What's inside a clam? A retractable foot, a siphon for sucking up water, powerful muscles, and, sometimes, a pearl. And you thought oysters were fancy. Following is the transcript of the video.

Pearls are made by marine oysters and freshwater mussels as a natural defence against an irritant such ... Nacre can form naturally around almost any irritant that gets inside the shell, creating some ...

Oysters are the primary producers of pearls, clams and mussels can also ... This ligament keeps the valves open, allowing the oyster to feed. Inside the shell, the oyster has several parts ...

A natural pearl will form in an oyster when a foreign object, like a grain of sand, gets inside the shell. To protect itself, the oyster will coat the unwelcome visitor with layers of nacre ...