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The ocean quahog ( Arctica islandica) is a species of edible clam, a marine bivalve mollusc in the family Arcticidae. This species is native to the North Atlantic Ocean, and it is harvested commercially as a food source. This species is also known by a number of different , including Icelandic cyprine,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. Available from:
The typical A. islandica resembles the hard clam, 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 pallial sinus. Unlike the quahog, which lives intertidal zone and can be collected by clam digging, this species lives littoral zone, and can only be collected by fishing dredge. They grow to sizes exceeding 50 mm or two inches shell height. An individual specimen was reported to have lived 507 years, making it the longest-lived non-clonal metazoan whose age was accurately known.
This characteristic has proven useful in the science of sclerochronology, the study of periodic physical and chemical features in the hard tissues of animals that grow by accretion, and is especially valuable for modeling of paleoclimates. 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.
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. In contrast to the exceptionally long-lived populations in relatively deep, cold parts of its range, more southern populations that experience greater seasonal variations in salinity and temperature are typically far shorter-lived. For example, A. islandica from the German Bay of Kiel typically only reach an age of about 30 years and those from the German Bight about 150.Strahl, Julia (2011). Life strategies in the long-lived bivalve Arctica islandica on a latitudinal climate gradient – Environmental constraints and evolutionary adaptations. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, University of Bremen.
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