Six Pack of Facts

Long Lifespans & The Mayfly

• Alex Skjong • Episode 27

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Intro:

Hello everyone and welcome to Six Pack of Facts, the weekly way of expanding your brain six refreshing facts at a time. My name is Alex and this week, we’re taking a look at the long game and the short game and I’m not talking about football. It’s time to break down three amazing organisms with long lifespans and one amazing (ly disgusting) organism with a short one.

Topic One:

One: 

When it comes to ocean predators, some sharks comfortably sit atop the food chain as ferocious hunters. But not all sharks are swift killers. 

Greenland sharks can reach lengths of more than 20 feet which sounds imposing… until you realize they grow and move very, very slowly. The shark grows about 1 centimeter each year and swims along at a leisurely pace of around 1.8 miles per hour. Not exactly prime hunter material. But what Greenland sharks lack in speed, they more than make up for in longevity. 

While the age of other sharks can be measured by counting growth bands on fins and spines, Greenland sharks don’t have either. They don’t have any hard tissue whatsoever, actually, which makes them very tricky to age definitively. But a recent study of a captive Greenland shark using carbon dating estimated the arctic beast to be between 272 and 512 years old. Even at the low end of 272, it still makes the Greenland shark the longest living vertebrate on the planet. 

Two: 

Counting growth bands on fins and spines sounds an awful lot like counting the rings of a tree, but if you were to take on that task for our next subject, you’d be counting for a long time. Thankfully, someone already did that work for us.

In the White Mountains of southeastern California resides the oldest living organism on planet — a bristlecone pine. According to an intrepid ecologist who actually counted the rings, Methuselah (as the tree is called) is 4,841 years old. That means the tree sprouted two thousand years before the rise of Rome and just a few hundred years before the Egyptians constructed the Great Pyramid of Giza. 

Thanks to Methuselah’s cold environment, it and the rest of the bristlecone pines grow at an exceptionally slow rate. The temperatures also help make bristlecone wood dense and resistant to disease. 

It’s possible Methuselah has an even older bristlecone friend out there, but we might not ever know about it. When the trees get that old, they can lose their bark, allowing the environment to weather away growth rings and making accurate ages impossible to determine. 

Three: 

Aging to nearly 5,000 years is definitely impressive. But what’s 5,000 when immortality is one your side? Just ask Turritopsis dohrnii AKA the immortal jellyfish. 

Now, the immortal jellyfish is not really immortal. They die all the time, in fact. But, when faced with starvation, physical damage, or another danger that brings the lil jelly to the brink of death, it does something incredible — it de-ages.  

That’s right — Turritopsis dohrnii transforms into a bloblike cyst that develops into a polyp colony — pretty much the first stage of its life. Then, through asexual reproduction, the jellyfish is reborn! The polyp colony can spawn hundreds of genetically identical jellyfish to its original form. During the full process, the creature’s cells are often completely reassigned — muscle cells into nerve cells, nerve cells into sperm and egg cells… all different. 

Because this amazing property involves cells essentially turning off certain genes and switching on other genes, scientists are examining the potential of unlocking something similar in humans. It wouldn’t make us immortal (…probably), but it could lead to breakthroughs in certain treatments against cancers. 

Segue:

Those three examples show organisms that reach ages humans can only dream of, but not all things are so lucky, of course. When it comes to short lifespans, one insect reigns supreme. The mayfly.  

Topic Two

One:

Mayflies are the oldest living group of winged insects, dating back to about 300 million years ago, and they are the only insect group to have two winged adult stages. But their anatomy isn’t their most noteworthy trait. 

To explore the mayfly, we’ll first cover the initial stage of a its life ­— the nymph. These tiny creatures actually betray the notion of a short lifespan a bit. Mayfly nymphs live in riverbeds and, over the course of about two years, feed on organic material while molting more than 20 times, growing larger with each shed. Once they’re ready to enter the skies, a final nymph molt occurs. 

Two:

When a nymph molts for the last time, it enters the second phase of its life known as a dun. A dun isn’t a fully formed adult mayfly. Duller in color and sexually immature, the duns can’t fly very well and basically only exist to molt for a final time to reach adulthood. The second phase of life typically lasts one or two days, but some species only exist as a dun for minutes. The dun molts one last time and enters the final, fleeting stage of its life.  

Three:

When mayflies reach adulthood, they don’t do it alone. Massive swarms of mayflies ascend into the sky at once — possibly an evolutionary survival method to prevent predators from gobbling them all up before reproduction — and search for a mate. We’re talking billions of insects at once here. Satellites have mistaken mayfly swarms for rainstorms before.

The lifespan of an adult mayfly depends on the species (with one species living no more than five minutes), but they typically last around 24 hours. During that time, the only thing they’re programmed to do is mate. Once they’ve done that, the females fly a bit upstream to find calmer waters and then deposit between 400 and 3,000 eggs. These sink the bottom of the riverbed where the nymphs hatch and, as the clock ticks out for the adult mayflies just hours after reaching maturity, the entire cycle repeats.

Outro:

From thousands of years to just minutes, the world is made up of organisms that stretch across all timespans. I hope you live longer than a mayfly (much, much longer) and until the next Six Pack of Facts, as always, stay thirsty.