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101-635: Crassostrea gigas The Pacific oyster , Japanese oyster , or Miyagi oyster ( Magallana gigas ) is an oyster native to the Pacific coast of Asia . It has become an introduced species in North America , Australia , Europe , and New Zealand . The genus Magallana is named for the Portuguese explorer Ferdinand Magellan and its specific epithet gígās is from the Greek for "giant". It

202-500: A yolk sac ), then to motile larvae (often known as fingerlings due to them roughly reaching the length of a human finger ) that have to forage for themselves after the yolk sac resorbs, and then to the juvenile stage where the fish progressively start to resemble adult morphology and behaviors until finally reaching sexual maturity . In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Frogs , toads , and newts all hatch from

303-561: A Pacific oyster larva finds a suitable habitat , it attaches to it permanently using cement secreted from a gland in its foot. After settlement, the larva metamorphoses into a juvenile spat. The growth rate is very rapid in optimum environmental conditions, and market size can be achieved in 18 to 30 months. Unharvested Pacific oysters can live up to 30 years. The genome of M. gigas has been sequenced, revealing an extensive set of genes that enables it to cope with environmental stresses. The expression of genes such as arginine kinase and cavortin

404-465: 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

505-399: A butterfly 2 – The pupa is now spewing the thread to form chrysalis 3 – The chrysalis is fully formed 4 – Adult butterfly coming out of the chrysalis In cephalochordata , metamorphosis is iodothyronine -induced and it could be an ancestral feature of all chordates . Some fish, both bony fish (Osteichthyes) and jawless fish (Agnatha) , undergo metamorphosis. Fish metamorphosis

606-648: A complete metamorphosis, including a pupal or resting stage between the larval and adult forms. A number of hypotheses have been proposed to explain the evolution of holometaboly from hemimetaboly, mostly centering on whether or not the intermediate stages of hemimetabolous forms are homologous in origin to the pupal stage of holometabolous forms. According to a 2009 study, temperature plays an important role in insect development as individual species are found to have specific thermal windows that allow them to progress through their developmental stages. These windows are not significantly affected by ecological traits, rather,

707-413: A considerable role during physiological processes of multicellular organisms, particularly during embryogenesis , and metamorphosis. Additional research in 2019 found that both autophagy and apoptosis , the two ways programmed cell death occur, are processes undergone during insect metamorphosis. Below is the sequence of steps in the metamorphosis of the butterfly (illustrated): 1 – The larva of

808-609: A cream roux . In the case of Oysters Rockefeller , preparation can be very elaborate. They are sometimes served on edible seaweed, such as brown algae . Metamorphosis Generally organisms with a larval stage undergo metamorphosis, and during metamorphosis the organism loses larval characteristics. The word metamorphosis derives from Ancient Greek μεταμόρφωσις , "transformation, transforming", from μετα- ( meta- ), "after" and μορφή ( morphe ), "form". In insects, growth and metamorphosis are controlled by hormones synthesized by endocrine glands near

909-442: 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

1010-497: A larger proportion of male adults. Spawning in the Pacific oyster occurs at 20 °C. This species is very fecund , with females releasing about 50–200 million eggs in regular intervals (with a rate at 5–10 times a minute) in a single spawning . Once released from the gonads , the eggs move through the suprabranchial chambers ( gills ), are then pushed through the gill ostia into the mantle chamber, and finally are released in

1111-454: A long stage of growth followed by a more gradual metamorphosis to the migrating phase. In the pre-adult freshwater stage, the eel also has phenotypic plasticity because fish-eating eels develop very wide mandibles, making the head look blunt. Leptocephali are common, occurring in all Elopomorpha ( tarpon - and eel -like fish). Most other bony fish undergo metamorphosis initially from egg to immotile larvae known as sac fry ( fry with

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1212-419: 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,

1313-541: 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

1414-420: A relatively long, spiral‐shaped gut to digest that diet. Recent studies suggest tadpoles do not have a balanced homeostatic feedback control system until the beginning stages of metamorphosis. At this point, their long gut shortens and begins favoring the diet of insects. Rapid changes in the body can then be observed as the lifestyle of the frog changes completely. The spiral‐shaped mouth with horny tooth ridges

1515-483: 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

1616-449: 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

1717-612: A settlement stage when dark eye spots and a foot develop. During this time, settlement materials (cultch), such as roughed PVC sheets, fluted PVC pipes, or shells, are placed into the tanks to encourage the larvae to attach and settle. However, particularly on the US West Coast, mature larvae are commonly packed and shipped to oyster farms, where the farmers set the oysters themselves. Pacific oyster spat can be grown in nurseries by sea-based or land-based upwelling systems. Nursery culture reduces mortality in small spat, thus increasing

1818-583: 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

1919-501: 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 )

2020-436: 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,

2121-746: 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

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2222-543: 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

2323-500: Is incomplete, and that criteria other than the genetic sequence should have been considered. The shell of M. gigas varies widely with the environment where it is attached. Its large, rounded, radial folds are often extremely rough and sharp. The two valves of the shell are slightly different in size and shape, the right valve being moderately concave . Shell colour is variable, usually pale white or off-white. Mature specimens can vary from 80 to 400 mm long. Right and left valve of

2424-555: Is iodothyronine-induced and an ancestral feature of all chordates . All three categories of metamorphosis can be found in the diversity of insects, including no metamorphosis ("ametaboly"), incomplete or partial metamorphosis ("hemimetaboly"), and complete metamorphosis ("holometaboly"). While ametabolous insects show very little difference between larval and adult forms (also known as " direct development "), both hemimetabolous and holometabolous insects have significant morphological and behavioral differences between larval and adult forms,

2525-636: Is outcompeting native species, such as the Olympia oyster in Puget Sound , Washington; the rock oyster, Saccostrea commercialis , in the North Island of New Zealand ; and the blue mussel, Mytilus edulis , in the Wadden Sea . Numerous methods are used in the production of Pacific oysters. These techniques depend on factors such as the seed supply resources, the environmental conditions in

2626-421: Is outside the parental body, development is subject to many adaptations due to specific ecological circumstances. For this reason tadpoles can have horny ridges for teeth, whiskers, and fins. They also make use of the lateral line organ. After metamorphosis, these organs become redundant and will be resorbed by controlled cell death, called apoptosis . The amount of adaptation to specific ecological circumstances

2727-572: Is particularly important in regulating the metabolic response of this species to stress events including the reduction of seawater pH, as observed under ocean acidification. M. gigas was originally described by the Swedish naturalist Carl Peter Thunberg in 1795. It is native to the Northwest Pacific , and occurs primarily in temperate waters between 30° N and 48° N. It is now the most widely farmed and commercially important oyster in

2828-518: 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

2929-549: Is reabsorbed, due to the higher thyroxin concentrations required for tail resorption. Salamander development is highly diverse; some species go through a dramatic reorganization when transitioning from aquatic larvae to terrestrial adults, while others, such as the axolotl , display pedomorphosis and never develop into terrestrial adults. Within the genus Ambystoma , species have evolved to be pedomorphic several times, and pedomorphosis and complete development can both occur in some species. In newts, metamorphosis occurs due to

3030-402: Is remarkable, with many discoveries still being made. With frogs and toads, the external gills of the newly hatched tadpole are covered with a gill sac after a few days, and lungs are quickly formed. Front legs are formed under the gill sac, and hindlegs are visible a few days later. Following that there is usually a longer stage during which the tadpole lives off a vegetarian diet. Tadpoles use

3131-401: Is resorbed together with the spiral gut. The animal develops a big jaw, and its gills disappear along with its gill sac. Eyes and legs grow quickly, a tongue is formed, and all this is accompanied by associated changes in the neural networks (development of stereoscopic vision, loss of the lateral line system, etc.) All this can happen in about a day. It is not until a few days later that the tail

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3232-409: 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

3333-403: Is typically under strong control by the thyroid hormone. Examples among the non-bony fish include the lamprey . Among the bony fish, mechanisms are varied. The salmon is diadromous , meaning that it changes from a freshwater to a saltwater lifestyle. Many species of flatfish begin their life bilaterally symmetrical , with an eye on either side of the body; but one eye moves to join

3434-627: 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

3535-626: The Marlborough Sounds , and farming began there in the 1990s. Marlborough farmers developed a different method of cultivation in comparison to the North Island method of racks; they instead suspended their oysters on longlines. The Pacific oyster is one of the three main aquaculture species in New Zealand along with Chinook/king salmon and the greenshell mussels . Pacific oyster aquaculture production has grown from an export value of $ 11 million in 1986 to $ 32 million in 2006. In 2006,

3636-476: 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

3737-696: 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

3838-469: 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

3939-532: 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

4040-410: The gonads , and it can change from year to year, normally during the winter. In certain environmental conditions, one sex is favoured over the other. Protandry is favoured in areas of high food abundance and protogyny occurs in areas of low food abundance. In habitats with a high food supply, the sex ratio in the adult population tends to favour females, and areas with low food abundances tend to have

4141-416: The prodissoconch 1 stage. The larvae move through the water column via the use of a larval foot to find suitable settlement locations. They can spend several weeks at this phase, which is dependent on water temperature, salinity, and food supply. Over these weeks, larvae can disperse great distances by water currents before they metamorphose and settle as small spat . Similar to other oyster species , once

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4242-526: 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

4343-558: 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

4444-543: The 23 Pacific oyster farms throughout New Zealand covered a total of 750 hectares of marine space and produced 2,800 tonnes of product per year. Annual production is now between about 3,300 and 4,000 tonnes . In 2005, the value of New Zealand's Pacific oyster production was $ 12 million domestically, and $ 16.9 million for export. New Zealand's main export markets are Japan, Korea, the US, the EU and Australia. However, research has demonstrated that changes in global ocean temperature and

4545-722: The Pacific oyster can be described as the amount of meat produced in relation to the amount of seed planted on cultch. The productivity of a farm also depends on the interaction of biotic factors, such as mortality , growth, and oyster size, as well as the quality of the seed and the growing technique used (off bottom, bottom, suspended or floating culture). The main causes of mortality in the Pacific oysters are natural mortality (age), predators, disease, environmental conditions (ice, freak winds), competition for space (crowding of cultch), silting (sediment runoff from land), and cluster separation (process of breaking up clusters of oysters into as many individual oysters as possible). In New Zealand,

4646-416: The Pacific oyster outgrew the endemic species in most areas, and constantly was attaching to the rock oyster collection sticks. A few years later, Pacific oysters were the dominant species in the farms, as it grew three times faster than the rock oyster, produced a reliable and constant supply of spat, and had an already established market overseas. In 1977, the Pacific oyster was accidentally introduced to

4747-487: The Pacific oyster was unintentionally introduced in the 1950s, most likely through ballast water and from the hulls of ships. Aquaculture farmers at the time noticed the Pacific oyster outcompeted the endemic species, the Sydney rock oyster ( Saccostrea glomerata ), which naturally occurs in intertidal areas in the North Island. Early experiments in rock oyster cultivation procedures attached spat to cement-covered sticks and laid them down in racks. The farmers noticed, however,

4848-529: 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

4949-448: The advent of ocean acidification may alter the growth, reproduction, and development of this species with variable responses 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

5050-435: 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

5151-409: 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

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5252-411: The change in habitat, not a change in diet, because newt larvae already feed as predators and continue doing so as adults. Newts' gills are never covered by a gill sac and will be resorbed only just before the animal leaves the water. Adults can move faster on land than in water. Newts often have an aquatic phase in spring and summer, and a land phase in winter. For adaptation to a water phase, prolactin

5353-506: The character of the beach is changed and that other users may be endangered. In the preparations for the Tokyo 2020/2021 Summer Olympics , equipment for the canoeing and rowing was found to be contaminated with 14 metric tons (15 short tons) of M. gigas , necessitating US$ 1,280,000/£930,000 in removal expenditures. Ocean acidification due to increasing atmospheric carbon dioxide impacts shellfish such as oysters. The increasing acidity of

5454-541: 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

5555-549: 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

5656-462: The development of adult characteristics during ecdysis . In holometabolous insects, molts between larval instars have a high level of juvenile hormone, the moult to the pupal stage has a low level of juvenile hormone, and the final, or imaginal , molt has no juvenile hormone present at all. Experiments on firebugs have shown how juvenile hormone can affect the number of nymph instar stages in hemimetabolous insects. In chordates, metamorphosis

5757-444: 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

5858-538: The eggs as larvae with external gills but it will take some time for the amphibians to interact outside with pulmonary respiration. Afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin , which counteracts its effect. Specific events are dependent on threshold values for different tissues. Because most embryonic development

5959-653: The eggs from a small sample of females (about six) are more commonly stripped from the gonads using Pasteur pipettes and fertilized by sperm from a similar number of males. Pacific oysters have a pelagic veliger larval stage which lasts from 14 to 18 days. In the hatcheries, they are kept at temperatures of 25–28 °C with an optimum salinity between 20 and 25%. Early-stage veligers (<120 nm shell length) are fed daily with flagellated algal species ( Isochrysis galbana or Pavlova lutherii ) along with diatom species (either Chaetoceros calcitrans or Thalassiosira pseudonana ). The larvae are close to

6060-655: The evolution of metamorphosis in insects is thought to have fuelled their dramatic radiation (1,2). Some early ametabolous "true insects" are still present today, such as bristletails and silverfish . Hemimetabolous insects include cockroaches , grasshoppers , dragonflies , and true bugs . Phylogenetically, all insects in the Pterygota undergo a marked change in form, texture and physical appearance from immature stage to adult. These insects either have hemimetabolous development, and undergo an incomplete or partial metamorphosis, or holometabolous development, which undergo

6161-630: The farm's efficiency. Sea-based nursery systems are often located in estuarine areas where the spat are mounted on barges or rafts. Land-based nursery systems have spat mounted on barges in large saltwater tanks, which either have a natural algae supply or are enriched with nutrients from fertilizers. This stage of oyster culture is almost completely sea-based. A range of bottom, off-bottom, suspended, and floating cultures are used. The technique used depends on site-specific conditions, such as tidal range, shelter, water depth, current flow, and nature of substrate . Pacific oysters take 18–30 months to develop to

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6262-411: The front of the body ( anterior ). Neurosecretory cells in an insect's brain secrete a hormone, the prothoracicotropic hormone (PTTH) that activates prothoracic glands, which secrete a second hormone, usually ecdysone (an ecdysteroid ), that induces ecdysis (shedding of the exoskeleton). PTTH also stimulates the corpora allata , a retrocerebral organ, to produce juvenile hormone , which prevents

6363-412: 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

6464-419: 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

6565-521: 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

6666-540: 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

6767-666: 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

6868-504: The market size of 70–100 g live weight ( shell on). Growth from spat to adults in this species is very rapid at temperatures of 15–25 °C and at salinities of 25 to 32 ppt. In 2000, the Pacific oysters accounted for 98% of the world's cultured oyster production, and are produced in countries all over the world. Global production has increased from about 150 thousand tonnes in 1950 to 1.2 million tonnes in 1990. By 2003, global production had increased to 4.38 million tonnes. The majority

6969-566: The most significant being the inclusion, in holometabolous organisms, of a pupal or resting stage between the larval and adult forms. In hemimetabolous insects , immature stages are called nymphs . Development proceeds in repeated stages of growth and ecdysis (moulting); these stages are called instars . The juvenile forms closely resemble adults, but are smaller and lack adult features such as wings and genitalia. The size and morphological differences between nymphs in different instars are small, often just differences in body proportions and

7070-425: 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

7171-488: The number of segments; in later instars, external wing buds form. The period from one molt to the next is called a stadium. In holometabolous insects, immature stages are called larvae and differ markedly from adults. Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa (called a "chrysalis " in butterfly species), and finally emerge as adults. The earliest insect forms showed direct development ( ametabolism ), and

7272-460: The ocean reduces oyster reproduction, lowers the survival rate of juvenile oysters, and causes delayed sexual maturation . Overall, these effects combine to lower recruitment to oyster populations, reduce the maximum sustainable yield that can be harvested, and reduce the profitability of oyster farms . It is unknown if acidification alters the flavor of shellfish or other qualities that make them desirable for human consumption. Productivity of

7373-750: The open water. The movement towards hatchery-reared spat is important, as wild seed is susceptible to changeable environmental conditions, such as toxic algal blooms, which can halt the supply of seed from that region. In addition, several pests have been noted as considerable dangers to oyster seed. The Japanese oyster drill ( Ocenebra inornata ), flatworm ( Koinostylochus ostreophagus ), and parasitic copepod ( Mytilicola orientalis ) have been introduced accidentally to aquaculture areas, and have had serious impacts on oyster production, particularly in British Columbia and Europe . Pacific oyster broodstocks in hatcheries are kept in optimum conditions so

7474-469: The other side of the fish – which becomes the upper side – in the adult form. The European eel has a number of metamorphoses, from the larval stage to the leptocephalus stage, then a quick metamorphosis to glass eel at the edge of the continental shelf (eight days for the Japanese eel ), two months at the border of fresh and salt water where the glass eel undergoes a quick metamorphosis into elver, then

7575-489: 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

7676-463: 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,

7777-415: The production of large amounts of high quality eggs and sperm can be achieved. Pacific oyster females are very fecund , and individuals of 70–100 g live weight can produce 50–80 million eggs in a single spawn . Broodstock adults are held in tanks at 20–22 °C, supplied with cultured algae and with salinities of 25–32 ppt. These individuals can be induced to spawn by thermal shock treatment. Yet,

7878-430: 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

7979-471: The region, and the market product, i.e., whether the oysters are sold in a half shell, or shelled for meat extraction. Production can either be entirely sea-based or rely on hatcheries for seed supply. Most of the global Pacific oyster spat supply comes from the wild, but some is now produced by hatchery methods. The seed from the wild can either be collected by the removal of seaweed from beaches or by hanging shell ( cultch ) in suspension from long lines in

8080-402: The same specimen: M. gigas is an estuarine species , but can also be found in intertidal and subtidal zones. They prefer to attach to hard or rocky surfaces in shallow or sheltered waters up to 40 m deep, but have been known to attach to muddy or sandy areas when the preferred habitat is scarce. The Pacific oyster can also be found on the shells of other animals. Larvae often settle on

8181-533: The shell of adults, and great masses of oysters can grow together to form oyster reefs. The optimum salinity for Pacific oysters is between 20 and 35 parts per thousand (ppt), and they can tolerate salinities as high as 38 ppt; at this level, however, reproduction is unlikely to occur. The Pacific oyster is also a very temperature tolerant species , as it can withstand a range from −1.8 to 35 °C. The Pacific oyster has separate sexes, but hermaphrodites sometimes do exist. Their sex can be determined by examining

8282-569: 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

8383-454: 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

8484-424: 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

8585-866: The surrounding water. These can accumulate in the tissues of the animal and leave it unharmed ( bioaccumulation ). However, when the concentrations of the metals or biotoxins are high enough, shellfish poisoning can result when they are consumed by humans. Most countries have strict water regulations and legislation to minimise the occurrence of such poisoning cases. Various diseases are known to affect Pacific oyster: Numerous predators are known to damage Pacific oyster stocks. Several crab species ( Metacarcinus magister , Cancer productus , Metacarcinus gracilis ), oyster drills , and starfish species ( Pisater ochraceus , Pisater brevispinus , Evasterias troschelii , and Pycnopodia helianthoides ) can cause severe impacts to oyster culture. Increasing numbers of frames for oysters to grow on has led to claims that

8686-529: 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

8787-484: 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

8888-503: 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

8989-548: 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

9090-416: 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

9191-599: The water column. This presents major issues for virus management of open-water shellfish farms, as shellfish like the Pacific oyster have been found to contain norovirus strains which can be harmful to humans. Globally, noroviruses are the most common cause of nonbacterial gastroenteritis , and are introduced into the water column by faecal matter, either from sewage discharge or land runoff from nearby farmland. Pacific oysters, like other shellfish, are able to remove heavy metals , such as zinc and copper , as well as biotoxins (microscopic toxic phytoplankton ), from

9292-433: The water, forming a small cloud. In males, the sperm is released at the opposite end of the oyster, along with the normal exhalent stream of water. A rise in water temperature is thought to be the main cue in the initiation of spawning, as the onset of higher water temperatures in the summer results in earlier spawning in the Pacific oyster. The larvae of the Pacific oyster are planktotrophic , and are about 70 μm at

9393-490: 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

9494-480: 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

9595-529: The windows are phylogenetically adapted to the ecological circumstances insects are living in. According to research from 2008, adult Manduca sexta is able to retain behavior learned as a caterpillar . Another caterpillar, the ornate moth caterpillar , is able to carry toxins that it acquires from its diet through metamorphosis and into adulthood, where the toxins still serve for protection against predators. Many observations published in 2002, and supported in 2013 indicate that programmed cell death plays

9696-467: The world, as it is very easy to grow, environmentally tolerant, and easily spread from one area to another. The most significant introductions were to the Pacific Coast of the United States in the 1920s and to France in 1966. In most places, the Pacific oyster was introduced to replace the native oyster stocks which were seriously dwindling due to overfishing or disease. In addition, this species

9797-679: 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

9898-566: Was in China , which produced 84% of the global production. Japan , France and the Republic of Korea also contributed, producing 261 000, 238 000 and 115 000 tonnes, respectively. The other two major producers are the United States (43 000 tonnes) and Taiwan (23 000 tonnes). In 2003, global Pacific oyster production was worth $ 3.69 billion. Pacific oysters are nonspecific filter feeders , which means they ingest any particulate matter in

9999-698: 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

10100-434: Was introduced to create an industry that was previously not available at all in that area. In addition to intentional introductions, the Pacific oyster has spread through accidental introductions either through larvae in ballast water or on the hulls of ships. In some places in the world, though, it is considered by biosecurity, primary industry, and conservation departments and ministries to be an invasive species , where it

10201-526: Was placed in the genus Crassostrea until 2017; from the Latin crass meaning "thick", ostrea meaning "oyster". In 2017, the WoRMS , following the DNA-based opinion of Salvi et al. , moved all pacific members of Crassostrea to Magallana . Parts of the scientific community resist this change and continue to argue that Crassostrea gigas should be the proper name. They argue that Salvi's DNA sampling

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