Like many jelly species, members of the group Hydra have a polyp stage that reproduces asexually by budding off little clones, and people have speculated this could last for thousands of years. So Daniel E. Martínez closely watched members of one species, Hydra vulgaris, for 4 years, and in that time very few animals died [3]. Dr. Martínez suggests that since animals that start reproducing only a few days after birth, such as Hydra, tend to kick the bucket earlier than animals that wait, 4 years is a pretty long time. But does that really mean they’re immortal?

More information is needed about Hydra, but it’s not the only species people keep for decades, nor the only species that could help us understand if some jellies may last forever. So, to get to the bottom of this I polled the experts.  I sent emails to some of the top jelly aquarists asking: do polyp clone populations change over time?

Most public aquaria display jellyfish, and to do this they take advantage of the peculiar jelly life cycle.  The life of jellies is broken into two parts: the polyp-type stage, which looks like Hydra and divides asexually, and the jelly stage, which grows from polyps and gets on with the busy act of sexual reproduction. To keep the number of exhibit jellies constant, aquarists use polyps as a literal clone bank, cueing them to produce more jellies as needed.

And do these clone banks ever change or grow old? The answer was a unanimous “yeah, kinda.” According to aquarists at both the Monterey Bay Aquarium and the New England Aquarium, over about six years clonal populations do get “tired.” They become more fragile, don’t produce healthy jellies, and stop responding to environmental signals. Many aquarists replace their polyp stocks with new baby polyps quite regularly, so that none of this fickleness gets in the way of jelly production. The whole colony may continue to kick, but it gets more and more fragile over time. To me, this sounds a lot like aging.

When humans die it’s not because a special gene turns on that shouts: “YOUR TIME IS UP!” Rather, little things start breaking all over, cells stop dividing and those that do accumulate mutations, this is why getting older is often accompanied by all sorts of biological issues. The truth is, accumulating mutations and cell gunk isn’t something special about aging people, even clone lines of E. coli bacteria accumulate harmful cellular products over time [4]. This is just the cost of being alive. So does the “immortal jellyfish” Turritopsis dohrnii really last forever, even with all this gunk slowly working its way into its cells and genomes?

I’m not convinced. Just because you can reverse your life cycle or clone yourself doesn’t mean you’ve got a get out of jail free card for all the consequences that come with being a living thing in the first place. You are still subject to that nasty gunk build up.  Some species like Hydra vulvaris may have evolved ways to clean this gunk and beat the system, but the jury is still out on how, and for how long. While the “immortal” jellyfish Turritopsis dohrnii may be able to turn back its life cycle, it may not escape the inevitable slowing down that comes with age. In other words, while reversing your fate and escaping death for a short while may be a neat trick, it doesn’t guarantee immortality.

Work Cited

[1] Stefano Piraino, Ferdinando Boero, Brigitte Aeschbach and Volker Schmid (1996). Reversing the Life Cycle: Medusae Transforming into Polyps and Cell Transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa). Biological Bulletin , Vol. 190, No. 3 (Jun., 1996), pp. 302-312

[2] Stefano Piraino, Ferdinando Boero, Brigitte Aeschbach and Volker Schmid (1996). Reversing the Life Cycle: Medusae Transforming into Polyps and Cell Transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa). Biological Bulletin vol. 190, no. 3  pp 302-312

[3] Martínez DE (1998). Mortality patterns suggest lack of senescence in hydra. Exp Gerontol. vol 33 no 3 pp 217-25.

[4] Ariel B. Lindner, Richard Madden, Alice Demarez, Eric J. Stewart and François Taddei (2008). Asymmetric segregation of protein aggregates is associated with cellular aging and rejuvenation. PNAS vol. 105 no. 8 pp 3076-3081 doi: 10.1073/pnas.0708931105

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The year is 9CE. Fourteen years later Pliny the Elder will be Pliny the Newly Born. Cai Lun will invent paper one hundred years later. In Northern Germany a storm unleashes on 30,000 Roman soldiers under the command of Publius Quinctilius Varus. Varus’s most trusted advisor, Arminius, was the son of a Germanic war chief. At a very young age, Irmin (meaning “great” later Latinized to Arminius) was tributed by his father to Emperor Augustus. Maturing in Rome, Arminius received military training reaching the rank of Equestrian. He eventually followed Varsus to Germania providing tactical advice for the conquest*. Secretly, Arminius was uniting the Germanic chieftains to amass a force of 10,000. Arminius advised Varsus to progress the Roman Legions on a predetermined route. Here the Legions were ambushed and after 2-3 days 20,000 Roman bodies littered the Germanic country side. It is said that many years later Emperor Augustus, desperately needing the lost legions, went around the palace late at night muttering, “Varus, give me back my legions.” Of course, you don’t care about the Battle of the Teutoburg Forest. You’re a coral larva and just settling into a nice spot in the Gulf of Mexico. You’ve no idea what awaits you 2,000 years later.

September 20, 2009 is like any other day. You awake**. You are an Anitpatharian, an elite member of 230 species of tree-like black corals. Like Arminius, you are proud of your heritage. And like Arminius, you have Latenized name, Leiopathes. You begin feeding on particles of food drifting by in the surrounding water column. You ponder the good and bad times. Just last year you were almost covered in oil and your food contaminated with Corexit and hydrocarbons. But you, proud Leiopathes, survived all that. All of sudden bright lights are upon you. You are snatched by a large robotic arm and shoved in box.

Like Arminius, you travel far from your home. You start at 1000 feet deep on the ocean floor just a few kilometers off Louisiana traveling to labs in California, Texas, North Carolina, and Florida. This is the most you have traveled since a young larva. But, you now live a new life as Sample GOM-JSL09-3728-BC1 and hold secrets to your species, much as Varsus and Augustus believed Arminius held secrets to Germania.

Scientists learn your tissues show evidence of nuclear bomb testing. In the 1950’s and 1960’s, widespread atmospheric testing of atomic bombs laced the oceans with a 100% increase in radiocarbon. Damn nuclear bomb testing contaminated your food, material originating at the ocean’s surface. Your radioactively laced tissues told all this. From counting and radiocarbon dating the rings in your trunk, scientists find that your kind can grow continuously for at least two millennia. Each year you grow no more than 0.00087 inches. It takes you almost 70 years to grow the width of penny.

However, here is where our tale of Arminius and Leiopathes diverges. Unlike the Romans, scientists will use this information to save your kind not conquer them. We know that the slow growth rate and long lifespan of your kind may mean that recovery of deep-sea corals could take decades to centuries. Hopefully in return, dear Leiopathes you will not secretly unite corals and ambush us. Although maybe you should.

Prouty, N., Roark, E., Buster, N., & Ross, S. (2011). Growth rate and age distribution of deep-sea black corals in the Gulf of Mexico Marine Ecology Progress Series, 423, 101-115 DOI: 10.3354/meps08953

*Perhaps it was not the wisest to take train the enslaved Arminius in military tactics and then make him a trusted advisor

**Do corals sleep?

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