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Hermit crabs are decapod crustaceans of the superfamily Paguroidea. They are not closely related to true crabs. Hermit crabs are quite commonly seen in the intertidal zone, for example in tide pools. Most species of hermit crabs have long soft abdomens which are protected from predators by the adaptation of carrying around a salvaged empty seashell, into which the whole crab's body can retract. Most frequently hermit crabs utilize the shells of sea snails, marine gastropod mollusks. The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell. As the hermit crab grows in size, it has to find a larger shell and abandon the previous one.

Hermit Crab

Hermit crabs are decapod crustaceans of the superfamily Paguroidea. They are not closely related to…

An illustration of hermit craps shedding their shells and finding new ones. As hermit crabs grow they require larger shells. Since suitable intact gastropod shells are a limited resource, there is frequently strong competition among hermit crabs for the best available shells. The availability of empty snail shells at any given place depends primarily on the relative abundance of gastropods in the right range of sizes, compared to the demographics of the population of hermit crabs.

Hermit Crabs

An illustration of hermit craps shedding their shells and finding new ones. As hermit crabs grow they…