Arctica islandica

Ocean quahog
A shell of Arctica islandica with the valves separated
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Veneroida
Family:	Arcticidae
Genus:	Arctica
Species:	A. islandica
Binomial name
Arctica islandica Linnaeus, 1767

The dark periostracum is flaking off this dried valve of Arctica islandica from Wales

Arctica islandica, commonly known as the ocean quahog, is an edible marine bivalve mollusk native to the North Atlantic ocean, which is harvested commercially. This species is also known by a number of different common names, including Icelandic cyprine,^[1] mahogany clam, mahogany quahog, black quahog, and black clam.^[2]

The typical Arctica islandica resembles the quahog, but the shell of the ocean quahog is rounder, the periostracum is usually black, and on the interior of the shell, the pallial line has no indentation, or sinus. Unlike the quahog, which lives intertidally and can be collected by clam digging, this species lives subtidally, and can only be collected by dredging. They grow to sizes exceeding 50 mm shell height.^[3]

These animals show exceptional longevity and have been estimated to live up to 400 years in the wild.^[4] In 1868 one specimen, collected alive near Iceland, was 374 years old. The study of its growth rate and the oxygen isotope data showed that it had a highly variable growth at the peak of the Little Ice Age around 1550-1620 and mild climate near its end around 1765-1780 and had recorded the volcanic eruption of Mount Tambora in 1815. ^[5] One study found that in animals aged 4–192 years, antioxidant enzymes declined rapidly in the first 25 years, which includes the growth and sexual maturity stages, but afterwards remained stable for over 150 years. Though more detailed studies are warranted, it appears this species is a case of negligible senescence.^[6]

See also

• List of long-living organisms
• Maximum life span

Notes

1. ^ Sabatini, M. & Pizzola, P.F., 2007. Arctica islandica. Icelandic cyprine. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 14 September 2007]. Available from: <http://www.marlin.ac.uk/species/Arcticaislandica.htm>
2. ^ Hackney, Cameron R.; Thomas E. Rippen (2000). "The Molluscan Shellfish Industry". In Roy E. Martin, Emily Paine Carter, Jr., George J. Flick, Lynn M. Davis. Marine and Freshwater Products Handbook. CRC Press. pp. 323–324. ISBN 1566768896. 
3. ^ R. Witbaard, M.J.N. Bergman (2003). "The distribution and population structure of the bivalve Arctica islandica L. in the North Sea: what possible factors are involved?". Journal of Sea Research 50: 11–25. http://www.vliz.be/imisdocs/publications/56725.pdf. 
4. ^ http://www.sciencedaily.com/releases/2007/10/071028100032.htm
5. ^ Schone B.R. et al. 2005. Palaeogeography, Palaeoclimatology, Palaeoecology 228, 130-148.
6. ^ http://genomics.senescence.info/species/entry.php?species=Arctica_islandica

External links

• Ocean quahog, Arctica islandica, Life history and habitat from the NOAA.
• Climate records from a bivalved Methuselah