Mercenaria mercenaria Linnaeus, 1758
This large bivalve is home to an edible clam. The mollusk, also known as the Hard-Shelled Clam, has three different names which correspond to size: “Littlenecks” are the smallest; “Cherrystones” are mid-sized; and “Quahogs” are the largest.
The adult Northern Quahog (pronounced “Co-hog”) may be as big as 6 inches across. The moderately inflated, ovaloid shell is very heavy and strong. The hinges have lateral and cardinal teeth which interlock. The exterior of the shell is pale grayish, ridged with numerous concentric lines (except for a smooth area near the center of the shell). The center of the interior of the shell is dull, chalky white, frequently bordered in shinier purple.
There are two muscle scars where the abductor muscles, which hold the clam shut, were attached. The living mollusk has a strong foot with which it burrows into mud and sand. To eat, the clam opens its shell enough to extend its siphon up into the water. It is a filter feeder.
Algonquin Indians, who gave Quahogs their name, ate the clam and used the shells to make ornaments and tools. Native Americans also cut beads from the shell. The beads were used as wampum, their form of money. Beads made from the purple part of the shell were worth two to four times as much as beads cut from the white portion of the shell.
It is possible to find pearls under the fleshy mantle of the Northern Quahog, but the pearls are not of commercial value.
Clams reproduce by sending out eggs and sperm into the water. This seemingly haphazard method is successful because each female may release as many as 24 million eggs during a single spawning. Such an abundance obviously improves the odds of the seeking sperm.
A prime use of the bivalve was described by John Greenleaf Whittier:
The chowder on the sand beach made,
Dipped by the hungry, steaming hot,
With spoons of clam-shells from the pot.
In the United States there are 60 commecially important clam species for food use. Quahogs, the largest Hard-Shell Clam, are typically used in chowder. Littlenecks and Cherrystones are often served raw on the half shell.
“Treading” for hard clams is one way to catch lunch. The treader wades barefoot in a bay or in the surf, feeling with feet and toes for a clam. When one is found, the treader curls his toes over it, and draws it up against the other leg until it can be grasped. He then drops it into a waiting floating basket.
The clam has others out to eat him besides just humans. Whelks and Sea Stars (“Starfish”) pry open the bivalve for their lunch; and Moon Snails and Oyster Drills bore through the thick clam shells using their tongue-like radulas.
If the clam is not eaten it may live 40 years, gradually getting bigger, up to the aforementioned width of 6 inches.
The Northern Quahog bivalve is found as far south as Florida (perhaps it's a “snowbird”?) up the East Coast to the Gulf of St. Lawrence. Incidentally, Mercenaria mercenaria is the official state seashell of both New Jersey and Rhode Island.