Mollusca - Phylum Mollusca

Profile of Phylum Mollusca - the Mollusks

Octopus in aquarium
Stephanie Hager - HagerPhoto/Photolibrary/Getty Images

Mollusca is a taxonomic phylum that contains a diverse array of organisms (referred to as 'mollusks'), and the taxonomic classes that include snails, sea slugs, octopuses, squid, and bivalves such as clams, mussels, and oysters. From 50,000 to 200,000 species are estimated to belong to this phylum. Imagine the obvious differences between an octopus and a clam, and you'll get an idea of the diversity of this phylum.

Mollusk Characteristics

Characteristics common to all mollusks:

  • They have a soft body
  • They have a usually distinguishable 'head' and 'foot' region. They use their muscular foot to move.
  • Some may have a hard covering, or exoskeleton.
  • They have a heart that pumps blood through their blood vessels, digestive system, and a nervous system.


  • Kingdom: Animalia
  • Phylum: Mollusca


Many mollusks feed using a radula, which is basically a series of teeth on a cartilage base. The radula can be used for complex tasks, from grazing on marine algae or drilling a hole in another animal's shell.


Some mollusks have separate genders, with males and females represented in the species. Others are hermaphroditic (reproductive organs associated with both male and female).


Mollusks may live in salt water, in fresh water, and even on land.

Conservation & Human Uses

Thanks to their ability to filter large quantities of water, mollusks are important to a variety of habitats. They are also important to humans as a food sourceĀ and have been historically important for making tools and jewelry.


  • Martinez, Andrew J. 2003. Marine Life of the North Atlantic. Aqua Quest Publications, Inc.:New York
  • University of California Museum of Paleontology. The Mollusca. Accessed August 23, 2010.