The Mysteries of Evolution: 5. The Immortal Jellyfish

Is it a paradox or just a fluke of nature? How could a tiny jellyfish be immortal?
Here are some quick facts about the transdifferentiation process that seem to make jellyfish immortal:

My question is: if tiny jellyfish can technically be immortal, what stops us from being immortal or being able live forever or at least much longer than 70-85 years ?

If the immortal jellyfish evolved to have the ability to live forever, will we be able to as well?

Or is it possible that we humans already had the ability to live indefinitely and somehow lost it?

Many experts working  in the field of anti-aging seem to agree that our bodies should technically continue to live forever…and yet they don’t really know why that doesn’t happen… For unknown reasons… scientist still don’t really know why we age and die while there are many contradictory theories…

Why the tiny jellyfish evolved the ability to be immortal and we didn’t, even though many scientists think we should be able to be immortal or at least have the ability to rejuvenate our bodies forever?

Well, this is just one the many mysteries of evolution…but this one is more puzzling than the previous 4  I have posted…at least to me…

I’ve written the above a while back… However, in the view of the many tragic events in the world recently, with so many innocent people dead; in Spain, Finland, Charlottesville  and many other to come…unfortunately… I have been reflecting on two main issues; death and the possibility of living again (resurrection) in the view of just God who allows evil…

While these issues are probably separate issues, worth separate OP for each, my focus was on the ability of the lowly jellyfish being able to live indefinitely and human’s relatively short lifespan without the ability to revert youthful body…

 

 

 

110 thoughts on “The Mysteries of Evolution: 5. The Immortal Jellyfish”

  1. J-MacJ-Mac Post author

    Allan Miller:
    J-Mac,

    ‘Bacterial immortality’ is selected for in the germ line of multicellular organisms. That lineage of cells is immortal. It’s only somatic lines that aren’t, for mechanistic reasons. You are very vague about why it would be a fitness advantage to have immortal somas. It would be nice, but that’s not the same thing.

    What you are referring to is germline cell is immortal in the sense that it is part of a lineage that has reproduced indefinitely since the beginning (as far as it is known or so its claimed)…

    There is not guarantee it will continue indefinitely…
    This is clearly not the same thing as the transdifferentiation process of the jellyfish…It is just another mystery of evolution…

    I’m not into the fitness thingy of populations genetics..I was just inquiring how viewed it…

  2. AcartiaAcartia

    What about autogamy that occurs in some ciliates? Ciliates typically reproduce by fission, resulting in two genetically identical cells. But a culture of ciliates that are kept under ideal conditions will eventually senesce and die unless it undergoes meiosis. The most commonly known way of doing this is conjugation, in which the cell undergoes meiosis and exchanges genetic material with another cell. Protozoan sex. But there are some ciliates that undergo meiosis but don’t pair up with another ciliate (autogamy). Protozoan masturbation. The result of both processes is that the cell line is rejuvinate and can proceed to grow at the previous rate.

  3. Corneel

    J-Mac: Interesting…so why would the longevity be the secondary result of selection and why only in one species? Should there be at least some intermittent evolutionary changes related to longevity and the process of transdifferentiation in other species of the jellyfish?

    Not necessarily, but as it happens this is indeed the case. Following some of the links that KN posted (thanks KN), I found that info in the primary publication; Several Hydrozoans are also displaying characteristics that are responsible for the longevity of the species in the OP. Citing from the original source (Piraino at el. 1996 Biol. Bulletin):

    Ontogeny reversal, with direct formation of isolated medusa buds into polyps, has been demonstrated to occur in Podocoryne carnea (Miiller, 1913; Frey, 1968; Schmid, 1972), Eleutheria dichotoma (Hauenschild, 1956), Cladonema sp. and Cladonema uchidai (Kakinuma, 1969), and Perarella schneideri (Piraino, unpubl. obs.). These isolated medusa buds can revert to polyp structures only at the beginning of their development, completely losing this ability before they are liberated

    So ontogeny reversal is present in other members of the group, but is limited to the budding medusa. Apparantly, this particular species found a way to initiate the process in released medusae.

  4. Corneel

    It seems that Hydrozoans as a group are poised for long life. The species Hydra vulgaris is also reported to be lacking senescence (Martinez 1998 Exp. Geront.). The author suggests that this is related to the low level of differentiation of cells and the tremendous rate of cell turnover in these critters:

    Escaping senescence, however, might be restricted to animals with simpler, dynamic bodies that can be constantly renewed from populations of stem cells. Given the tissue dynamics of hydra, over a period of four years somatic epithelial cells have divided on average 300 times and the whole hydra body may have been fully replaced at least 60 times. The evolution of more complex bodies with tissues and organs with a higher degree of specialization might have resulted in, or perhaps required, a loss of the capacity of renewal and thus permitted the evolution senescence (Jones 1982).

    Bad news for us, I am sorry to say.

  5. Corneel

    J-Mac: What you are referring to is germline cell is immortal in the sense that it is part of a lineage that has reproduced indefinitely since the beginning (as far as it is known or so its claimed)…
    There is not guarantee it will continue indefinitely…

    As a matter of fact, it is guaranteed to end someday 🙂

  6. Allan Miller

    J-Mac,

    What you are referring to is germline cell is immortal in the sense that it is part of a lineage that has reproduced indefinitely since the beginning (as far as it is known or so its claimed)…

    There is not guarantee it will continue indefinitely…

    Well, same for bacteria and jellyfish. Not really the point.

    This is clearly not the same thing as the transdifferentiation process of the jellyfish…

    You have cell lines continuing when in ‘normal’ animals the somatic lineages terminate. In that respect, it is the same.

    I’m not into the fitness thingy of populations genetics..I was just inquiring how viewed it…

    You’re not into the fitness thingy, but are sure that indefinite longevity should be selected for?

    Consider a ‘gene for longevity’ – it makes diploid somas immortal. Therefore, the offspring carrying this gene are also immortal. In order to spread around the population, this gene has to get into more offspring than its allele in non-immortals. How does a ‘gene for immortality’ take over a population? It seems at least as likely to me that a ‘gene for longevity’ may get into no offspring at all. Why reproduce?

  7. Corneel

    Allan Miller: Consider a ‘gene for longevity’ – it makes diploid somas immortal. Therefore, the offspring carrying this gene are also immortal. In order to spread around the population, this gene has to get into more offspring than its allele in non-immortals. How does a ‘gene for immortality’ take over a population? It seems at least as likely to me that a ‘gene for longevity’ may get into no offspring at all. Why reproduce?

    Precisely. This is basically the mirror image of my previous example. The “immortality allele” will spread only if the difference in survival becomes apparant before all organisms have died of extrinsic sources of mortality (predation, disease, accidents, starvation, etc.). That should be obvious: if noone dies of old age, potential immortality is useless. Once the last member of a birth cohort has died, we have entered the selection shadow ; no organisms alive => no phenotypes => no selection.

  8. Allan Miller

    Just chucking out a factoid here – pound for pound, birds live significantly longer than mammals (apart, that is, from bats). Nick Lane goes into this in Oxygen. You want to live longer, start flapping!

  9. Corneel

    Allan Miller: Just chucking out a factoid here – pound for pound, birds live significantly longer than mammals (apart, that is, from bats). Nick Lane goes into this in Oxygen. You want to live longer, start flapping!

    I have heard of that. The proposed explanation for that is that powered flight releases birds from a lot of extrinsic mortality by predation. Hence, increased life span became beneficial for them. This also explains why bats are the exception among mammals.

  10. Allan Miller

    Corneel,

    I have heard of that. The proposed explanation for that is that powered flight releases birds from a lot of extrinsic mortality by predation. Hence, increased life span became beneficial for them. This also explains why bats are the exception among mammals.

    I don’t think that’s the case though. I don’t think birds realise their potential life spans in the wild – flying predators, inter alia. Lane hypothesises that it’s to do with the quality of their mitochondria. Flying makes high aerobic demands, leaving fewer damaging free radicals around.

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