Everything You Didn't Know About Starfish

This is a starfish. Starfish have five arms and...wait a sec, that's not right. Starfish don't have five arms. Huh, how about that? Here's a starfish with six arms and another with nine. This one has ten arms and here's one with too many to count. Starfish can have any number of arms. They could be spiky, flat, or inflated like a balloon. But there's something strange about these starfish. They all have something in common that's very odd. Right here, a small dot on their top. It seems almost out of place. Every starfish has this same spot on their top, a little off-center. Well, what is it? Huh, it turns out this spot is actually a small hole called a madriporite. Starfish suck water into their bodies through their madriporite. They use that water to inflate their feet right here. You see those tiny wiggly tubes? These are starfish feet. I thought starfish stayed in place, but I was wrong. Watch this time lapse. They walk around on those hundreds of tiny feet. Here's how. This is a computer model of how starfish walk. Each foot will reach out and grab the surface the starfish is walking on. Then if any foot gets stretched out, the foot lets go and reaches forward again. When all the feet do this, it scoots the starfish forward. Take a look and watch this. It uses its arms to push itself forward too. This starfish... Wait, that's not right? Huh, I thought everything that kind of looked like a starfish was a starfish, but it's not because look here. It has skinny arms and a clear center disc. Starfish have thicker arms without a clear center disc. This is not a starfish. Instead, it's something different called a brittle star. That made me think, is this a starfish? It has a center disc too. If you have an idea what it is, let me know in the comments. So starfish move around, but I've always wondered, how do they see where they're going? Do starfish see at all? Do they have eyes? Starfish do have eyes. I'll tell you where they are, but first, these videos take a lot of work to put together, so it would really mean a whole lot to me if you sat through this short segment about this video's sponsor, Fishing Clash. Lately, I've been learning a lot about fish diversity, but not from a book. Instead, from this game. Look, I caught something. I wonder what it is. A yellow tail snapper. I love learning about animals, and Fishing Clash is a surprising way to learn a lot about fish diversity, because all the fish in the game are real examples of fish in real life. Like Queen Triggerfish, French Angelfish, and Tambaki. If you'd like to learn and have some fun, give it a try. And in the game, use my gift code by pressing this button, then gift codes, and entering the code STARFISH to claim a $20 reward of items and power-ups to help you catch bigger fish. What was I wondering again? Oh yeah, where are a starfish's eyes? They aren't here, or on their underside, like you'd expect. Instead, look here, at the starfish's arm. Do you see that small dot at the very tip of the starfish's arm? That spot is a simple starfish eye. Starfish have simple eyes on the end of each of their legs, but how well can they see? Well, here's an image of a scene. Can starfish see the whole thing? Or maybe they can only see blue, or have high contrast vision. A starfish would see this scene kind of like this. It's not that great, but it does the job. I wonder what they're looking for. Probably something to eat, like algae. Well, I thought they ate algae, but I was wrong. Starfish are carnivorous, and some hunt other animals. Watch closely. Did you see that? Something's rustling under the sand. What is it? It just swam away. Oh, it's a scallop. This starfish is hunting scallops, which swim away so they don't get eaten. Starfish eat mollusks. Watch here. They'll grab hold of the mollusk and move it towards their mouth with their tiny tube feet, then chomp on it with their teeth. Wait a sec. Starfish don't have teeth? I thought starfish were like sea urchins and ate food using their teeth on their underside, but that's not right. Instead, watch closely right here. This cloudy goo is the starfish's stomach. Starfish can push their stomach out of their body. Next, it'll squeeze its stomach in between the mollusk's shells to digest the mollusk from the inside out. And just like me, after a nice meal, starfish like to poop. But how do starfish poop? They probably do it from their underside. Oh, I'm so sorry. That wasn't right. The answer is quite simple. Starfish poop out of a tiny hole in the very middle of their top. And remember, use the gift code starfish to get a $20 reward and these bonuses to help you catch bigger fish in Fishing Clash.