When a hermit crab locates a shell, it slips its abdomen out of the
old shell and quickly into the new one. If the fit is good, the hermit is on
its way. Sometimes, hermit crabs may pull one another from desirable shells.
If a match is uneven, one crab, having been intimidated by another, will
voluntarily leave the shell without a fight and go in seach of another, a
very dangerous voyage for these highly edible crabs.
Photo: Genevieve Johnson
November 15, 2000
The Land Hermit Crab
This is Genevieve Johnson talking to you from Kiribati in
the tropical pacific.
How utterly laborious to be required to drag ones home wherever you go. The
mere thought of it is tiring in itself. When you actually take the time to
consider the fact that this is the only way of life the hermit crab knows,
we can better appreciate the efforts of this small crab.
On second thought, the crew of the Odyssey can relate quite
closely to this lifestyle, like the hermit crab, we also take out home with
us where ever we go.
The land hermit crab is vibrant, orange in color and
seeks refuge in abandoned sea snail shells; which they
scavenge along the seashore and tide pools, exchanging for larger models,
several times during their life as they grow.
Hermit crabs appear to be a permanent fixture of the land and seascape of
pacific atolls. We have encountered them alone or in small groups at the
waters edge, high on the shoreline and in groups of more than 100 piled on
top of one another under driftwood, in the ongoing struggle for shade from
the blazing equatorial sun. We even find them far back in the desert scrub,
where they hide in burrows amongst nesting terns and boobies.
At the first sign of a threat, we watched these crabs
withdraw into their shell, closing their legs inward, the claws, also used
as the first pair of walking legs, forming a hard almost impenetrable
in the shell opening. Despite the protection of their borrowed shells,
larger crabs, octopus, and wrasses prey upon smaller hermits, as well as
other reef fishes with jaws for crushing shelled invertebrates.
The hermit crab's abdomen is soft and curved to fit the shell, which will
help protect it from predators. Hermit crabs have five pairs of legs, the first
pair is modified into claws and the last two pairs anchor the crab's body
within the shell by holding on.
When a hermit crab locates a shell, it carefully checks the inside and
outside of the new prospect with its antennae and claws. Then, releasing its
anchoring limbs from the old shell, it slips its abdomen out of the old
shell and quickly into the new one. If the fit is good, the hermit
is on its way;
if not, it quickly transfers back to the old shell. Sometimes, hermit crabs
may pull one another from desirable shells, if a match is uneven one
crab having been intimidated by another will voluntarily leave the
shell with out a fight and go in seach of another, a very dangerous
voyage for these highly edible crabs
The number of available shells on the shore or on reef flats is very
important to the survival of hermit crabs and can limit their numbers. So,
all of us should leave all seashells, even empty ones, where hermit
crabs can reach them.
Log by Genevieve Johnson
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