Ostrea edulis 
System : Marine
Kingdom
Phylum
Class
Order
Family
Animalia
Mollusca
Bivalvia
Ostreida
Ostreidae
- General
- Distribution
- Impact
- Management
- Bibliography
- Contact
Common name
istiride (English, Turkmenistan), stridia (English, Bulgaria), edible oyster (English), ustritsa (English, Russia), hu�tre comestible (French), eetbare oester (Dutch), Essbare euster (German), European oyster (English), platte oester (Dutch), European flat oyster (English), native oyster (English), hu�tre plate Europ�enne (French), ostra Europa (Spanish), common oyster (English), oester (Dutch), stridie (English, Romania)
Synonym
Ostrea taurica , Krynicki 1837
Ostrea adriatica , Lam-Middendorff 1848
Ostrea adriatica , Lam-Middendorff 1848
Similar species
Crassostrea virginica
Summary
Ostrea edulis (the European flat oyster) is native to Europe and the Mediterranean. It has been introduced to the northwestern Atlantic Ocean for aquaculture. Usually found in muddy areas, Ostrea edulis has long been harvested for food. Overharvesting of Ostrea edulis in its native range, however, has caused it to be reintroduced to Europe. While in Atlantic waters, Ostrea edulis became infected with the disease bonamiasis (Bonamia ostrae). This disease has caused widespread mortality in the vast majority of Ostrea edulis.
Species Description
O. edulis is a hermaphroditic (Mirella de Silva et al. 2005) bivalve mollusk with a distinct beak that is patterned with delicated foliation. O. edulis can grow up 20cm or more and live up to 20 years. O. edulis is ovular and has a rough scaly surface with two distinct halves. The two halves of the shell are different shaped; the left shell is concave and attached to the substratum and the right is flat with tough edges and acts as a lid for the left shell. Its right valve is cream-coloured with light brown or blue circular bands. The inner surface of O. edulis is smooth and white or bluish-grey and shiny with some dark blue spots. At the narrow ends of the shell are stretch ligaments that hold the shells together. \"A large central muscle serves to close the valve against the pull of the ligament.\" The outer shell is composed of flaky layers which may include laminar and hollow chambers. O. edulis contains a creamy beige to pale grey meat that is slightly salty or bland in taste. The meat's texture can be tender or firm. (FIGIS(a), 2006)
Notes
The bacteria Nocardia crassostreae infects O. edulis and makes it heat sensitive. Oyster herpesvirus infects O. edulis and results in larval and seed mortality (Ruesink et al. 2005). O. edulis is threatened by two introduced species in its native range, Urosalpinx cinerea (drill shellfish) and Crepidula fornicata. The United Kingdom has listed O. edulis as a priority species in the UK Biodiversity Action Plan (ARKive, 2006). Between 1957 and 1959, 16,000 of this species was imported from Conway, North Wales, to St. Andrews and Ellersie, Prince Edward Island (Vercaemer et al. 2003).
Lifecycle Stages
Temperature affects O. edulis, making the species exist as a series of physiological races. In Spain, one low temperature race occurs where 12º-13ºC is required for spawning. A temperature of 25ºC is required in the Norwegian fjords for spawning and in France, O. edulis spawns between 14º-16ºC (FIGIS(a), 2006). Once hatched, larvae (called trocophores at this stage) (Weichtiere, undated) are about 160µm in size and spend 8-10 days in a pelagic state before settlement (FIGIS(a), 2006). In this pelagic state, O. edulis goes through 2 metamorphoses. After the first metamorphosis, the trocophore transforms into a veligar with 2 ciliated snail-like protrusions. A second metamorphosis changes the veligar into a bivalve small oyster that uses its byssus threads to cling to a suitable substrate (TCO, undated). Prior to substrate attachment, O. edulis explores the substrate with its foot protruded in the front which functions as a tactile sense organ. Matamorphosis can be delayed if a suitable attachment site is not located (Cole, 1938).
Healthy larval growth and survival rates occur at salinities as low as 20% and some can even survive environments with 15% salinity (FIGIS(a), 2006). Johnson et al (1999) report that completion of larval development depends upon the proper intake of Omega-3 polyunsaturated fatty acids. O. edulis start their lives as males and mature sexually as males between 8-10 months. After this period, they change sex regularly. Temperature can affect the sex of O. edulis; if the temperature reaches 16ºC, O. edulis becomes a female every 3-4 years. \"If the temperature reaches 20ºC,they will change to females each year.\" Cooler water temperatures force the oysters to revert back to males (ARKive, 2006).
Uses
O. edulis has been harvested for 6,000 years (Diaz-Almela et al. 2004). O. edulis when abundant was often eaten by Europeans, however a decline in numbers have made them a delicacy (Weichtiere, undated).
Habitat Description
Ostrea edulis prefers the firm bottoms of mud, rocks, muddy sand, muddy gravel with shells, hard silt, and artificial habitat created with broken shells or \"culch\" (Jackson, 2003). O.edulis can be found in muddy areas attached to hard surfaces at depths of 30 ft (9.144 metres) (CZM, undated).
Reproduction
O. edulis is a protatric hermaphrodite that changes sexes twice during one season. They are males early in the spawning season and females later and vice versa. During reproduction, female gametes are released into the palleal cavity where they are fertilized by externally released sperm (FIGIS(a), 2006) which is passed through the gills as part of the normal feeding process (ARKive, 2006). Females produce between 500,000-1,000,000 fertilzed eggs per spawning period. The eggs are incubated for a period of 8-10 days (depending on temperature) and released into the environment (FIGIS(a), 2006). In their native range, O. edulis spawns between late June and mid-September. Young oyster spat can be seen from late summer on. (Kennedy & Roberts, 1999).
Nutrition
Ostrea edulis is a filter feeder that eats microalgae or phytoplankton. Autotrophic flagellates and diatoms are also important food for O. edulis (Jonsson et al. 1999).
Principal source:
Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Review:
Publication date: 2007-05-14
Recommended citation: Global Invasive Species Database (2024) Species profile: Ostrea edulis. Downloaded from http://iucngisd.org/gisd/species.php?sc=798 on 29-11-2024.
General Impacts
The disease Bonamia ostrae (bonamiosis) was contracted by O. edulis shortly after its introduction to the northwest Atlantic coast. For the last 25 years, B. ostrae has caused extensive mortalities among populations of the European flat oyster (Mirella da Silva et al. 2005). O. edulis was eventually re-introduced to Europe where the disease was transferred to other established populations. Programs have been implemented to limit the spread of this disease (FIGIS(a), 2006).
Management Info
The management of O. edulis is vital to controlling the spread of diseases (FIGIS(a), 2006). A disease of concern is the protist Bonamia ostrae which causes a 70-80% mortality rate in O. edulis. Another protist, Marteilia refringens causes 75-100% mortality in O. edulis. Mikrocytos mackini also affects the oyster (Ruesink et al. 2005). When importing O. edulis, it should be transported from countries where no disease has been present for the past 2 years. The Office International des Épizooties (OIÉ) set forth guidelines to ensure that no parasites are detected while under an official surveillance program for two years. European zoosanitary directives implemented a zoning system to restrict the spread of diseases. Site selection and density reduction are a major focus in matters concerning management (FIGIS(a), 2006). In the United Kingdom efforts to manage O. edulis involve maintaining the abundance of stock at the fisheries while decreasing local densities to limit the spread of disease, especially Bonamia ostrae (UKBAP, 1999).
