Portuguese oyster

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The Portuguese oyster, Magallana angulata (formerly Crassostrea angulata), is a shellfish found along the southwest coast of the Iberian Peninsula. It is closely related to the Pacific oyster. Genetic studies suggest it originated from the Pacific coast of Asia and was brought to Europe by Portuguese traders in the 16th century.

Habitat and appearance
It lives in coastal rivers, estuaries, and other sheltered waters, attaching itself to rocks and other hard surfaces. The shell is roughly triangular and grows to about 10–15 cm. Each shell has a rough exterior with ridges and grooves and a smooth, pearly interior with a deep cup that holds the animal.

Ecology and feeding
The Portuguese oyster is a filter feeder that uses its gills to take in tiny plants and particles from the water. It tolerates a wide range of salinity (about 25–35 parts per thousand) and can live in both intertidal and subtidal zones. Oysters like this species provide habitat for other organisms and are useful indicators of water quality and pollution.

Commercial importance and challenges
For centuries, it has been important for European oyster production, cultivated using bottom, floating, or rack-and-bag methods. A disease known as Gill Disease damages gills and has caused high oyster deaths in parts of France, Spain, and Portugal. Because of this, the Pacific oyster, which is more resistant to disease, was introduced in the 1970s and has become the main commercial species in many areas. Today, the Portuguese oyster is still cultured in places such as Taiwan.