105-401: A pearl is a hard object produced by mollusks. Pearl may also refer to: For fictional characters, see Pearl (given name) § Fictional characters Pearl A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle ) of a living shelled mollusk or another animal, such as fossil conulariids . Just like the shell of a mollusk, a pearl
210-542: A malacologist would still consider them to be pearls. Valueless pearls of this type are sometimes found in edible mussels , edible oysters , escargot snails, and so on. The GIA and CIBJO now simply use the term 'pearl' (or, where appropriate, the more descriptive term 'non-nacreous pearl') when referring to such items and, under Federal Trade Commission rules, various mollusk pearls may be referred to as 'pearls', without qualification. A few species produce pearls that can be of interest as gemstones. These species include
315-466: A metaphor for something rare, fine, admirable and valuable. The most valuable pearls occur spontaneously in the wild, but are extremely rare. These wild pearls are referred to as natural pearls. Cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those currently sold. Imitation pearls are also widely sold in inexpensive jewelry. Pearls have been harvested and cultivated primarily for use in jewelry , but in
420-473: A South Sea pearl – as described by CIBJO and GIA – is a pearl produced by the Pinctada maxima pearl oyster. South Sea pearls are the color of their host Pinctada maxima oyster – and can be white, silver, pink, gold, cream, and any combination of these basic colors, including overtones of the various colors of the rainbow displayed in the pearl nacre of the oyster shell itself. South Sea pearls are
525-415: A beaded cultured pearl is generally a polished sphere made from freshwater mussel shell. Along with a small piece of mantle tissue from another mollusk (donor shell) to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk. In freshwater perliculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of
630-465: A bed and reaching sexual maturity within a year. Oysters are filter feeders , drawing water in over their gills through the beating of cilia . Suspended plankton and non-food particles are trapped in the mucus of a gill, and from there are transported to the mouth, where they are eaten, digested, and expelled as feces or pseudofeces that fall to the bottom and remain out of the water column. Oysters feed most actively at temperatures ranging from
735-456: A body color that may be assessed as silver, silver blue, gold, brown-black, green-black, or black. Black cultured pearls from the black pearl oyster – Pinctada margaritifera – are not South Sea pearls, although they are often mistakenly described as black South Sea pearls. In the absence of an official definition for the pearl from the black all use to, these pearls are usually referred to as "black pearls". The correct definition of
840-442: A distinct family, the feathered oysters ( Pteriidae ). Both cultured pearls and natural pearls can be extracted from pearl oysters, though other molluscs, such as the freshwater mussels , also yield pearls of commercial value. The largest pearl-bearing oyster is the marine Pinctada maxima , which is roughly the size of a dinner plate. Not all individual oysters produce pearls. In nature, pearl oysters produce pearls by covering
945-419: A minute invasive object with nacre . Over the years, the irritating object is covered with enough layers of nacre to become a pearl. The many different types, colours and shapes of pearls depend on the natural pigment of the nacre, and the shape of the original irritant. Pearl farmers can culture a pearl by placing a nucleus, usually a piece of polished mussel shell, inside the oyster. In three to seven years,
1050-414: A natural pearl shows a series of concentric growth rings. A beadless cultured pearl (whether of freshwater or saltwater origin) may show growth rings, but also a complex central cavity, witness of the first precipitation of the young pearl sac. Some imitation pearls (also called shell pearls) are simply made of mother-of-pearl , coral or conch shell, while others are made from glass and are coated with
1155-532: A popular treat celebrated in oyster festivals in many cities and towns. It was once assumed that oysters were only safe to eat in months with the letter 'r' in their English and French names. This myth is based in truth, in that in the Northern Hemisphere, oysters are much more likely to spoil in the warmer months of May, June, July, and August. In recent years , pathogens such as Vibrio parahaemolyticus have caused outbreaks in several harvesting areas of
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#17328477824331260-483: A resting state, even when they are permanently submersed. Their behaviour follows very strict circatidal and circadian rhythms according to the relative moon and sun positions. During neap tides, they exhibit much longer closing periods than during the spring tide. Some tropical oysters, such as the mangrove oyster in the family Ostreidae , grow best on mangrove roots. Low tide can expose them, making them easy to collect. The largest oyster-producing body of water in
1365-449: A result of global change are also negatively impacting oysters around the world, with many impacts affecting molecular, physiological, and behavioral processes in species including Magallana gigas. Recycled oyster shells can help restore oyster reefs to provide marine life habitat that reduces flooding, and protects shorelines from storms. Shell-recycling non-profits retrieve shells from restaurants, wash and dry them, and set them in
1470-564: A site where pollution was affecting beach tourism. Currently, for the installation cost of $ 3000, roughly 4.8 million liters of water are being filtered daily. In New Jersey, however, the Department of Environmental Protection refused to allow oysters as a filtering system in Sandy Hook Bay and the Raritan Bay, citing worries that commercial shellfish growers would be at risk and that members of
1575-475: A solution containing fish scales called essence d'Orient . A well-equipped gem testing laboratory can distinguish natural pearls from cultured pearls by using gemological X-ray equipment to examine the center of a pearl. With X-rays it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated by thin layers of conchiolin. The differentiation of natural pearls from non-beaded cultured pearls can be very difficult without
1680-450: A species of small pearl oyster, Pinctada fucata martensii , which is no bigger than 6 to 8 cm (2.4 to 3.1 in) in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly priced. Today, a hybrid mollusk is used in both Japan and China in the production of akoya pearls. Cultured Pearls were sold in cans for the export market. These were packed in Japan by
1785-509: A spherical bead as a nucleus. Most saltwater cultured pearls are grown with beads. Trade names of cultured pearls are Akoya ( 阿古屋 ), white or golden South sea, and black Tahitian . Most beadless cultured pearls are mantle-grown in freshwater shells in China, and are known as freshwater cultured pearls. Cultured pearls can be distinguished from natural pearls by X-ray examination. Nucleated cultured pearls are often 'preformed' as they tend to follow
1890-522: Is a particularly large one weighing 14 lb (6.4 kg). The largest known pearl (also from a giant clam) is the Pearl of Puerto , also found in the Philippines by a fisherman from Puerto Princesa , Palawan Island . The enormous pearl is 30 cm wide (1 ft), 67 cm long (2.2 ft) and weighs 75 lb (34 kg). The ancient chronicle Mahavamsa mentions the thriving pearl industry in
1995-495: Is believed to be the last-built Connecticut oyster sloop, completed in 1948. Oysters can also be collected by divers . In any case, when the oysters are collected, they are sorted to eliminate dead animals, bycatch (unwanted catch), and debris. Then they are taken to market, where they are either canned or sold live. Oysters have been cultured since at least the days of the Roman Empire . The Pacific oyster ( Magallana gigas )
2100-402: Is caused by the overlapping of successive layers, which breaks up light falling on the surface. In addition, pearls (especially cultured freshwater pearls ) can be dyed yellow, green, blue, brown, pink, purple, or black. The most valuable pearls have a metallic, highly reflective luster. Because pearls are made primarily of calcium carbonate, they can be dissolved in vinegar . Calcium carbonate
2205-430: Is composed of calcium carbonate (mainly aragonite or a mixture of aragonite and calcite ) in minute crystalline form, which has deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls , can occur. The finest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of this, pearl has become
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#17328477824332310-436: Is dominated by the larger Pacific oyster and Rock oyster species which are farmed year-round. Oysters are harvested by simply gathering them from their beds. In very shallow waters, they can be gathered by hand or with small rakes . In somewhat deeper water, long-handled rakes or oyster tongs are used to reach the beds. Patent tongs can be lowered on a line to reach beds that are too deep to reach directly. In all cases,
2415-746: Is estimated that one acre (0.40 ha) can produce nearly 750,000 oysters, which could filter between 57,000 to 150,000 m (2.0–5.3 million cu ft) of water daily. Also see nutrient pollution for an extended explanation of nutrient remediation . As an ecosystem engineer , oysters provide supporting ecosystem services , along with provisioning, regulating and cultural services. Oysters influence nutrient cycling , water filtration , habitat structure, biodiversity , and food web dynamics. Oyster reef habitats have been recognized as green infrastructure for shoreline protection. Assimilation of nitrogen and phosphorus into shellfish tissues provides an opportunity to remove these nutrients from
2520-459: Is grown at a time. This limits the number of pearls at a harvest period. The pearls are usually harvested after one year for akoya, 2–4 years for Tahitian and South Sea, and 2–7 years for freshwater. This perliculture process was first developed by the British biologist William Saville-Kent who passed the information along to Tatsuhei Mise and Tokichi Nishikawa from Japan . The second category includes
2625-530: Is held in September. In fact, in Victorian England, it was quite common for people to go to the pub and enjoy their favorite beer with some oysters. They quickly realized that the "rich, sweet, malty stouts" were great with the "briny, creamy oyster". Then brewers found that oyster shells naturally clarify a beer and they started putting crushed oyster shells into their brews. The first known brewery to start this
2730-445: Is made from layers of nacre , by the same living process as is used in the secretion of the mother of pearl which lines the shell. Natural (or wild) pearls, formed without human intervention, are very rare. Many hundreds of pearl oysters or mussels must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way pearls were obtained, and why pearls fetched such extraordinary prices in
2835-549: Is more valuable than these pearls. However, it is more abundant than the South Sea pearl, which is more valuable than the black cultured pearl. This is simply because the black pearl oyster Pinctada margaritifera is far more abundant than the elusive, rare, and larger south sea pearl oyster Pinctada maxima , which cannot be found in lagoons, but which must be dived for in a rare number of deep ocean habitats or grown in hatcheries. Natural black pearls are rare, with black pearls having
2940-518: Is presently the most widely grown bivalve around the world. Two methods are commonly used, release and bagging. In both cases, oysters are cultivated onshore to the size of spat, when they can attach themselves to a substrate. They may be allowed to mature further to form "seed oysters". In either case, they are then placed in the water to mature. The release technique involves distributing the spat throughout existing oyster beds, allowing them to mature naturally to be collected like wild oysters. Bagging has
3045-415: Is required to positively verify natural pearls found today. A keshi pearl is a pearl composed entirely of nacre and results from mishaps in the culturing process. Most are quite small, typically only a few millimeters in diameter, and are often irregular in shape. In seeding a cultured pearl, a piece of mantle muscle from a sacrificed oyster is placed with a bead of mother of pearl within a host oyster. If
3150-925: Is susceptible to even a weak acid solution because the crystals react with the acetic acid in the vinegar to form calcium acetate and carbon dioxide . Freshwater and saltwater pearls may sometimes look quite similar, but they come from different sources. Freshwater pearls form in various species of freshwater mussels, family Unionidae , which live in lakes, rivers, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates, but also in colder, more temperate areas such as Scotland (where they are protected under law). Most freshwater cultured pearls sold today come from China. Saltwater pearls grow within pearl oysters, family Pteriidae , which live in oceans. Saltwater pearl oysters are usually cultivated in protected lagoons or volcanic atolls. The mollusk's mantle (protective membrane) deposits layers of calcium carbonate (CaCO 3 ) in
3255-409: Is technically possible for an oyster to fertilize its own eggs. The gonads surround the digestive organs, and are made up of sex cells, branching tubules, and connective tissue. Once her millions of eggs are fertilized, the female discharges them into the water. The larvae develop in about six hours and exist suspended in the water column as veliger larvae for two to three weeks before settling on
Pearl (disambiguation) - Misplaced Pages Continue
3360-618: Is the conch pearl (sometimes referred to simply as the 'pink pearl'), which is found very rarely growing between the mantle and the shell of the queen conch or pink conch, Strombus gigas , a large sea snail or marine gastropod from the Caribbean Sea . These pearls, which are often pink in color, are a by-product of the conch fishing industry, and the best of them display a shimmering optical effect related to chatoyance known as 'flame structure'. Somewhat similar gastropod pearls, this time more orange in hue, are (again very rarely) found in
3465-502: Is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk and settles inside the shell. The mollusk, irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant. This secretion process is repeated many times, thus producing a pearl. Natural pearls come in many shapes, with perfectly round ones being comparatively rare. Typically,
3570-516: The Broome area of Australia, while golden colored ones are more prevalent in the Philippines and Indonesia. A farm in the Gulf of California , Mexico, is culturing pearls from the black lipped Pinctada mazatlanica oysters and the rainbow lipped Pteria sterna oysters. Also called Concha Nácar, the pearls from these rainbow lipped oysters fluoresce red under ultraviolet light. Biologically speaking, under
3675-611: The European flat oyster , eastern oyster , Olympia oyster , Pacific oyster , and the Sydney rock oyster . Ostreidae evolved in the Early Triassic epoch : The genus Liostrea grew on the shells of living ammonoids . Almost all shell-bearing mollusks can secrete pearls, yet most are not very valuable. Pearls can form in both saltwater and freshwater environments. Pearl oysters are not closely related to true oysters, being members of
3780-841: The Indian Ocean in areas such as the Persian Gulf , the Red Sea and the Gulf of Mannar . Evidence also suggest a prehistoric origin to pearl diving in these regions. Starting in the Han dynasty (206 BC–220 AD), the Chinese hunted extensively for seawater pearls in the South China Sea , particularly in what is now Tolo Harbour in Hong Kong . Tanka pearl divers of twelfth century China attached ropes to their waists in order to be safely brought back up to
3885-470: The Philippines , a local thorny oyster species known as Tikod amo is a favorite seafood source in the southern part of the country. Because of its good flavor, it commands high prices. Oysters breathe primarily via gills . In addition to their gills, oysters can exchange gases across their mantles , which are lined with many small, thin-walled blood vessels . A small, three-chambered heart , lying under
3990-577: The United States is the Chesapeake Bay , although these beds have decreased in number due to overfishing and pollution. Other large oyster farming areas in the US include the bays and estuaries along the coast of the Gulf of Mexico from Apalachicola, Florida , in the east to Galveston, Texas , in the west. Large beds of edible oysters are also found in Japan and Australia. In 2005, China accounted for 80% of
4095-469: The adductor muscle , pumps colorless blood to all parts of the body. At the same time, two kidneys , located on the underside of the muscle, remove waste products from the blood. Their nervous system includes two pairs of nerve cords and three pairs of ganglia . There is no evidence that oysters have a brain. While some oysters have two sexes ( European oyster and Olympia oyster ), their reproductive organs contain both eggs and sperm. Because of this, it
4200-575: The eastern oyster ( Crassostrea virginica ) was introduced to California waters in 1875, while the Pacific oyster was introduced there in 1929. Proposals for further such introductions remain controversial. The Pacific oyster prospered in Pendrell Sound , where the surface water is typically warm enough for spawning in the summer. Over the following years, spat spread out sporadically and populated adjacent areas. Eventually, possibly following adaptation to
4305-437: The family Pteriidae . Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae . The unique luster of pearls depends upon the reflection , refraction , and diffraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display
Pearl (disambiguation) - Misplaced Pages Continue
4410-515: The tides . He was so famous for this, the Romans used to say he could breed oysters on the roof of his house. In the early 19th century, oysters were cheap and mainly eaten by the working class . Throughout the 19th century, oyster beds in New York Harbor became the largest source of oysters worldwide. On any day in the late 19th century, six million oysters could be found on barges tied up along
4515-547: The 14th century. The French derived from the Latin ostrea , the feminine form of ostreum , which is the latinisation of the Ancient Greek ὄστρεον ( ostreon ) 'oyster'. Compare ὀστέον ( osteon ) 'bone'. True oysters are members of the family Ostreidae . This family includes the edible oysters, which mainly belong to the genera Ostrea , Crassostrea , Magallana , and Saccostrea . Examples include
4620-468: The English name Margaret . All shelled mollusks can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within its mantle folds, but the great majority of these "pearls" are not valued as gemstones . Nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluskan bivalves or clams . A nacreous pearl
4725-576: The Fifth Avenue mansion that is now the New York Cartier store in exchange for a matched double strand of natural pearls Cartier had been collecting for years; at the time, it was valued at US$ 1 million.) The introduction and advance of the cultured pearl hit the pearl industry hard. Pearl dealers publicly disputed the authenticity of these new cultured products, and left many consumers uneasy and confused about their much lower prices. Essentially,
4830-466: The I.C.P. Canning Factory (International Pearl Company L.T.D.) in Nagasaki Pref. Japan. Oyster All other members of: Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified , and many are somewhat irregular in shape. Many, but not all oysters, are in
4935-519: The King found it so beautiful that he kept it for himself. Later, he elevated it to be part of the Spanish Crown Jewel. From then on, the pearl was recorded in every royal inventory for more than 200 years. According to Garcilasso de la Vega , who says that he saw La Peregrina at Seville in 1607, this was found at Panama in 1560 by a slave worker who was rewarded with his liberty, and his owner with
5040-515: The United Kingdom, the town of Whitstable is noted for oyster farming from beds on the Kentish Flats that have been used since Roman times. The borough of Colchester holds an annual Oyster Feast each October, at which "Colchester Natives" (the native oyster, Ostrea edulis ) are consumed. The United Kingdom hosts several other annual oyster festivals; for example, Woburn Oyster Festival
5145-518: The attractions which drew Julius Caesar to Britain. They are, for the most part, freshwater pearls from mussels. Pearling was banned in the U.K. in 1998 due to the endangered status of river mussels. Discovery and publicity about the sale for a substantial sum of the Abernethy pearl in the River Tay had resulted in heavy exploitation of mussel colonies during the 1970s and 80s by weekend warriors. When it
5250-459: The bailer shell Melo , the giant clam Tridacna , various scallop species, Pen shells Pinna , and the Haliotis iris species of abalone. Pearls of abalone are cultured pearls , or blister pearls, unique to New Zealand waters, and are commonly referred to as 'blue pearls'. They are admired for their luster and naturally bright vibrant colors that are often compared to opal . Another example
5355-435: The beds by the early 20th century. Oysters' popularity has put ever-increasing demands on wild oyster stocks. This scarcity increased prices, converting them from their original role as working-class food to their current status as an expensive delicacy. In Britain, the native species ( European flat oyster ) has five years to mature and is protected by the people during their May-to-August spawning season. The current market
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#17328477824335460-435: The build-up of a natural pearl consists of a brown central zone formed by columnar calcium carbonate (usually calcite, sometimes columnar aragonite) and a yellowish to white outer zone consisting of nacre (tabular aragonite). In a pearl cross-section such as the diagram, these two different materials can be seen. The presence of columnar calcium carbonate rich in organic material indicates juvenile mantle tissue that formed during
5565-409: The capacity to dramatically alter nitrogen levels in estuaries. In the U.S., Delaware is the only East Coast state without aquaculture, but making aquaculture a state-controlled industry of leasing water by the acre for commercial harvesting of shellfish is being considered. Supporters of Delaware's legislation to allow oyster aquaculture cite revenue, job creation, and nutrient cycling benefits. It
5670-487: The case. Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to another part of the mollusk's body. These small particles or organisms gain entry when the shell valves are open for feeding or respiration. In cultured pearls, the irritant is typically an introduced piece of the mantle epithelium, with or without a spherical bead (beaded or beadless cultured pearls). Natural pearls are nearly 100% calcium carbonate and conchiolin . It
5775-534: The city's waterfront. They were naturally quite popular in New York City , and helped initiate the city's restaurant trade. New York's oystermen became skilled cultivators of their beds, which provided employment for hundreds of workers and nutritious food for thousands. Eventually, rising demand exhausted many of the beds. To increase production, they introduced foreign species, which brought disease; effluent and increasing sedimentation from erosion destroyed most of
5880-428: The conjunctive tissue of the mantle, these cells may survive and form a small pocket in which they continue to secrete calcium carbonate, their natural product. The pocket is called a pearl sac, and grows with time by cell division. The juvenile mantle tissue cells, according to their stage of growth, secrete columnar calcium carbonate from pearl sac's inner surface. In time, the pearl sac's external mantle cells proceed to
5985-458: The controversy damaged the images of both natural and cultured pearls. By the 1950s, when a significant number of women in developed countries could afford their own cultured pearl necklace, natural pearls were reduced to a small, exclusive niche in the pearl industry. Previously, natural pearls were found in many parts of the world. Present day natural pearling is confined mostly to the Persian Gulf , in seas off Bahrain . Australia also has one of
6090-549: The cultivator putting spat in racks or bags and keeping them above the bottom. Harvesting involves simply lifting the bags or rack to the surface and removing the mature oysters. The latter method prevents losses to some predators, but is more expensive. The Pacific oyster has been grown in the outflow of mariculture ponds. When fish or prawns are grown in ponds, it takes typically 10 kg (22 lb) of feed to produce 1 kg ( 2 + 1 ⁄ 4 lb) of product ( dry-dry basis). The other 9 kg (20 lb) goes into
6195-503: The culturing process for them dictates a smaller volume output and they can never be mass-produced because, in common with most sea pearls, the oyster can only be nucleated with one pearl at a time, while freshwater mussels are capable of multiple pearl implants. Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced naturally black pearls, and black pearl oysters rarely produced any natural pearls at all. Since
6300-549: The development of pearl culture technology, the black pearl oysters Pinctada margaritifera found in Tahiti and many other Pacific islands including the Cook Islands and Fiji are being extensively used for producing cultured pearls. The rarity of the black cultured pearl is now a "comparative" issue. The black cultured pearl is rare when compared to Chinese freshwater cultured pearls, and Japanese and Chinese akoya cultured pearls, and
6405-490: The early stage of pearl development. Displaced living cells with a well-defined task may continue to perform their function in their new location, often resulting in a cyst . Such displacement may occur via an injury. The fragile rim of the shell is exposed and is prone to damage and injury. Crabs, other predators and parasites such as worm larvae may produce traumatic attacks and cause injuries in which some external mantle tissue cells are disconnected from their layer. Embedded in
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#17328477824336510-444: The eastern United States during the summer months, lending further credence to this belief. Oysters can be eaten on the half shell, raw, smoked , boiled , baked , fried , roasted , stewed , canned , pickled , steamed , or broiled , or used in a variety of drinks. Eating can be as simple as opening the shell and eating the contents, including juice. Butter and salt are often added. Poached oysters can be served on toast with
6615-401: The form of the mineral aragonite or a mixture of aragonite and calcite (polymorphs with the same chemical formula, but different crystal structures) held together by an organic horn-like compound called conchiolin . The combination of aragonite and conchiolin is called nacre , which makes up mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely
6720-435: The formation of tabular aragonite. When the transition to nacre secretion occurs, the brown pebble becomes covered with a nacreous coating. During this process, the pearl sac seems to travel into the shell; however, the sac actually stays in its original relative position the mantle tissue while the shell itself grows. After a couple of years, a pearl forms and the shell may be found by a lucky pearl fisher. Cultured pearls are
6825-412: The global oyster harvest. In Europe, France remained the industry leader. Common oyster predators include crabs , seabirds , starfish , and humans . Some oysters contain crabs, known as oyster crabs . Bivalves , including oysters, are effective filter feeders and can have large effects on the water columns in which they occur. As filter feeders, oysters remove plankton and organic particles from
6930-419: The high 60s to the high 70s (20–26 °C). Under ideal laboratory conditions, an oyster can filter up to 190 L (50 US gal) of water per day. Under average conditions, mature oysters filter 11–45 L (3–12 U.S. gal). Chesapeake Bay 's once-flourishing oyster population historically filtered excess nutrients from the estuary's entire water volume every three to four days. As of 2008 it
7035-463: The horse conch Triplofusus papillosus . The second largest pearl known was found in the Philippines in 1934 and is known as the Pearl of Lao Tzu . It is a naturally occurring, non-nacreous, calcareous concretion (pearl) from a giant clam . Because it did not grow in a pearl oyster it is not pearly; instead the surface is glossy like porcelain. Other pearls from giant clams are known to exist, but this
7140-454: The host mussel. South Sea and Tahitian pearl oysters, also known as Pinctada maxima and Pinctada margaritifera , which survive the subsequent surgery to remove the finished pearl, are often implanted with a new, larger beads as part of the same procedure and then returned to the water for another 2–3 years of growth. Despite the common misperception, Mikimoto did not discover the process of pearl culture. The accepted process of pearl culture
7245-435: The largest and rarest of the cultured pearls – making them the most valuable. Prized for their exquisitely beautiful 'orient' or lustre, South Sea pearls are now farmed in various parts of the world where the Pinctada maxima oysters can be found, with the finest South Sea pearls being produced by Paspaley along the remote coastline of North-Western Australia. White and silver colored South Sea pearls tend to come from
7350-521: The late 1880s, when the bay's population was in the billions, and watermen harvested about 910,000 m (25 million imp bsh) annually. The 2009 harvest was less than 7,300 m (200,000 imp bsh). Researchers claim the keys to the project were: The "oyster-tecture" movement promotes the use of oyster reefs for water purification and wave attenuation. An oyster-tecture project has been implemented at Withers Estuary, Withers Swash, South Carolina, by Neil Chambers-led volunteers, at
7455-524: The local conditions, the Pacific oyster spread up and down the coast and now is the basis of the North American west coast oyster industry. Pendrell Sound is now a reserve that supplies spat for cultivation. Near the mouth of the Great Wicomico River in the Chesapeake Bay , five-year-old artificial reefs now harbor more than 180 million native Crassostrea virginica . That is far lower than in
7560-666: The loss of half of California's Olympia oysters . Oyster reefs occupy a small fraction of their distribution prior to mass harvesting during the last three centuries. In October 2017, it was reported that underwater noise pollution can affect oysters as they close their shells when exposed to low frequencies of sounds in experimental conditions. Oysters rely on hearing waves and currents to regulate their circadian rhythms , and perception of weather events—such as rain —may induce spawning . Cargo ships , pile drivers , and explosions conducted underwater produce low frequencies that may be detected by oysters. Environmental stressors as
7665-425: The next two or three years and develop greater energy reserves, they spawn as females by releasing eggs . Bay oysters usually spawn from the end of June until mid-August. An increase in water temperature prompts a few oysters to spawn. This triggers spawning in the rest, clouding the water with millions of eggs and sperm. A single female oyster can produce up to 100 million eggs annually. The eggs become fertilized in
7770-575: The non-beaded freshwater cultured pearls, like the Biwa or Chinese pearls. As they grow in the mantle, where on each wing up to 25 grafts can be implanted, these pearls are much more frequent and saturate the market completely. An impressive improvement in quality has taken place over ten years when the former rice-grain-shaped pebbles are compared with the near round pearls of today. Later, large near perfect round bead nucleated pearls up to 15mm in diameter have been produced with metallic luster. The nucleus bead in
7875-498: The office of alcalde of Panama. Margarita pearls are extremely difficult to find today and are known for their unique yellowish color. Before the beginning of the 20th century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all mussels and oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls. Pearls were one of
7980-489: The oyster can produce a perfect pearl. Since the beginning of the 20th century, when several researchers discovered how to produce artificial pearls, the cultured pearl market has far outgrown the natural pearl market. A number of bivalve molluscs (other than true oysters and pearl oysters) also have common names that include the word "oyster", usually because they either taste like or look somewhat like true oysters, or because they yield noticeable pearls. Examples include: In
8085-589: The past were also used to adorn clothing. They have also been crushed and used in cosmetics, medicines and paint formulations. Whether wild or cultured, gem-quality pearls are almost always nacreous and iridescent , like the interior of the shell that produces them. However, almost all species of shelled mollusks are capable of producing pearls (technically "calcareous concretions") of lesser shine or less spherical shape. Although these may also be legitimately referred to as "pearls" by gemological labs and also under U.S. Federal Trade Commission rules, and are formed in
8190-434: The past. Cultured pearls are formed in pearl farms, using human intervention as well as natural processes. One family of nacreous pearl bivalves – the pearl oyster – lives in the sea, while the other – a very different group of bivalves – lives in freshwater; these are the river mussels such as the freshwater pearl mussel . Saltwater pearls can grow in several species of marine pearl oysters in
8295-432: The pearl industry is making ongoing attempts to improve culturing technique so that keshi pearls do not occur. All-nacre pearls may one day be limited to natural found pearls. Today many "keshi" pearls are actually intentional, with post-harvest shells returned to the water to regenerate a pearl in the existing pearl sac. Tahitian pearls , frequently referred to as black pearls, are highly valued because of their rarity;
8400-403: The piece of mantle should slip off the bead, a keshi pearl forms of baroque shape about the mantle piece. Therefore, while a keshi pearl could be considered superior to cultured pearls with a mother of pearl bead center, in the cultured pearl industry the oyster's resources used to create a mistaken all-nacre baroque pearl is a drain on the production of the intended round cultured pearl. Therefore,
8505-463: The pond and after mineralization, provides food for phytoplankton, which in turn feeds the oyster. To prevent spawning, sterile oysters are now cultured by crossbreeding tetraploid and diploid oysters. The resulting triploid oyster cannot propagate, which prevents introduced oysters from spreading into unwanted habitats. In many areas, non-native oysters have been introduced in attempts to prop up failing harvests of native varieties. For example,
8610-602: The port of Oruwella in the Gulf of Mannar in Sri Lanka . It also records that eight varieties of pearls accompanied Prince Vijaya 's embassy to the Pandyan king as well as king Devanampiya Tissa 's embassy to Emperor Ashoka . Pliny the Elder (23–79 AD) praised the pearl fishery of the Gulf as most productive in the world. For thousands of years, seawater pearls were retrieved by divers in
8715-430: The public might disregard warnings and consume tainted oysters. New Jersey Baykeepers responded by changing their strategy for utilizing oysters to clean up the waterway, by collaborating with Naval Weapons Station Earle. The Navy station is under 24/7 security and therefore eliminates any poaching and associated human health risk. Oyster-tecture projects have been proposed to protect coastal cities, such as New York, from
8820-404: The response of the shell to a tissue implant. A tiny piece of mantle tissue (called a graft ) from a donor shell is transplanted into a recipient shell, causing a pearl sac to form into which the tissue precipitates calcium carbonate. There are a number of methods for producing cultured pearls: using freshwater or seawater shells, transplanting the graft into the mantle or into the gonad, and adding
8925-486: The right set of circumstances, almost any shelled mollusk can produce some kind of pearl. However, most of these molluskan pearls have no luster or iridescence . The great majority of mollusk species produce pearls which are not attractive, and are sometimes not even very durable. Such pearls usually have no value at all, except perhaps to a scientist or collector, or as a curiosity. These objects used to be referred to as "calcareous concretions" by some gemologists, even though
9030-502: The same way, most of them have no value except as curiosities. The English word pearl comes from the French perle , originally from the Latin perna ' leg ' , after the ham- or mutton leg-shaped bivalve . The scientific name for the family of pearl-bearing oysters, Margaritiferidae comes from the Old Persian word for pearl * margārīta- which is the source of
9135-433: The shape of the implanted shell bead nucleus. After a bead is inserted into the oyster, it secretes a few layers of nacre around the bead; the resulting cultured pearl can then be harvested in as few as twelve to eighteen months. When a cultured pearl with a bead nucleus is X-rayed, it reveals a different structure to that of a natural pearl. A beaded cultured pearl shows a solid center with no concentric growth rings, whereas
9240-569: The sun for up to a year to kill bacteria. Some states encourage shell recycling by offering tax incentives. Jonathan Swift is quoted as having said, "He was a bold man that first ate an oyster". Evidence of oyster consumption goes back into prehistory, evidenced by oyster middens found worldwide. Oysters were an important food source in all coastal areas where they could be found, and oyster fisheries were an important industry where they were plentiful. Overfishing and pressure from diseases and pollution have sharply reduced supplies, but they remain
9345-399: The superfamily Ostreoidea . Some species of oyster are commonly consumed and are regarded as a delicacy in some localities. Some types of pearl oysters are harvested for the pearl produced within the mantle . Others, such as the translucent Windowpane oysters , are harvested for their shells. The word oyster comes from Old French oistre , and first appeared in English during
9450-424: The surface area of a flat bottom 50-fold. An oyster's mature shape often depends on the type of bottom to which it is originally attached, but it always orients itself with its outer, flared shell tilted upward. One valve is cupped and the other is flat. Oysters usually reach maturity in one year. They are protandric ; during their first year, they spawn as males by releasing sperm into the water. As they grow over
9555-541: The surface. When Spanish conquistadors arrived in the Western Hemisphere, they discovered that around the islands of Cubagua and Margarita , some 200 km north of the Venezuelan coast, was an extensive pearl bed (a bed of pearl oysters). One discovered and named pearl, La Peregrina pearl , was offered to Philip II of Spain who intended to give it as a gift for his daughter on the occasion of her marriage, but
9660-529: The task is the same: the oysterman scrapes oysters into a pile, and then scoops them up with the rake or tongs. In some areas, a scallop dredge is used. This is a toothed bar attached to a chain bag. The dredge is towed through an oyster bed by a boat, picking up the oysters in its path. While dredges collect oysters more quickly, they heavily damage the beds, and their use is highly restricted. Until 1965, Maryland limited dredging to sailboats , and even since then motor boats can be used only on certain days of
9765-478: The threat of rising sea levels due to climate change . Additionally Oyster reef restoration has shown to increase the population of oyster beds within the oceans while also conserving the biolife within the oyster reefs. The accidental or intentional introduction of species by humans has the potential to negatively impact native oyster populations. For example, non-native species in Tomales Bay have resulted in
9870-810: The use of this X-ray technique. Natural and cultured pearls can be distinguished from imitation pearls using a microscope . Another method of testing for imitations is to rub two pearls against each other. Imitation pearls are completely smooth, but natural and cultured pearls are composed of nacre platelets, making both feel slightly gritty. Fine quality natural pearls are very rare jewels. Their values are determined similarly to those of other precious gems, according to size, shape, color, quality of surface, orient and luster. Single natural pearls are often sold as collectors' items, or set as centerpieces in unique jewelry. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars. (In 1917, jeweler Pierre Cartier purchased
9975-503: The water and develop into larvae, which eventually find suitable sites, such as another oyster's shell, on which to settle. Attached oyster larvae are called spat. Spat are oysters less than 25 mm (1 in) long. Many species of bivalves, oysters included, seem to be stimulated to settle near adult conspecifics . Oysters filter large amounts of water to feed and breathe (exchange O 2 and CO 2 with water) but they are not permanently open. They regularly shut their valves to enter
10080-541: The water column. In California's Tomales Bay , native oyster presence is associated with higher species diversity of benthic invertebrates. As the ecological and economic importance of oyster reefs has become more acknowledged, restoration efforts have increased. Middens testify to the prehistoric importance of oysters as food, with some middens in New South Wales , Australia, dated at ten thousand years. They have been cultivated in Japan from at least 2000 BC. In
10185-416: The water column. Multiple studies have shown individual oysters are capable of filtering up to 190 litres (42 imp gal; 50 US gal) of water per day, and thus oyster reefs can significantly improve water quality and clarity. Oysters consume nitrogen-containing compounds ( nitrates and ammonia ), phosphates , plankton, detritus, bacteria, and dissolved organic matter, removing them from
10290-480: The water. What is not used for animal growth is then expelled as solid waste pellets, which eventually decompose into the atmosphere as nitrogen. In Maryland , the Chesapeake Bay Program had implemented a plan to use oysters to reduce the amount of nitrogen compounds entering the Chesapeake Bay by 8,600 t (9,500 short tons) per year by 2010. Several studies have shown that oysters and mussels have
10395-474: The week. These regulations prompted the development of specialized sailboats (the bugeye and later the skipjack ) for dredging. Similar laws were enacted in Connecticut before World War I and lasted until 1969. The laws restricted the harvesting of oysters in state-owned beds to vessels under sail. These laws prompted the construction of the oyster sloop-style vessel to last well into the 20th century. Hope
10500-468: The world's last remaining fleets of pearl diving ships. Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry. The catch of pearl oysters is similar to the numbers of oysters taken during the natural pearl days. Hence significant numbers of natural pearls are still found in the Australian Indian Ocean waters from wild oysters. X-ray examination
10605-543: Was developed by the British Biologist William Saville-Kent in Australia and brought to Japan by Tokichi Nishikawa and Tatsuhei Mise. Nishikawa was granted the patent in 1916, and married the daughter of Mikimoto. Mikimoto was able to use Nishikawa's technology. After the patent was granted in 1916, the technology was immediately commercially applied to akoya pearl oysters in Japan in 1916. Mise's brother
10710-679: Was estimated that a complete cycle would take nearly a year. A group of oysters is commonly called a bed or oyster reef . As a keystone species , oysters provide habitat for many marine species. Crassostrea and Saccostrea live mainly in the intertidal zone , while Ostrea is subtidal . The hard surfaces of oyster shells and the nooks between the shells provide places where a host of small animals can live. Hundreds of animals, such as sea anemones , barnacles , and hooked mussels , inhabit oyster reefs . Many of these animals are prey to larger animals, including fish, such as striped bass , black drum and croakers . An oyster reef can increase
10815-674: Was in 1938 at the Hammerton Brewery in London. That is where the oyster stout was first started. The French seaside resort of Cancale in Brittany is noted for its oysters, which also date from Roman times. Sergius Orata of the Roman Republic is considered the first major merchant and cultivator of oysters. Using his considerable knowledge of hydraulics , he built a sophisticated cultivation system, including channels and locks, to control
10920-661: Was permitted it was carried on mainly by Scottish Travellers who found pearls varied from river to river with the River Oykel in the Highlands being noted for the finest rose-pink pearls. There are two firms in Scotland that are licensed to sell pre-1998 freshwater pearls. Today, the cultured pearls on the market can be divided into two categories. The first category covers the beaded cultured pearls, including akoya, South Sea and Tahiti. These pearls are gonad grown, and usually one pearl
11025-527: Was the first to produce a commercial crop of pearls in the akoya oyster. Mitsubishi's Baron Iwasaki immediately applied the technology to the south sea pearl oyster in 1917 in the Philippines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured south sea pearl – although it was not until 1928 that the first small commercial crop of pearls was successfully produced. The original Japanese cultured pearls, known as akoya pearls, are produced by
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