SURROUNDED by darkness, eating whatever drifts by, the life of a deep sea
anemone is far from glamorous. But what it lacks in quality it gains in
quantity because it now seems that an anemone called Gerardia can live more
than a thousand years 鈥� longer than any other marine creature known.
Ellen Druffel of the University of California, Irvine, and her colleagues
have used radiocarbon dating to assess the age of three specimens of Gerardia
collected in the Bahamas in 1982 by the US Navy鈥檚 Alvin submersible. The
animals lived 620 metres below the surface, and had apparently been around for
between 1500 and 2100 years (Geochimica et Cosmochimica Acta, vol 59, p 5031).
鈥淚 was astounded,鈥� says Druffel. 鈥淚 figured that a lifetime of one to two
millennia was just too long for a single animal.鈥�
Whether Gerardia can really be considered a single animal, however, is a
moot point. Like corals, Gerardia are colonies of tiny animals, known as
polyps, living together on a branching skeleton which they deposit in
successive layers. 鈥淚t more resembles a modern plastic than a natural tissue,鈥�
says Druffel. Eventually the organism resembles a tree, with a trunk and
branches.
Advertisement
To calculate the anemones鈥� age, Druffel and her colleagues measured the
relative amount of carbon-14, a radioactive isotope, in several sections of
the anemones鈥� skeletons, including the oldest, innermost layers of their
trunks. Since carbon-14 decays at a known rate, the researchers were able to
determine how much time had elapsed since those layers were deposited.
Fred Grassle, director of the Institute of Marine and Coastal Sciences at
Rutgers University in New Jersey, says that scientists have previously found
evidence of corals living for hundreds of years 鈥� but not for millennia. 鈥淭his
is a surprise. I think it鈥檚 very exciting,鈥� he says.
Nevertheless, the anemones鈥� longevity may not be unique. Most colonial
animals can reproduce asexually, and therefore have no finite lifespan. This
means that they can, in theory, survive as long as their environment stays the
same. 鈥淚 wouldn鈥檛 be surprised if some reef corals lived into the thousands of
years,鈥� says Ted Bayer, a zoologist at the Smithsonian Institution in
Washington DC. 鈥淚t鈥檚 just that no one has looked into it yet.鈥�
Whether or not the deep-sea Gerardia are record-breakers, their longevity
is a bonus for scientists. The carbon in their skeletons came from the food
they ate, presumably plankton or organic debris that rained down from the
surface. So the anemones may serve as a kind of time capsule, preserving a
record of the ocean鈥檚 productivity over the past two thousand years.