This urchin appears oval rather than circular when viewed from above. Its body is purple-black, and its long spines range from purple to green, sometimes having white tips. At the base of each spine is a pale ring – characteristic of this species.
Oval urchins are incredibly common in rock pools on South Africa’s eastern shores. It forages by catching fragments of floating algae with its tube feet or moving at night to scour rocks.
They use their spines and teeth to dig into limestone, dead corals and basaltic rocks where they hide during the daylight. This tendency to burrow into hard rock has resulted in the bioerosion of several reefs where overfishing has reduced the number of fishes that prey on them.
The oval urchin has a symbiotic relationship with a tiny shrimp, Athanas indicus, which will often live between the urchin's spines and eat its leftovers and, in return, keep the urchin free of parasites and protect its eggs.