Oysters (ostrea gigas tnunb), commonly known as sea oysters, oysters, etc., belong to the mollusk phylum, bivalves, pearl shellfish, is the world's largest farmed shellfish, is one of the important marine biological resources available to humans, for the global distribution of species. Oysters are not only delicious and nutritious, but also have unique health care functions and medicinal value, and are a seafood treasure with high nutritional value. Oysters have the highest zinc content in human food.
The shell can be divided into three layers on the cross-section; the outermost layer is a thin and transparent stratum corneum, the thickest layer is a columnar structure composed of calcium carbonate called the prismatic layer, and the inner layer is a flaky structure of calcium carbonate, called a nacre layer. The shell is formed by the secretion of the mantle membrane below, the mantle membrane extends from the top of the shell to the abdominal margin, it is two layers of epithelial cells, sandwiched in the middle of the membrane formed by connective tissue, there are muscle fibers in the membrane to make it attach to the inner surface of the shell, the edge of the mantle membrane is thickened to form three folds, and there are radiation muscles and ring muscles on the inner folds to make the edges close to the shell. There are a large number of sensory cells or sensory organs on the middle fold, which have functions such as touch and vision. The outer folds have a strong secretory function.
The two shells are not equal, the left shell or lower shell is large and concave, and the left shell is fixed to the rock or seabed stake. Usually in the late stages of the metamorphosis of the face disc larvae, the mucus is secreted by the filament of the foot, and the edge of the mantle membrane is fixed to the substrate, and then the shell secreted by the mantle membrane is directly adhered to the substrate. The foot has completely disappeared, the anterior occlusal muscle has also degenerated and disappeared, and the posterior occlusal muscle has moved to the middle of the body, completely losing the ability to move. The closed muscles have an antagonistic effect on the ligaments. As a result of permanently fixed life, well-developed small tentacles or senses appear at the edge of the mantle membrane, which never appears to heal or form water pipes, because they live on hard surfaces, where there is very little large amount of sediment present, which has been cleared by tidal movements.
Habits of life
Fix life
Solidified by shell sticking to other objects. It is generally distributed in the intertidal and subtidal zones with a water depth of no more than 10 meters.
Resistance
Oysters are also one of the most resistant aquatic animals, 200 million years of intertidal changing environment has cultivated the oyster's strong resistance to temperature, salinity, open air and common pathogens in the sea area, when the tide is exposed to the water, can tolerate the summer heat and dry weather, but also successfully adapt to the winter freezing weather, in the water dew conditions can survive for 1 to 2 weeks, or even 1 month.
Gender reversal
In natural populations, most oyster individuals are hermaphrodites, a small number are hermaphrodites, oysters can also spontaneously "transgender", the same individual in different years or different environmental conditions, showing different sexes.
Feeding habits
Filter feeding. Feeds on miniature seaweeds and organic detritus from the ocean.
reproduction
According to statistics, a female oyster can produce up to 400 million egg cells in a breeding season, while the oyster's gonads are only fully developed during the breeding season.
Oysters are a world-class shellfish species found in more than 100 species, produced in almost all coastal countries around the world. Most of the oysters in Japan are the same as those in China, and the oysters in Europe and the United States mainly include edible oysters, American oysters, and European oysters, and their total production ranks first among shellfish. During the Han Dynasty in China, bamboo was planted to raise oysters, and it has a history of more than 2,000 years.