Most jewellery is made from valuable metals such as gold and silver, but natural pearls are produced by living creatures. Do you know that abalones, clams, or mussels can make a pearl? Any mollusk that can produce a shell has this ability, but in nature, this is a rare occasion✨! Pearl oyster, 𝘗𝘪𝘯𝘤𝘵𝘢𝘥𝘢 𝘧𝘶𝘤𝘢𝘵𝘢 (A. Gould, 1850), a marine bivalve mollusk (soft-bodied enclosed in a shell), inhabits subtropical and tropical coral reefs, and is widely distributed in the Indo-Pacific area. Pearl oyster can grow its shell up to 60-80mm with a life span of 7-8 years. Just like other bivalves, 𝘗. 𝘧𝘶𝘤𝘢𝘵𝘢 is a filter feeder. It filters and eats tiny particles like planktonic organisms from the water by slightly opening the shell. It acts as a nature vacuum cleaner which can filter around 50 gallons of water a day💧! What makes 𝘗. 𝘧𝘶𝘤𝘢𝘵𝘢 different from other bivalves is its irregular shell form which is susceptible to environmental constraints. 𝘗. 𝘧𝘶𝘤𝘢𝘵𝘢, like many other marine invertebrates, is hermaphroditic. This simply means that it can produce male and female germ cells at the same time.
Many of you know that oysters can produce luxury pearls, but how can this inconspicuous animal create them? As the oyster grows in size, its protective shell has to grow with it. The mantle is the body part of the oyster, which is responsible for forming the outer shell. The formation of a pearl begins when intruders such as parasitic animals drill through the cover of the pearl oyster and attack the mantle tissue. The attack may disrupt epithelial cells that are the outer surface of the mantle and sink into the connective tissues. The continuously growing cells thus form a pearl sac. Then, something unique happens🔮. The pearl sac encapsulates and dissolves the parasite. As the oyster successfully survives, the pearl sac releases layers of a material called nacre, also known as mother-of-pearl. It is mainly composed of a crystallized form of calcium carbonate and is the same as the inner shell material. Finally, a pearl is created by stacking layers of nacre🤩.
If you take a close look at the pearl, it can appear in different colors such as yellow, pink or black, etc, but its color is commonly shown as milky white. Only on some pearls can you see many bright colors that change with the movement on their surface 🌈. The layers of nacre give that colorful look because the thickness of the calcium carbonate plates is similar to the visible light wavelength. The hue of the pearl changes gradually with the angle of view as different wavelengths of light intervene with the plates.
If you are interested in this wonderful natural jeweller, come and meet it at the HKBM😜!
Text: Joyce Chan
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