Crustacea

1)   Hermit crabs have a soft abdomen and they need to protect this soft part with an empty snail shell. As they grow, they have to search out larger snail shells.

2)   Hermit crabs are crustaceans (crusty-shelled animals that live in the sea).

3)   Hermit crabs are not true crabs (Brachyura) with a completely hard carapace, but are called anomurans (Anomura) and they only have four pairs of developed legs (including the claws).
     True crabs have five pairs of legs including the claws.
     Link to the photograph showing the reduced fifth pair of legs

4)   Most hermit crabs live in the sea, but there are a few species that spend almost the whole of  their life on land. These are the land hermit crabs of the family Coenobitidae. Sometimes they are on sale in pet shops.

5)   Even land hermit crabs must return to the sea to breed. The female crab discharges her eggs into the sea. Larvae develop in the sea before they change into miniature hermit crabs, find a shell to protect themselves, and clamber out on to the land.

6)   Hermit crabs, like all crustaceans and insects, must shell their exoskeleton (the armoured covering their claws and front part of their body) in order to grow. The new larger exoskeleton grows underneath and needs to time to harden and protect them. This process is called "moulting". (The American spelling is "molting". )

7)   The two claws of hermit crabs are different sizes.
      Each species of hermit crab has the largest claw on the right or left (when viewed form the front with the pointed end of the snail shell on the left).

8)   Hermit crabs have a varied diet. They often scavenge around for rotting food, both in the sea and on land.

9)   If land hermit crabs are kept in captivity the pet shop owner should advise of their food and upkeep needs.

10) If hermit crabs  that are live in the sea are to be kept, they need a properly set-up marine aquarium.

11) Some hermit crabs that live in the sea, regularly give a lift to sea anemones and other animals on their shells. Sometimes a ragworm will live inside the snail shell with the hermit crab.

12) Hermit crab are very quarrelsome amongst themselves over the availability of snail shells.
 

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