Also know as Biscuit Urchin, Cake Urchin, Cushion Sea Star, Heart Urchin, Irregular Urchin, Sand Dollar, Sea Biscuit.
Found singly or in vast numbers partially buried over sandy areas and occasionally on rocky reefs.
They feed on micro organisms of algae, small copepods, crustacean larvae and detritus.
Length - 7.5cm
Depth - 0-125m
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!! Ref: https://en.wikipedia.org/wiki/Clypeaster_reticulatus