Stony Sea Urchin – Paracentrotus lividus
The Stony Sea Urchin, also known as Rock or Purple Sea Urchin, is a species in the class of the Sea Urchins and thus belongs to the phylum of the Echinodermata. Paracentrotus lividus was first described in 1816 by Lamarck.
The Stony Sea Urchin has a variable colouring. The spines may be beige, olive green, violet or brown.
It reaches a diameter of up to 7cm. Its spines can be up to 3cm long.
Habitat and Distribution
Paracentrotus lividus lives on rocky ground and in sea grass meadows, down to 20m depth. It is also less likely that it is found up to 80m deep. It therefore favours shallower waters and is also found in tide pools.
When diving in the Canaries you can observe it regularly.
In addition, its distribution area spreads from the British Isles, along the European coast to Morocco. It is also found in the Mediterranean Sea, around the Azores and Madeira.
It occurs particularly frequently in regions where the water temperature is between 10 and 15 ° C in winter and between 18 and 25 ° C in summer.
The Stony Sea Urchin feeds on various algae and sea grasses. In addition, it eats sponges, hydrozoans and copepods. In case of a great competition from conspecifics, cannibalism can also occur.
While Paracentrotus lividus is active during day time on the Irish saltwater lake Lough Hyne, it eats at night time in the Mediterranean Sea. It is assumed that they are active during the day in regions with many night active predators.
With his suction cups on the tube feet, it often masks itself in order to be better camouflaged. So you can find the Stony Sea Urchin often covered with shells, stones or algae. The Paracentrotus lividus is also known to build small caves in order to protect itself from strong water movement and predators. These chambers are both temporarily and permanently inhabited.
The reproduction of Paracentrotus lividus takes place in spring and / or autumn depending on the region. 10-20 animals gather at the same time, and sperm and oocytes are simultaneously discharged into the water. Although they have usually separated sexes, hermaphroditic animals have also been observed. The larvae live planktonic for about 28 days, until they settle down and undergo a metamorphosis to the sea urchin.