1 00:00:01,920 --> 00:00:06,360 Speaker 1: Welcome to brain Stuff production of I Heart Radio, Hey 2 00:00:06,440 --> 00:00:11,520 Speaker 1: brain Stuff lorn Volga Baum Here. While starfish live underwater, 3 00:00:11,840 --> 00:00:15,920 Speaker 1: they're not actually fish at all. In fact, marine scientists 4 00:00:15,920 --> 00:00:18,960 Speaker 1: have replaced the beloved starfish is common name with the 5 00:00:19,040 --> 00:00:23,919 Speaker 1: name sea star because the starfish isn't a fish? So 6 00:00:24,079 --> 00:00:27,480 Speaker 1: what exactly are they? For the article this episode is 7 00:00:27,520 --> 00:00:30,560 Speaker 1: based on How'stuff works, spoken by email with Kim Stone, 8 00:00:30,720 --> 00:00:35,160 Speaker 1: the Georgia Aquarium's curator of Fish and Invertebrates. As she said, 9 00:00:35,600 --> 00:00:38,800 Speaker 1: they're a type of invertebrate, meaning they don't have a backbone. 10 00:00:39,280 --> 00:00:42,280 Speaker 1: Their body consists of a central disk with arms that 11 00:00:42,440 --> 00:00:45,960 Speaker 1: radiate out and on the underside there are hundreds to 12 00:00:46,040 --> 00:00:50,000 Speaker 1: thousands of small suction cups called tube feet that helped 13 00:00:50,040 --> 00:00:53,160 Speaker 1: the c star move around, stick to different surfaces, and eat. 14 00:00:54,400 --> 00:00:57,320 Speaker 1: There are some other big differences that set starfish apart 15 00:00:57,400 --> 00:01:02,160 Speaker 1: from fish. These cool creatures don't of gills, scales, or fins. 16 00:01:02,200 --> 00:01:04,880 Speaker 1: They live only in salt water, and they use sea 17 00:01:04,959 --> 00:01:08,320 Speaker 1: water instead of blood to pump nutrients through their bodies 18 00:01:08,400 --> 00:01:13,080 Speaker 1: by means of a water vascular system, unlike fish that 19 00:01:13,160 --> 00:01:16,759 Speaker 1: have gills and mammals that have lungs. See stars breathe 20 00:01:16,840 --> 00:01:19,640 Speaker 1: by absorbing oxygen from the water through different parts of 21 00:01:19,640 --> 00:01:23,680 Speaker 1: their body, such as their skin and tube feet. Stone 22 00:01:23,720 --> 00:01:26,959 Speaker 1: explained sea stars belonged to a group of marine invertebrates 23 00:01:27,040 --> 00:01:30,399 Speaker 1: called kinoderms, which first appeared more than five hundred million 24 00:01:30,480 --> 00:01:34,120 Speaker 1: years ago. The ancestors of modern day sea stars appeared 25 00:01:34,160 --> 00:01:36,640 Speaker 1: more than four hundred and fifty billion years ago during 26 00:01:36,640 --> 00:01:41,760 Speaker 1: the or Division period. Chinoderms include five classes of marine 27 00:01:41,840 --> 00:01:45,880 Speaker 1: life see stars, brittle and basket stars, sea urchins and 28 00:01:45,920 --> 00:01:50,440 Speaker 1: sand dollars, sea cucumbers and sea lilies, and feather stars. 29 00:01:51,360 --> 00:01:54,480 Speaker 1: There are around two thousand different species of sea stars. 30 00:01:54,920 --> 00:01:57,520 Speaker 1: A Stone said they can be found in a variety 31 00:01:57,520 --> 00:02:01,640 Speaker 1: of habitats, from shallow sandy bottoms, cold rocky environments to 32 00:02:01,680 --> 00:02:05,720 Speaker 1: the bottom of the sea floor. The different species have 33 00:02:05,800 --> 00:02:09,880 Speaker 1: many different features, but all have their mouth on their underside. 34 00:02:10,400 --> 00:02:13,880 Speaker 1: Upon capturing food, often a bivalve such as a clamor 35 00:02:13,960 --> 00:02:17,000 Speaker 1: muscle with its tube feet, the sea star wraps its 36 00:02:17,080 --> 00:02:20,440 Speaker 1: arms around the animal's shell and pulls it open just slightly. 37 00:02:21,120 --> 00:02:24,000 Speaker 1: Then the sea star pushes its stomach through its own 38 00:02:24,040 --> 00:02:27,640 Speaker 1: mouth and into the praise shell. It then digests the 39 00:02:27,680 --> 00:02:31,040 Speaker 1: animal and slides its stomach back into its own body. 40 00:02:31,520 --> 00:02:35,040 Speaker 1: This unique feeding mechanism allows the sea star to eat 41 00:02:35,120 --> 00:02:37,640 Speaker 1: larger prey than it would otherwise be able to fit 42 00:02:37,720 --> 00:02:42,400 Speaker 1: into its tiny mouth. But starfish eat a wide variety 43 00:02:42,440 --> 00:02:45,359 Speaker 1: of planted animal life, and they're chosen menu can depend 44 00:02:45,360 --> 00:02:49,360 Speaker 1: on the species, the Stone said. Many species are scavengers 45 00:02:49,360 --> 00:02:53,680 Speaker 1: and carnivores that eat gastropods, bivalves, barnacles, marine worms, and 46 00:02:53,800 --> 00:02:58,000 Speaker 1: other invertebrates. In some species are suspension feeders that capture 47 00:02:58,040 --> 00:03:01,799 Speaker 1: plankton and organic material from the water or and some 48 00:03:01,880 --> 00:03:04,840 Speaker 1: species of c star may have as many as ten, twenty, 49 00:03:05,000 --> 00:03:10,040 Speaker 1: or even forty arms. Although starfish have five point radial symmetry, 50 00:03:10,120 --> 00:03:13,919 Speaker 1: that doesn't mean that all of them have five arms. Furthermore, 51 00:03:13,960 --> 00:03:16,040 Speaker 1: if one of these arms is lost, a sea star 52 00:03:16,160 --> 00:03:20,600 Speaker 1: has the amazing ability to regenerate it. The ability to 53 00:03:20,680 --> 00:03:23,679 Speaker 1: regenerate lost arms is especially useful if a c star 54 00:03:23,800 --> 00:03:26,519 Speaker 1: is injured by a predator, it can drop an arm, 55 00:03:26,720 --> 00:03:30,160 Speaker 1: escape and grow a new one later. This won't happen 56 00:03:30,240 --> 00:03:32,640 Speaker 1: too quickly, though, it takes about a year for an 57 00:03:32,680 --> 00:03:35,640 Speaker 1: arm to grow back, as some require the central body 58 00:03:35,680 --> 00:03:38,000 Speaker 1: to be intact in order to regenerate. But a few 59 00:03:38,000 --> 00:03:40,920 Speaker 1: species can grow an entirely new sea star from just 60 00:03:40,960 --> 00:03:43,920 Speaker 1: a portion of a severed limb, depending on which organs 61 00:03:43,960 --> 00:03:48,280 Speaker 1: that limb houses. Sea stars also have an eye spot 62 00:03:48,360 --> 00:03:51,080 Speaker 1: at the end of each arm. That means of five 63 00:03:51,200 --> 00:03:54,119 Speaker 1: armed sea star has five eyes, while the forty armed 64 00:03:54,160 --> 00:03:57,720 Speaker 1: sun star has forty eyes. Each c star eye is 65 00:03:57,880 --> 00:04:00,920 Speaker 1: very simple. It looks like a red spot. It doesn't 66 00:04:00,920 --> 00:04:04,520 Speaker 1: seem much detail, but consents light and dark, and that's 67 00:04:04,600 --> 00:04:06,960 Speaker 1: just enough for the environments in which these animals live. 68 00:04:07,920 --> 00:04:11,040 Speaker 1: And speaking of the average lifespan of a starfish is 69 00:04:11,080 --> 00:04:14,880 Speaker 1: an impressive thirty five years. A large starfish species tend 70 00:04:14,920 --> 00:04:19,280 Speaker 1: to live longer than their smaller counterparts, but however long 71 00:04:19,320 --> 00:04:23,000 Speaker 1: they live, see stars don't swim. They instead use those 72 00:04:23,040 --> 00:04:26,400 Speaker 1: tube feet, hundreds of small suction cups on the underside 73 00:04:26,400 --> 00:04:29,000 Speaker 1: of their bodies to move from one area to another. 74 00:04:29,640 --> 00:04:32,159 Speaker 1: The tube feet also helps sea stars hold their prey. 75 00:04:34,080 --> 00:04:38,200 Speaker 1: Some starfish do have spiky protrusions, but generally they're not 76 00:04:38,360 --> 00:04:42,520 Speaker 1: dangerous to us, though we humans are dangerous to them 77 00:04:42,560 --> 00:04:46,040 Speaker 1: because they're literally shaped like stars. Humans have the tendency 78 00:04:46,080 --> 00:04:48,920 Speaker 1: to keep starfish as souvenirs, or even hold them out 79 00:04:48,920 --> 00:04:51,960 Speaker 1: of the water for photos. But forcing starfish out of 80 00:04:51,960 --> 00:04:55,480 Speaker 1: the water or throwing them back in can do serious damage, 81 00:04:55,800 --> 00:04:59,520 Speaker 1: and starfish have intricate, fragile arms and tiny body structures 82 00:04:59,800 --> 00:05:03,320 Speaker 1: to spite their regeneration capabilities. Even the slightest poke can 83 00:05:03,400 --> 00:05:07,279 Speaker 1: hurt them. Aside from that, human hands are naturally dangerous 84 00:05:07,279 --> 00:05:09,799 Speaker 1: to all seek creatures due to the billions of bacteria 85 00:05:09,880 --> 00:05:12,520 Speaker 1: that exist on our skin, and contact can lead to 86 00:05:12,520 --> 00:05:15,840 Speaker 1: a possible slow death, so if you have the chance 87 00:05:15,880 --> 00:05:24,479 Speaker 1: to see one, appreciate it from a respectful distance. Today's 88 00:05:24,480 --> 00:05:26,920 Speaker 1: episode is based on the article some starfish have up 89 00:05:26,920 --> 00:05:30,240 Speaker 1: to forty arms, plus ten other starfish facts on how 90 00:05:30,279 --> 00:05:33,359 Speaker 1: stuff works dot Com, written by Wendy Bowman. Brain Stuff 91 00:05:33,400 --> 00:05:35,559 Speaker 1: is production by Heart Radio in partnership with how stuff 92 00:05:35,560 --> 00:05:38,320 Speaker 1: works dot Com, and it's produced by Tyler Klein. Four 93 00:05:38,320 --> 00:05:41,200 Speaker 1: more podcasts my heart Radio, visit the i heart Radio app, 94 00:05:41,320 --> 00:05:44,080 Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.