Hermit crabs are classified as decapod crustaceans. The average size of an individual is 9-10 cm, the largest representatives reach 17 cm in length. More than 450 species of such crayfish are known.
External characteristics
The body of hermit crabs is predominantly soft, they do not have a strong shell, so most species protect their abdomen with empty shells of mollusks. They hunt with them, and they also hide in them in case of danger. Three pairs of limbs, including claws, usually protrude from the shell. The crayfish hunts with the left claw, and the right one protects the entrance to the shell. In the process of evolution, hermits have greatly shortened the hind pair of paws. It is with them that they now hold the shell while moving.
Habitat
Hermit crabs are found in the waters of the Baltic, North, Mediterranean seas, off the islands of the Caribbean, on the coasts of Europe. As a rule, they choose shallow water and only some species prefer a depth of 70-80 meters.
Food
Hermit crabs are predators. They eat molluscs, worms, and other crustaceans. In addition, they are scavengers. Eating up the remains of decaying animals near the coast, crayfish thereby contribute to the maintenance of cleanliness in their habitat.
Hermit crabs shell
As a shelter, hermit crabs choose shells of about 25 species of mollusks. Without them, they are very vulnerable and easily become prey for predators. The main selection criterion is the ratio of the internal volume to the weight of the shell.
Since the hermit crab grows constantly, it regularly searches for a new shell. Usually, immediately after molting, he begins to look for a more spacious house. If there are many shells where it lives, then the replacement process takes place quickly and without problems. But if there are no shells, then the hermit crab looks closely at other crayfish of the same kind. If he finds someone whose shell is clearly not in size, then with special tapping he offers his brother an exchange. In case of agreement, the neighbor crawls out of the sink. However, if something does not suit him, then the hermit crab blocks the entrance with a claw. Very often, real battles take place between the crayfish for a cozy living space.
Symbiosis of hermit crabs and anemones
Very often, hermit crabs settle on the shell of anemones, which protect them from enemies. Anemones, in turn, move very quickly with them in search of prey. Anemones have poisonous tentacles with which they paralyze the victim. Some crayfish prefer to settle anemones directly on the claw, with which they block the entrance to the shell in case of danger. If it is necessary to change the shell, then the hermit crab gently transfers its neighbor to its new home with a claw. Very often, hermit crabs, which have not found a shell for themselves, settle anemones directly on their bodies.
