Several species of crabs are considered ‘decorator crabs‘ because they conceal themselves with sponges, bryozoans, anemones, and other vegetation. The crabs will hold a piece of decoration against it shell until it begins to grow there. They are equipped with velcro-like bristles to keep their camouflage attached. Surprisingly enough, the decorations remain with the crab even when it sheds its exoskeleton. When the old shell splits, the vulnerable crustacean crawls out. The crab hides from predators while a new shell forms.
Image (c) thosenorthernskies.blogspot.com.