as you know now what the answer is, right? Okay, so everyone will get the full points on that one. We'll select all of them.

There, happiness. Oh, there is no E. Okay, if you picked E, you don't get points.

Okay, all right, are we good with that? So let's talk a little bit about more where development goes. So we see here, we can see radial cleavage. with the eight cells stacked. We go to a blastula.

We gastrolate. We form the mesoderm. Now, in enterocilia, the mesoderm and the coelom form at the same time.

And we pouch out and we form a fluid-filled cavity around the gut. In echinoderms, this development at this stage keeps going till you get these larval forms. And the larval forms are really interesting for a bunch of different reasons that'll come up later through this lecture.

But basically, first they start out as little sort of ball-like structures with cilia all over the surface. But then in the developing larva, the skeleton starts to form. And so what you have is a ball-like larvae with cilia, and then cilia. calcium plates start to form inside the body.

So those calcium plates push the skeleton out in interesting ways that are predictable. So depending on what the larva looks like, you can identify what it's going to turn into. And basically this general form here is going to turn into a sea urchin. Basically you have this skeletal part here.

The skeleton forms these stiff rods and pushes it out in strange ways. And then this larva swims around the ocean feeding for quite a long time Okay Yeah, okay, it swims around feeding then it goes through metamorphosis, and then it turns into an adult urchin So that's the body plan okay, that's the developmental plan okay, so what does that look like well? This is one here.

This is a sea star larva and You can see here that it's pushed out into all these interesting patterns and And you don't have to know any of the rest of this, but how it gets into a sea star is really strange. Because at the back end here, this starts to turn into a sea star, and all this fancy stuff is just shed. So it's a really unusual development. And so you go from a bilaterally symmetrical larva.

Can you guys see that that's bilaterally symmetrical? So you go from a bilaterally symmetrical to forming the back end of that larva into a pentagonal larva. Penta-radial sea star and then you just jettison all the bilateral tissue Really weird right all right, so that's the development And then we'll talk as we get to the groups about how some of them go back to bilateral symmetry So you started as a bilateral larva? most of them turn into penta-radial adults But then evolution takes some of those penta-radial adult lineages and brings them back to bilateral And that's what you can see here in this sea cucumber it's bilateral and in this one a sand dollar you probably never thought of a sand dollar is bilateral but if you look right here there's a plane of symmetry right through the middle that gives you two identical halves okay so that's why it's called secondary bilateral symmetry because you come back to it evolutionarily after being penta radial okay very strange okay so there's the bilateral symmetry part so now I'm going to go briefly through the classes and then we're going to end with a little bit of ecology so the classes are the crinoids or the sea lilies asteroids are the sea stars ophieroids are brittle stars Kinoids are the urchins and hollow thyroids are the cucumbers.

So we'll do, and we're going to do this morphology using the rubber sea star, which is cut out of a yoga mat. Whoops, I'm trying to get more light. I don't think these work super well. Okay, there we go. This is a rubber cut out of a yoga mat meant to represent the sea star.

There's the mouth. Here's the five arms, right? Why is this useful?

It's useful because it helps us understand how this basic body plan occurs in different groups. So in the crinoids or the sea lilies, most of which are present in fossil form, but there are a few left, the body plan is as if all the arms come out from the center and face up, and there's a stalk or little feet down here. So they're stuck down in, if they have a stalk, they stick themselves down, then they sit with their tube feet up and they collect particles. Okay, that's the basic body plan of the crinoid.

If we go to the next one. In the sea star, you already know that, that basic body plan is to face the mouth down, have the tube feet face down, and crawl along surfaces. Yeah, we good with that?

just ask a question if you have anything that's not clear as we go through these body plans in the brittle stars which is this is a brittle star right here the key characteristic is that the central disc is set off from the arms so if you want to know am I looking at a sea star or brittle star their bodies are brittle first that's the thing the plates are very heavy and hard but right here you can see this central disk clearly ends and the arms clearly begin you can't see that in a sea star okay if their arms branch more you get a basket star and some of them are bioluminescent this is one that's glowing okay does anybody got a lot of the baskets a lot of the brittle stars are predators they actually have little jaws inside that they use to chew things if you had an aquarium and you want to feed them you can give them a hard-boiled egg and they'll just chow right through it something else you might not need in life case you're going to grow those okay and then the sea urchins and the sand dollars how are they made well they are made as if you took this yoga mat again we've got our five arms we take it and we put it's as if the five arms are connected together at the top to create an orange like shape right now if we do that the mouth down anus is at the top there's five rows of tube feet all around the outside of the orange okay and it can crawl along like this Do we get that? So that's the body plan. And then in the center here there's a mouth, the gut coils around inside, and the anus is still back at the top. So we have this basic five-part body plan that we modify in a whole bunch of different directions. Are we good so far?

Questions? Okay, suppose we want to make this into a sand dollar. Then we flatten it like this, and it crawls along this way. If you crawl along with one edge at the front, what kind of symmetry gets selected for?

bilateral right because you're moving forward with one edge at the front so we get bilateral symmetry in this in the sand dollars now the cucumbers take the same body plan as the orange okay and then they tip it sideways And then they go like this. So now they got a mouth out here at one end, an anus at the other end. The two feet run long ways down the body. And they're crawling along kind of like this.

Right, they don't make any noise. But they go along like this. okay there they go and their two feet run this way so what kind of symmetry gets selected for once you start doing that bilateral right so we see how evolution takes the body plan and keeps turning it in really strange and unpredictable directions and that's how you get so in them they've got a mouth here an anus here gut goes basically linearly two feet run along are the two feet on the top of the body going to be doing much no so mostly in the in the more evolved forms the ones that have changed that the two feet all migrate to the bottom and basically become a foot so we get these amazing changes in body plan Okay, and that gets us to these guys, the cucumbers. Okay. So I'm going to skip this question and go to a little bit of their ecology.

So in the urchins, so the urchins that we've just been talking about... They feed on kelp, which is a brown alga. The kelp forests are very rich in number of species, but the urchins, with their little chewing jaws, can chew huge numbers of things, right?

So if they become extremely abundant, they can wipe out the kelp forest. And when they do that, they change the ecosystem. As they wipe out the kelp forest, then all of the things that used to live in, on, and around the kelp become what's called an urchin barren.

okay so you're and that makes them a keystone ecological species in this to be you learned about the very top of this system does anybody remember what the top predator is orcas right killer whales so there's there is sea otters you're right so there's urchins and they're eaten by otters and so the otters can knock the urchins down but the top predator is killer whales and the killer whales do what to the otters Eat them, right? So what does that mean for the urchins if the otters get eaten? Urchins are up, right? So this was an example you covered in an ecological food web in 2B.

And then the other thing is that in BIS 2C, we're just going to mention this disease that the sea stars and some urchins get. You read a paper about this? Can you summarize the paper?

Who is willing to summarize the paper? One sentence or less. Can you summarize the paper? Anybody summarize the paper? Uh oh.

Okay. Well basically, the paper, maybe you're just being shy. Can you summarize the paper?

Okay, well basically the paper says that there's a virus, densovirus, that attacks them and turns them into soft white blobs, where they disintegrate, their arms fall off. It sounds like a horrendous disease, okay? Basically they disintegrate, so that brings us to our last clicker question.

Go. What community changes might result from an outbreak of the wasting virus? Okay. Since we just did food webs, you should be able to figure this out.

Okay, I think we're there. Let's stop. Yes, I would say that the majority are correct.

And the answer is survivorship and increased competition. Okay, thanks. Now that the lecture is finished, you should be able to describe the key features of echinoderms.

You should also ask yourself the questions that are posed on the screen. In particular, you should wonder how many times you would need to watch the video or listen to the audio podcast to grasp everything. Watch this as many times as you need, and then we will offer you a practice test. The practice test will help you figure out how much you've assessed, and the key thing is not to be able to look at your notes, but just try the test.

We're now going to do the post-lecture sample test. Please take out a piece of paper so that you can record your answers. The first question is, if developing embryos of protostome animals are cut in half, neither half can develop properly. If the developing embryos of deuterostome animals split into two halves at an early stage, both halves can continue to develop. Which of the following choices are deuterostomes?

I'll now give you about 20 seconds to read the choices and select the answer you think is best. Let's do the second question. The second question says the echinoderm water vascular system, colon, and gives you five choices, some of which would accurately describe the water vascular system.

Please read the choices and select your preferred answer. Question 3 asks about vertebrates. It says, the vertebrates and most other deuterostomes exhibit bilateral symmetry and can be divided into two identical halves.

How would you describe the pattern of symmetry in echinoderms? Again, there are five choices, so select your best answer. Question 4 asks, what morphological feature is shared by echinoderms and vertebrates but not present in corals and crabs?

Check your answers and make your best choice, please. We're coming up to question five on our practice test. Sea cucumbers are very soft echinoderms. Which of the following are likely to be found in a sea cucumber but not present in a sea urchin? Check your choices.

We're now halfway through the practice test. Question 6 asks, which of the following best describes how sea stars feed? So recall what you saw in the video and make your selection. Question 7 asks, for many animals, the anterior-posterior axis is typically seen from the head to the tail.

Why do we have to use the oral-aboral axis in echinoderms? Choose one. Question 8 asks about the water vascular system and in particular the echinoderm tube foot. You have five choices to correctly describe a tube foot.

Question 9 is the following. Which of the following pairs are most closely related to each other? And you have five groups of taxa to choose from. We are now at the final question of our post-lecture sample test. Question 10 asks, sea urchins are globular echinoderms with skeletons made from hard plates that press together tightly.

How can they grow? You'll have to recall material from the lecture to answer this question. Now that you've finished the sample test, you should think about your scores and the questions that were on the tests.

One of the things to notice is that each question was paired with one of the learning goals that was on the first slide in the lecture. The learning goals are what you see here. ways that you can figure out what is considered to be important and you should be able to answer learning goals and discuss them without looking at your notes. Another key point is the grading scale in your classes.

Some classes will be curve graded but many will not. not. Introductory biology is graded on a straight scale, and you see that I have written here the percentages roughly associated with each of the letter grades. The key thing to notice is that students at Davis must maintain a C average, which on a straight scale is about 73% to be in good standing.

Anything below this, including the C-grade, means that you are not in good standing. Students must be in good standing to stay on the campus, and this means that you have to be in good standing. to get a C-.

So it's very important that you keep track of your grades and performance in classes to make sure that you always stay in good standing throughout your time at Davis. As you can see in this slide, I've posted the answers to the 10 practice questions. You should now mark yourself and then ask what percentage of the questions did you get right? Are you satisfied with your score? As you think back, you can ask about an efficient learning strategy.

If you go and visit the BASC website, which stands for Bias and Biology Academic Success Center, we do have study tips posted from other students. But my hope with this video is that it gave you a chance to figure out how you would perform in class and to give you some time to think about study strategies that are going to work for you when you come to Davis. I'm looking forward to seeing you at orientation, and thanks for listening to this and watching it.

Transcript for:Introduction to Echinoderms Overview

Transcript for:
Introduction to Echinoderms Overview