- There are over 800 species of hermit crabs worldwide, and almost all are ocean dwellers—though people are likely most familiar with the dozen semi-terrestrial species, called land hermit crabs, which are often kept as pets. There’s only one freshwater hermit crab, Clibanarius fonticola, which is native to Vanuatu.
- Hermit crabs are omnivorous scavengers, eating microscopic mussels and clams, bits of dead animals, and macroalgae.
- These crustaceans have been misnamed for two reasons: First, they’re not true crabs, like blue crabs, in that they don’t have a uniformly hard exoskeleton and can’t grow their own shells. Instead, hermit crabs have a hard exoskeleton on the front part of their bodies but a soft tail on the other half, which they protect using the discarded shells of other animals, like whelks. They’re more closely related to certain kinds of lobsters than to true crabs.
- Hermit crabs have a curled tail with a hook that enables their bodies to fit inside these borrowed shells. Sometimes when a new shell turns up, hermit crabs will form a line, biggest to smallest, to see which animal fits the new shell. The next smallest will take that crab’s hand-me-down home, and so on.