Bay Nature magazineFall 2020

Ask the Naturalist

Do Sea Anemones Live Forever?

September 27, 2020
giant green anemone
Looking into the center of a giant green anemone, this one at Fitzgerald Marine Reserve, is one way to glimpse possible immortality. (Photo by Charity Vargas)

Groucho Marx once said, “I intend to live forever, or die trying”—and he did, it seems. But when it comes to sea anemones, if you lop off a hunk or a tentacle it will grow right back. Are anemones everlasting? Have they managed to do what Groucho didn’t? 

We do know that some anemones can live over 100 years. Basically, as long as they’re not poisoned or eaten, they keep on keeping on. I myself haven’t met any anemones that are quite that old. But in 1984 the late Dr. Gordon Chan, biology professor at the College of Marin, introduced me to a colossal giant green anemone living at Duxbury Reef that he’d been feeding for decades and named “Mr. Tony.” I suspect he—or she—still lives there, off the coast of Bolinas.

One reason for an anemone’s longevity may lie in its telomeres. A telomere is a structure that caps each chromosome and protects it from damage during cell division, sort of like the plastic tips at the ends of shoelaces. Without those tips, the laces will slowly fall apart, until you can’t tie your shoes. Similarly, without telomeres, the DNA in those chromosomes eventually becomes so damaged that cells can no longer divide. Our human telomeres grow shorter each time our cells divide, and current research indicates that how quickly they shorten may be associated with how our bodies age.

Corals, close relatives of anemones, seem to have methods of repairing their telomeres; this process has been linked to their ability to live for hundreds if not thousands of years. Some of the genes involved in telomere repair in corals are also found in anemones, although those genes’ function in anemones specifically has yet to be studied. Other features of sea anemones’ genomes, like very low rates of mutation in genes that mutate much more rapidly in other animals, also suggest anemones have ways to repair their DNA. And they don’t seem to develop tumors as they age the way other animals do.

Another trait that makes anemones unusual in the animal kingdom: many (but not all) reproduce asexually by cloning, creating perfect copies of themselves. Those copies produce copies, and on and on. The clones, and clones of clones, can create a long-lived lineage of genetically identical individuals. In that sense, I reckon anemones may indeed be immortal. They and their relatives have been on this planet for over 500 million years. As the saying goes, “If it ain’t broke, don’t fix it.” Still, don’t get too jealous! While anemones are among the simplest animals we know of with a nervous system, they can’t appreciate a good Marx Brothers joke—or pull off a grease paint mustache.

One of the most abundant anemones along our Pacific coast—one you’re likely to see if you check out a tidepool during this fall’s afternoon low tides—is the aggregating anemone, Anthopleura elegantissima (and they do have an elegant, streamlined shape). They dwell in large clusters on rocks or pilings with tiny bits of pebbles and shells attached to their bodies. Their green color is derived in part from algae that live within their tissues and provide them with food, in exchange for a swell place to live. These anemones can reproduce by longitudinal fission (splitting evenly in two) and also by shedding sperm or eggs into the water, forming larvae that go find their new promised land, er, tidepool. When settled in a suitable location, they go back to simply cloning themselves, hedging their genetic bets with both asexual and sexual reproduction.

Their neighbors, the giant green anemone (Anthopleura xanthogrammica), thrive a bit deeper in their tidepools. They represent one of the largest anemone species in the world and glow a striking emerald green when dwelling in full sunlight. But unlike their close cousins, they only reproduce sexually—no splitting apart for Mr. Tony.

When I lived at Muir Beach, I tracked one giant green anemone for a couple of years. This individual got buried in the sand during the summer. When the winter storms removed the sand, it was still alive, albeit a bit smaller. It had apparently digested its own tissues to survive for six months. Sounds like the recipe for immortality to me! I should have named it Groucho.

About the Author

Send your questions to Rosa-based naturalist Michael Ellis leads nature trips throughout the world with Footloose Forays (

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