Very Social Hermits

Ever since I was a child I looked with curiosity upon these unusual creatures. When I finally met them in real life, my fascination and attraction grew bigger.  That day, it wasn’t just one but thousands that covered the beach.  Falling silent, we could hear their steps among the leaves and branches along with the screeches they emit when conversing amongst themselves.


Despite their name, the hermits crabs are really very sociable beings, that live in colonies of between 10 to 150 individuals and establish relationships of cooperation with other beings such as anemone and sponges, which act as their defense and camouflage.  In addition, each marine hermit is accompanied by a polichetus, a small cleaning worm that lives with him and feeds on the discards the crab leaves behind. 

There are some 500 species of hermits in the world.  The great majority are aquatic even though in the tropics there are several terrestrial species that so delight the children who play in our beaches.

 

What makes these little crabs so special is their abdomen so soft and delicate that they are obliged to search for empty conch shells to hide their most vulnerable parts.  In the case of the terrestrial hermits, the shells are also necessary to keep their bronchi humid and so to be able to breathe even while on land.
 
For these crustaceous getting a good shell is truly a matter of life or death.  They carefully inspect every shell of their size they encounter until they find one better than the one they have and without giving it a second thought they grab it.  In areas where there is a scarcity of shells, they have been seen trying on bottle caps and other objects with a cavity.

If a crab wishes to possess another’s shell, before doing battle for it, it will softly nudge the shell that holds its interest and according to the resonance, it will estimate the size of its current occupant.  If it considers that the shell is too large for its user, then it will demand in battle its right to possess it. 

However, if it fits the size of its owner, rarely there will be a confrontation, unless it comes equipped with good extras such as anemone or sponges, two of the most valuable luxuries when you are a marine hermit…

On occasions a crab cuts a piece of sponge and places it over the shell so it will grow there and camouflage it, helping it to go unnoticed by its predators.  Others associate themselves with itchy anemones, who in exchange for protection receive transportation and access to the remainders of the hermit’s food.  Curiously, when the crab changes to another shell, it gives time and “instructions” to its anemone to re-accommodate itself in its new house.

As the crab grows it will need to change house several times, and for this reason they are always alert to what may be available on the market.  The young ones change their “skin” and their shell several times a year, while the adults do it every 12 to 18 months.  The terrestrial hermits live 5 years at the most, but some of the marine species can have a lifespan of longer than 20 years.
 

DID YOU KNOW
The Hermits are decapods (from the Latin “ten feet”) crustaceans, that is, the group of crustaceans with the highest degree of evolution; the same group to which lobsters, Spider crabs and shrimps belong.


CURIOUS FACT

The large Coenobita crabs from Bermuda only fit in the shells of one species of conch, the Cittarium.  It is their bad luck that those conchs were so tasty and appetizing that they became extinct some 100 years ago.  Ever since, the Coenobita has managed to survive by using the shells left by the mollusks that died over a century ago.  Save a big evolutionary change, the Bermuda Coenobitas, no doubt, have their days numbered.