Mole crabs live in the swash zone of Long Island beaches. The swash zone is where waves break onto the sand. The constant crashing of waves and tidal changes do not make life easy for these small crustaceans that are usually about an inch long. Luckily, they are perfectly adapted to living in this turbulent habitat.
Mole crabs dig into the sand with their 5 sets of legs under their barrel shaped exoskeleton. Their telson, an appendage underneath their body that looks like a tail, helps them dig into the sand backwards and anchor their body in place. Research has shown that mole crabs can dig into the sand in under 1 second! Once under the crashing waves, the mole crabs leave their feathery antennae just above the sand to filter feed on minuscule plankton and detritus.
The whole population travels constantly throughout the day to stay in the swash zone as the tide rises and falls. Dr. Quinton White of Jacksonville University posed the question – do mole crabs travel with the movement of the tide or do they have an internal clock, a circadian rhythm, as humans do? “It turns out that mole crabs also have an internal activity trigger too. When placed in an aquarium with no tides, they still move with a sort of tidal pattern, or circatidal.”
Predators of mole crabs include fish, shorebirds, and people who sometimes collect mole crabs for bait. The lifespan of mole crabs range between two to three years. Females are typically larger than males, and can carry up to 45,000 bright orange eggs underneath her telson.
Don’t worry if you’re walking in the swash – mole crabs don’t bite or sting! And mole crabs are not harmed when we enjoy their home alongside them. Look for these fascinating creatures next time you visit the beach this summer!
By Cara Fernandes