Common Sea Urchin, Echinus esculentus

Image Caption: Sea urchin test (Echinus esculentus). Credit: Daniel P. B. Smith/Wikipedia (CC BY-SA 3.0)

The common sea urchin (Echinus esculentus), also known as the European edible sea urchin, can be found in northwestern coastal areas of Europe. Its range includes Spain, France, Portugal, Belgium, Denmark, Sweden, The Netherlands, Ireland, Norway, and the United Kingdom. It prefers to reside at depths of up to 3,937 feet.

The common sea urchin is relatively spherical in shape, although its top and bottom are slightly flattened. It can reach an average diameter of about 3.9 inches and is typically reddish orange or purple in color. This species test, or outer shells, is marked with five distinct areas, separated by five darker markings. Each of these areas holds two rows of protective plates, giving this species twenty plates in total. The entire body is covered with spines, with longer spines occurring in every second or third plate area. These spines are actually blunt and hold a whitish purple color. The underside of the body holds pincer like defensive organs, each hold about three teeth.

The teeth of the common sea urchin are used to consume a number of food types including algae, worms, barnacles, tunicates, and other types of food. The spawning season of this species typically occurs in the spring months, during which time females can produce up to twenty million eggs within the water column. The larvae intermix with the plankton, and after a period of forty-five to sixty days, they float down to the sea floor. This species can have commensal relationship with Adyte assimilis, a type of worm, and Pseudoanthessius liber, a type of copepod. These two species benefit from living within the spines of the sea urchin, but do not negatively or positively affect it. It can contract a parasitic copepod known as Asterocheres echinola.

The scientific species name of the common sea urchin, esculentus, literally means edible. The sea urchin roe, or eggs, and the gonads of both males and females are consumed. Typically, fishing of this species is conducted of most European coasts, and studies are currently being conducted on the viability of cultivating it. A similar study conducted in Scotland showed that by feeding the sea urchins a common type of salmon food, the growth of both males and females gonads increased.