Crassostrea gigas

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Crassostrea gigas

The Pacific oyster, Crassostrea gigas, is a native oyster of the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand.

Taxonomy
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Ostreodia
Family: Ostreodae
Genus: Crassostrea
Species: C. gigas

Description

The shell of Crassostrea gigas is extremely variable in shape, which is based on the place where it has grown. The two valves are slightly different in size and shape, with the right valve being moderatly cup shaped. The color of the shell is variable but usually pale and white or off-white, with large, rounded, radial folds, and is often times extremely rough and sharp. Mature specimens can be from 80 mm all the way up to 400 mm

Crassostrea gigas right and left valves

Ecology

Crassostrea gigas can be found in intertidal and sub-tidal zones. The prefer to attach to a hard or rocky surfaces in shallow or sheltered waters but have been known to attach to muddy or sandy areas when the preferred habitat is scarce. They can also be found on the shells of other shellfish.

Life Cycle

For reproduction Pacific Oysters need a temperature of about 20° Celsius or higher in order to reproduce. Larvae are planktonic and spend several weeks in the free swimming phase, once an acceptable location has been found the oyster attaches itself to its chosen surface and spends the first year of its life as male before eventually becoming female. Un-harvested oysters may live up to 30 years.

Introduction

Crassostrea gigas has been introduced from its native home to all over the world, ranging from North America to Australia and Europe it has become an important commercial harvest in many of these places and is the number one shellfish resource in Washington State. In some places the Oyster is considered an invasive species such as the Wadden Sea where it is out competing native shellfish such as the blue mussel Mytilus edulis