Hermit crab Facts

About the hermit crab

Unlike most crabs, a hermit crab has a soft abdomen without a hard shell of its own, so it must borrow shelter made by other creatures or stay unprotected. There are more than 800 species, and most have a lopsided abdomen tucked snugly into a shell. Almost 800 of them carry portable homes, usually old snail shells.

Living in a movable home has shaped almost everything about these crustaceans, and it helps explain why there are so many kinds living in nearly every marine environment. Most begin life as symmetric larvae that swim freely, then change into lopsided crabs that live on the seafloor and hunt for shells. That big shift prepares them for a sheltered life and helps explain the group's success.

Did you know?

• Hermit crabs belong to the crustacean superfamily Paguroidea, part of the decapods.
• Most hermit crab species have an asymmetric abdomen.
• Hermit crabs live in nearly every kind of marine environment on the planet.