Species in Focus: Ocean Quahog

Identification: The Ocean Quahog (Arctica islandica) is a long-lived, edible, marine bivalve. It has a solid, heavy, oval to rounded shell up to 13cm in length. The shell is sculptured with numerous, fine concentric lines and is covered in a thick, glossy periostracum. In juveniles the periostracum is straw coloured, becoming darker with age and finally black in old animals. On dead shells the periostracum peels away to reveal the white shell.

The shell of the ocean quahog clam (Arctica islandica) showing its dark periostracum, next to a ruler for size comparison
Ocean Quahog (Arctica islandica). I estimated this one to be well over 100 years old

Behaviour: The Ocean Quahog spends most of its time buried in soft sediments (sand and muddy sand) with its inhalant and exhalant siphons at the surface. Like many bivalves, as an adaption to its habitat it is also able to respire anaerobically when it is buried. It uses its siphons to feed on particulate matter suspended above the sediment or in the sediment surface film. Growth is rapid in juveniles but becomes very slow in adults. Its sedate lifestyle is thought to contribute to its exceptionally long life.

Where to see: Subtidally from 4-482m in exposed waters. It is found all over the British Isles and entire NE Atlantic. It is also found from Labrador to North Carolina in the West Atlantic. You are much more likely to see its shell washed up on the beach than a living specimen.

Did you know? Ming, the nickname given to an Ocean Quahog collected off Iceland in 2006 was found to be 507 years old! That makes it the oldest non-colonial animal ever discovered.

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