Purple Heart Urchin

• It has lost the radial symmetry typical of echinoderms and regained a bilateral one, with a front and a back, an adaptation to a buried and mobile life.
• It maintains a clean-water shaft to the surface using specialised tube feet that build and clean the tunnel.
• Its empty tests, heart-shaped and pale violet, are often found on beaches.
• It is not radially symmetrical like ordinary urchins: the irregular urchins regained bilateral symmetry, with a front and a back, on adapting to life buried in sediment.
• Its heart shape gives it its name, and the deep purple colour distinguishes it from the other European burrowing urchins.
• It digs in with spade-shaped modified spines and keeps a shaft open to the surface through which it renews its water.
• It swallows sediment and extracts the organic matter, turning over and aerating the seabed as it goes.

Habitat & environment

Coarse sand and gravel bottoms of the eastern Atlantic and the Mediterranean, from 5 to 900 m

Sources consulted: Linneo (1758); Marine Life Information Network; Mortensen, Monograph of the Echinoidea