They’re also one of the world’s largest arthropods, animals with no backbone, external skeletons, and multiple-jointed appendages. In this crab’s case, those appendages are its 10 legs.

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 ...