Black sea urchin (Lat. Arbacia lixula). Black sea urchin is spread throughout the Mediterranean, mostly on a stone base.  It is found typically at shallow waters, at depths from 0 to 30 m, in rocky shores. It has a good resistance to hydrodynamism due to a good attachment strength to rocks. It is characterized by its deep black color and its hemispherical shape. The spines around the mouth are brown. The maximum diameter of the shell is up to 6 cm, and the spines are 3 cm long.  It does not have brain, it is thought to use its simplified nervous system to respond to stimuli and potentially communicate. Diet Arbacia lixula are classified as omnivores, although isotope analysis considers them more on the carnivorous side. This species tends to feed on barnacles, hydrozoans as well as bryozoans and is also typical consumer of encrusted coralline algae. The gonads are edible.