The Decorator Crab & the Sponge. The decorator crab who is part of spider crab family snips of portions of sponge and covers itself with them to camouflage it from predators. The sponges are initially able to stick to the crab before they start to grow more because the crab is covered in hooked hairs. Both the crab & the sponges continue to grow together. The sponges benefit by filter feeding in a wide variety of areas as the crab moves around and the crab benefits by both blending in and being able to eat the algae that collects on the sponges.