Hermit Crabs - Facts

All crabs of the families Paguridae and Coenobitidae (order Decapoda of the class Crustacea) are call Hermit crabs. There are several interesting hermit crab facts, one of which is that despite what their name belies one to believe, hermit crabs are more closely related to lobsters than to crabs! Hermit crabs exist almost all over the world, except in the Arctic and Antarctic. They are common and widespread in north-west Europe among other area. They live in waters with sandy, muddy-bottoms, and sometimes on land and in trees. They inhabit rocky and sandy areas that are up to the depths of 140 m from the shore.

Fun Facts about Hermit Crabs

As the distribution of hermit crabs is very wide, they have been able to adapt to several different kinds of habitats. Though they are usually found in shallow waters, some hermit crabs even live in plant stems, while several species are found in kelp forests.

Possibly the best known fact is that their bodies do not have a hard, protective carapace. They need a shell to protect then from predators, which is why they use discarded snail shells or other hollow objects. They move around by dragging their shell with them, and retreat into it when threatened.

The front half of a hermit crab does have a hard exoskeleton, but it is the longish abdomen that is soft and can be change shape to fit into a spiraled snail shell. It contracts its longitudinal muscles and presses its abdomen against the inner walls of the shell.

Hermit crabs stalked eyes and very good vision. They also have two pairs of antennae, one of which is used for feeling, while the other is used for smelling and tasting. They have a large left claw, which they use to grab onto things, to defend themselves and to balance. The relatively much smaller right claw, and subsequent appendages are used in the process of collect food and passing it to the mouth.

Among surprising fact about these crabs is that they molt, which basically means that as they grow, they shed their exoskeleton, and grow a bigger new one. The shedding takes place when the build up of water pressure in the crabs body split its old skin. Often times a crab will consume its molted skin, to attain calcium, vitamins, and minerals.

Another intriguing hermit crabs fact is that while many of them live on land, they all return to the water to procreate. Once in saltwater, they partially emerge from their shells to mate. The eggs are discharged into the sea from which larvae hatch and then go through life stages and molts. Baby hermit crabs look a little like shrimp. On reaching adulthood, they find themselves a shell and resume life on land.

The shell of the hermit crab is both its amour and its home. As it is such an intrinsic part of the crab's life, each shell is subjected to an investigation process before the crab moves in. Sometimes a crab may select a new shell, but find it uncomfortable after a while and move back into the old shell. Hermit crabs compete with each other for the best shells, and often fights break out.

Hermit crabs that live in the sea (sometimes referred to as saltwater hermit crabs), often provide lifts to sea anemones on their shells, and consequently develop a mutualistic relationship with the house guest. The anemone usually lives on the hermit crab's shell, and may play a role in protecting it by stinging tentacles and providing camouflage. There are occasions where the crab and anemone forms a strong bond, due to which the crab will take the anemone with it when it moves shell. Sometimes the crab will allow a ragworm to will live inside the snail shell with it.

I hope you enjoyed these fascinating hermit crab facts, and understand why this creature is best left in the wild, instead of spending its life trapped in a glass box. One more fact - the average lifespan of a land hermit crab is about ten years!