Also know as Biscuit Urchin, Heart Urchin, Sand Dollar, Sea Biscuit, Sea Potato.
Found singly or in vast numbers often half buried or buried over mud and sand bottoms of coral and rocky reefs.
They feed on micro organisms in the sand.
Length - 7cm
Depth - 0-90m
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 piece through a wet-suit.
Some are sensitive to light and have the ability to shoot venom loaded spines at a short distance.
To be avoided!! (edit) Ref: x