Crabs and lobsters are part of an enormous group of creatures called crustaceans.
Most crabs and lobsters have their own shell, but hermit crabs live inside the discarded shells of other creatures.
Crabs and lobsters are decapods, which means they have ten legs — although the first pair are often strong pincers which are used to hold and tear food.
For spotting prey, crabs and lobsters have two pairs of antennae on their heads and a pair of eyes on stalks.
One of a lobster’s claws usually has blunt knobs for crushing victims. The other has sharp teeth for cutting.
Male fiddler crabs have one giant pincer which they waggle to attract a mate.
Robber crabs have claws on their legs which they use to climb up trees to escape from predators.
Lobsters are dark green or blue when alive and only turn red when cooked.
Apart from climbing trees the robber crab is notable for another strange and unfortunate characteristic — it drowns in water!
The giant Japanese spider crab can grow to measure 3 m across between the tips of its outstretched pincers.
When American spiny lobsters migrate, they cling to each others’ tails in a long line, marching for hundreds of kilometers along the seabed.
Sponge crabs hide under sponges which they cut to fit. The sponge then grows at the same rate as the crab and keeps it covered.