Chapter 8 – Pearl Production

Publisher Summary Pearls are the result of a mollusc's ability to produce shell material in response to an injury to the mantle tissue, and the process is identical to the laying down of the shell that protects the soft body tissues. This unique process has been termed biomineralization. The mantle of pearl oysters is responsible for both shell and pearl formation. In the mantle epithelium there were large secretory cells containing carbohydrates, acid proteins, sulphated acid mucopolysaccharides, and calcium granules. The most recent body of evidence suggests that natural pearls are the result of an oyster's response to mantle tissue injury only, and that the presence of a foreign body is not required for pearl formation. The formation of a pearl is the result of a rather accidental occurrence within the normal life cycle of a mollusc. Most nucleated pearl production is from Pinctada species. The general technique involves surgical implantation of a shell-based nucleus (or nuclei) together with a section of mantle tissue removed from a selected donor oyster. There are several key steps in the nucleation process which is commonly called grafting or seeding. First and foremost, both the donor that provides mantle tissue and the hosts that will receive the graft must be in excellent health.