nature guides: introducing sea stars
are sea stars?
Sea stars are animals!
stars and you
are not fish! Although commonly called starfish, these
animals are not fish. So we prefer to call them sea stars.
stars have five-part symmetry
Many common stars we see have five arms. Although some may have
more arms, or less arms.
stars need sea water Instead of blood, a sea star uses
sea water to pump its body parts and move. Water inside the sea
star may also help it keep cool at low tide. So please don't remove
sea stars from the water for too long.
- Let's NOT take the group photo with each person holding the
sea star in the hand. Let's put the sea stars in the water
and get close to them for the group photo.
- See also why
we should not pick up sea stars on the wild shores of
are fragile! When
stressed, a star may purposely drop off an arm. Just like a gekko
drops its tail. So don't carry the sea star by the tip of an arm.
The star might think a predator is chomping on it and will purposely
drop off the arm.
of a sea star When showing this, make sure the sea star
is always immersed in seawater, either in a pool or in your pot.
- The sea
star has grooves under its arms where tube feet emerge. The
tubefeet help it to move, to gather food.
- The mouth
is in the middle of all the feet.
Sea stars are sadly harvested to make cheap trinkets like Christmas
ornaments, bathroom decorations and tourist souvenirs. Please don't
buy souvenirs made from marine life.
Sea star myths to dispel
- It is
NOT true that all sea stars can regenerate from a broken piece
of their arms.
- You won't
get two sea stars when an arm of a sea star is separated.
So please don't purposely mutilate sea stars!! VERY
FEW stars can generate a new animal from a broken off arm.
In MOST STARS the broken off bit dies.
sea stars can regenerate lost arms. But this takes time and
resources. Some species take up to a year to replace a lost
limb. In the meantime, the sea star is probably disadvantaged.
- If the
central disk is damaged, the sea star may die.
- Can I
take this dead sea star home? All the sea stars that you see
are probably alive.
You are unlikely to come across a skeleton of a sea star. Dead
sea stars disintegrate quickly and do not leave behind whole skeletons.
A live sea star also has moving tube feet. When removed from the
water, however, sea stars will retract their tube feet and may
Those dead sea stars you see sold as souvenirs were taken alive
and dried. What a cruel way to die!
sea stars bad for reefs? Don't they eat up all the hard corals? The Crown-of-Thorns sea star (Acanthaster planci) is notorious
for decimating reefs. This sea star eats the polyps of hard corals
leaving behind dead white skeleton.
sea stars are only a danger to reefs when there is a population
explosion of them. Such a situation is generally is believed
to be due to an imbalance in the natural system. For example,
when their predators are overharvested.
there are low numbers of this sea star, they do not cause
sea star has not been encountered on our shores.
Finding sea stars Most are well hidden. Some burrow into
the sand leaving only tell-tale signs on the surface. Others
hide under stone or among coral rubble.
Don't step on sea stars They are living animals.
Don't carry a sea star by the tip of the arm! Some sea stars
will drop off the arm if they think a predator is chomping on
Don't remove sea stars out of water sea stars need sea water
the way we need blood.
Don't take photos with the sea star out of water Don't
encourage visitors to remove sea stars to take photos with them.
Don't make a sea star flip over: Not all sea stars can
do this easily. Even for those than can, it consumes energy
and if the same sea star is made to do this several times, it
can exhaust and thus injure the animal.
Don't leave a sea star upside down If you had turned
it upside down to show the underside, turn it back around after
quickly explaining the features.