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Fun Facts and Trivia About Echinoderms



So what are echinoderms? Echinoderms are invertebrates with a water vascular system and an internal skeleton called an endoskeleton. They can only live in salt water. Echinoderms include sea stars, brittle stars, sea cucumbers, and sea urchins. All echinoderms have radial symmetry (many lines of symmetry through a central point).

1. Echinoderms Have No Blood

Does this surprise you? Almost all animals contain some amount of blood. But not echinoderms! Echinoderms have what's called a Water Vascular System. The water vascular system replaces the duties of a different animal's blood and veins by carrying oxygen to the vital organs. A water vascular system works a lot like a water balloon. If you squeeze one part of it, the water goes to the rest. In an echinoderm, the fluid filled tubes can contract to force oxynegated water to different parts of the system.

Tube feet

Tube feet

2. Echinoderms Have Tiny Feet All Over Their Arms

These tiny attatchments are called tube feet. Tube feet benefit from the squeezing methods of the water vascular system. When the tubes contract, the tube feet fill with water. They use this water to create suction in their feet that they can use to cling to surfaces, move, and capture prey.

3. Echinoderms Are Predators!

Do you have a picture of that sweet, little, cuddly sea star? Well you probably don't, but if you do, you are wrong. Even the sea cucumbers eat meat by filter feeding! Sea stars are much worse. Sea stars will find a bivalve (mollusks like clams, oysters, etc.) and grip it with their tube feet. Then they s l o w l y pry apart the shells. GROSS ALERT The sea star will then eject its stomach through its mouth and inside the shells. The stomach will begin to digest the soft gooey inside, then the star will suck back in its stomach along with the partially digested food.

4. Sea Stars Have Eyes- Or at least eyespots

That's right. That little starfish could be watching you. Well, not really. Eyespots can barely make an image at all, much less a detailed one. They mostly just detect light and dark. Sea stars have these little spots at the end of each arm.

5. Sea Cucumbers Can Puke Their Guts Out- Literally!

When sea cucumbers are threatened or scared by a predator, they can violently fling their internal organs at their attacker, often causing the predator to become confused and leave. But don't worry, it won't kill the little guy. Another handy skill they have is regrowing lost organs.

a purple sea urchin

a purple sea urchin

6. People Eat Sea Urchins

Sea urchins are considered a fine delicacy in many countries! 

7. If You Put A Sea Cucumber In Fresh Water It Will Explode

Well, after slowly swelling up, of course. This change is caused by the echinoderm's property of being isotonic with their environment. This means that the density of salt inside them is the same as the ocean water. Also, salt water is constantly in contact with their skin. As a result, when suddenly moved to water with zero salt content, the cucumber's body will try to quickly equalize the salt into the water, causing the poor guy to explode.

8. Their Name Literally Means "Spiny Skinned"

"Echinodermata" is greek for "spiny skinned".

9. Echinoderms Are The Most Complex Invertebrates

Scientists consider echinoderms the most complex out of all invertebrates!! That means they're better than mollisks (octopi, squids, snails, clams) arthropods (insects, arachnids, crustaceans) and a whole lot more!

10. Echinoderms Can Regenerate Lost Parts

Lost an arm? No problem if you're an echinoderm! They can regrow lost limbs in a form of asexual reproduction. Amazingly, sometimes the lost part will grow a new animal!

More About Echinoderms


Cool echinoderm pictures: Wonders of the Seas


Gilby Kid boi on February 19, 2020:

This was helpful but this never talks about defensive strategies

? on January 07, 2020:

This is very helpful. thank you.

Victoria on November 21, 2019:

This really helped! I am doing a school project on Echinoderms and this helped me a lot! Thanks!

Leser on July 09, 2019:

I found u

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bob on May 01, 2019:

me like chicken

seb on April 03, 2019:

i cheated :)

90's bit** on January 07, 2019:

Not bad

Sofia on December 04, 2018:

This is really helpful

But they could use a few more facts to support it

But overall it is really good

I have enjoyed it

4 star rating

Issac Cock on December 02, 2018:

this helps a lot

cs1888221 on November 18, 2018:

thanks a lot

aw on October 17, 2018:

thank you lot

algernique rolle on March 23, 2018:

this is crazy i don't like this website

#puppysrule on February 28, 2018:

What do they eat?

Jeff on February 23, 2018:

Echinoderms are awesome #suportechinodermslikeyeah!!!

Jhon mark Reyes on March 20, 2017:

It's good to all student this lesson

Savanna on March 09, 2017:

I never know this thanks

homework:( on March 02, 2017:

Thank you so much this gave me an A+ on my homework! :) :D

rushen charm on January 05, 2016:

lot of thanks

park hyi yin on August 12, 2014:

thank you

alex on May 19, 2014:

this is asome

FakerMCfakerberry on March 26, 2014:

Thx helped a lot

yolo on March 19, 2014:

thanks it helped with a section of my project

jmac on March 15, 2014:

nice facts!!

cj on February 12, 2014:

I really liked this website

Emily on March 25, 2013:

Thanks for all the great facts! really helped with homework! :P

i lik cows 101 on March 18, 2013:

great website and facts

bob on March 18, 2013:

hay it is really great ot helped my out

k on March 07, 2013:

more cool stuff like the exploding part

plb36 (author) from United States on February 13, 2013:

Hello k. I'm sorry you didn't enjoy the article. What would you suggest I add? Keep in mind this is supposed to be just a collection of fun facts rather than an in depth look at echinoderms.

k on February 13, 2013:

you need more info on the topic ok hi mike

mike on February 13, 2013:


he@ther on February 13, 2013:

wow that was good . it gave me a lot of my awesers to me ?

student named k on February 12, 2013:

i thought it was great it got me through my homework- thanks

Student on November 04, 2012:

thanks for the trivia!!!

i'm thrilled

plb36 (author) from United States on October 21, 2012:

Thanks for the comment and for catching my error. I'll go fix it right now.

he@ther on October 21, 2012:

Great, thanks for the helpful facts! Oh, but one thing - on fact 5 I think you mean sea cucumbers, not sea stars.

plb36 (author) from United States on September 26, 2012:

Thanks, monkey! I'm glad you like it!

monkey on September 26, 2012:

this is awosome

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