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You are here:   animal list > Pinctada margaritifera




Pinctada margaritifera

Black lipped pearl oyster

Megan Van Dyk (2011)




Fact Sheet


Brief Summary

Comprehensive Description


Physical Description

Identification Resources


Disease and Predation


Environmental Factors

Reproduction and Development

Sexual Morphology and Physiology

Spawning Seasonality

Larval Development

Evolution & Systematics

Fossil History


Morphology and Physiology

External Form and Function

Internal Anatomy and Function



Feeding Rate

Respiration and Gas Exchange

Molecular Biology & Genetics

Molecular Biology

Nucleotide Sequence

Pearl Aquaculture

Economics and Pearl Farming

Pearl Production and Formation


References & More Information

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Biomedical Terms

Names & Taxonomy

Related Names


Common Names

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Content Summary

Pearl Production and Formation

Pearls are unique in that they are the only gems produced by a living organism. The process of pearl formation, whether by natural means or human interference, is a fascinating practice and has been the subject of myth, scientific speculation and research throughout human history. Even in this modern age, pearl culturing techniques differ little from those developed for round pearl culture over one hundred years ago.


Contrary to the popular conception that natural pearls are formed by an irritant in the pearl oyster’s tissues, recent evidence suggests that pearls result from mantle tissue damage. Pearls form when the mantle is damaged and one or more epithelial cells from the upper epithelial layer of the mantle are transferred into the connective tissue. The transfer of cells may result from a multitude of causes. The mantle tissue may suffer an injury when any type of attacker or intruder, such as small gastropod or crab, reaches the space between mantle and shell and causes damage to the mantle tissue. Small pieces of broken shell, lumps of conchiolin, small stones and the frequently mentioned “grain of sand” can be counted among the potential intruders. The epithelial cells multiply and form a closed cyst, called a pearl-sac. Young cells lining the pearl-sac secrete conchiolin, then a prismatic layer of calcite crystals and then nacre layers. The pearl has similar structure to the shell but the layers are in reverse order and concentric. The nacre layer has the same polygonal shapes in a brick-like structure as in shell nacre. This special structure of the pearl’s surface gives rise to diffraction of light, which lead to the iridescent properties of pearls.


Southgate & Lucas 2008

There are essentially four major types of cultured pearls:

1.     Composite pearls (commonly called “mabé,” half-pearls or blister pearls) that are grown directly on the internal nacreous surface of shells.
2.     Non-nucleated pearls that are produced in the mantle tissue following surgical implantation of sections of donor mantle tissue.
3.     Nucleated pearls that are produced in the gonad of a variety of pearl oysters following surgical implantation of a spherical shell bead (the nucleus) and a section of donor mantle tissue.
4.     Pearls that may develop when the bead or nucleus is rejected from the gonad, but the tissue graft continues to form a pearl-sac. This is also a non-nucleated cultured pearl and is generally referred to as a “keshi” pearl.