Long-spine Slate Pen Sea Urchin

Overview

The Long-spine Slate Pen Sea Urchin (Cidaris cidaris) is a distinctive deep-water echinoderm found throughout the eastern Atlantic Ocean and the Mediterranean Sea. It is easily recognized by its small central body and sparse, exceptionally long, blunt primary spines that resemble pencils or slate pens.

Appearance

This species features a central test (shell) typically measuring 7 to 8 cm in diameter. Projecting from this are widely spaced, thick primary spines that can reach lengths up to twice the diameter of the test. These primary spines are generally pale grey with green tips, while a dense layer of shorter, pale green secondary spines covers the base of the test. Individuals often carry debris such as algae, sponges, or other organisms on their spines, which can obscure their natural coloration.

Distribution & habitat

Cidaris cidaris inhabits deep-water environments, ranging from the Faroe Islands and Norway in the north down to the Azores, Canary Islands, and Cape Verde. It is commonly found on rocky, coral, or gravel bottoms, as well as sandy and muddy substrates. While it can occur at shallower depths, it is most abundant in deep-sea habitats, including knolls and seamounts, often residing at depths between 50 and 1,000 meters.

Feeding

This urchin is known to feed on a variety of sessile organisms, including sponges, sea fans, and various types of algae found on the seafloor.