Atlantic Ribbed Mussel
Geukensia demissa Dillwyn, 1817
The adult Atlantic Ribbed Mussel is 2-4 inches long and has distinctive radial, bifurcating ribs. Its white exterior is usually obscured by the olive or brownish periostracum. The irridescent interior is bluish white, perhaps with a purple or purplish-red posterior end.
Mussels eat plankton. Some mussels filter 10 gallons (4.5 litres) of seawater per day to obtain enough food.
Geukensia usually lives in the mud in salt marshes which have twice daily tidal risings and fallings of the brackish water. The Ribbed Mussel is exposed to air more than it is submerged in water, making it one of the most terrestrial of all North American bivalves. When exposed to the air, the mollusk gaps open its shell a little and breathes air. When a shadow falls across the creature it closes its shell, and other nearby mussels, feeling the vibration from the closing, close their shells too.
The bivalve is found from the Gulf of St. Laurence to northeast Florida, and in the San Fransisco Bay. This mussel is edible.