One of the many wonderful things about a family reunion at the beach last week was watching ghost crabs on the sand.
These pale, sand-colored crustaceans, common along the U.S. east coast, blend in perfectly with their beach home. They even appear translucent, which may explain their spooky-sounding name.
It was a delight to walk along the beach and spot these little fellows, scuttling sideways, this way and that, along the sand. Often I would watch a crab perched motionless at the edge of the opening to its burrow. And before I could make a move for my camera, the crab had disappeared down the hole, out of sight.
Sometimes I noticed sand flying out from a burrow entrance. Below, an unseen ghost crab was industriously making improvements to the shaft or chamber that made up its home. Now, some burrows sported a neat little pyramid of sand beside the entrance, while other burrow entrances were surrounded by messy-looking little collections of sand.
Well, I had to learn more about these ghost crabs, so I did a little research.
Apparently, the orderly pyramids of sand denote a reproductively mature male’s burrow. The carelessly tossed sand indicates the home of a female or a young individual. Scientists speculate that females use the neat pyramids to find potential mates.
The burrow is an important part of a ghost crab’s life. In summer the burrow is a cool retreat from the hot sun, and during the winter it serves as shelter from the cold. In fact, a ghost crab may hibernate in its burrow for up to six weeks during the coldest part of the winter.
The ocean is also important to the ghost crab. The crab makes nocturnal trips down to the water line to wet its gills, which must be kept moist for breathing. And the female ghost crab releases her eggs into the ocean, where they develop into marine larvae.
A true sea creature, the ghost crab won’t drown if submerged. It is protected by its air-tight exoskeleton, which also prevents water loss from internal tissues.
While ghost crabs are sea creatures, they spend much more of their time on the shore, where they scavenge for food. And they are not picky eaters. They’ll eat just about any plant or animal material that washes up onto the shore. Mature ghost crabs do most of their scavenging at night, while the younger ones can be seen scurrying along the sand’s surface during the day as well.
And do these crabs scurry! The fastest crustacean on the planet, the ghost crab can reach a speed of 10 mph! Of its 10 legs, two (the largest) are used for feeding and digging a burrow. The other eight legs–slender and pointed at the end–are for movement. For a walking pace, the crab uses all four pairs of legs. To speed up, the crab lifts one pair of legs off the ground. And to speed up even more, the crab shifts into ‘high’ gear by pulling up all but two legs.  Then it runs across the sand!
Ghost crabs live as long as three years. And like other arthropods, they molt. Inside the hard, external skeleton, the crab’s body grows, encased in a new, soft skeleton within the rigid outer skeleton. After awhile, the tight, outer skeleton cracks, and the crab squeezes out. While the new skeleton is still soft, the crab enlarges it to gain some growing room (like buying shoes a size too large in order to grow into them). Once the new skeleton has hardened, the crab resumes foraging on the beach.
At maturity, a ghost crab is about two inches wide.–April Moore
