Ostrea edulis

Ostrea edulis,commonly known as theEuropean flat oyster,is a species ofoysternative toEurope.In Britain and Ireland, regional names includeColchester native oyster,mud oyster,oredible oyster.In France,Ostrea edulisare known ashuîtres plates(flat oysters) except for those that come from the Belon River estuary inBrittany,France, which are known asBelons.

Ostrea edulis Temporal range:
Valves ofOstrea edulis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Ostreida
Family:	Ostreidae
Genus:	Ostrea
Species:	O. edulis
Binomial name
Ostrea edulis Linnaeus,1758

The fossil record of this species dates back to theMiocene(age range: 15.97 million years ago to present day). Fossils have been found in Belgium, Italy, the Netherlands, Egypt, Greece, Spain, the United Kingdom, Austria, France and Germany.

Description

Right and left valve of the same specimen:

• 
  Right valve
• 
  Left valve

Fossil (Pliocene)

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  Right valve
• 
  Left valve

When mature,O. edulisadults range from 3.8 to 11 centimetres (1.5 to 4.3 in) across.

Shells are oval or pear shaped, white, yellowish or cream in colour, with a rough surface showing pale brown or bluish concentric bands on the right valve. The two valves are quite different in shape and size, as the left one is concave and fixed to the substratum, while the right one is almost flat and fits inside the left. The inner surface is smooth, whitish or bluish-grey.

Fossil ofOstrea edulisfrom Pliocene of Italy

Biology

Ostrea edulisare gregarious molluscs that start their lives as males. They mature sexually after eight–ten months and may change sex depending on the water temperature. Usually the lifespan can reach about six years, with a maximum of 15 years. Adult oysters feed by filtration.

Ostrea edulis;a) labial palpi b) gills c) mantle d) junction of the two folds of the mantle e) large adductor muscle f) the shell

Distribution

The species naturally ranges along the western and southern coasts ofEuropefromNorwaytoMoroccoand including most of theBritish Islesand theMediterraneancoast.Naturally viable populations have appeared in easternNorth AmericafromMainetoRhode Islandsubsequent to artificial introduction in the 1940s and 1950s.

Habitat

Ostrea eduliscan be found in estuarine and shallow coastal water with hard substrata of mud and rocks.

Human use

WorldwideO. edulisharvest in tonnes, 1950–2003

Ostrea edulishas been harvested throughout Europe as an important food source since prehistory.During Roman occupation of BritainO. edulisoysters were exported in large quantities back to Italy.However, due to their more robust nature and greater ease of cultivation thePacific oysters,Crassostrea gigas,now account for more than 75 percent of Europe's oyster production.

European flat oysters are famously grown in Brittany, France. The true Belon oyster is cultivated in the Belon River, France, and has theAOCprotected name.In the 1950s, Dutch scientists artificially introduced Belon oyster seed into the waters aroundMainein hopes to establish a viable stock. The initial project was abandoned but ten years later natural colonies of flat oysters were found in the wild.Many North American suppliers use the name 'Belon' to species that are found in the wild throughout theUnited States.

Loch Ryan oysters are sourced from Scotland's only commercial European flat oyster bed.

Ostrea edulisis now also beingmariculturedin the states ofCalifornia,Maine,andWashingtonin the United States. The species once dominated European oyster production but disease, pollution, and overfishing sharply reduced the harvest.Currently, there are efforts across Germany, the UK, France, Scotland, and Wales torestore oyster reefsand maintain the habitat.

U.S.oyster growersfarmO. edulisin small quantities on both coasts. They are prized for their unique tannic seawater flavour, sometimes described as dry and metallic, and are more expensive than other American oysters.The flavour is considered excellent for eating raw on the half shell.

The adductor muscle of the European flat in combination with the shape of the shell results in a somewhat weaker seal compared with other oyster species. It is common practice to use rubber bands to prevent oysters from spilling their liquor and dehydrating in storage before consumption.

See also

• Locmariaquer § History of oyster farming

External links

• UK Biodiversity Action Plan