Rock Sea Urchin

Facts about this animal

The Rock Sea Urchin is a regular sea urchin what means that its test shows a radial symmetry. The colour is dark violet, olive-green, brown or even black. The test can be 5-7 cm wide and the spines up to 3 cm long. The spines are thick and smooth. There are 5-6 meridian rows of paired pores on the ambulacral plates. As in all sea urchins there is a complex jaw mechanism with five teeth – called Aristotle’s lantern – within the ventral mouth.

By day it often rests in small cavities bore itself with its spines (or teeth?) or covers itself with shell debris or algae by means of its tube feet. By night it forages on red algae sometimes also blue-green algae, seagrass and sponges. Overgrazing rocks may cause visible clearings.

Known enemies are spiny lobsters, sea stars and fishes.

The sexes are separate and fertilization is external. Each animal has 5 edible gonads which develop during summer and autumn, mature in winter to spawn in spring and early summer. The larvae, called echinopluteus, are pelagic and show a bilateral symmetry. When the larva settles it metamorphoses to a small sea urchin.