Mollusks Facts and Information
Taxonomy [Mollusc] [Phylum: Mollusca] [Class: Cephalopods] [Family: Bivalves]
Mollusks list an enormous collection of invertebrate animals in fact almost 100,000 species.
Soft-bodied marine mollusks do not have typical leg formations, however some develop flexible appendages.
These tentacles are used as sensory organs or as a retractor.
The majorities of mollusk specimens live in the oceans and have a protective hard shell usually as a single unit and not jointed exoskeletons like crustaceans have.
They broadly exhibit an open circulatory system.
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Mollusks - Three Main Groups
- Snails [Gastropoda]
Studies suggest that there are more than 60,000 mollusk snail and slug species living in marine and freshwater habitats. Snails also exist in terrestrial environments. Snail mollusks are characterized by their single spiraling shell, whereas snails lacking shells are slugs.
- Clams [Bivalvia]
Bivalve mollusks have a hinged twin-valved shell and exist in marine and freshwater environments. Headless Bivalvia rely on a wedge-shaped foot for most of its body functions. They are classified as having two shells which lock closed as defense mechanisms. Examples of this diverse group of approximately 30,000 mollusks are giant clams, oysters, and mussels.
- Squids & Octopodes [Cephalopoda]
Squid and octopus species only exist in salt water and they do not possess any shell whatsoever. They are mostly predators and are generally larger and faster than their mollusk relatives. They feed on other mollusks, crustaceans, and small fishes. More than 800 different Cephalopods display bilateral symmetry and do not have a shell with the exception of the nautilus. The biggest mollusks include the giant squid and the giant clam.
The largest animal Phylum is Arthropoda followed by mollusks. The long list of mollusc invertebrates includes snails, squid, cuttlefish, octopuses, limpets, slugs, nudibranchs, nautilus, scallops, clams, mussels, oysters, sea hares and many more.
Common Marine Mollusks |> Nudibranch |> Giant Clam |> Nudibranch |> Cone Snail |> Octopuses |