Thing we were happiest to learn: Some things take not-aging one step further. A very few organisms are considered biologically immortal. This doesn’t mean they can’t be killed through injury, starvation, etc., but simply that they do not die of old age. Hydras—small freshwater animals about a centimeter long—reach maturity in only five to 10 days, reproduce asexually, and do not seem to age whatsoever. Their stem cells “have a capacity for infinite self-renewal,” and as such, they can regenerate and stay young indefinitely.
One type of jellyfish, Turritopsis dohrnii, replenishes its cells after mating, rendering it biologically immortal, as do planarian flatworms, whether they reproduce sexually or asexually.
Thing we were unhappiest to learn: A few animals have to go through that awkward age more than once. When the Turritopsis dohrnii, or “immortal jellyfish,” reaches sexual maturity, it reverts to larval stage, going back and forth between these two stages indefinitely.
Also noteworthy: Back to biological immortality for a minute. Lobsters are very nearly biologically immortal—they don’t seem to get slower or weaker with age, and may actually become more fertile. But as they age, they molt, growing ever-larger shells. This is an exhausting process, and eventually the expenditure of energy kills the animal.
But how they stay young in the meantime is especially interesting. Scientists believe lobsters produce an enzyme called telomerase, which is present in most embryonic vertebrates, but almost never in adult animals. When cells divide, each strand of DNA splits in two and recombines in the new cell. Every time this happens, the ends of each chromosome—called telomeres—fray. Eventually, this fraying reaches the part of the chromosome that carries genetic information. Essentially, every time a cell divides, the DNA held within is a copy of a copy of a copy, and eventually it becomes unreadable. The result is the body gradually breaking down, in a pattern we call aging.
Except lobsters don’t experience this. It’s theorized that, if we could use telomerase or some other method to stop human telomeres from fraying, we too could become biologically immortal. But rest assured, that probably won’t happen until long after you’ve grown old and died, so you’ve still got that to look forward to.
Best link to elsewhere on Wikipedia: One of earth’s most fascinating creatures is the tardigrade, a tiny and extremely hardy animal that’s able to survive everywhere from Antarctica to the depths of the ocean to volcanic mud. It can also survive 1,000 times more radiation than humans and pressure extremes ranging from 1,200 atmospheres to a vacuum, and is the only known animal to have survived in outer space. While the tardigrade is not considered to have negligible senescence—it tends to have a lifespan of between three months and two years, depending on which species—and age under normal circumstances, it has the rare ability to enter a state of suspended animation. The animals can almost completely dehydrate, and then rehydrate years later, springing back to life.
Further down the Wormhole: While there are animals that don’t age and live for remarkably long times, in the end no one can escape the grasp of death. The Onion’s Man Of The Millennium comes for us all, but sometimes rumors of people’s deaths are greatly exaggerated. We’ll look at a list of premature obituaries next week.
