Macoma Clams

Macoma clams are tiny clams that:

• Lack lateral teeth.
• Have a hatchet-shaped foot.
• Have two long, thin siphons that can be pulled completely into the shell.

What species of macoma clams live in the Bay?

Two species of macoma clams can be found in the Bay:

• The Baltic macoma clam, Macoma balthica, grows to about 1.5 inches long. Its broad, oval shells are thin and chalky white in color, sometimes with a pinkish tint.
• The narrowed macoma clam, Macoma tenta, only grows to about one-half to three-fourths of an inch long. Its thin, fragile shells are more elongated than the Baltic's, varying in color from white to yellowish with a smooth, pearly sheen. The narrowed posterior end of the shells is slightly twisted to the left.

Where do macoma clams live?

Macoma clams use their foot to bury themselves in bottom sands and mud.

• Baltic macoma clams live from the shoreline to the shallows of the middle and lower Bay. They are often found washed ashore.
• Narrowed macoma clams live in shallow areas of the lower Bay, ranging up into the middle Bay.

What do macoma clams eat?

Macoma clams use the longer of their two siphons to draw in microplankton from the water or tiny bits of food lying on the bottom. The siphons attract many predators, such as the American eel, because they look like worms crawling along the bottom.

How do macoma clams reproduce?

Macoma clams reproduce by releasing eggs and sperm into the water column.

• The eggs are fertilized and soon develop into larvae with two tiny, transparent shells and a small foot.
• After floating in the currents for a few weeks, the young macoma clams drop to the bottom and attach to sand grains by thin threads secreted from a gland on the foot. By attaching themselves to the bottom, the young do not get tossed around by waves.

Other facts about macoma clams:

• Even though they are not as well-known as the hard clam or soft shell clams, macoma clams are some of the most abundant clams in the Bay.
• Macoma clams can shift positions when buried in the sand or mud. Some will lie horizontally rather than vertically while searching for food, quickly moving downward if disturbed.