CLAMPERL’s sturdy shell is not only good for protection - it is also used for clamping and catching prey. A fully grown CLAMPERL’s shell will be scored with nicks and scratches all over.
CLAMPERL grows while being protected by its rock-hard shell. When its body becomes too large to fit inside the shell, it is sure evidence that this POKéMON is getting close to evolution.
A CLAMPERL slams its shell closed on prey to prevent escape. The pearl it creates upon evolution is said to be infused with a mysterious energy.
It is protected by a sturdy shell. Once in a lifetime, it makes a magnificent pearl.
It makes a single pearl during its lifetime. The pearl is said to amplify psychic power.
— Pokédex entries (via PokeAPI)