The Immortal Jellyfish

There is a species of small jellyfish that will, when it is sick or injured, instead of dying, fully regenerate itself. It will sink “to the bottom of the ocean floor, where its body folds in on itself—assuming the jellyfish equivalent of the fetal position. The bell reabsorbs the tentacles, and then it degenerates further until it becomes a gelatinous blob. Over the course of several days, this blob forms an outer shell. Next it shoots out stolons, which resemble roots.” These stolons grow into new jellyfish.

Turritopsis dohrnii  (Wikipedia)

The description is from Nathaniel Rich’s article in the New York Times Magazine (Dec. 2, 2012). Over two years, one lab colony of such jellyfish rebirthed itself ten times. The jellyfish’s official name is Turritopsis dohrnii; its nickname, the Benjamin Button jellyfish. As different from humans as it may look, our genetic makeups are similar.

The immortal jellyfish is a specialty of Dr. Shin Kubota at Kyota University’s Seto Marine Biological Laboratory. Dr. Kubota spends much of his days feeding, caring for, and observing his wards. His expressed goal is to become young again himself, perhaps even to achieve immortality, or at least to point a way towards a cure for cancer.

We think of dying as a boundary that all living things share, part of the definition of being alive. But death is not so absolute. Clichés such as “you live and then you die” and “life is short” inadvertently call all the more attention to their exceptions. Bacteria, for example, don’t always die; they often divide. An individual bacterium may be destroyed or die from illness, injury, or antibiotics, but usually bacteria divide (or is it multiply?) into identical clones, which in turn will divide again.

And as for life being “short,” Buffalo grass, a prairie plant resistant to extreme weather, sprouts underground stems which in some locations may have been growing for the last 15,000 years. Among individual plants, the Bristlecone Pine named “Methuselah” still grows in California as it approaches its 5000th birthday. And Wikipedia’s lengthy “List of longest-living organisms” is not only long itself but has spawned the likes of “List of oldest dogs.”

I can understand that words for death and dying help people share their fears and grief when one of their group passes away from the circle of the living. And I can understand the simultaneous desire to imagine that that person is not “really dead” but is still alive in another realm. But perhaps we don’t need to reach into a spiritual world for such consolation. We might take to heart the models here on Earth of how living, reproducing, self-healing, and dying vary so widely among species.

 

 

Feeling Old? Envy the Lobster

Death may be difficult to accept, but it is a clear state of affairs: when an organism no longer lives, it has died. Aging, however—wrinkling, weakening, deteriorating and the rest of the assault—seems less self-explanatory. Why does it take place? Do all living things go through it?

lobster (anvilcloud.blogspot.com)

(anvilcloud.blogspot)

Not all species do. The paths that organisms follow after maturity vary enormously. Some plants live for one year only, others come back every season. Bacteria clone themselves and don’t die from age at all but from hostile organisms or conditions in their environment. Seabirds age very slowly; as long as they can fly, they can stay ahead of most predators.  Lobsters don’t age; they can continue to grow and remain fertile for 45 years or more in the wild, dying only when they can no longer molt and grow a larger shell.

How and why the declines of aging are included in the final phases of some species’ lives is complex. Wikipedia’s “Senescence” introduces the range of theories and uncertainties. Here are three insights from the evolutionary perspective that make sense to me.

One is that certain harmful genetic mutations switch on later in life after the end of an organism’s reproductive period. Many cancers in humans do, for example. Because they don’t impact the number or health of the offspring, such genes do no harm to the persistence of the species and so they are unlikely to be lost over the generations. The diseases of the elderly get passed along by the young.

Even more unfortunately, some mechanisms in our bodies boost our health when we’re young and then come back to bite us when we get older. Digesting calcium, for instance, builds strong bones early on but helps clog and stiffen arteries decades later. As long as such a function improves our fitness to make and raise babies, whatever damage it does later on doesn’t matter much in the very long run.

A third way in which selection seems indifferent to the pains of aging is statistical: even if natural selection did reduce the ravages of aging and prolong the fertile period, the population of such organisms would still decline with age as accidents and predators took their inevitable toll. The body invests its resources where they are the most effective for the future, in youth and early reproduction, not in a comfortable old age.

In these ways and others, aging is linked to the importance of reproduction and the dangers of predators and other external forces. For primates, including me, we reproduce early because the big cats—leopards, jaguars, cougars, tigers—stalked us for millions of years in the forests and grass lands. And for most other species as well, the safest bet for continuity is simple: reproduce early. Still, the exceptions are fascinating. Lobsters in their suit of armor run little risk from ancient predators, so they can reproduce throughout their lives without ever aging into genetic irrelevance.

So, armed with such insights, do I experience my weakening muscles, declining sexuality, distracted thinking,  and dulled senses with any less resentment? Yes, a little. Knowing that the decline has its place, even though it’s a melancholy one, in the evolution that brought me to being in the first place is some consolation.