Cidaris cidaris
Cidaris cidaris is a species of sea urchin commonly known as the long-spine slate pen sea urchin. It is found in deep water in the eastern Atlantic Ocean and the Mediterranean Sea. Description. "Cidaris cidaris" has a small central test from which project a number of long, blunt, widely separated primary spines and a dense covering of short secondary spines. The primaries are pale grey, tipped with green and the secondaries are pale green. The test has a diameter of to and the spines are twice as long as this. The sea urchin often has bits of  algae, sponge or other organisms adhering to the spines. Distribution. "Cidaris cidaris" is found in the eastern Atlantic Ocean and the Mediterranean Sea in deep water on coral, rock and gravel bottoms. Its range extends from Cape Verde, the Azores and the Canary Islands northwards to the Faroe Islands and Norway. It is also found on knolls and seamounts at depths down to about . Biology. "Cidaris cidaris" feeds on sponges, sea fans and algae. "Cidaris cidaris" is one of a number of species of sea urchin that can suffer from bald sea urchin disease.