How Do Starfish Work?

Starfish, more properly called sea stars, have some amazing (and amazingly weird) abilities. Learn about them in today's episode of BrainStuff, based on this article: https://animals.howstuffworks.com/marine-life/starfish.htm

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of I Heart Radio, Hey
brain Stuff lorn Volga Baum Here. While starfish live underwater,
they're not actually fish at all. In fact, marine scientists
have replaced the beloved starfish is common name with the
name sea star because the starfish isn't a fish? So

(00:24):
what exactly are they? For the article this episode is
based on How'stuff works, spoken by email with Kim Stone,
the Georgia Aquarium's curator of Fish and Invertebrates. As she said,
they're a type of invertebrate, meaning they don't have a backbone.
Their body consists of a central disk with arms that
radiate out and on the underside there are hundreds to

(00:46):
thousands of small suction cups called tube feet that helped
the c star move around, stick to different surfaces, and eat.
There are some other big differences that set starfish apart
from fish. These cool creatures don't of gills, scales, or fins.
They live only in salt water, and they use sea
water instead of blood to pump nutrients through their bodies

(01:08):
by means of a water vascular system, unlike fish that
have gills and mammals that have lungs. See stars breathe
by absorbing oxygen from the water through different parts of
their body, such as their skin and tube feet. Stone
explained sea stars belonged to a group of marine invertebrates
called kinoderms, which first appeared more than five hundred million

(01:30):
years ago. The ancestors of modern day sea stars appeared
more than four hundred and fifty billion years ago during
the or Division period. Chinoderms include five classes of marine
life see stars, brittle and basket stars, sea urchins and
sand dollars, sea cucumbers and sea lilies, and feather stars.

(01:51):
There are around two thousand different species of sea stars.
A Stone said they can be found in a variety
of habitats, from shallow sandy bottoms, cold rocky environments to
the bottom of the sea floor. The different species have
many different features, but all have their mouth on their underside.
Upon capturing food, often a bivalve such as a clamor

(02:13):
muscle with its tube feet, the sea star wraps its
arms around the animal's shell and pulls it open just slightly.
Then the sea star pushes its stomach through its own
mouth and into the praise shell. It then digests the
animal and slides its stomach back into its own body.
This unique feeding mechanism allows the sea star to eat

(02:35):
larger prey than it would otherwise be able to fit
into its tiny mouth. But starfish eat a wide variety
of planted animal life, and they're chosen menu can depend
on the species, the Stone said. Many species are scavengers
and carnivores that eat gastropods, bivalves, barnacles, marine worms, and
other invertebrates. In some species are suspension feeders that capture

(02:58):
plankton and organic material from the water or and some
species of c star may have as many as ten, twenty,
or even forty arms. Although starfish have five point radial symmetry,
that doesn't mean that all of them have five arms. Furthermore,
if one of these arms is lost, a sea star
has the amazing ability to regenerate it. The ability to

(03:20):
regenerate lost arms is especially useful if a c star
is injured by a predator, it can drop an arm,
escape and grow a new one later. This won't happen
too quickly, though, it takes about a year for an
arm to grow back, as some require the central body
to be intact in order to regenerate. But a few
species can grow an entirely new sea star from just

(03:40):
a portion of a severed limb, depending on which organs
that limb houses. Sea stars also have an eye spot
at the end of each arm. That means of five
armed sea star has five eyes, while the forty armed
sun star has forty eyes. Each c star eye is
very simple. It looks like a red spot. It doesn't
seem much detail, but consents light and dark, and that's

(04:04):
just enough for the environments in which these animals live.
And speaking of the average lifespan of a starfish is
an impressive thirty five years. A large starfish species tend
to live longer than their smaller counterparts, but however long
they live, see stars don't swim. They instead use those
tube feet, hundreds of small suction cups on the underside

(04:26):
of their bodies to move from one area to another.
The tube feet also helps sea stars hold their prey.
Some starfish do have spiky protrusions, but generally they're not
dangerous to us, though we humans are dangerous to them
because they're literally shaped like stars. Humans have the tendency
to keep starfish as souvenirs, or even hold them out

(04:48):
of the water for photos. But forcing starfish out of
the water or throwing them back in can do serious damage,
and starfish have intricate, fragile arms and tiny body structures
to spite their regeneration capabilities. Even the slightest poke can
hurt them. Aside from that, human hands are naturally dangerous
to all seek creatures due to the billions of bacteria

(05:09):
that exist on our skin, and contact can lead to
a possible slow death, so if you have the chance
to see one, appreciate it from a respectful distance. Today's
episode is based on the article some starfish have up
to forty arms, plus ten other starfish facts on how

(05:30):
stuff works dot Com, written by Wendy Bowman. Brain Stuff
is production by Heart Radio in partnership with how stuff
works dot Com, and it's produced by Tyler Klein. Four
more podcasts my heart Radio, visit the i heart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.