Stormy seas make for good beachcombing and while walking a strandline you might meet a member of the oldest species on Earth. This curious creature has an even more curious name: the ocean quahog, Arctica islandica.
What is an ocean quahog?
At first sight, though, an ocean quahog is just a fairly plain, quite large and rounded clam. As with all clams, its shell is made up of two hinged parts called valves that protect the soft body parts inside. When fresh and alive, the ocean quahog is covered in a dark, skin-like layer called the periostracum, so it’s also known as a black or mahogany clam.
How big are ocean quahogs and where do they live?
Older ocean quahogs can be over 5cm thick and 13cm long. Empty shells washed up on the shore are probably the closest most of us will get to seeing one, as the living animals bury themselves in sediment 4-500m underwater.
- Seashells expert guide: what are they, where do they come from, and how are they made?
What do ocean quahogs eat?
Ocean quahogs, like nearly all clams, are filter feeders. In the cool waters off our North Atlantic shores, they get on with the slow, steady and unexciting occupation of filter feeding. This involves sucking in water through their inhalant siphon. A current generated by thousands of tiny, beating hairs, called cilia, pulls this water into a clam’s gill cavity.
Here, the cilia and mucous trap any goodies, such as algae and decomposed organic material. This is then passed down to the mouth while the surplus water exits via a separate exhalent siphon, and on it goes. The process is almost continuous and the only things that might add a note of excitement to a clam’s day are changing environmental factors, such as water temperature, currents and daylight.
If need be, the clam might use its short, stubby, muscular ‘foot’ to go for a slow walk, repositioning itself in a better place to suck at the never-ending ocean.
So what has qualified this pretty unremarkable-sounding animal for a mention here? Well, it turns out that this sub-sedimentary sloth is a remarkable survivor.
Ocean quahogs lifespan
As well as being the last of its family, the Arcticidae, a group of clams that dates back to the Jurassic period, it’s also capable of record-breaking feats of longevity. Many populations of this clam live to well over 100 years old, with the oldest, slowest-growing and largest coming from the northern parts of their range.
One specimen made the news in 2006 when it was dredged up off the coast of Iceland by
a Bangor University expedition. This large ocean quahog turned out to be the oldest known individual ever discovered, and the oldest substantiated animal on Earth. It was nicknamed Ming, as the Chinese dynasty of the same name was coming into power at the time the mollusc was born and settled on the ocean floor, some 507 years ago.
Unfortunately, Ming was frozen and preserved in the name of science (the researchers regret this) so we have no idea how old these creatures can get. We do know, however, that animals like the ocean quahog exhibit a rare phenomenon known as negligible senescence. This means they don’t seem to show any signs of ageing as they get older, maintaining bodily and reproductive fitness. This humble mollusc starts slow, matures in about eight years and then, as its metabolic costs are minimal, it just ticks over in cool northern waters.
- Weirdest sea creatures - meet strange sea creatures of the deep
- Weirdest animals: meet the weird freaks and oddballs of the natural world
- Deadliest sea creatures: Meet the most dangerous animals in the ocean
Illustration by Peter David Scott/Art Agency