1erizo de mar masculine
- The inner shell of a sea urchin is a hollow globe, scored in five curved sections that taper at the ends into a small hole at the top and bottom.
- The red sea urchin's body is domed above and flat below.
- The sea urchin is one of the few marine organisms whose genome has been sequenced.
- This sea urchin defends itself with two sets of mobile spines.
- The sea urchin occupies an important evolutionary position with respect to vertebrates and humans.