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Why do oysters make pearls?

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Who’d have thought the immune response of a mollusk could result in something so pretty?

Asked by: Susan Bragg, Barnstaple


It’s an immune response designed to protect the oyster from a parasite or an injury (not just a grain of sand as is commonly believed). Cells from the mantle of the oyster form a pearl sac around the irritation. The pearl sac then secretes calcium carbonate and conchiolin protein that builds up in layers to form an impermeable barrier.


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luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.


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