The Pacific Long-spined Black Sea Urchin is one of several Black Sea Urchins, all covered with sharp, black spines.

Native to the Indo-Pacific, it can be differentiated from other Diadema species by the 5 small white spots and the orange ring on its "eye" (its anus - its mouth is on the underside with its tubular feet).

The spines, reaching 10-30cm, are mildly venomous. Some young fish hide in them for protection.

Rarely, some or all of the spines can be grey/white. It can point the spines to potential threats and can even run on its spines in emergencies.

Body diameter can reach 7 cm. Diet is algae. They are important to keep coral reefs free of overgrowth of algae.

The Atlantic Long-spined Black Sea Urchin is one of several Black Sea Urchins, all covered with sharp, black spines. Native to the eastern and Caribbean Atlantic coasts, it can be differentiated from its Indo-Pacific counterpart (see above) by the lack of 5 small white spots and the orange ring and from the Black Sea Urchin, Arbacia species, by the much longer and irregular lengths of spines.

The spines, reaching 10-30cm, are mildly venomous. Some young fish hide in the spines for protection. Rarely, spines can be grey/white. Diet is algae. They are important to keep coral reefs free of overgrowth of algae.