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ANATOMY OF THE OYSTER AND COMPOSITION OF THE POLYNESIAN BLACK PEARLS

More than 70 types of mollusks (from the phyllum Molluscs) that can create pearls, the majority fit in with the Pinctada gang. Pinctada maxima, the white-lipped or gold-lipped shellfish, is prized for both its shell and the extensive gold-hued and white pearls it produces. It lives in the South Seas, Burma, New Guinea, the Philippines, Australia, and Indonesia Pearls or Lombok Pearls.

Pinctada fucata martensii, generally called Alzoya, has a slight shell of no business significance yet is esteemed for its little (typically under 9 mm] white pearls, which are rich on the world market today. These mollusks are found in China and Japan. Pinctada margaritifera, the blaclz-lipped clam, is prized for both its mother-of-pearl shell and its extensive gray to black pearls. Pearl-bearing inargaritifera are found in Peru, Baja California, Panama, Indonesia, Micronesia, the Red Sea, the Philippines, and Olzinawa, and French Polynesia.

Shellfish, bivalve mollusks like the Pinctada, have two symmetrical shells pivoted together by a ligament. The life range of l? inargaritifera ranges up to 30 years; a solitary shellfish can weigh up to 11 lbs. (around 5 kg) and achieve a distance across of 12 in. (around 30 cm). An intense adductor muscle holds the two shells together, leaving a space on the inward surface. A standout amongst the most unmistakable qualities of the black-lipped shell is the greenish black shading on its inside edges, which is copied in a hefty portion of the fine pearls from this molluslz. The two most imperative organs in delivering

pearls are the mantle and the gonad (figure 8). Does the mantle shape the shell, as well as every part of the mantle additionally secretes diverse layers of nacre. The gonad is the regenerative organ, a vast whitish sack that holds the eggs or sperm. In the culturing process, the bead core and a bit of mantle tissue are embedded into the gonad to create a cultured pearl.

Nacre, the crucial element of all pearls, is made out of roughly 90% aragonite (orthorhombic calcium carbonate gems) and 5% conchiolin (a natural protein that ties the aragonite gems together), together with other natural material; the most bottomless follow components in I? margaritifera are magnesium, strontium, and sodium (Wada, 198 1, p. 154). The nacre is emitted in concentric layers around a micron thick. Cultured pearls have a refractive file of 1.53-1.69 and a particular gravity scope of 2.72-2.78. The normal hardness is 3.5.

CULTURING POLYNESIAN BLACK PEARLS

While natural black pearls are still discovered every so often, about all the black pearls available today are cultured. Most natural black pearls have slightly less luster and have a tendency to be bigger than their cultured reciprocals. Culturing is basically a two-section process: to start with, the development of the clam, P. margaritifera, and second, the development of the pearl in this clam. The procedure is basically the same one Mikimoto used to build up the Japanese pearl-culturing industry (Shirai, 1970). Mikimoto even did some culturing explores different avenues regarding l? margaritifera in 1920, when he set up a trial station at Palau (Cahn, 1949; George, 1979).

The clams utilized as a part of the culturing procedure are still drawn from the restricted assets in the water around the islands. Albeit some are recovered by autonomous jumpers (who keep on being confined by the Tahiti government to specific zones of the atolls), most are delivered by spat development. In a contemporary adjustment of Bouchon Brandely’s original project, youthful shellfish are put in nurseries, suspended from metal nets by stainless steel or nylon wires, until they are mature enough no less than a few years of age to be utilized for pearl culturing (figure 9). A few farms are additionally exploring different avenues regarding developing mollusks in tanks; positive results are foreseen.

Pearl culturing comprises of embeddings into the gonad of the clam a bead made of freshwater mussel shell alongside a union of mantle tissue from another live black-lipped shellfish. The core is regularly produced using the mother-of-pearl of a Mississippi River (U.S.) molluslz. Once, just the pigtoe mussel was utilized; today, three species found in focal and southern tributaries of the Mississippi River likewise give great cores. The mantletissue union is a crucial segment of the culturing process, both as far as fortifying the emission of nacre and in deciding the shading and different components of the completed pearl.

The whole operation of embeddings the bead and tissue takes one to two minutes and is typically done by Japanese, Australian, or Polynesian specialists. The professional picks the fitting core size for the shellfish being utilized, regularly a bead 5-9 mm in width, and afterward makes a little entry point in the gonad, into which the core and mantle-tissue union are put (figure 10). The experience of the expert is precious in guaranteeing that the shellfish utilized is solid, that the biggest bead conceivable is chosen, and that the different segments are not harmed throughout the operation.

Once the system is finished, the clams are joined to a nylon rope through gaps bored in the shells. In a few farms, the clams are set exclusively in net packs, which get any beads that are rejected. A jumper then joins the chain of clams to a submerged stage (figure 11). The operation happens regularly in the middle of June and September, the winter months for this district, when the water is cooler and there is less danger of vicious tempests.

On the off chance that a shellfish rejects the bead, it will for the most part do as such in the initial two months taking after the surgery. Some very much prepared farms have been lznown to X-ray the shellfish to check whether the core has been rejected or on the off chance that it is set up legitimately, yet this system is utilized a great deal less regularly today than it was previously (R. Wan, pers. comm., 1989). Shellfish that reject their beads can be re-worked on following a few months of rest. On a few farms, these clams are rather used to make mabes or collected cultured rankle pearls.

Roughly two years must go before the achievement of this operation is lznown. Around then, a couple of mollusks are conveyed to the surface and verified whether a pearl has shaped and, assuming this is the case, how thick the nacre is. With three or four layers of nacre stored a day, a pearl cultured in P. margaritifera will add to a nacre thickness of 2 to 2.5 in mm in two yea&, contrasted with 1 mm created by an Akoya pearl over the same time range.

Amid the development period, the clams must be observed always. They are conveyed to the surface and the barnacles cleaned up a few times each year. Predators, parasites, tropical storms, contamination, and robbery are a steady risk. In both 1983 and 1985, typhoons did significant harm to shellfish, hardware, and structures in French Polynesia on farms in the Tuamotu Archipelago (Cohen, 1983; C. Rosenthal, pers. comm., 1989).

Right now the tidal ponds of two archipelagos – the Tuamotu Archipelago and the Gambler Islands – are utilized basically to cultivate pearls and the mother-of-pearl shells that are presently the result of this essential industry in French Polynesia. Endeavors are being made to discover other suitable tidal ponds.

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