The hermit crab is one of the most interesting species of crustaceans. The name ‘hermit’ is based on its behavior of constantly moving from one ‘home’ to another on its own. But contrary to this belief, the hermit crab is a gregarious crustacean, except when it comes to sharing a home. Here are some interesting facts about this crab.
Fact 1: Hermit crabs are also called ‘anomurans’, or false crabs, because of their distinctively smaller fifth and sixth legs and the ‘uropod’ at the end of their soft abdomen. Both the uropod and the smaller limbs are used by the hermit crab to effectively anchor itself to its protective shell.
Fact 2: Hermit crabs, like most other crustaceans, have blue blood in their bodies. This is because the oxygen-carrying component in their body is copper, which when oxidized, turns blue in colour.
Fact 3: It is known that a hermit crab grows by molting – shedding its outer exoskeleton and creating a newer, larger one. For this process to take place, the hermit crab builds up a large amount of water pressure inside its body, effectively rupturing its outer skin and making way for a new one.
Fact 4: A hermit crab always occupies an abandoned snail shell. It never kills the original occupant. In fact, the availability of shells greatly determines the number and growth of the hermit crab population in an area.
Fact 5: It is also a fact that snail shells rarely survive more than six months after the snail has died. This is another reason why hermit crabs have to constantly find a new home. Small worms that look like white specks start appearing around the mouth of the shell, indicating that the shell can no longer be used.
Fact 6: Hermit crabs thrive in regions with very high humidity since their specialized gills have evolved to work in highly moist conditions. However, a certain species of hermit crab, known as the striped hermit is resistant to ‘drying out’. It is able to retain moisture in its body for the gills to function even in drier regions, unlike other species of hermit crabs.
Fact 7: Hermit crabs are known to be cannibalistic in nature. The smell of a dead hermit crab has been found to excite hunger and the instinct to feed among its fellow species. Scientists conclude that hermit crabs have evolved to recognize that the smell of death is usually the sign of an in-house battle, rather than an external predator.
Fact 8: There is a thin grove on each of the hermit crab’s legs and claws, as in other crabs. These allow it to shed or ‘cut off’ its appendage in case of danger, stress, loss of blood, infection or illness. This process is known as ‘autotomy’. The crab is then able to grow this appendage back in due course of time.
Fact 9: It has been observed that hermit crabs vacate their old shells and move into a new one in a sort of hierarchal ritual. When a new shell has been discovered, a large gathering of hermit crabs may be seen. The biggest crab will move into the new shell, providing it is of the right size, and the second-biggest crab will move into the newly vacated shell, and so on.
Fact 10: : Hermit crabs are known to form ‘symbiotic’ or mutually beneficial associations with other creatures, for example, the anemone. These invertebrates are sometimes found attached to the shells of the hermit crabs. The anemone feeds off the scraps of food that float towards it from the hermit crab’s meal, in turn protecting the hermit crab with its stinging tentacles.