Phylum: Echinodermata

Class: Echinoidea

 

Norwegian: sjøpiggsvin

(Storsteinan - The Trondheim fjord / 19 meters / 7.29.2001)

The regular sea urchins, Echinoida, are well known. However there are two other orders of this class in Norwegian waters: irregular sea urchins, Spatangoida and the order Cidaroida, only represented by a single species.

The regular sea urchins are easily recognized by the rounded shape and distinct spines. These are used for protection, movement and attach food and camouflage like algae drifting by. The mouth is located on the underside of the spherical, calcareous shell. The irregular sea urchins are often smaller, have soft spines, almost like a fur and lives buried in sandy or muddy sea beds.