There are approximately 800 species of hermit crabs around the globe, and virtually all of them live in the water. However, the dozen semi-terrestrial species known as land hermit crabs, sometimes kept as pets, are perhaps the ones most familiar to people. The only endemic to Vanuatu freshwater hermit crab is called Clibanarius fonticola.
Hermit crabs are omnivorous scavengers who devour small fragments of dead animals, macroalgae, microscopic mussels, and clams.
There are two reasons why these crustaceans have the wrong name: They are not real, like blue crabs, because they cannot develop their shells and lack a consistently hard exoskeleton. On the other hand, Hermit crabs have a soft tail on the back of their bodies that is protected by the shells of other creatures, such as whelks, and a hard exoskeleton on the front of their bodies. They resemble some lobster species more closely than actual crabs.
Hermit crabs can fit within these lent shells because of their curled tails with hooks on them. Hermit crabs occasionally line up from most recognizable to least to choose which animal best matches a newly discovered shell. The tiniest crab will pass on its hand-me-down to the next, and so on.
They get their name from the way they hide inside shells. However, the term “hermit crab” is inaccurate for these gregarious crabs, which may dwell in vast groups of hundreds or more.
Mating and reproduction
Hermit crabs have a variety of mating behaviors. For instance, the Caribbean hermit crab, which usually inhabits marshes, will migrate to the ocean in large groups when it is time to mate.
During the confusion, men and females come across one another and partially emerge from their shells to allow the male to pass the female a sperm packet, fertilizing her eggs. Later, she brings her eggs to the water’s edge, where the larvae float away when the eggs rupture due to contact with the ocean.
The crab larvae will feed on ocean plankton and go through numerous molting phases before getting their shell and returning to land.
Dangers to hermit crabs
Hermit crabs do not reproduce well in captivity. Hence it is unsustainable to take them from the wild and sell them as pet crabs and souvenirs.
Hermit crabs are another species affected by plastic pollution. According to 2020 research published in the Journal of Hazardous Materials on two tropical islands in the South Pacific, some 570,000 hermit crabs perish yearly after being entangled in plastic garbage.
More crabs are drawn into the death trap due to the pheromones released by these dead trapped crabs, which alert other crabs to the possibility of a shell being available.
As opposed to other crabs, hermit crabs’ abdomen is soft and sensitive and is not protected by an exoskeleton. They employ discarded snail shells as protection to get around this issue. Like other crustaceans, hermit crabs molt to increase in size, but when their shell gets too tiny, they must look for a new one. Before leaving the protection of their present habitat, they hold the shells up and turn them over to examine them. Sometimes the selected shell is incorrect, in which case they return to their previous shell and resume their search. Competition for the best shells can be challenging, and hermit crab battles occasionally occur.