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True Oysters
Pacific oyster, Crassostrea gigas
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Bivalvia Order: Ostreoida Suborder: Ostreina Superfamily: Ostreoidea Family: Ostreidae Rafinesque, 1815
Genera and species
See text.

The members of the family Ostreidae are the true oysters, and include all the species that are commonly eaten under the title "oyster". They do not include the pearl oysters; these species are only distantly related to the true oysters, since although they are also bivalves, they are members of the family Pteriidae, in the order Pterioida.

Like scallops (family Pectinidae), true oysters have a central adductor muscle, which means that the shell has a characteristic central scar, marking its point of attachment. Oysters have a larger adductor muscle than scallops. Their shell shape tends to be irregular as a result of attaching to other objects.

Members of genus Ostrea generally live continually immersed in sea water, brood their fertilized eggs for various proportions of the period from fertilization to hatching and are quite flat with roundish shells. They differ from most bivalves by having shells completely comprised of calcite but with internal muscle scars of aragonitic composition. They do best in water with a not too thick concentration of phytoplankton.

Members of genera Saccostrea and Crassostrea generally live in the intertidal zone, broadcast sperm and eggs into the sea and can thrive in water which is very rich in phytoplankton. One of the most commonly cultivated oysters is Saccostrea gigas, the Japanese oyster, which is ideally suited for oyster cultivation in seawater ponds.

Both oviparous (egg bearing) and larviparous (larvae bearing) species are known within the Ostreidae. Both types are hermaphrodites. However, the larviparous species (which include the edible oyster Ostreia edulis) show a pattern of alternating sex within each individual, whereas the oviparous species (such as the eastern oyster Crassostrea virginica) are simultaneous hermaphrodites producing either female or male gametes according to circumstances.

• Crassostrea Sacco, 1897
  • Crassostrea angulata Lamarck
  • Crassostrea ariakensis (Fujita, 1913) - Suminoe oyster
  • Crassostrea chilensis Hertlein
  • Crassostrea columbiensis (Hanley, 1846)
  • Crassostrea corteziensis (Hertlein, 1951)
  • Crassostrea gigas (Thunberg, 1793) - Pacific oyster
  • Crassostrea glomerata (Gould, 1850) - Auckland oyster
  • Crassostrea rhizophorae Guilding
  • Crassostrea virginica (Gmelin, 1791) - Eastern oyster
  • Crassostrea iredalei Sacco, 1932 - Faustino
• Cryptostrea Harry, 1985
  • Cryptostrea permollis (G. B. Sowerby II, 1871) - Sponge oyster
• Dendostrea Swainson, 1835
  • Dendostrea frons (Linnaeus, 1758) - Frond oyster
• Hyotissa
• Lopha Roding, 1798
  • Lopha cristagalli (Linnaeus)
  • Lopha frons (Linnaeus, 1758)
• Ostrea Linnaeus, 1758
  • Ostrea angasi
  • Ostrea conchaphila (Carpenter, 1857)
  • Ostrea cristata Born, 1778
  • Ostrea digitalina - Extinct
  • Ostrea edulis Linnaeus, 1758 - Edible oyster
  • Ostrea equestris (Say, 1834) - Crested oyster
  • Ostrea gryphoides - Extinct
  • Ostrea lurida Carpenter, 1864
  • Ostrea megadon Hanley, 1846
  • Ostrea sandvicensis
• Ostreola
  • Ostreola conchaphila (Carpenter, 1857) - Olympia oyster
  • Ostreola equestris (Say, 1834) - Crested oyster
• Saccostrea
  • Saccostrea glomerata (Iredale and Roughley, 1933) - Sydney rock oyster
  • Saccostrea cuccullata
  • Saccostrea gigas Japanese oyster
• Teskeyostrea Harry, 1985
  • Teskeyostrea weberi (Olsson, 1951) - Threaded oyster, weber oyster

• TSN 79866. Integrated Taxonomic Information System.