There are approximately 800 species of hermit crabs worldwide, and virtually all of them live in water. However, the dozen or so semi-terrestrial species known as terrestrial hermit crabs, which are sometimes kept as pets, are perhaps the most familiar to people. The only freshwater hermit crab endemic to Vanuatu is called Clibanarius fonticola.
Hermit crabs are omnivorous scavengers that devour small fragments of dead animals, macroalgae, microscopic mussels and clams.
There are two reasons these crustaceans get the wrong name: They’re not real, like blue crabs, because they can’t develop their shells and they lack a consistently hard exoskeleton. On the other hand, hermit crabs have a soft tail at the back of the body that is protected by the shells of other creatures, such as whelks, and a hard exoskeleton at the front of the body. They are more like some species of lobsters than king crabs.
Hermit crabs can fit inside these borrowed shells due to their hooked, curled tails. Hermit crabs occasionally line up from the most recognizable to the least to choose which animal best fits a newly discovered shell. The smallest crab will pass from its inheritance to the next, and so on.
They get their name from the way they hide inside the shells. However, the term “hermit crab” is incorrect for these gregarious crabs, which can live in large groups of hundreds or more.
mating and reproduction
Hermit crabs have a variety of mating behaviors. For example, the Caribbean hermit crab, which usually lives in swamps, will migrate to the ocean in large groups when it is time to mate.
During the confusion, the males and females meet and partially emerge from their shells to allow the male to pass a packet of sperm to the female, fertilizing her eggs. Later, he carries his eggs to the water’s edge, where the larvae float away when the eggs hatch from contact with the ocean.
Crab larvae feed on ocean plankton and go through numerous molting phases before obtaining their shell and returning to land.
Dangers to Hermit Crabs
Hermit crabs do not breed well in captivity. Therefore, it is unsustainable to remove 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 die each year after becoming entangled in plastic trash.
More crabs are drawn to the death trap due to the pheromones released by these dead-trapped crabs, which alert other crabs to the possibility that a shell is available.
Unlike other crabs, hermit crabs’ abdomens are soft and sensitive and not protected by an exoskeleton. They use discarded snail shells as protection to solve this problem. Like other crustaceans, hermit crabs shed their skin to get bigger, but when their shell becomes too small, they must find a new one. Before leaving the protection of their current habitat, they pick up the shells and turn them over to examine them. Sometimes the shell selected is the wrong one, 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 do occasionally occur.