Kingdom : Animalia
                        Class : Echinoidea
      Scientific Name : Echinoidea
                      Origin : Worldwide

                          Size : 3 - 10cm (1.2 - 3.9in)
             Water Type : Salt
Optimum pH Level : 6.0 - 9.0
                 Life Span : 15 - 200 years

                Skin Type : Plates
     Special Features : Small stinging 
                                     structures and claw 
                                     like mouth
  1. Sea urchins are found in the oceans all around the world except the polar regions.
  2. There are around 200 species of sea urchins that have been recognized in the world.
  3. Some of them have a hard shell of chalky plates while others have long thin spikes around their body.
  4. They are a little round in shape with long spine, that come off easily.
  5. They have five paired rows of tube feet which are amongst the spines.
  6. The suckers on their feet help them hold on to the ocean floor, to move around and to capture food.
  7. They have small claw-like structures amongst the spines and are known as pedicellarines.
  8. These structures are used for their defense, to keep them clean and to obtain food.
  9. Their mouth is known as the Aristotle’s lantern and on their underside at the middle.
  10. They do not have a brain and depend upon a circulatory system that involves water-filled channels running through their body.
  11. They inhabit the shallow and deep rocky ocean floor and sometimes even the coral reefs.
  12. Interestingly, they are the longest living creatures on earth with some individuals living to be 200 years old.
  13. They are omnivores, feeding on algae and decomposing animals like dead fish, barnacles, sponges and mussels.
  14. Their natural predators are large fish, crab, eels, birds, sea otters and humans.
  15. They spawn in spring, with the female sea urchin laying millions of jelly-coated eggs.
  16. The eggs get fertilized and become a part of the plankton.
  17. Once the eggs hatch, the larvae stay attached to the plankton and come apart after 2-5 years.
  18. Ocean-floor dredging and water pollution have made sea urchins a threatened species.

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