WEBVTT - How Do Starfish Work? 0:00:01.920 --> 0:00:06.360 Welcome to brain Stuff production of I Heart Radio, Hey 0:00:06.440 --> 0:00:11.520 brain Stuff lorn Volga Baum Here. While starfish live underwater, 0:00:11.840 --> 0:00:15.920 they're not actually fish at all. In fact, marine scientists 0:00:15.920 --> 0:00:18.960 have replaced the beloved starfish is common name with the 0:00:19.040 --> 0:00:23.919 name sea star because the starfish isn't a fish? So 0:00:24.079 --> 0:00:27.480 what exactly are they? For the article this episode is 0:00:27.520 --> 0:00:30.560 based on How'stuff works, spoken by email with Kim Stone, 0:00:30.720 --> 0:00:35.160 the Georgia Aquarium's curator of Fish and Invertebrates. As she said, 0:00:35.600 --> 0:00:38.800 they're a type of invertebrate, meaning they don't have a backbone. 0:00:39.280 --> 0:00:42.280 Their body consists of a central disk with arms that 0:00:42.440 --> 0:00:45.960 radiate out and on the underside there are hundreds to 0:00:46.040 --> 0:00:50.000 thousands of small suction cups called tube feet that helped 0:00:50.040 --> 0:00:53.160 the c star move around, stick to different surfaces, and eat. 0:00:54.400 --> 0:00:57.320 There are some other big differences that set starfish apart 0:00:57.400 --> 0:01:02.160 from fish. These cool creatures don't of gills, scales, or fins. 0:01:02.200 --> 0:01:04.880 They live only in salt water, and they use sea 0:01:04.959 --> 0:01:08.320 water instead of blood to pump nutrients through their bodies 0:01:08.400 --> 0:01:13.080 by means of a water vascular system, unlike fish that 0:01:13.160 --> 0:01:16.759 have gills and mammals that have lungs. See stars breathe 0:01:16.840 --> 0:01:19.640 by absorbing oxygen from the water through different parts of 0:01:19.640 --> 0:01:23.680 their body, such as their skin and tube feet. Stone 0:01:23.720 --> 0:01:26.959 explained sea stars belonged to a group of marine invertebrates 0:01:27.040 --> 0:01:30.399 called kinoderms, which first appeared more than five hundred million 0:01:30.480 --> 0:01:34.120 years ago. The ancestors of modern day sea stars appeared 0:01:34.160 --> 0:01:36.640 more than four hundred and fifty billion years ago during 0:01:36.640 --> 0:01:41.760 the or Division period. Chinoderms include five classes of marine 0:01:41.840 --> 0:01:45.880 life see stars, brittle and basket stars, sea urchins and 0:01:45.920 --> 0:01:50.440 sand dollars, sea cucumbers and sea lilies, and feather stars. 0:01:51.360 --> 0:01:54.480 There are around two thousand different species of sea stars. 0:01:54.920 --> 0:01:57.520 A Stone said they can be found in a variety 0:01:57.520 --> 0:02:01.640 of habitats, from shallow sandy bottoms, cold rocky environments to 0:02:01.680 --> 0:02:05.720 the bottom of the sea floor. The different species have 0:02:05.800 --> 0:02:09.880 many different features, but all have their mouth on their underside. 0:02:10.400 --> 0:02:13.880 Upon capturing food, often a bivalve such as a clamor 0:02:13.960 --> 0:02:17.000 muscle with its tube feet, the sea star wraps its 0:02:17.080 --> 0:02:20.440 arms around the animal's shell and pulls it open just slightly. 0:02:21.120 --> 0:02:24.000 Then the sea star pushes its stomach through its own 0:02:24.040 --> 0:02:27.640 mouth and into the praise shell. It then digests the 0:02:27.680 --> 0:02:31.040 animal and slides its stomach back into its own body. 0:02:31.520 --> 0:02:35.040 This unique feeding mechanism allows the sea star to eat 0:02:35.120 --> 0:02:37.640 larger prey than it would otherwise be able to fit 0:02:37.720 --> 0:02:42.400 into its tiny mouth. But starfish eat a wide variety 0:02:42.440 --> 0:02:45.359 of planted animal life, and they're chosen menu can depend 0:02:45.360 --> 0:02:49.360 on the species, the Stone said. Many species are scavengers 0:02:49.360 --> 0:02:53.680 and carnivores that eat gastropods, bivalves, barnacles, marine worms, and 0:02:53.800 --> 0:02:58.000 other invertebrates. In some species are suspension feeders that capture 0:02:58.040 --> 0:03:01.799 plankton and organic material from the water or and some 0:03:01.880 --> 0:03:04.840 species of c star may have as many as ten, twenty, 0:03:05.000 --> 0:03:10.040 or even forty arms. Although starfish have five point radial symmetry, 0:03:10.120 --> 0:03:13.919 that doesn't mean that all of them have five arms. Furthermore, 0:03:13.960 --> 0:03:16.040 if one of these arms is lost, a sea star 0:03:16.160 --> 0:03:20.600 has the amazing ability to regenerate it. The ability to 0:03:20.680 --> 0:03:23.679 regenerate lost arms is especially useful if a c star 0:03:23.800 --> 0:03:26.519 is injured by a predator, it can drop an arm, 0:03:26.720 --> 0:03:30.160 escape and grow a new one later. This won't happen 0:03:30.240 --> 0:03:32.640 too quickly, though, it takes about a year for an 0:03:32.680 --> 0:03:35.640 arm to grow back, as some require the central body 0:03:35.680 --> 0:03:38.000 to be intact in order to regenerate. But a few 0:03:38.000 --> 0:03:40.920 species can grow an entirely new sea star from just 0:03:40.960 --> 0:03:43.920 a portion of a severed limb, depending on which organs 0:03:43.960 --> 0:03:48.280 that limb houses. Sea stars also have an eye spot 0:03:48.360 --> 0:03:51.080 at the end of each arm. That means of five 0:03:51.200 --> 0:03:54.119 armed sea star has five eyes, while the forty armed 0:03:54.160 --> 0:03:57.720 sun star has forty eyes. Each c star eye is 0:03:57.880 --> 0:04:00.920 very simple. It looks like a red spot. It doesn't 0:04:00.920 --> 0:04:04.520 seem much detail, but consents light and dark, and that's 0:04:04.600 --> 0:04:06.960 just enough for the environments in which these animals live. 0:04:07.920 --> 0:04:11.040 And speaking of the average lifespan of a starfish is 0:04:11.080 --> 0:04:14.880 an impressive thirty five years. A large starfish species tend 0:04:14.920 --> 0:04:19.280 to live longer than their smaller counterparts, but however long 0:04:19.320 --> 0:04:23.000 they live, see stars don't swim. They instead use those 0:04:23.040 --> 0:04:26.400 tube feet, hundreds of small suction cups on the underside 0:04:26.400 --> 0:04:29.000 of their bodies to move from one area to another. 0:04:29.640 --> 0:04:32.159 The tube feet also helps sea stars hold their prey. 0:04:34.080 --> 0:04:38.200 Some starfish do have spiky protrusions, but generally they're not 0:04:38.360 --> 0:04:42.520 dangerous to us, though we humans are dangerous to them 0:04:42.560 --> 0:04:46.040 because they're literally shaped like stars. Humans have the tendency 0:04:46.080 --> 0:04:48.920 to keep starfish as souvenirs, or even hold them out 0:04:48.920 --> 0:04:51.960 of the water for photos. But forcing starfish out of 0:04:51.960 --> 0:04:55.480 the water or throwing them back in can do serious damage, 0:04:55.800 --> 0:04:59.520 and starfish have intricate, fragile arms and tiny body structures 0:04:59.800 --> 0:05:03.320 to spite their regeneration capabilities. Even the slightest poke can 0:05:03.400 --> 0:05:07.279 hurt them. Aside from that, human hands are naturally dangerous 0:05:07.279 --> 0:05:09.799 to all seek creatures due to the billions of bacteria 0:05:09.880 --> 0:05:12.520 that exist on our skin, and contact can lead to 0:05:12.520 --> 0:05:15.840 a possible slow death, so if you have the chance 0:05:15.880 --> 0:05:24.479 to see one, appreciate it from a respectful distance. Today's 0:05:24.480 --> 0:05:26.920 episode is based on the article some starfish have up 0:05:26.920 --> 0:05:30.240 to forty arms, plus ten other starfish facts on how 0:05:30.279 --> 0:05:33.359 stuff works dot Com, written by Wendy Bowman. Brain Stuff 0:05:33.400 --> 0:05:35.559 is production by Heart Radio in partnership with how stuff 0:05:35.560 --> 0:05:38.320 works dot Com, and it's produced by Tyler Klein. Four 0:05:38.320 --> 0:05:41.200 more podcasts my heart Radio, visit the i heart Radio app, 0:05:41.320 --> 0:05:44.080 Apple Podcasts, or wherever you listen to your favorite shows.