Speaker 1: Welcome to brain Stuff production of I Heart Radio, Hey
Speaker 1: brain Stuff lorn Volga Baum Here. While starfish live underwater,
Speaker 1: they're not actually fish at all. In fact, marine scientists
Speaker 1: have replaced the beloved starfish is common name with the
Speaker 1: name sea star because the starfish isn't a fish? So
Speaker 1: what exactly are they? For the article this episode is
Speaker 1: based on How'stuff works, spoken by email with Kim Stone,
Speaker 1: the Georgia Aquarium's curator of Fish and Invertebrates. As she said,
Speaker 1: they're a type of invertebrate, meaning they don't have a backbone.
Speaker 1: Their body consists of a central disk with arms that
Speaker 1: radiate out and on the underside there are hundreds to
Speaker 1: thousands of small suction cups called tube feet that helped
Speaker 1: the c star move around, stick to different surfaces, and eat.
Speaker 1: There are some other big differences that set starfish apart
Speaker 1: from fish. These cool creatures don't of gills, scales, or fins.
Speaker 1: They live only in salt water, and they use sea
Speaker 1: water instead of blood to pump nutrients through their bodies
Speaker 1: by means of a water vascular system, unlike fish that
Speaker 1: have gills and mammals that have lungs. See stars breathe
Speaker 1: by absorbing oxygen from the water through different parts of
Speaker 1: their body, such as their skin and tube feet. Stone
Speaker 1: explained sea stars belonged to a group of marine invertebrates
Speaker 1: called kinoderms, which first appeared more than five hundred million
Speaker 1: years ago. The ancestors of modern day sea stars appeared
Speaker 1: more than four hundred and fifty billion years ago during
Speaker 1: the or Division period. Chinoderms include five classes of marine
Speaker 1: life see stars, brittle and basket stars, sea urchins and
Speaker 1: sand dollars, sea cucumbers and sea lilies, and feather stars.
Speaker 1: There are around two thousand different species of sea stars.
Speaker 1: A Stone said they can be found in a variety
Speaker 1: of habitats, from shallow sandy bottoms, cold rocky environments to
Speaker 1: the bottom of the sea floor. The different species have
Speaker 1: many different features, but all have their mouth on their underside.
Speaker 1: Upon capturing food, often a bivalve such as a clamor
Speaker 1: muscle with its tube feet, the sea star wraps its
Speaker 1: arms around the animal's shell and pulls it open just slightly.
Speaker 1: Then the sea star pushes its stomach through its own
Speaker 1: mouth and into the praise shell. It then digests the
Speaker 1: animal and slides its stomach back into its own body.
Speaker 1: This unique feeding mechanism allows the sea star to eat
Speaker 1: larger prey than it would otherwise be able to fit
Speaker 1: into its tiny mouth. But starfish eat a wide variety
Speaker 1: of planted animal life, and they're chosen menu can depend
Speaker 1: on the species, the Stone said. Many species are scavengers
Speaker 1: and carnivores that eat gastropods, bivalves, barnacles, marine worms, and
Speaker 1: other invertebrates. In some species are suspension feeders that capture
Speaker 1: plankton and organic material from the water or and some
Speaker 1: species of c star may have as many as ten, twenty,
Speaker 1: or even forty arms. Although starfish have five point radial symmetry,
Speaker 1: that doesn't mean that all of them have five arms. Furthermore,
Speaker 1: if one of these arms is lost, a sea star
Speaker 1: has the amazing ability to regenerate it. The ability to
Speaker 1: regenerate lost arms is especially useful if a c star
Speaker 1: is injured by a predator, it can drop an arm,
Speaker 1: escape and grow a new one later. This won't happen
Speaker 1: too quickly, though, it takes about a year for an
Speaker 1: arm to grow back, as some require the central body
Speaker 1: to be intact in order to regenerate. But a few
Speaker 1: species can grow an entirely new sea star from just
Speaker 1: a portion of a severed limb, depending on which organs
Speaker 1: that limb houses. Sea stars also have an eye spot
Speaker 1: at the end of each arm. That means of five
Speaker 1: armed sea star has five eyes, while the forty armed
Speaker 1: sun star has forty eyes. Each c star eye is
Speaker 1: very simple. It looks like a red spot. It doesn't
Speaker 1: seem much detail, but consents light and dark, and that's
Speaker 1: just enough for the environments in which these animals live.
Speaker 1: And speaking of the average lifespan of a starfish is
Speaker 1: an impressive thirty five years. A large starfish species tend
Speaker 1: to live longer than their smaller counterparts, but however long
Speaker 1: they live, see stars don't swim. They instead use those
Speaker 1: tube feet, hundreds of small suction cups on the underside
Speaker 1: of their bodies to move from one area to another.
Speaker 1: The tube feet also helps sea stars hold their prey.
Speaker 1: Some starfish do have spiky protrusions, but generally they're not
Speaker 1: dangerous to us, though we humans are dangerous to them
Speaker 1: because they're literally shaped like stars. Humans have the tendency
Speaker 1: to keep starfish as souvenirs, or even hold them out
Speaker 1: of the water for photos. But forcing starfish out of
Speaker 1: the water or throwing them back in can do serious damage,
Speaker 1: and starfish have intricate, fragile arms and tiny body structures
Speaker 1: to spite their regeneration capabilities. Even the slightest poke can
Speaker 1: hurt them. Aside from that, human hands are naturally dangerous
Speaker 1: to all seek creatures due to the billions of bacteria
Speaker 1: that exist on our skin, and contact can lead to
Speaker 1: a possible slow death, so if you have the chance
Speaker 1: to see one, appreciate it from a respectful distance. Today's
Speaker 1: episode is based on the article some starfish have up
Speaker 1: to forty arms, plus ten other starfish facts on how
Speaker 1: stuff works dot Com, written by Wendy Bowman. Brain Stuff
Speaker 1: is production by Heart Radio in partnership with how stuff
Speaker 1: works dot Com, and it's produced by Tyler Klein. Four
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