The Common Sea Urchin (Echinus esculentus) is a spiny marine (saltwater) echinoderm in the Echinidae family. It is an animal that lives on the bottom of the ocean. It is related to the Starfish (Sea Star). It is also called a Sea Hedgehog.
The Common Sea Urchin has a hard shell, called a test. It is spherical (round like a globe), shiny and spiny. Young urchins have bilateral symmetry, and as they become adults, they have fivefold symmetry (similar to starfish with five appendages). Its mouth, with a small jaw, is in the centre of the urchin on its underside.
It does not have eyes. It is sensitive to touch, light, and chemicals, due to the numerous sensitive cells in its spines, tube feet, and around its mouth.
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