How many spines does a sea urchin have?

The number of spines on a sea urchin varies depending on the species. Some species may have as few as a few hundred spines, while others may have over a thousand. The spines are typically longest near the equator of the urchin's body and become shorter towards the poles. The spines are made of calcium carbonate and are covered with a thin layer of skin. They are used for protection, locomotion, and feeding.