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Difference Between Oysters and Clams

clamsOysters vs Clams

Oysters and clams are often considered as the same thing but there are many differences between these two. Though both belong to the Mollusc class and are bivalves, there are quite a lot of differences in the morphology, anatomy, and uses.

An oyster is often found attached at the same spot, except for the first few weeks of its life. After the initial stage, it gets attached to a safe spot and remains there for the entire life. Clams are more motile and often move around on its foot. The foot is actually a muscle specialized for its locomotion. This foot can be used like an anchor and the body is dragged along in the course of the movement. The oysters also have this foot in the initial stages of its life when it moves around searching for a safe spot to attach to.

Both clams and oysters are used as food in different parts of the world. But many prefer the flesh of clams to oysters owing to the taste. There are differences in the shell textures of oysters and clams. The shell of a clam is smooth and shiny while an oyster has a rough outer shell. Both the organisms take in water through the shells but the filtering procedure is different. Oysters produce pearls which are in much demand but clams do not.

The word clam can denote a variety of mollusks in different parts of the world. If in US, it denotes the most of the bivalves, but in UK it is not used as a general term for bivalves.

Clams are usually found in freshwaters while oysters thrive in brackish or marine habitats. There are different varieties of oysters and clams. True oysters do not produce pearls of gem quality. Pearl oysters yield pearls of commercial value. The largest pearl oyster is of the size of a dinner plate. The pearl oysters can be stimulated to produce pearls naturally or artificially. Some other varieties of oysters are the thorny oysters, saddle oysters, and pilgrim oysters.

Oysters draw in water through the gills and feed on the entrapped planktons and other particles. These organisms have cilia, gills, and mantle which help in exchanging gases. Clams have open circulatory system and oysters have a three chambered heart.

1. Oysters are found in brackish and marine habitats. Clams are usually found in freshwaters.
2. Clams remain motile for their entire lives while oysters are motile only for the first few weeks of their lives.
3. The foot of the oysters disappears after they become attached to a safe place for the rest of the life. The clam’s foot is used life long and functions like an anchor while the body is dragged along
4. Pearl Oysters produce pearls of commercial value and clams do not produce any pearls.

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  1. Clam vs Oyster shell: which shell type will hold up better if used in driveway in Maryland?

  2. Thank you. That was extremely helpful and succinct.

  3. Some clams DO produce pearls. It could be said it is much less often, but to say they do not is incorrect.


  4. To add on to that, the largest pearl in the world, the pearl of Lao Tzu, was found in a giant clam.


  5. More than the shell description, a picture of each one would’ve been helpful. Had to search another site to find those.

  6. Last name is Oyster. I think that clustered oysters in South Carolina are the best in the world.

  7. I learned a lot of facts about clams and oysters!

  8. Please check your facts clams can produce a pearl it is very different from an oyster pearl where it is made from fibers instead of nacre so most clam pearls have what they call a fire ring or a sun burst look to them

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