Like a ghost among a forest of spines, the Urchin Pea Crab (Dissodactylus primitivus), seen in this gorgeous Coral Morphologic video, hides out on a Red Heart Sea Urchin. This crab shares a commensal relationship with the sea urchin. It lives among the spines of the urchin, feeding on detritus and any other food particles that get close enough. The urchin is a sand dweller that feeds on decaying organic matter. It buries itself in the sand, where it hides from predators and feeds on anything it can find.
Urchin Pea Crab on the Morphologic Blog0