Pacific oyster
Pacific oyster | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Mollusca |
Class: | Bivalvia |
Order: | Ostreida |
Family: | Ostreidae |
Genus: | Magallana |
Species: | M. gigas
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Binomial name | |
Magallana gigas (Thunberg, 1793)
| |
Synonyms | |
Crassostrea gigas |
The Pacific oyster, Japanese oyster, or Miyagi oyster (Magallana gigas
Etymology
The genus Magallana is named for the Portuguese explorer
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 is incomplete, and that criteria other than the genetic sequence should have been considered.[7][8]
Description
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.
Ecology
Habitat
M. gigas is an
Biology
Sexuality
The Pacific oyster has separate sexes, but
Spawning
Spawning in the Pacific oyster occurs at 20 °C.[10] 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.[10] 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 the water, forming a small cloud.[10] In males, the sperm is released at the opposite end of the oyster, along with the normal exhalent stream of water.[10] 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.[11]
Life cycle
The
Genetics
The genome of M. gigas has been sequenced, revealing an extensive set of genes that enables it to cope with environmental stresses.[12] The expression of genes such as arginine kinase and cavortin 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.[13]
Aquaculture
Historical background
M. gigas was originally described by the
Production techniques
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 the region, and the market product, i.e., whether the oysters are sold in a half shell, or shelled for meat extraction.[9] Production can either be entirely sea-based or rely on hatcheries for seed supply.[9]
Seed supply
Most of the global Pacific oyster spat supply comes from the wild, but some is now produced by hatchery methods.[9] 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 the open water.[9] 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.[10] 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.[10]
Broodstock
Pacific oyster
Larval and postlarval culture
Pacific oysters have a pelagic veliger larval stage which lasts from 14 to 18 days.[9] In the hatcheries, they are kept at temperatures of 25–28 °C with an optimum salinity between 20 and 25%.[9] 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).[9] The larvae are close to a settlement stage when dark eye spots and a foot develop.[9] 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.[9] However, particularly on the US West Coast, mature larvae are commonly packed and shipped to oyster farms, where the farmers set the oysters themselves.[9]
Nursery
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 the farm's efficiency.[9] Sea-based nursery systems are often located in estuarine areas where the spat are mounted on barges or rafts.[9] 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.[9]
Ongrowing techniques
This stage of oyster culture is almost completely sea-based.
General production
In 2000, the Pacific oysters accounted for 98% of the world's cultured oyster production, and are produced in countries all over the world.[15]
Production statistics
Global production has increased from about 150 thousand
Current issues
Virus management
Pacific oysters are nonspecific
Heavy metal pollution
Pacific oysters, like other shellfish, are able to remove heavy metals, such as zinc and copper, as well as biotoxins (microscopic toxic phytoplankton), from the surrounding water.[10] These can accumulate in the tissues of the animal and leave it unharmed (bioaccumulation).[10] 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.[18][19][20]
Diseases
Various diseases are known to affect Pacific oyster:
Disease | Agent | Type | Measures | Reference |
Denman Island disease | Mikrocytos mackini | Protozoan parasite | Restricted modified culture practices | [16] |
Nocardiosis | Nocardia crassostreae | Bacterium | Modified culture practices | [16] |
Oyster velar virus disease (OVVD) | Unnamed icosahedral DNA virus | Virus | None known | [16][21] |
Herpes-type virus disease of C. gigas larvae | Ostreid herpesvirus 1 |
Virus | Potential selective breeding | [22][23] |
Viral gametocytic hypertrophy | Papova-like virus | Virus | [24] |
Predators
Numerous
Competition with other uses of the seashore
Increasing numbers of frames for oysters to grow on has led to claims that the character of the beach is changed and that other users may be endangered.[26]
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.[27]
Ocean acidification
Productivity
Aquaculture in New Zealand
In New Zealand, the Pacific oyster was unintentionally introduced in the 1950s, most likely through ballast water and from the hulls of ships.
Production status
The Pacific oyster is one of the three main aquaculture species in New Zealand along with
See also
- Philippine cupped oyster(Magallana bilineata)
References
- ^ PMID 25250663.
- ^ Definition of giga at dictionary.com.
- ^ Definition of crass at dictionary.com.
- ^ Definition of ostrea Archived 2010-07-09 at the Wayback Machine at dictionary.com.
- ^ "Crassostrea gigas (Thunberg, 1793)". World Register of Marine Species.
- .
- .
- S2CID 91311410.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak Pacific Oyster factsheet, Food and Agriculture Organization of the United Nations (FAO)
- ^ a b c d e f g h i j k l m n o Quayle, D.B (1969). Pacific oyster culture in British Columbia, p. 23. First Edition. Ottawa: The Queen’s Printer.
- .
- ^
Zhang, G.; Fang, X.; Guo, X.; Li, L.; Luo, R.; Xu, F.; Yang, P.; Zhang, L.; Wang, X.; Qi, H.; Xiong, Z.; Que, H.; Xie, Y.; Holland, P. W. H.; Paps, J.; Zhu, Y.; Wu, F.; Chen, Y.; Wang, J.; Peng, C.; Meng, J.; Yang, L.; Liu, J.; Wen, B.; Zhang, N.; Huang, Z.; Zhu, Q.; Feng, Y.; Mount, A.; Hedgecock, D. (2012). "The oyster genome reveals stress adaptation and complexity of shell formation". Nature. 490 (7418): 49–54. PMID 22992520.
- ^ .
- ISSN 1572-9710.
- ^ "Industry Groups Pacific Oysters". Australian Aquaculture Portal. Archived from the original on 2005-02-09.
- ^ a b c d e f g h i "Cultured Aquatic Species Information Programme | Crassostrea gigas". FAO Fisheries & Aquaculture. Retrieved 2019-01-26.
- ^ S2CID 22696341.
- ^ "Defra, UK - Environmental Protection - Water - Water Quality - Shellfish Waters Directive". Archived from the original on 2010-08-18. Retrieved 2010-09-07. Scottish water quality regulations
- ^ [1] Archived 2010-11-24 at the Wayback Machine Irish water quality regulations
- ^ [2] American water quality regulations
- ^ Government of Canada, Fisheries and Oceans Canada (4 December 2018). "Oyster Velar Virus Disease (OVVD)". www.dfo-mpo.gc.ca.
- PMID 30310074.
- PMID 28672223.
- ISBN 9780470674949.
- ^ a b [3] Nonindigenous aquatic species of concern for Alaska: Pacific oyster fact sheet
- ^ Doward, Jamie (9 March 2019). "Trouble in Oysteropolis: Whitstable in uproar over booming fisheries trade". The Observer. Retrieved 22 March 2019 – via www.theguardian.com.
- ^ "Tokyo Olympics: 'Plague of oysters' threatens key venue". BBC News. 2021-07-19. Retrieved 2021-07-24.
- .
- ^ a b "Aquaculture | MPI – Ministry for Primary Industries. A New Zealand Government Department". Archived from the original on 2011-07-24. Retrieved 2010-09-07. Aquaculture.govt.nz
- ^ a b c [4] TeAra: The encyclopaedia of New Zealand
- ^ a b [5] Aquaculture.govt.nz: farmed species
- ^ a b "Blue Horizon Program Report from Friends of Blue Hill Bay" (PDF). Archived from the original (PDF) on 2011-07-26. Retrieved 2010-09-07. New Zealand Government, Blue Horizon document
External links
- Clara Massapina, Sandra Joaquim, Domitilia Matias and Nicole Devauchelle, Oocyte and embryo quality in Crassostrea gigas (Portuguese strain) during a spawning period in Algarve, South Portugal; Aquat. Living Resour. 12 (1999) 327–333
- Crassostrea gigas, Food and Agriculture Organization of the United Nations
- Pacific oyster, United States National Oceanic and Atmospheric Administration
- http://findarticles.com/p/articles/mi_m0QPU/is_2_24/ai_n15384489
- https://web.archive.org/web/20061223014748/http://www.stefannehring.de/downloads/142_Nehring-2003_Aliens-17_pacific-oyster.pdf