Sea urchin
Echinoidea
Sea urchins, as well as starfishs and brittle stars, belong to the echinoderms. There are about 950 species of sea urchins, which are represented in all oceans of the world.
Most species of sea urchins have a large number of spines for defense against predators, such as lobsters, crabs, some species of fish and sea otters. The spines of some sea urchin species are also poisonous. In addition, the spaces between the spines provide a safe refuge for smaller animal species.
| Related to | Ethinoderms, Eleutherozoa |
| Habitat | Worldwide in the sea, up to a depth of 5,000 meters |
| Body length | The hard calcareous internal skeleton can have a usually a diameter of 10 cm. The largest urchin species has a diameter of up to 36 cm. |
| Diet | Algae, carrion, occasionally smaller creatures |
| Reproduction | Males and females release egg and sperm cells into the water in large quantities. The fertilized eggs evolve into planktonic-living secondary larvae. |
| Commerce | Aquaristics; The gonads and eggs are considered a delicacy in some countries. |
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