The total of around 500 different species of Hermit Crabs are divided into the larger sea-dwelling (aquatic) group, and the small land dwelling (terrestrial) group of crabs which inhabit the tropics. The aquatic crabs live in varying depths: from the shallow coral reefs and shorelines, to the ocean depths. They can be found inhabiting the coasts of Europe and the Americas and seas close by.
Anatomical Characteristics:
Hermit Crabs are not true crabs! True crabs have a hard exoskeleton protecting all of their body, whereas Hermit Crabs have a softer exoskeleton at the hind part of its body, the abdomen, which is therefore exposed to predators. To compensate, Hermit Crabs place this vulnerable area into a shell. Aquatic Hermit crabs use an abandoned whelk shell of gastropod molluscs. If the occupant is still present, it is evacuated by the Hermit. Terrestrial Hermits use a land snail’s shell. At the very beginning and end of the abdomen, one finds little appendages with which it holds on tightly to its shell. Hermit Crabs have ten jointed legs in all, and so are called decapods. The two front legs are modified into claws, also called chelipeds, but one is larger than the other. This way it can fit better into its shell. They have two compound eyes located at the end of stalks, and they have two sensory antennae. Their colouration is very variable. Their size varies between 2-5cm up to 46cm. Hermit Crabs grow in stages, where first they lose their exoskeleton in a process lasting a few days or weeks called moulting, and then they grow rapidly until their exoskeleton hardens again.
Behavioral Characteristics:
As they grow rapidly after moulting, the Hermit Crab searches frantically for a new shell. In crowded colonies where shells are scarce, there is often fierce fighting over them. Once a new home is found, they drag it behind them. Aquatic species have a lighter load to carry thanks to buoyancy. Hermit Crabs can be tamed if handled regularly, usually by letting them climb onto your open hand in their own time. Terrestrial Hermit Crabs must return to the sea to breed. Being born in the sea, they start going through a series of moults in which they progressively develop their ability to breathe air, eventually modifying their gills enough to allow them to live entirely on land. Aquatic Hermit Crabs can have polyps growing on their shells which feed off the crumbs let loose by the Hermits. These polyps return the favour by providing protection through the stings they inflict upon possible predators. They do not harm the Hermit Crab itself. The two are said to live in symbiosis (from Greek word “symbioun” which means “to live together”)
Feeding:
Hermit Crabs are omnivores (they eat both plants and animals). They are also scavengers. Some people keep Hermits in fish aquariums to help clean the water from algae and other debris. Terrestrial Hermit Crabs eat worms, fresh fruit and vegetables apart from purposely produced food found commercially from pet shops, which can suffice most of the time.
Buying:
One can choose to buy either an aquatic or terrestrial Hermit Crab. There is a much larger number of the aquatic species to choose from, as compared to the terrestrial ones. However, aquatic Hermits require a fully equipped aquarium to maintain and hence, more expense. Land Hermits need only an aquarium or terrarium filled with enough sand to allow them to burrow themselves under. You should also have a water dish, a food dish, an enclosure and something for them to climb onto. Temperatures should be kept between 70-85° F (21-29°C). Humidity should be kept to around 80%. Regular misting is a must.
Sexing:
The female land hermit crab has tiny genital openings called gonopores which are located on the first segment of the back pair of walking legs. They are close in to the body, near the joint of the cephalothorax and abdomen
