Crassostrea gigas, Marennes-Oléron

Crassostrea gigas, Marennes-Oléron

Crassostrea gigas, Marennes-Oléron, opened

An ostreolith from the Middle Jurassic Carmel Formation of southern Utah. The Pacific oyster, Crassostrea gigas, is a native oyster of the Pacific coast of Asia. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning This ball of oysters is made up almost entirely of the species Liostrea strigilecula.

The common name oyster is used for a number of different groups of bivalve mollusks, most of which live in marine habitats or brackish water. Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 The shell consists of two usually highly calcified valves which surround a soft body. Gills filter plankton from the water, and strong adductor muscles are used to hold the shell closed. Filter feeders (also known as suspension feeders) are Animals that feed by straining suspended matter and food particles from water typically by passing the water Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of

Some types of oysters are highly prized as food, both raw and cooked. Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an Other types, such as pearl oysters, are not widely eaten. Pinctada is a Genus of pearl oysters. These are saltwater clams marine Bivalve Molluscs of the Genus Pinctada

True (edible) oysters are incapable of making gem-quality pearls, although the opposite idea is a commonly-encountered misapprehension, often seen in illustrations or photographs where an edible oyster shell is mistakenly paired with a gem-quality pearl.

The oyster is used as a metaphor in an idiomatic saying, "The world is your oyster", which means that the whole world is laid out before you like a wonderful living buffet. An idiom is a Phrase whose meaning cannot be deduced from the literal Definition, but refers instead to a figurative meaning that is known only ^[1]

True oysters

The "true oysters" are members of the family Ostreidae. The members of the family Ostreidae are the true oysters, and include all the Species that are commonly eaten under the title " Oyster This family includes the edible oysters, which mainly belong to the genera Ostrea, Crassostrea, Ostreola or Saccostrea. The members of the family Ostreidae are the true oysters, and include all the Species that are commonly eaten under the title " Oyster The members of the family Ostreidae are the true oysters, and include all the Species that are commonly eaten under the title " Oyster The Olympia oyster, Ostreola conchaphila, is the native Oyster of the Pacific coast of North America from Alaska to Mexico Rock oysters are Oysters of the genus Saccostrea. The best known species of rock oyster is the Sydney rock oyster ( Saccostrea glomerata Examples are the Edible Oyster, Ostrea edulis, Eastern oyster Crassostrea virginica, Olympia Oyster Ostreola conchaphila, Pacific Oyster Crassostrea gigas, Sydney rock oyster Saccostrea glomerata, and the Wellfleet oyster (a variety of C. The Eastern oyster, Crassostrea virginica, also known as the American oyster, Atlantic oyster, or the Virginia oyster, is a Species The Olympia oyster, Ostreola conchaphila, is the native Oyster of the Pacific coast of North America from Alaska to Mexico The Pacific oyster, Crassostrea gigas, is a native oyster of the Pacific coast of Asia. The Sydney rock oyster, Saccostrea glomerata, formerly known as Saccostrea commercialis, is an Oyster species endemic to Australia and The Eastern oyster, Crassostrea virginica, also known as the American oyster, Atlantic oyster, or the Virginia oyster, is a Species virginica).

Physical characteristics

• Oysters are filter-feeders: they draw water in over their gills through the beating of cilia. Filter feeders (also known as suspension feeders) are Animals that feed by straining suspended matter and food particles from water typically by passing the water A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately Suspended food plankton and 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. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of Feeding activity is greatest in oysters when the water temperatures are above 50°F (10°C). Healthy oysters consume algae and other water-borne nutrients, each one filtering up to five litres of water per hour. Scientists believe that the Chesapeake Bay's once-flourishing oyster populations historically filtered the estuary's entire water volume of excess nutrients every three or four days. The Chesapeake Bay is the largest Estuary in the United States. Today that process would take almost a year,^[2] and sediment, nutrients, and algae can cause problems in local waters. Oysters filter these pollutants, and either eat them or shape them into small packets that are deposited on the bottom where they are harmless.

• Oysters breathe much like fish, using both gills and mantle. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two A gill is an anatomical structure found in many aquatic organisms The mantle is lined with many small, thin-walled blood vessels which extract oxygen from the water and expel carbon dioxide. The blood vessels are part of the Circulatory system and function to transport Blood throughout the body A small, three-chambered heart, lying under the abductor muscle, pumps colorless blood, with its supply of oxygen, to all parts of the body. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic At the same time two kidneys located on the underside of the muscle purify the blood of any waste products they have collected. The kidneys are complicated organs that have numerous biological roles

• There is no way of determining male oysters from females by examining their shells. While oysters have separate sexes, they may change sex one or more times during their life span. The gonads, organs responsible for producing both eggs and sperm, surround the digestive organs and are made up of sex cells, branching tubules and connective tissue. The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries.

Habitat and life habits

As a keystone species, oysters provide habitat for an extensive array of marine life. A keystone species is a Species that has a disproportionate effect on its environment relative to its abundance A habitat (which is Latin for "it inhabits" is an Ecological or environmental area that is inhabited by a particular Species. There are three main groups of oysters, the Ostrea species, the Crassostrea species and the Saccostrea species.

Crassostrea and Saccostrea species live mainly in the intertidal zone while Ostrea species are 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 anemones, barnacles, and hooked mussels use oyster reefs as habitat. Anemone ( A-ne-mó-ne, from the Gr Άνεμος wind is a Genus of about 120 Species of flowering plants in the A barnacle is a type of Arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence distantly related to The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats Many of these animals serve as food for larger animals, including fish such as striped bass, black drum and croakers. The striped bass ( Morone saxatilis, also called rock or rockfish is the state fish of Maryland, Rhode Island, South Carolina, and The Black Drum ( Pogonias cromis) is a saltwater Fish similar to its cousin the Red Drum. Sciaenidae is a family of Fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds

An oyster reef can encompass 50 times the surface area of an equally extensive flat bottom. The oyster contributes to improved water quality through its filter feeding capacity. 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. The submerged shell opens periodically to permit the oyster to feed.

Oysters usually mature by one year of age. They are protandric, which means that during their first year they spawn as males (releasing sperm into the water). As they grow larger over the next two or three years and develop greater energy reserves, they release eggs, as females. Bay oysters are usually prepared to spawn by the end of June. An increase in water temperature prompts a few initial oysters to spawn. This triggers a spawning 'chain reaction', which clouds 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 the water and develop into larvae, which eventually find suitable sites on which to settle, such as another oyster's shell. Attached oyster larvae are called 'spat'. Spat are oysters 25 mm or less in length. Many species of bivalve, oysters included, seem to be stimulated to settle by the proximity of adults of their species.

Some tropical oysters in a different family, the family Isognomonidae, grow best on mangrove roots, and are exposed at low tide, making them easy to collect. Isognomonidae is a family of marine Bivalve Mollusks They are related to the Pearl oysters Some of the species in the family Mangroves (generally are Trees and Shrubs that grow in saline coastal habitats in the Tropics and Subtropics. In Trinidad in the West Indies tourists are often astounded when they are told that in the Caribbean, "oysters grow on trees. Trinidad ( Spanish: " Trinity " is the largest and most populous of the two major islands and "

The oyster's greatest predators include crabs, sea birds, sea stars, and humans. Some oysters contain live crabs, known as an Oyster crab. An Oyster Crab ( Pinnotheres ostreum) is a small whitish or translucent Crab, less than half an inch across that lives inside the gills of an Oyster

Raw oysters presented on a plate.

Oysters as food

Although Jonathan Swift is often quoted as having said, "He was a bold man that first ate an oyster",^[3] evidence of oyster consumption goes back into prehistory, as evidenced by oyster middens found worldwide. Jonathan Swift (30 November 1667 A midden, also known as a kitchen midden, or a shell heap, is a dump for domestic waste. 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 a popular treat, celebrated in oyster festivals in many cities and towns. An oyster festival is a Food festival centered around the Oyster.

Oysters are a favorite among exotic foods and research now shows this shellfish to be a rich source of zinc, one of the minerals required for the production of testosterone.

Oyster fishing and oyster cultivation

commercial
molluscs
abalone
clams
cockles
periwinkle
mussels
oysters
scallops
whelk
cuttlefish
octopus
squid
fishing industry
fisheries
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Oyster culture in Belon, France. Commercial fishing, also known as industrial fishing, is the activity of capturing Fish and other Seafood for commercial Profit, mostly Shellfish is a Culinary and Fisheries term for those aquatic Invertebrate animals that are used as Food: various species of molluscs Abalone (from Spanish Abulón) are medium-sized to very large edible sea Snails marine Gastropod Mollusks in the Clam is a word which can be used for all some or only a few Species of Bivalve Mollusks the word is a Common name which has Cockle is the common name for edible Bivalve Mollusks of the family Cardiidae. "Winkle" redirects here For the contract bridge play see Winkle squeeze. The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats The common name oyster is used for a number of different groups of Bivalve Mollusks most of which live in marine habitats or Brackish water. A scallop (ˈskɒləp or /ˈskæləp/ is a marine Bivalve Mollusk of the family Pectinidae. A whelk is one of several Species of large sea Snails marine Gastropod Mollusks found in temperate waters Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses The Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species The fishing industry includes any industry or activity concerned with taking culturing processing preserving storing transporting marketing or selling fish or fish products For the fishing industry and the practice of fishing see Fishing.

Giant oyster in south Angola.

Oysters are fished by simply gathering them from their beds. A variety of means are used. In very shallow waters they can be gathered by hand or with small rakes. A rake ( Old English raca, cognate with Dutch raak, German Rechen, from a root meaning "to scrape together" In somewhat deeper water, long-handled rakes or oyster tongs are used to reach the beds. Tongs are gripping and lifting Tools of which there are many forms adapted to their specific use Patent tongs can be lowered on a line to reach beds which are too deep to reach directly. In all cases the manner of operation is the same: the waterman scrapes together a small pile of oysters, and then collects these by scooping them up with the rake or tongs.

In some areas a dredge is used. Dredging is an Excavation activity or operation usually carried out at least partly underwater in shallow seas or Fresh water areas with the purpose of This is a toothed bar attached to a chain bag. The dredge is towed through an oyster bed by a boat, picking up those oysters in its path. While dredges collect oysters more quickly, they can be very damaging to the oyster beds, and their use is in general strictly limited. In the state of Maryland, dredging was until 1965 limited to sailboats, and even since that date motor power can only be used on certain days of the week. In some cases less is more The purpose of this article is to give an overview These regulations prompted the development of specialized sailboats (the bugeye and later the skipjack) for dredging. In some cases less is more The purpose of this article is to give an overview The bugeye is a type of sailboat developed in the Chesapeake Bay for oyster dredging. The skipjack is a type of Sailboat developed on the Chesapeake Bay for oyster dredging.

Oysters can also be collected by divers. This article refers to underwater diving by humans For other uses of the term diving see Dive and Diving Underwater diving is

In any case, when the oysters are collected, they are sorted to eliminate dead shells, unwanted catch, and other debris. Then they are taken to market where they are either canned or sold live.

Oysters have been cultured for well over a century. Two methods are commonly used. In both cases oysters are cultivated to the size of "spat", the point at which they attach themselves to a substrate. They may be allowed to mature further to form "seed" oysters. In either case they are then set out to mature. They may be distributed over existing oyster beds and left to mature naturally, to be collected using the methods for fishing wild oysters. Or they may be put in racks or bags and held above the bottom. The oysters are harvested by lifting the bags or rack to the surface and removing mature oysters. The latter method avoids losses to some predators, but is more expensive. ^[4]

The Pacific (Japanese) oyster, Crassostrea gigas has also been grown in the outflow of mariculture ponds. When fish or prawns are grown in ponds, it takes, typically 10kg of feed to produce 1kg of product (dry-dry basis). The other 9kg goes into the pond and after mineralization, provides the food for phytoplankton. This phytoplankton is the food for the oyster. (ref coming with results)

In many areas non-native oysters have been introduced in attempts to prop up failing harvests of native varieties. For example, the eastern oyster was introduced to California waters in 1875, while the Pacific oyster was introduced there in 1929. The Eastern oyster, Crassostrea virginica, also known as the American oyster, Atlantic oyster, or the Virginia oyster, is a Species ^[5] 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 the local conditions, the Pacific oyster spread up and down the coast and now is the basis of the west coast oyster industry. Pendrell sound is now a reserve for the catching of spat for cultivation ^[6]To avoid spawning, sterile oysters are now cultured by crossbreeding tetraploid and diploid oysters. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. "Haplo" redirects here For the fictional character see The Death Gate Cycle. Because the resulting triploid oyster cannot propagate, the oyster spawning season does not occur. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. ^[7]

Preparation and storage

Oysters can be eaten half shelled, raw, smoked, boiled, baked, fried, roasted, stewed, canned, pickled, steamed, broiled (grilled) or used in a variety of drinks. Preparation can be as simple as opening the shell and adding butter and/or salt, or can be very elaborate. Butter is a Dairy product made by churning fresh or fermented Cream or Milk. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants

Perhaps the definitive work on oysters as food is Consider the Oyster, by M. F. K. Fisher. Consider the Oyster (ISBN 0865473358 is a book by MFK Fisher that deals in the history preparation and eating of Oysters The work was first published Mary Frances Kennedy Fisher ( July 3, 1908 &ndash June 22, 1992) was a prolific and well-respected writer writing more than 20 books during

Oysters are low in food energy; one dozen raw oysters contain approximately 110 kilo-calories (460 kJ), and are rich in zinc, iron, calcium, and vitamin A. Food energy is the amount of Energy in food that is available through Digestion. Vitamin A refers to a family of similarly shaped molecules the Retinoids.

Unlike most shellfish, oysters can have a fairly long shelf-life: up to around two weeks; however, they should be consumed when fresh, as their taste reflects their age. For maximum shelf life, oysters should be stored out of water in refrigeration but not frozen and in 100% humidity. Oysters stored in water under refrigeration will open, utilize the small reserves of oxygen and die. Precautions should be taken when consuming them (see below). Purists insist on eating oysters raw, with no dressing save perhaps lemon juice, vinegar, or cocktail sauce. The lemon ( Citrus × limon) is a hybrid in cultivated wild plants Raw oysters are regarded like wines in that they have complex flavors that vary greatly among varieties and regions: some taste sweet, others salty or with a mineral flavor, or even like melon. The texture is soft and fleshy, but crisp to the tooth. This is often influenced by the water that they are grown in with variations in salinity, minerals, and nutrients.

Oysters are generally an expensive food in places where they are not harvested, and often they are eaten only on special occasions, such as Christmas. Whether oysters are predominantly eaten raw or cooked is a matter of personal preference. In the United States today, oysters are most often cooked before consumption, but there is also a high demand for raw oysters on the half-shell (shooters) typically served at oyster bars. Canned smoked oysters are also widely available as preserves with a long shelf life. Raw oysters were once a staple food for the poor in many countries with coastal access such as the United Kingdom of Britain and along the East Coast of the US and are thus still easily found in any areas bordering a sea/ocean. Oysters are commonly eaten raw in France in bars and as a 'bar fast food' but the home use tends to be mixed with a large usage in cooking - steamed or in paella or soups.

Special knives for opening live oysters, such as this one, have short and stout blades and the best have a downward curve at the tip.

Fresh oysters must be alive just before consumption. There is a simple criterion: oysters must be capable of closing the shell tightly. Any open oysters should be tapped on the shell: a live oyster will close up and is safe to eat. Oysters which are open and unresponsive are dead, and must be discarded. Some dead oysters, or oyster shells which are full of sand may also be closed, but they will make a distinctive noise when tapped: they are known as "clackers" for this reason.

Opening oysters requires skill, for live oysters, outside of the water, tend to shut themselves tightly with a powerful muscle thus sealing in their fluids. The generally used method for opening oysters is to use a special knife (called an oyster knife, a variant of a shucking knife), with a short and thick blade about 2 inches long.

The blade needs to be inserted (with some moderate force and vibration if necessary) at the hinge in the rear of the shell. with the blade inserted slightly you need to twist until a slight pop is heard/felt. Then the blade should be slid upward to cut the adductor muscle (which holds the shell closed). Inexperienced shuckers tend to apply excessive force, which may result in injuries if the blade slips. A heavy glove should always be worn: if you don't cut yourself with the knife you can just as easily cut yourself on the oyster shell itself, which can be razor sharp.

A good demonstration of the opening technique is available here. There is also a second way in, referred to as the "sidedoor", which is about halfway along one side where the lips of the oyster widen so there is a slight indentation where a knife may successfully be inserted. This is generally a better way to open an oyster when it is a "crumbler" (i. e. one with a particularly soft shell either due to drills or the amount of calcium in the water). Either way, however, can be tricky when an oyster's shell is in such a poor condition.

An alternative to opening raw oysters before consumption is to cook them in the shell – the heat kills the oysters and they open by themselves. Cooked oysters are slightly sweet-tasting and considered savory, and all the different varieties are mostly equivalent.

A piece of folk wisdom concerning oysters is that they are best to eat in months containing the letter r, as illustrated by the famous phrase: "oysters 'r' in season. " This is because oysters spawn in the warmer months, from roughly May to August in the Northern Hemisphere, and their flavor when eaten raw can be somewhat watery and bland during spawning season; additionally their meats are much reduced in size. Oysters from the Gulf of Mexico spawn throughout the year, but are delicious cooked or raw to the oyster connoisseur. The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world

Oysters are sometimes cited as an aphrodisiac. ^[8] It is disputed whether this is true. According to the Telegraph of London a team of "American and Italian researchers analysed bivalve molluscs - a group of shellfish that includes oysters - and found they were rich in rare amino acids that trigger increased levels of sex hormones. "[1] If there is such an effect, it may be due to the soft, moist texture and appearance of the oyster; it may also be due to their high zinc content. Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30

History

The Whaleback Shell Midden in Maine was used for oyster harvesting from 2,200 to 1,000 years ago. Whaleback Shell Midden is a shell midden, or dump comprised primarily of Oyster shells located on the east side of the Damariscotta River in The State of Maine ( is a state in the New England region of the northeastern United States of America, bordering the Atlantic Ocean

Middens testify to the prehistoric importance of oysters as a foodstuff. A midden, also known as a kitchen midden, or a shell heap, is a dump for domestic waste. Within the United Kingdom, the town of Whitstable in the county of Kent is particularly noted for oyster farming from beds on the Kentish Flats that have been used since Roman times. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Whitstable ( is a seaside town in northeast Kent, southeast England KENT (1400 AM) is a Radio station broadcasting a Adult Standards/MOR format Oyster farming is an Aquaculture (or Mariculture) practice in which Oysters are raised for human consumption Roman Britain refers to those parts of the island of Great Britain controlled by the Roman Empire between AD 43 and 410 The borough of Colchester (which was briefly the capital of Roman Britain - during the Roman invasion) holds an annual Oyster Feast in October of each year, at which the "Colchester Natives" (the native oyster, Ostrea Edulis) are consumed. Colchester ( /ˈkəʊltʃɛstə/ is a town and the largest settlement within the borough of Colchester, in Essex, England. The Oyster Feast is the centrepiece of the annual civic calendar in the ancient borough of Colchester located in Essex in the East of England. There are several oyster festivals held annually in the UK, e. g. Woburn Oyster Festival which is held in September.

Similarly the seaside resort of Cancale in France is noted for its oysters, which also date from Roman times. This article is about the country For a topic outline on this subject see List of basic France topics. In fact, Sergius Orata of the Roman Republic is considered to have been the first major merchant and cultivator of oysters. Sergius Orata (fl c 95 BC was a Roman merchant and hydraulic engineer who was famous during the Roman Republic. The Roman Republic was the phase of the ancient Roman civilization characterized by a Republican form of government a period which began with the overthrow of the Using his very considerable hydraulic knowledge, he built a complex cultivation system including channels and locks to control the sea tides. Characteristics A tide is a repeated cycle of sea level changes in the following stages Over several hours the water rises or advances up a beach in the flood He was famous for this, and Roman people used to say he was so good that he could breed oysters on the roof of his house. ^[9]

The world-famous Clarenbridge and Galway Oyster Festivals are held in Galway, Ireland. each September. Ireland enjoys a long-standing tradition with regard to oysters where, typically, the shellfish is eaten live in conjunction with the national beverage, Guinness.

In the early nineteenth century, oysters were very cheap and were mainly eaten by the working classes. (Oysters were quite popular in New York City during the middle and late 19th century. The City of New York [2]) However, increasing demands from the rapidly-growing cities led to many of the beds running short. The Oyster Injustice of 1834 - 1835 was the result of an unusually poor oyster season in the Chesapeake Bay fishery and President Andrew Jackson To increase production, foreign varieties were introduced and this soon brought disease which, combined with pollution, and increasing sedimentation resulted in oysters becoming rare. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in This has been exacerbated worldwide by ever-increasing demands on wild oyster stocks. ^[10] This scarcity increased prices leading to their current status as a delicacy.

In the United Kingdom, the native variety is still held to be the finest, taking five years to mature and protected by an Act of Parliament during the May-August spawning season. An Act of Parliament is a Law enacted as Primary legislation by a national or sub-national Parliament. The current market is dominated by the larger Pacific oyster and rock oyster varieties which are farmed all year round. The Pacific oyster, Crassostrea gigas, is a native oyster of the Pacific coast of Asia. Rock oysters are Oysters of the genus Saccostrea. The best known species of rock oyster is the Sydney rock oyster ( Saccostrea glomerata

Pearl oysters

All types of oysters (and, indeed, almost all other shelled molluscs) can secrete concretions that are known by biologists as pearls, but those which sometimes form in edible oysters are unattractive and have no market value at all. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk.

Pearl oysters however are not closely related to true oysters. Pinctada is a Genus of pearl oysters. These are saltwater clams marine Bivalve Molluscs of the Genus Pinctada They are in a totally different family, the Pteriidae (Feathered Oysters). Pteriidae is a family of medium-sized to large saltwater clams Both cultured pearls and natural pearls can be obtained from these oysters, though other molluscs, such as the freshwater mussels, also yield pearls of commercial value. A cultured pearl is a Pearl created by a pearl farmer under controlled conditions The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats

The largest pearl-bearing oyster type is the saltwater Pinctada maxima, which is roughly the size of a dinner plate. Not all individual oysters produce pearls naturally. In fact, in a haul of three tons of oysters, only around three or four oysters produce perfect pearls. Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United

Pearls being removed from pearl oysters.

In nature, pearl oysters produce natural pearls by covering a minute invading parasite with nacre. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer Over the years, the irritating object is covered with enough layers of nacre to form what we know as a pearl. There are many different types and colours and shapes of pearl; these qualities depend on the natural pigment tone of the nacre, and the shape of the original irritant which was being covered over.

Pearls can also be cultivated by pearl farmers placing a nucleus, usually a piece of polished mussel shell, inside the oyster. In three to six years, the oyster will produce a perfect pearl. These pearls are not as valuable as natural pearls, but look exactly the same. In fact 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. Natural pearls have become scarcer and scarcer and a necklace with only natural pearls can easily cost several hundred thousand (US) dollars. ^[11]

Oyster diseases

Oysters are subject to various diseases which can reduce oyster harvests and often severely deplete local populations. Control focuses on containing infections and breeding resistant strains and is the subject of much ongoing research.

Dermo

"Dermo" (Perkinsus marinus) is caused by a protozoan parasite. Perkinsus marinus is a prevalent Pathogen of Oysters causing massive mortality in oyster populations Protozoa (in Greek πρῶτον proton "first" and ζῷα zoia "animals" are unicellular Eukaryotes (singular Parasitism is a type of symbiotic relationship between Organisms of different Species. It is a prevalent pathogen of oysters, causing massive mortality in oyster populations and poses a significant economic threat to the oyster industry. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious The disease is of no direct threat to any humans consuming infected oysters. ^[12]

Dermo first appeared in the Gulf of Mexico in the 1950s, and until 1978 it was believed to be caused by a fungus. The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ While it is most serious in warmer southern waters, it has gradually spread up the East coast of the United States. ^[13]

MSX

MSX (Multinucleated Sphere X) is caused by the protozoan Haplosporidium nelsoni, generally seen as a multi-nucleated plasmodium. A plasmodium is also the macroscopic form of the Protist known as a Slime mould. It is infectious and causes heavy mortality in the Eastern Oyster; survivors, however, are seen to develop resistance and can be used to help propagate resistant populations. It is associated with high salinity and water temperatures. ^[14]

MSX was first noted in Delaware Bay in 1957 and is now found all up and down the Eastern coast of the United States. Delaware Bay is a large Estuary outlet of the Delaware River on the Northeast seaboard of the United States whose fresh water mixes for many miles Evidence suggests that it was brought to the United States when Crassostrea gigas, a Japanese oyster variety, was introduced to Delaware Bay. ^[15]

Other mollusks named "oyster"

A number of bivalve mollusks other than edible oysters and pearl oysters also have common names that include the word "oyster", usually because they either taste or look like oysters, or because they yield noticeable pearls. Examples include:

• the family Spondylidae, the thorny oysters;
• the Pilgrim oyster, a kind of scallop. Spondylus is a Genus of Bivalve Mollusks the only genus in the family Spondylidae.
• the Saddle oyster (Anomia ephippium)

See also

• Auckland oyster
• Belon oyster
• Eastern oyster
• Olympia oyster
• Ostrea angasi (Australian southern mud or native flat oyster)
• Oyster cracker
• Oyster farming
• Oyster festival
• Oyster pail
• Oyster sauce
• Oysters Rockefeller
• Pacific oyster
• Pearl
• Pearl oyster
• Red tide
• Rock oyster
• Sydney rock oyster

External links

• Colchester Native Oysters
• Oysters grown on trestles in Ireland
• Why Do Oysters Choose to Live Where They Could be Eaten? University of Maryland Center for Environmental Science

References