The future of the Amazon may depend on tapir poop

Each pile of dung contains a cornucopia of seeds, perfect for reforesting.

Image source: slowmotiongli/Shutterstock
  • Tapirs produce towering piles of feces full of large-tree seeds other animal can't pass.
  • Stashing tasty fecal morsels for later, dung beetles bury the seeds.
  • Tapirs prefer burned-out areas, making them ideal re-foresters.

The Amazon rainforest has been in trouble for some time. In the last 40 years, more than 18% of Brazil's rainforest, for example, has been decimated by logging, farming, mining, and cattle ranching. That's an area about the size of California. If it isn't deliberate deforestation for commercial purposes, it's fires. Last years's unprecedented rainforest conflagrations, 85% more severe than the previous year's, were absolutely devastating, burning away some 10.123 square kilometers of forest. This year looks worse — in the first four months of 2020 alone, 1,202 square kilometers have been incinerated.

Often poking their way though the charred remains are trunk-nosed lowland tapirs (Tapirus terrestris), and that's a great thing. "Tapirs in Brazil are known as the gardeners of the forests," says ecologist Lucas Paolucci of Amazon Environmental Research Institute in Brazil. They're prodigious defecators whose feces is packed with a remarkable assortment of seeds from the plants they ingest. Paolucci has great hopes for the role that tapirs, along with dung beetles, their partners in grime, can play in reforesting the Amazon. It's something they're already doing on their own.

Tapir poop in a zoo

Image source: Kulmalukko/Wikimedia

The tapir is South America's largest native mammal, looking a bit like a pig with a trunk. It's actually more closely related to a horse or rhinoceros, and is believed to have been around for tens of millions of years.

Paolucci found tapir's massive mounds of dung — "bigger than my head" — hard to miss. Inside each pile is a treasure trove of seeds including those from large, carbon-storing trees that are just too big to pass through the digestive tracts of smaller mammals. This makes them invaluable disseminators of exactly the sort of trees needed to rebuild a forest.

Tapirs seem to prefer the burned-out areas in which they're most needed, too. In 2016, Paolucci joined other researchers in studying the type of areas tapirs like to frequent. In eastern Mato Grasso, they tracked the goings-on in three plots of forest land. Two of these plots had been subjected to controlled burns from 2004 to 2010. One of then was burned every year, while the other was torched every three. The third plot was left unburned as a control.

Patrolling the plots, the researchers recorded the locations of 163 tapir-dung piles, confirming their source with camera-trap recordings of the perpetrators. The tapirs, it turned out, spend much more time in the burned out forest plots than the untouched one. Paolluccis suggests they may prefer the warm sunshine in areas not covered by forest canopy.

When the researchers extracted and counted up the seeds in those piles, an impressive array was cataloged: 129,204 seeds representing 24 plant species. Biodiversity writ in poo.

Distribution

Image source: Jasper_Lensselink_Photography/Shutterstock

Seeing the tapirs' deposits leading to widespread new growth meant that something, or someone, else, had been spreading them out for planting: Dung beetles, of the superfamily Scarabaeoidea. Paolucci conducted an experiment that confirmed that dung beetles break off piles of tapir dung, roll them away, and bury them for later munching. The seeds in their snacks are in effect planted where they can grow.

Early last year, Paolucci retrieved 20 kilograms of tapir poop from the Amazon, breaking it apart into 700-gram clumps. He returned these clumps to the Amazon after stuffing each one with plastic pellets to serve as as dummy seeds. After 24 hours, Paolucci collected the clumps and counted the pellets gone missing, a simple way to calculate the number of new plants the dung beetles had planted that day. He hopes to publish the details of his study next year.

Looking forward

While tapirs and their dung-beetle buddies clearly can help reforest the Amazon, they, like everything else trying to live in the rainforest region, are themselves endangered by the raging forest fires. If they're lost, going with them will be a fantastic means of spreading large-tree seeds through the region.

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Photos: Courtesy of Let Grow
Sponsored by Charles Koch Foundation
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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
Surprising Science
  • 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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Photo Illustration by Joe Raedle/Getty Images
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