Hippidae and Albuneidae - Sand and Mole Crabs

Sand and mole crabs are small square or oval-shaped crabs that burrow into the sand in the swash zone (from the highest reaches of waves to the lowest reaches of waves) of sandy beaches, although some may be found in deeper waters. They cannot walk forwards or sideways, only backwards. They use their hind appendages for burrowing and swimming. Sand and mole crabs burrow backwards into the sand so that their head and antennae are near or at the surface. As the tides move in and out, so do the crabs locations. The small bubbling holes you see on the beach are usually sand and mole crab burrows. Unlike other crabs, they have no claws or only have half-claws (subchelate). It was once thought that they catch their food by waving their feathery antennae around to filter the water. However, recent studies have suggested that they are scavengers and predators. They are all marine and are found world-wide except in the Arctic and Antarctica.