According to the subject's question, my answer is as follows. As we all know, pearl is an ancient organic gem, which mainly comes from mollusks such as pearl shellfish and Pinctada. So why do pearls grow in mussels? Pearls grow in mussels mainly because of the invasion of parasites or foreign bodies. When small particles of foreign matter accidentally enter the mussel body, the mussel can't discharge the foreign matter in its own body in time. However, after being stimulated by the invasion of foreign bodies, the mantle of mussels will soon secrete nacre, which will gradually surround the invading foreign bodies. After a long time, the foreign body is coated with a thick layer of nacre, thus forming a delicate and lovely pearl.

It doesn't mean that the bigger the mussel shell, the bigger the pearl inside, which is determined by the length of time when foreign objects enter the mussel shell. The longer the time, the bigger the pearl. The mussel has two thick backs on its body surface. On the inner surfaces of the two back surfaces, there is a soft film called the outer film. The cover wraps the soft body of mussels. The shell of mussel body surface is secreted by mantle.

mussels have a fleshy axe foot in the front of their bodies. When the environment is quiet, mussels slightly open their backs and extend their axe feet. Axe foot muscles contract, which can make the body of mussel move slowly. When the clam is disturbed, the axe foot retracts immediately and the two backs are tightly closed to protect the soft body. When we were young, we often went to the river to catch mussels and put them on the windowsill to dry for a while. The shell opens, sticks out the foot of the meat axe and moves slowly, but the mussel can't leave the water and stay in the sun for too long, so the mussel will die soon. ?

Furthermore, the mantle of mussels can secrete nacre, forming bright nacre on the inner surface of shells. When the local mantle is stimulated by foreign bodies such as sand, the mantle will secrete a large number of pearls to wrap the foreign bodies, thus forming dazzling pearls. The pearls thus formed are a small amount of natural pearls. Pearls can not only be used as beautiful decorations, but also have medicinal value and sedative effect. In order to meet people's large demand for pearls, people use the principle of pearl formation to implant artificially made pearl cores into pearl shellfish through certain surgical treatment, and then put the pearl shellfish back into the water for culture, so that a large number of artificially cultured pearls can be obtained. China is the first country in the world to cultivate pearls artificially. The method of cultivating pearls artificially was invented as early as the Song Dynasty. China's artificial pearl culture has developed rapidly. The above is my answer, I hope you like it.