The variety of forms amongst crabs is extreme. Swimming crabs such as the blue swimmer, are well suited for rapid swimming and burrowing in soft sediments with their flattened feet and swimming paddles. The box crabs on the other hand are no example of agility. As the name suggests, the body is thick and box-like. Their specialty, however, is food processing.
Spider crabs are experts in camouflage.
They often foster the growth of seaweed, sponges and soft corals on their carapace. A motionless spider crab in its natural enviroment may be near impossible to detect. Crabs of the family Parthenopidae may possess the most grotesque forms. Daldorfia horrida , for instance, is covered in knobs, spines, tubercles and sometimes even seaweed, that again serve as protection. Not all crabs of course live in the ocean.