Hermit crabs are invertebrates with tough outer exoskeletons on the front part of their body. However, unlike many other crustaceans, the rear part of their body (called the abdomen) is soft and uncovered. These creatures must seek out protection by adopting another structure as their “home”, usually a discarded shell of a sea snail.
Hermit crabs vary in size, with some species only being a few millimeters, while others can grow to a body size of several inches. The largest hermit crab, the coconut crab, is shell-less and can have a body length of up to almost a foot and a half long.
Hermit crabs are able to retract their bodies completely into their shell-home, and usually only the head, legs and claws are visible, with the rest occupying the shell. When a hermit crab outgrows its shell, it must search for a new, larger one.