Oysters are a kind of shellfish, the shell in section can be divided into three layers, the outermost layer is a thin and transparent cuticle, the middle layer of the thickest is composed of calcium carbonate columnar structure called prismatic layer, the inner layer of calcium carbonate flake structure, called pearl layer.

Oysters are commonly known as sea oysters, oysters, etc., belonging to the phylum Mollusca. Bivalve, oyster order, oyster family under the species collectively known as oysters. The oyster is the world's first large farmed shellfish, is one of the important marine biological resources available to mankind, for the global distribution of species.

There are many species of oysters, among which there are about 20 species of commercially valuable oysters, and the species of oysters that can be eaten by human beings usually come from the genus Crassostrea virginica and Giant Oyster. They are not only meaty, flavorful and nutritious, they are a delicious seafood treasure.

Morphological Characteristics

Shell is formed by the secretion of the coat membrane below, which extends from the top of the shell to the ventral edge, it is two layers of epithelial cells, sandwiched between the connective tissues of the membrane formed by the membrane, the membrane has muscle fibers to make it attached to the inner surface of the shell. The edge of the outer membrane is thickened to form three folds, and on the inner fold there are radial and circular muscles to keep the edge close to the shell. The middle fold has a large number of sensory cells or sensory organelles, which have functions such as touch and vision.

The two shells are unequal, the left or lower shell is larger and concave, and the left shell is fixed to rocks or seabed stakes. Generally in the late stage of metamorphosis of the larvae of the face plate, the mucus secreted by the foot filaments, fixed the edge of the coat membrane on the substrate, and then the shell secreted by the coat membrane is directly adhered to the plug material. The foot completely disappeared, the anterior shell-closing muscle also degenerated and disappeared, and the posterior shell-closing muscle moved to the middle of the body, and had completely lost the ability to move.