A quahog eats by opening its shell, sticking part of its body out (the yellow tube in this photo), and filtering tiny plants out of the water. By Almandine via Wikimedia Commons
Clams live in the water near the edge of the ocean and spend most of their time buried in the sand. The quahog (pronounced co-hog) clam grows two large shells that it holds together with a strong muscle. The quahog can open its shells to look for food and close the shells completely if it is feeling threatened.
Quahog clams eat tiny plants called phytoplankton that float in the water. A quahog eats by pumping water through its body. The quahog filters out the plants it wants to eat and lets the rest of the water pass through.
The quahog has a strong muscle that it uses to pull itself underneath the sand when it becomes unburied. The quahog stretches the muscle out under the sand, expands the lowest part of the muscle, and then contracts the muscle to move its body into the sand. The quahog repeats this motion until it is completely buried.
These quahogs were collected from muddy sand in a river mouth in South Carolina. Courtesy of the NOAA Photo Library
Some clams, including quahogs, are edible. People all over the world cook food with clams in it. By Tory via Wikimedia Commons
The above links plus:
Kaplan, Eugene H. A Field Guide to Southeastern and Caribbean Seashores. Houghton Mifflin Company: Boston, 1988. Pp. 251-258.