Common sea urchin, (Echinus esculentus) is either male or female and during the spring the female can release up to 20 million eggs. The sea urchin moves over the bottom with the help of the spines. If it wants to move up along the wall it also have suction cups. Sometimes you can see them camouflaging themselves with shells and algae.
The mouthparts are designed for rasping and the sea urchin feeds on algae and encrusting invertebrates, but also worms, barnacles, hydroids, tunicates and bryozoans. The teeth, five in numbers, can be moved both in and out but also sideways.
The design of the sea urchin has not been changed for the last 475 million years. It is now considered Near Threatened in the IUCN Red List of Threatened Species (25 June 2011).