Oysters are bivalves with irregular shells, which are large and heavy. The left shell is attached to other objects, with a groove in the middle, and the software is hidden inside. The right shell is flat and small, covering the soft body like a lid. Oysters are oval, round, triangular, elongated and fan-shaped. Oysters only open and close their shells all their lives, and only the right shell is inclined up and down. Vegetarians, the staple food is unicellular plankton and organic debris. Oysters are hermaphroditic, hermaphroditic and often have sexual communication. There are more than 400 species of oysters in the world, of which more than 20 species live in the coastal areas of China. Although oysters have two shells, they are asymmetrical. The left shell is large and concave, which is used to fix on rocks and other foundations, while the right shell is small and flat. Once attached, you can never leave. Oysters feed on microorganisms in seawater. However, oysters have only one inlet pipe and no outlet pipe. When the water flows through the gills from the coat cavity, the oyster eats and breathes, and its strong filtering ability ensures the survival of the oyster. An oyster weighing 20 grams can filter 8 liters to 22 liters of seawater per hour, and the speed can reach 3 1 liter to 34 liters. Mature oysters discharge sperm and eggs into water for in vitro fertilization. A female oyster can lay tens of millions of eggs in 15 minutes, sometimes up to hundreds of millions. After a period of natural incubation, fertilized eggs develop into larvae. The larvae of oysters are very different from adults. They are called trochophore, and the larger larvae are called face-plate larvae. The larva has grown two shells, but they are incomplete, just like naked beggars. They can swim freely with the help of cilia and feed on plankton. After half a month's short and free wandering life, the larvae grew feet and tried to find a suitable place to live with them. Once it finds a hard place, it secretes adhesive from the gland connected to the foot and fixes the left shell there. After fixation, they grow more rapidly, the face plate disappears gradually, the feet degenerate, the gills develop gradually, and the shell grows bigger and bigger. Within three weeks after fixation, the body of the oyster can be increased by 30 times.