Oysters are salt-water bivalve molluscs that live in marine or brackish habitats. They belong to several families, with the "true oysters" mainly in the family Ostreidae, which includes edible species such as the European flat oyster, eastern oyster, and Pacific oyster
. Oysters have two hinged shells and are related to other bivalves like scallops and mussels
. They live attached to hard surfaces in shallow waters, often forming colonies called beds or reefs, which provide habitat for many marine species and increase biodiversity
. Oysters feed by filtering water, extracting algae and other particles, which helps clean coastal waters and prevents algal blooms
. Oysters have a simple anatomy without a central nervous system, consisting of two nerve centers controlling their mouth, mantle, and internal organs. They have a small heart and use their gills and cilia to process water for feeding and respiration
. They reproduce by releasing sperm and eggs into the water, with larvae eventually settling on suitable surfaces to grow into adults
. Some oysters, known as pearl oysters (family Pteriidae), produce pearls by coating irritants with nacre, but these are distinct from true edible oysters
. Oysters are also valued for their shells, which are primarily made of calcium carbonate and can vary in shape and color depending on their environment
. In summary, oysters are marine bivalve molluscs that play important ecological roles by filtering water and creating habitats, while also being harvested for food and pearls in some species
