Heart Urchins

Heart urchins belong to the phylum Echinodermata, class Echinoidea, order Spatangoida. These are urchins that lie buried in the sand and push their way through the sand using their moveable spines. They are bilaterally symmetrical with the mouth on their underside (ventral side) and the anus at the rear. They possess a ‘petal’ which is a star-shaped set of perforations on the topside (dorsal side). These perforations allow special tube feet to emerge and these are responsible for gaseous exchange. On the underside the mouth takes in sand and extracts any organic material that the animal can use for food. Around the mouth are a set of tube feet that push sand (food) into the mouth.