The giant Japanese spider crab is the largest crustacean in the world. The crab can grow to have a 13-foot leg span.
The Alaskan king crab is also one of the largest crustaceans. These crabs can weigh slightly more than 20 lbs. when fully grown. Crustaceans all have an external skeletal system. They also have jointed appendages. Some crustaceans on the other end of the spectrum never grow to be more than 1/100 of an inch big. Crustaceans live in all types of habitats around the world. There are more than 70,000 different species of crustaceans, many of which are edible.