Times of the Islands Fall 2023

Hermit crabs change shells after each molting, usually moving to a larger space, as this crab is doing.
Hermit crabs are one-of-a-kind evolutionary crustacean
anomalies. Although they are called crabs, they
aren’t true crabs, which have thick chitinous exoskeletons.
Instead, hermit crabs have soft, long, spiral-coiled
abdomens that end in an asymmetrically hooked tail,
which they use to secure themselves in an abandoned
mollusk shell. This protects their soft and vulnerable bodies,
which have no natural protection from the elements
or predators.
Before becoming anything resembling their adult
appearance, hermit crabs go through several stages of
change. The eggs will develop into tiny, free-swimming
larvae called zoea, which have spiny carapaces and rudimentary
limbs on the abdomen and thorax. From this
stage they molt numerous times before reaching the
next stage of growth, the megalops, where appendages
appear, the abdomen lengthens, and the eyes enlarge.
After several more moltings, megalops becomes juvenile
hermit crabs, little replicas of adults.
Over their lifetime, hermit crabs molt regularly as
they grow. The smaller the crab, the more often it molts.
Tiny ones (0.7 inch in diameter) will bury themselves in
the sand for about two weeks for the molting process,
and they will do this several times a year. Then, as they
reach about 0.96 inch in diameter, the process takes
about a month and happens three or four times per year.
The next phase (1.68 inches in diameter) doubles in duration
but only happens once or twice a year. Finally, when
a hermit crab reaches adulthood, the process still takes
about two months, but decreases in frequency to once
every eighteen months or so. All these moltings are part
of the aging process, but unlike some other crustaceans,
there is little difference in their appearance pre- and postmolting.
Another fun fact about these interesting critters is
that they will change shells after each molting, usually
upgrading to slightly more space than their previous
home. Sometimes this consists of very complex shell
exchanges with dozens of post-molting hermit crabs.
One crab will leave their current shell and a smaller one
will move into the vacant real estate. This event can be
one or two hermit crabs moving homes, or an entire procession
of home-swappers moving into little efficiency
shells that are less than an inch in size all the way up to
giant hermits in the grandioso shells of Queen conch and
Triton trumpets.
You can also get an idea of their age by the thickness
of their antennae and the little sharp nodules on
their grasping claw, which is what they use to snag food.
They aren’t the pickiest eaters and will dine on just about
anything that is near them—small fish, invertebrates like
worms, plankton, and floating food particles in the water
that pass by them. Keeping your fingers out of reach is
advised because they just might resemble little fishy bits
to near-sighted hermits!
These hardy characters can live thirty years or more
in their natural environment, and with over 800 species,
and most of them marine, you are bound to encounter
30 www.timespub.tc