Why do oyster not need to shed its shell?

Oysters do shed their shells, but not in the same way that other animals shed their skin or exoskeletons. Oysters have a hard outer shell made of calcium carbonate, which they secrete from their mantle. As the oyster grows, it adds new layers of shell material to the outside of the existing shell. The inner layer of the shell is dissolved and reabsorbed by the oyster, so the overall thickness of the shell remains constant.

Over time, the outer layer of the shell can become damaged or worn away. When this happens, the oyster will secrete a new layer of shell material to repair the damage. In some cases, the oyster may completely shed its outer shell and grow a new one. This process is called exuviation, and it is relatively rare.

Unlike some other animals, oysters do not need to shed their shells in order to grow. They can simply add new layers of shell material to the outside of the existing shell. This allows them to grow to a much larger size than other animals that have to shed their exoskeletons.