Oysters, commonly known as oysters, oysters and so on. It belongs to mollusks, bivalves, oysters and oyster families. Oyster is the largest cultured shellfish in the world, one of the important marine biological resources available to human beings, and also a globally distributed species.
Oyster is a kind of marine shellfish, which mainly feeds on green phytoplankton such as natural algae. Many people mistakenly think that the green thing in an oyster is its excrement, but it is not. It is an undigested algae.
In another case, the living environment of some oysters may be polluted, or some diseases of their own may cause the meat to become loose, green and smelly, so this kind of oyster is inedible.
Morphological characteristics of oysters;
The shell can be divided into three layers in section. The outermost layer is a thin and transparent stratum corneum, the thickest layer is a columnar structure composed of calcium carbonate called prismatic layer, and the inner layer is a flaky structure called nacre. The shell is secreted by the lower mantle, which extends from the top of the shell to the abdominal edge.
It is two layers of epithelial cells, sandwiched by a membrane made of connectivetissue. There are muscle fibers in the membrane that make it adhere to the inner surface of the shell. The edge of the mantle thickens to form three folds. There are radial muscles and annular muscles in the inner fold, which makes the edge close to the shell. The middle fold has a large number of sensory cells or sensory organs, which have tactile and visual functions, while the outer fold has a strong secretory function.