You might not think of sea stars as being very intelligent, and you'd be right, but
you might be impressed by some of the amazing things they can do, especially considering
they don't have a brain!
Hi, I'm Jonathan Bird and welcome to my world!
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Starfish, more correctly called sea stars, live just about everywhere in the ocean, from
the tropics, to Antarctica and everywhere in between. They come in all shapes and sizes
from fat and stubby... to long and skinny.
This brittle star walks with a coordinated effort using its rays like legs.
But most sea stars get around using hundreds or thousands of tiny tube feet on their underside.
This is a Northern Sea star, living in the coastal waters of New England, and it's
a predator.
It's hunting a scallop. It's a drama played out in slow motion as the sea star moves in
for a grip on the scallop's shell.
But the scallop is not defenseless. With a mighty blast of water, the scallop jets away
to safety.
So the sea star wraps itself around a mussel. Mussels are attached to the bottom and can't
get away.
The sea star uses it's strong tube feet with suction cups to pull the mussel open
a tiny bit, and digests its victim by injecting its stomach inside the mussel.
Picking up the sea star, I can see that it has the mussel firmly in its grip.
But not all sea stars feed on mussels and scallops. A Basket star feeds on plankton
in the water. It has finely branched arms that act like a net, to catch the tiny bits
of food floating by. It positions itself to be able to grab as much plankton as possible
in the current.
Some sea stars eat something even more surprising. Come take a look!
Exploring a reef in the tropical Pacific, I find a Crown-of-thorns sea star dining on
the coral.
This thorny, armored sea star is one of only a few animals that can digest living coral.
It wraps itself around a coral colony and eats the polyps, leaving a dead, bleached
coral skeleton behind.
Here's a healthy colony of plate coral. And here's one that has been eaten by a
crown-of-thorns. Outbreaks of these sea stars have been known to kill entire reefs.
Carefully picking one up to avoid the sharp and venomous spines, I can see the stomach,
which the sea star inverts out of its mouth to digest the coral outside of its body.
These sea stars are the second largest in the world, growing bigger than a dinner plate.
But if you think these are big, wait until you see the largest sea star in the world!
To find it, I've come all the way to British Columbia. I'm looking for the Giant Pacific
Sun Star, and you won't believe the size of this thing!
In the cold, murky waters of the Canadian north Pacific, I swim through beautiful gardens
of sponges, anemones and soft coral, searching for a Giant Sun star.
And then, down on the bottom, I find what I'm looking for. It has up to twenty-four
arms, more properly called rays and reaches three feet across. WOW! This is the world's
largest sea star!
Compared to most sea stars, the Giant Sun Star is a speed demon, cruising along the
bottom in search of its favorite food—other sea stars and the occasional sea cucumber!
Here, a sea cucumber makes an emergency retreat to escape this hungry Sun Star on the move!
A thousand miles south on a reef in the tropics, I find a blue Linckia sea star on the bottom.
Like the vast majority of sea stars, this one has only five rays.
With tiny tube feet on its underside, this sea star barely seems to move, but when I
speed things up with time lapse photography, Linckia sea stars appear very active, moving
about and grazing the bottom for food.
But even more curiously, they're polite, restraining from walking on top of each other.
Like bumper cars, when one Linckia touches another, they each go the other direction.
It's all very civilized.
In an hour, a Linckia on the move can travel several car lengths.
Sea stars are amazing animals. They might look like they are just sitting there doing
nothing, but they survive by hunting for food, and they do that in many ways from catching
it as it floats by... to chasing it down. They're such good predators that sometimes
they can destroy entire reefs. It just goes to prove that just because something is slow,
doesn't mean it isn't up to something. You never know where a sea star is going to
turn up!
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