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18 Sea Urchin Facts for Kids

navajocodetalkersadmin on February 16, 2015 - 12:00 pm in Fun Facts for Kids

1. Sea Urchins have over 200 species. They come in a full range of colors from sand colored to bright pinks and dark purples. They are interesting creatures that are bilateral. They have five sections that are equally the same size.

2. Sea urchins have spiny shells for protection. Some of the species have poisonous soft spines. They have five sets of “legs” that are really tubes that they use to propel themselves across the ocean floor. They live in warm water oceans.

3. They can grow from 3 cm round to 10 cm round. They can live up to 200 years in the wild although most species only live for 30 years. They do not have a discernible face. They have a mouth and an anus. They have a simple digestive system. Basically they can easily eliminate what they take in.

4. Their diet consists mainly of algae and other easily digestible vegetation. Their mouth is at the bottom half of their body and they scoot around on their “legs” eating whatever they come across on the ocean floor.

5. Sea Urchins are harmless animals that pose no threat except for one sea urchin that is poisonous to fish.

The Flower Urchin

6. The flower urchin is the only poisonous species and it has an unusual symbiotic (equally rewarding) with the clown fish. The spines on the flower urchin contain a paralytic that will paralyze predators. The clown fish builds an immunity to this paralytic so that it can feed off the flower urchin.

7. The clown fish does a funny dance where it gently brushes up against the spines of the flower urchin to expose itself to just a bit of the poison at a time. After a few hours of its dance it can easily approach the flower urchin and feed off the parasites that live in and around the spines.

8. This helps the flower urchin by removing the parasites that can cause disease and cause the spines to fall out leaving it defenseless. So the relationship works out for everybody involved.


9. Sea Urchins breed by releasing their egg into the ocean. The egg is fertilized and quickly, within about 12 hours becomes an embryo. A surprising number of sea urchin survive this process. Once the embryo floats to the ocean floor it takes a few months for it to become an actual sea urchin.

10. It goes through many different stages from larvae to sea urchin. It eventually builds its spiny shell and becomes a full-fledged sea urchin. The female sea urchin can release up to 1000 eggs at a time, a small percentage of these eggs go on to become sea urchins because there are a lot of sea animals that dine on them before they are ever fertilized.

Life Span

11. The sea urchin lives in warm ocean waters. They can live up to 200 years (the red sea urchin is the longest living creature on the planet) most species live for about 30 years. They spend their days moving around the ocean floor feeding. They can live in warm waters at depths as low as 20 feet all the way to depths of 5000 feet.

12. They do not do well in captivity because the breeding conditions can not be completed duplicated without the ocean currents so while a sea urchin may live in captivity it will not reproduce well.

Their “Test”

13. A sea urchins shell can be called a test or a shell. They are self made homes. The spines are movable and jointed. If you touch a sea urchin all of their spines will face the direction of the touch. They use their spines to help them propel around the bottom of the ocean.

14. Some species use their spines to anchor themselves to rocks and other things in the bottom of the ocean. These hard shells protect their soft bodies and they also act as camouflage of sorts to ward off predators. They look like flowers instead of animals this confuses predators.


15. The sea urchin has quite a few natural predators. The sea otter is it biggest natural predator in the ocean. They will eat as many sea urchins as they can find. Man is the next biggest predator, although some people would say that man is the biggest predator.

16. Sea urchin is a delicacy in some cultures. Their row (eggs) are also a delicacy so they are hunted by divers in the warm ocean waters.

Endangered Species

17. There are some members of the species that are endangered. Ocean pollution and over harvesting are two of the biggest concerns for conservationist. Education and conservation efforts are being promoted to help preserve these amazing creatures.

18. Keeping the beaches clean and reducing waste can help to protect the sea urchins. Everyone can do their part so that all the species of sea urchins can continue to thrive.

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