This week's episode is all about echinoderms, or at least the star-shaped echinoderms! Thanks to Llewelly for the suggestion about feather stars and crinoids! A very pretty starfish: Crown of thorns starfish. Do not touch: Pumpkin starfish or orange throw pillow? YOU DECIDE: Sea daisies. Not much to look at tbh: A banded arm brittle star: Ruby brittle stars: Brittle stars riding around in a jelly: A basket star: Basket stars got TEETH THINGS: A stemmed crinoid: A lovely feather star: Further reading: Echinoblog, a really amazing resource and so much fun to browse Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re going to look at some marine animals that most people barely think about, but which are really interesting. It was going to just be about starfish and maybe one other animal, but while I was still researching starfish, listener Llewelly suggested I cover feather stars and crinoids. They’re related to starfish, so I thought I’d tack them on. And if you talk about starfish, you really have to talk about brittle stars too, and if you talk about brittle stars you have to talk about basket stars. Basically, I had to stop myself from breaking this episode into two big episodes about echinoderms. It’s just the stars this time. Before we get into echinoderms, though, a quick note about my schedule. Next week I’m going on a trip to Paris, France! I know it sounds like I’m rich and just travel as my whim takes me, but actually I just have really generous relatives. A week and a half after I return from Paris, I’ll be in Atlanta, Georgia for DragonCon, where I’ll be on a panel about podcasting. In other words, I won’t be around much on social media for the rest of August, but don’t worry, I’ll have episodes recorded and scheduled to run normally while I’m gone. Okay, now let’s get into echinoderms. Echinoderms include sand dollars, sea urchins, starfish, and many others, and every single echinoderm lives in the ocean. Many of them can regenerate limbs and other body parts, and instead of blood they have a water vascular system. In most echinoderms, seawater enters the body through slits or pores, then travels through canals within the body to transport oxygen to cells and waste products out of cells. Echinoderms have internal skeletons made of calcium carbonate, but they’re invertebrates because they don’t have a backbone. Heck, technically they don’t even have a back. Echinoderms show radial symmetry, which means their bodies are roughly the same in all directions instead of having a clear front and rear. The echinoderms we’re talking about this week are ones that also exhibit pentaradial symmetry, which means they have five sides. And the best-known echinoderms out there are starfish. There are about 1,500 species of starfish known, and some of them are really weird and some are only kind of weird. Most have five arms but some have a whole lot more. Starfish are members of the class Asteroidea, which just delights me. A better name for them is sea star, since they’re not fish at all. Starfish have been around for at least 450 million years, but in 2012 paleontologists found a fossil of the oldest known ancestor of starfish in the mountains of Morocco. It’s about 515 million years old, from the Cambrian period. It was only about an inch and a half long, or 4 cm, and looked similar to the modern-day sea lily, or crinoid. If you recall, the Cambrian period was when life was expanding rapidly in the oceans and evolving sometimes quite strange body plans. You know, like things with FIVE LEGS. Most starfish have ossicles in their skin, little hard beads of calcium carbonate that help protect the animal. In some starfish, the ossicles are more like spines or even spikes. Although cartoons of starfish usually make them look like their legs are always exactly star-shaped,