Echinoderms Fun Facts And Trivia

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.

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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 intside 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 stars 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

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!