Dead – yes, dead – tardigrade found beneath Antarctica

A completely unexpected discovery beneath the ice.

(Goldstein Lab/Wkikpedia/Tigerspaws/Big Think)
  • Scientists find remains of a tardigrade and crustaceans in a deep, frozen Antarctic lake.
  • The creatures' origin is unknown, and further study is ongoing.
  • Biology speaks up about Antarctica's history.

So it turns out our favorite real-world superheroes, tardigrades, aren't completely indestructible. But even in death, they continue to amaze. Scientists boring a hole one kilometer beneath the ice deep within a buried Antarctic lake recently got a bit of a shock. They came across the remains of once-living creatures, some ancient crustaceans, and — you guessed it — a water bear. How all of the creatures got there remains unclear.

The discovery was "completely unexpected," micropaleontologist David Harwood tells Nature. The drilling was done under the auspices of the SALSA (Subglacial Antarctic Lakes Scientific Access) project. Glaciologist Slawek Tulaczyk, who's not involved with SALSA, says, "This is really cool. It's definitely surprising."

Welcome to Subglacial Lake Mercer

The scientists were drilling in Subglacial Lake Mercer, a frozen body of water undisturbed for millennia. SALSA's is the first direct sampling of its contents. Prior to the drilling, it had only been examined with ice-penetrating radar and some other indirect detection devices.

Boring details

SALSA drilled down a kilometer into the ice above Lake Mercer using a hot-water drill . At its maximum width, the hole was just 60 centimeters across.

On December 30, the team retrieved a temperature sensor from the frozen lake and noticed some gray-brown mud stuck to the bottom of it. Looking at the mud under a microscope, Harwood saw the glassy remains of photosynthetic diatoms, which he expected, but also a shrimp-like crustacean shell with its legs still intact. And then another, even better-preserved one.

To double-check, the team cleaned off their sensor and sent it down for more mud. This time, more crustacean shells and some other things that looked a bit like worms appeared under the microscope. On January 8, at a National Science Foundation base 900 kilometers away, animal ecologist named Byron Adams had a look. He confirmed the crustaceans, found the tardigrade, and identified the worm-like organisms as being thread-like plants or fungi. He'd seen all three types of creatures previously in the glacier-free Dry Valleys of Antarctica, as well as in the Transantarctic Mountains.

Where the organisms were found, but why?

The animals could have come from other places, such as the ocean. Between five and ten thousand years ago, the Antarctic ice sheet became thinner for a while, and this could have allowed seawater to make its way beneath floating ice, carrying organisms along with it that eventually became trapped beneath the ice sheet when it returned to its normal thickness.

The water sampled from Lake Mercer has enough oxygen to sustain life, and is packed with bacteria, over 10,000 cells per millimeter. Harwood wonders if larger animals could have survived feeding on them, though the majority of biologists don't think it's likely to have been a substantial enough food source.

Adams suspects the creatures actually lived in the Transantarctic Mountains and were then transported after dying down to Lake Mercer. He says they seem too recent to have been neighbors of the millions-of-years-old diatoms. "What was sort of stunning about the stuff from Lake Mercer," Adams tells Nature, "is it's not super, super-old. They've not been dead that long." The eight-legged tardigrade from Lake Mercer resembles those found in damp soil, reinforcing Adam's conclusion.

Back to the lab

The next steps for these intriguing remains is an attempt at determine their age using radiocarbon dating. In addition, researchers will try and sequence DNA scraps from them to learn if they're of marine or freshwater species. Finally, scientists will perform chemical analyses of carbon the remains contain to see if a determination can be made as to whether the animals spent their days in sunlight or in the dark, far beneath the Antarctic.

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The surprise reason sleep-deprivation kills lies in the gut

New research establishes an unexpected connection.

Reactive oxygen species (ROS) accumulate in the gut of sleep-deprived fruit flies, one (left), seven (center) and ten (right) days without sleep.

Image source: Vaccaro et al, 2020/Harvard Medical School
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  • A study provides further confirmation that a prolonged lack of sleep can result in early mortality.
  • Surprisingly, the direct cause seems to be a buildup of Reactive Oxygen Species in the gut produced by sleeplessness.
  • When the buildup is neutralized, a normal lifespan is restored.

We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

An unexpected culprit

The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

"We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

"Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

fly with thought bubble that says "What? I'm awake!"

Image source: Tomasz Klejdysz/Shutterstock/Big Think

The experiments

The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

"We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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