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- Written by Clyde McMillan-Gamber Clyde McMillan-Gamber
Summer weather has arrived, and many people vacation along the Atlantic Coast, where numerous kinds of semi-aquatic creatures live, including related ghost crabs and fiddler crabs.
Ghost crabs live in burrows in sandy beaches, while fiddlers reside in tunnels in the mudflats of saltmarshes. Both species dig those shelters themselves, where they are relatively safe from rising tides and herons, gulls, raccoons, and other predators.
And by dwelling in different habitats, these crab cousins don’t compete with each other for living space and food.
These interesting and harmless creatures have characteristics in common. Both are about 1.5 inches wide when fully grown and are crustaceans with exoskeletons (shells they shed periodically to be able to grow).
Both have two eyes on stalks, eight legs, and two front claws. They both walk and run sideways at times and wet their gills from moist sand or mud so they can breathe on land. And both species spawn eggs in shallow ocean water, where their young hatch.
When the tide is out, ghost crabs pick up globs of damp sand with their front claws to filter out edibles, including rotting vegetation, algae, and detritus. Fiddlers do the same with mud along tidal creeks in saltmarshes.
But when the tide comes in, both ghosts and fiddlers run down their burrows and shut the entrance with sand or mud.
Atlantic ghost crabs reside on the upper parts of Atlantic shoreline beaches from Massachusetts to Florida. They are sand-colored, which camouflages them on beaches. They have white claws, with one a little larger than the other.
Ghost crabs are mostly nocturnal and run swiftly, both traits to their benefit. And they also prey on mole crabs and clams living in wet sand.
The many similar kinds of fiddler crabs are the more interesting of these related crabs. I’ve seen several fiddler crab colonies on mudflats in saltmarshes from Delaware City along the Delaware River, to Stone Harbor, New Jersey, and Charleston, South Carolina.
The one greatly enlarged front claw on each male fiddler is the most intriguing part of fiddler crabs. That claw can be up to 1.5 inches long, about the size of an adult male crab’s body. Each male uses that claw to wave at the girls and entice them to mate.
Although a genetic quirk with benefits to male fiddler crabs, that immense claw would be like one of our hands being as big as our bodies. The other claw remains small and is used to shuttle food to the mouth.
Ghost crabs and fiddler crabs are interesting crustaceans that are experienced along the sea coast in summer. But one must look for them because they are so small.
Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.