khai muk (ไข่มุก)

Thai for ‘pearl’ or ‘pearly egg’. As in many parts of the world, also in Southeast Asia and the Far East pearls are found, both in fresh water and in the sea, and both natural and cultured ones, hence the presence of numerous pearl farms, especially in coastal areas, where sea pearls are cultured, though there are also a few inland fresh water pearl farms, especially in China which today is the largest producer of freshwater pearls in the world. Though their shape is usually less perfect than that of cultured saltwater pearls, freshwater pearl mussels also occur in colder and more temperate areas, and have a much higher productivity rate, as a single mussel can produce multiple pearls with each production cycle, whereas in seawater pearl oysters (fig.) usually only one pearl is grown at a time. Pearls are formed within the shell of bivalve mollusks, typically —but not exclusively— in oysters, and are produced in reaction to an irritant within the soft tissue of the mollusk, which will secrete thousands of very thin concentric layers of nacre, i.e. a secretion of calcium carbonate that consists of mainly aragonite or a mixture of aragonite and calcite, and is the same composite material mollusks use to produce their inner shell layer, which is commonly known as mother-of-pearl. The nacre is deposited in a matrix that eventually completely surrounds the irritant, forming a hard, lustrous coating, which in cultured pearls is usually in the form of a small sphere, though a variety of other shapes is also possible and even more likely in natural pearls. To culture a perfect spherical pearl, a graft called saibo, i.e. a tiny piece of mantle tissue from a donor shell, which serves as a catalyst for the pearl sac, is surgically implanted into the mantle or into the gonad, i.e. the reproductive organ, of a recipient shell, together with a spherical bead called the nucleus. If the mollusk does not reject the nucleus then two weeks later the saibo has melted down and covers the entire nucleus, which becomes the artificial irritant around which the nacre will deposit, thus creating a perfectly round pearl. The pearls can be harvested after about 18 to 24 months, during which time the oysters are placed in metal frames with nets or —alternatively— attached to strings (fig.), that are hung from wooden racks or in between poles placed in shallow coastal marine waters, such as lagoons. The entire process is known as perliculture and the traditional weight measure used for loose pearls and pearl strands is the momme, which corresponds to 3.75 grams or 3750 milligrams. In freshwater perliculture, no bead is implanted to serve as nucleus, but instead only tiny pieces of mantel tissue are used as grafts throughout the host mussel, and unlike the single saibo used in sea oysters, here several grafts are implanted throughout the mantel. These grafts are sufficient to start pearl production around the implanted mantel tissue which over time will dissolve, thus creating full pearls that are nacre through and through, rather than just a thin coating of nacre around an artificial bead nucleus. In ancient Chinese mythology, pearls are said to come from inside the brains of dragons, while in Greek mythology, pearls were the tears of joy that Aphrodite, the goddess of love, shed when she was born from the sea froth. In Christianity, the gospel is compared to a pearl. In the Parable of the Pearl, Jesus Christ compares the Kingdom of Heaven to a priceless pearl, a valuable treasure that needs no polishing or cutting by man, whilst the Pearly Gates described in Revelation are the entranceway through which souls travel to reach Heaven, and akin to pearls that were formed by the suffering of the mollusk, the pearly gate represents the suffering that Jesus underwent in order to give man access to God. See also TRAVEL PICTURE and THEMATIC STREET LIGHT. 回