Great spider crab and bryozoa. Great spider crab (Hyas araneus) carrying a bryozoan colony. This crab lives at a depth of 500-2000 metres in Atlantic waters and the North Sea. The carapace (shell) of this specimen measures 3cm wide. Bryozoa are coral-like animals that live in colonies on the sea floor. These crabs are very skilled at disguising themselves. They pick up bryozoan colonies (shown here) and let them grow on their carapace, hiding the crab from predators.