Mollusca is the second largest phylum of the animal kingdom, which includes soft-bodied animals (Latin ‘mollis’ meaning soft-bodied). These animals are usually bilaterally symmetrical, possessing identical left and right halves. Molluscs are triploblastic coelomates with an organ-system level of organization and unsegmented bodies.
The members of phylum Mollusca are classified into seven classes, each of them housing a specific group of molluscs of various shapes and features. Pinctada or pearl oyster belongs to the family Pteriidae, which is a part of class Pelecypoda or Bivalvia (molluscs which are covered by two concave shells). All pearl oysters like Pinctada vulgaris have a strong inner shell layer composed of nacre, also known as “the mother of pearls”. All pearl oysters are exclusively marine, saltwater organisms found at the bottom of the ocean.
Unio and Mytilus (mussels) are bivalves which belong to the same class as oysters. Cypraea (cowrie) are gastropods which were previously used as a form of currency a long time ago.
