Sphaerechinus

Lore & Background

Sphaerechinus granularis is a large sea urchin, somewhat flattened dorsally and growing to fifteen centimetres in diameter. It has two distinct color forms: the test is purple in both, but one has purple spines and the other white. The spines are short and blunt, all the same length, and arranged neatly in rows. The species often covers itself with morsels of algae and shell fragments, held in place by tube feet and pedicellaria. It grazes on algae, especially encrusting coralline algae, seagrass blades and their epiphytic organisms, and detritus. Spawning takes place at any time of year, with a peak in spring and early summer; eggs and sperm are liberated into the water column, and the larvae are planktonic before settling and metamorphosing into juveniles.

Reader's Guide

Sphaerechinus granularis is notable as the sole member of its genus, Sphaerechinus, and is distinguished by its large size, flattened shape, and two color forms. It inhabits sheltered locations in the Mediterranean Sea and eastern Atlantic Ocean, from the Channel Islands to Cape Verde and the Gulf of Guinea, typically in the neritic zone down to about 30 metres but occasionally as deep as 130 metres. The species is found on rocks covered with seaweed, gravelly substrates, and in meadows of the seagrass Posidonia oceanica. In Tunisia, it lives in association with two other sea urchin species, Centrostephanus longispinus and Paracentrotus lividus. It is preyed upon by the starfish Marthasterias glacialis and Luidia ciliaris. The gonads of S. granularis are considered a delicacy in Italy, Provence, and Catalonia.

Did You Know?

• Sphaerechinus granularis is the only species in the genus Sphaerechinus.
• It has two color forms: one with purple spines and one with white spines, both on a purple test.
• Its gonads are eaten as a delicacy in Italy, Provence, and Catalonia.