David Fleetham / Slate pencil sea urchins (Heterocentrotus mammillatus) in reef scene, Hawaii.

David Fleetham / Red liomera crab (Liomera rubra) female holding a tail full of eggs in a slate pencil sea urchin (Heterocentrotus mammillatus) at night, Hawaii.

Pascal Kobeh / Slate pencil urchin (Heterocentrotus mamillatus), New Caledonia, Pacific Ocean.

Fred Bavendam / Slate Pencil Urchin (Heterocentrotus mammillatus) pair attached to rock wall, Kona, Hawaii

David Hall / Slate pencil sea urchin {Heterocentrotus mammillatus} Red Sea - nocturnal

Norbert Wu / Slate Pencil Urchin (Heterocentrotus mammillatus) spines are stony and used for wind chimes, Hawaii

Jeff Rotman / Spines of Slate pencil sea urchin {Heterocentrotus mammilatus} Red Sea.

Jeff Rotman / Slate pencil sea urchin {Heterocentrotus mammillatus} Hawaii, Pacific Ocean

David Fleetham / Giant / Commerson's frogfish (Antennarius commerson), juvenile, on Red slate pencil sea urchin (Heterocentrotus mammillatus), Hawaii.

David Fleetham / Hawaiian turkeyfish (Pterois sphex), endemic, and slate pencil sea urchin (Heterocentrotus mammillatus), Hawaii.

David Fleetham / Commerson's / Giant frogfish (Antennarius commerson), on Red slate pencil sea urchin (Heterocentrotus mammillatus), Hawaii.

David Fleetham / Commerson's / Giant frogfish (Antennarius commerson), juvenile, perched on a Red slate pencil sea urchin (Heterocentrotus mammillatus), Hawaii.