Difference Between Oysters and Clams

Seafood has always been a delicacy for people living by the seashores. They particularly enjoy the taste of shellfish and mollusks like oysters and clams.


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The mollusks make up about 23% of all marine organisms. They include organisms like snails, octopuses, oysters, and clams.

However, when it comes to seafood, people confuse oysters and clams as the same, although they are not.

Oysters vs Clams

The difference between oysters and clams is that oysters have a rough shell and many times a pearl inside, whereas clams have a smooth shell and can only be used for the purpose of eating.

Oysters vs Clams

Oysters are mollusks residing in saline water. They are consumed as seafood, and some of them also harbor pearls.

Clams are mollusks residing in fresh and saline water both. Their primary consumption is only in the form of seafood.

In the ancient times, they were also used as coins and jewellery.


Comparison Table

Parameter Of ComparisonOystersClams
ClassificationOysters belong to the Mollusca phylum and have Pteriomorphia as their subclass.Clams belong to the Mollusca phylum and have Heterodonta as their subclass.
Shell StructureThe shell of an oyster is rough and rich in calcium content.The shell of a clam is hard and lustrous.
Preferred ResidenceOysters prefer brackish, marine waters.Clams prefer freshwater bodies.
MotionOysters are born with a foot that helps them to stick at a particular place and then disappears.Clams have a muscular foot for movement. They also depend on water currents for their movement.
Nutritional RichnessOysters are rich in proteins, copper, zinc, riboflavin, Vitamin D, and B12.Clams are rich in proteins, iron, zinc, selenium, and vitamin B12.


What are Oysters?

Oyster is a popular seafood. The organism belongs to the phylum mollusk with class bivalves. Its subclass is Pteriomorphia.

They prefer saltwater and have rough shells rich in calcium. A group of oysters is termed as an Oyster Reef.

Pearl oysters enclose pearls within their shells.

Their gender is uncertain as they have both sperms and eggs. They are born as males, and after one year of their birth, convert into females.

They feed on planktons and other oceanic residues. However, they are fed on by crabs, starfish, and humans.

They provide several ecological benefits. They help in filtration of water, maintenance of nutrient cycle, and prevention of eutrophication.

However, they are affected by many diseases like Dermo and Multinucleated Sphere X. Also, they harbor bacterias like Vibrio Vulnificus that cause Gastroenteritis in humans.


What are Clams?

Clam is a tasty seafood. The organism belongs to the phylum mollusk with class bivalves.

Its subclass is Heterodonta.

They prefer freshwater and have shiny shells. They burrow themselves in the seafloor, and their age may vary from 1 to 500 years.

They are dioecious, which means that they have separate genders. When the conditions are favorable, they reproduce by releasing a large number of sperms and eggs in the ocean.

They feed on planktons, algae, and fish excreta. However, they are fed on by walrus, seals, and humans.

They have several associated ecological benefits. They filter water, remove Nitrogen from water, prevent algal blooms, and help in the sequestration of carbon from the atmosphere.

However, they are affected by many diseases like Dermo and Quahog Parasite Unknown ( QPX). Also, they harbor bacterias like Chlamydiales and Rickettsiales.


Main Differences Between Oysters and Clams

Oysters and clams are mollusks. They have varied shell structure and functions.

They both are enjoyed as seafoods and have several differences between them.

The main differences between the two are :

  1. Oysters have rough irregular shells, whereas clams have hard, lustrous shells.
  2. Oysters prefer saline water for breeding, whereas clams prefer freshwater.
  3. The gender of the oysters is uncertain as they behave as both males and females during specific times. On the other hand, the gender of most clams is definite.
  4. Oysters indulge in minimal movement throughout their lives, and they have a foot that disappears as soon as they get attached to a surface. On the other hand, clams have a muscular foot for movement.
  5. Animals like crabs and starfish feed on oysters, whereas animals like walrus and seals feed on clams.
Difference Between Oysters and Clams


  1. https://www.journals.uchicago.edu/doi/pdfplus/10.2307/1538972
  2. https://www.cabdirect.org/cabdirect/abstract/19531400195
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