Also known as Black Diadem Sea Urchin, Blue-black Sea Urchin, Dark Coloured Sea Urchin, Diadema Urchin.
Found in shallow waters hiding during the day amongst coral, rubble and sandy areas of bays and lagoons.
They feed nocturnally on corals, dead fish, invertebrates and sponges.
Length - 20cm
Depth - 1-40m
Widespread Indo-West Pacific
Sea Urchins use tubed feet to get around, often in large impenetrable masses for protection.
Sometimes they hitch a lift on the back of crabs.
They have well developed jaws for grinding their prey.
Their anus is on top in most sea urchins, except the heart urchins where it is at the rear.
Predators of sea urchins are triggerfish and large wrasses, who nibble away at their spines before turning them over to eat the fleshy undersides.
Sea Urchins are highly venomous and can pierce through a wet-suit.
Some are sensitive to light and have the ability to shoot venom loaded spines at a short distance.
They are to be avoided!! Ref: https://en.wikipedia.org/wiki/Echinothrix_diadema