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