Katherine J. Wu is a Digital Editor at NOVA and Story Collider producer. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University. Previously, she served as a AAAS Mass Media Fellow at Smithsonian magazine.

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This 100-million-year-old lizard represents a never-before-seen species that lived during the mid-Cretaceous. It measures a whopping 1.5 inches from snout to tail and probably weighed about as much as a kernel of popped corn. Photo Credit: Joseph Martinez, Museum of Comparative Zoology, Harvard University

This 100-Million-Year-Old Lizard Was the Size of A Paper Clip

Clocking in at about 0.0053 ounces—boasting all the weight of a hefty kernel of popped corn—it likely spent its days underfoot of gargantuan dinosaurs, wriggling through the leaf litter of muggy mid-Cretaceous forests. Measuring less than two inches from snout to tail, it never lived particularly large—but its death would be immortalized for 100 million years to come.Yesterday, in the journal Breviora, researchers <a href="http://www.bioone.org/doi/full/10.3099/MCZ49.1">reported</a> the discovery of a never-before-seen lizard species entombed in Burmese amber. This rare fossil represents one of the smallest and most complete Cretaceous lizards ever found. Despite its diminutive stature, the finding speaks volumes about the diversity contained within prehistoric jungles.
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“The Early Cretaceous seems to be a time when lizards really diversified,” says <a href="https://www.ucl.ac.uk/biosciences/departments/cdb/people/susan-evans/lab">Susan Evans</a>, a paleontologist who studies the evolution of amphibians and reptiles at University College London and did not participate in the new research. The finding, she explains, “adds a piece to the puzzle: It is the first example we have of a long-bodied, but fully-limbed, terrestrial lizard.”Dubbed Barlochersaurus winhtini, the new lizard has been tentatively sorted into a group of lizards called Anguimorpha, which originates at least as far back as the <a href="http://www.bioone.org/doi/abs/10.3374/014.053.0101">Late Jurassic</a> (some 150 million years ago), but includes contemporaries like Komodo dragons and Gila monsters. If truly an ancestor in this lineage, B. winhtini would be the smallest known anguimorph, alive or dead.A hundred million years ago, long before the invention of camcorders, fossilization begat the only remaining commemorations of the immense diversity that once decorated the mid-Cretaceous Earth. But small, fragile bones don’t tend to survive the test of time in rock-based records, leaving gaps in researchers’ knowledge of the most pint-sized reptiles from this period.
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<figcaption>Barlochersaurus winhtini may be smallest anguimorph ever recorded. This lizard lineage dates back to at least the Late Jurassic, around 150 million years ago. Photo Credit: Joseph Martinez, Museum of Comparative Zoology, Harvard University
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<a href="https://www.pbs.org/wgbh/nova/jewel/">Amber</a>, on the other hand, preserves life’s littlest forms far better than rock. And as it hardens around whatever it engulfs, this plant-based resin remains translucent: Through the years, tree-hugging insects, plants, microbes and more have been frozen in amber’s warm, hazy glow. Bigger-bodied creatures can’t usually be contained by the ooze (though amber has certainly trapped parts of big animals, often resulting in inadvertently amputated limbs).B. winhtini lies between these two extremes of encapsulation. “You tend to get small, soft-bodied, terrestrial organisms in amber,” explains <a href="http://victoriaemccoy.com/">Victoria McCoy</a>, a paleobiologist at the University of Bonn who studies fossil preservation in amber, but was not involved in the new find. But bony lizards, she adds, don’t often fossilize—meaning understanding these old lineages is the paleontological equivalent of fishing a needle out of a haystack of giants.
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When lead author <a href="http://www.shsu.edu/academics/biological-sciences/people/daza.html">Juan Daza</a>, a lizard morphologist at Sam Houston State University, first came across the resin-suspended corpse after a private collector loaned it to Harvard University’s Museum of Comparative Zoology, he knew it was an unmissable opportunity. The fossil was first discovered in the rich tropics of Myanmar, the source of amber deposits unearthed in the past several years that have already yielded an astounding array of ancient <a href="https://www.nature.com/articles/s41598-018-26848-w">frogs</a>, <a href="https://www.nature.com/articles/s41467-017-01550-z">insects</a>, and even a<a href="https://www.pbs.org/wgbh/nova/article/scientists-find-feathered-dino-tail-inside-99-million-year-old-amber/"> feathered dinosaur tail</a> in the past several years.“It was so intriguing,” Daza says of the new lizard fossil. “The amber is translucent, but there’s a lot of distortion, like looking into a glass bottle.”Daza and his team used CT scanning, a non-destructive method for probing the interior of the lizard’s amber mausoleum, to discern the lizard’s visible features. Its slinky shape and skeletal structure indicate that it was probably an anguimorph—but not everything about B. winhtini falls neatly in line with its modern relatives, making it difficult to determine exactly where it belongs in the ancient tree of lizard life. For now, the lizard is the sole ambassador of its genus and species.
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<figcaption>A photo of a 3D-printed replica of Barlochersaurus winhtini. The original fossil will reside in a private collection in Switzerland, but its replicas, blown up to ten times the original size, will be on display in two museums in Florida and Massachusetts. Photo Credit: Kristen Grace, Florida Museum of Natural History
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“The new specimen brings us important information [about] the diversity of lizards in the late Cretaceous in Myanmar,” explains <a href="http://www.xinglida.net/">Lida Xing</a>, a paleontologist at the China University of Geosciences in Beijing who did not participate in the new research. “This means that the evolution of lizards is more complicated than we might think.”And although the researchers could see straight through the amber shell, the fossil turned out to be murkier than its capsule. Over time, sediment from the exterior had penetrated the little lizard’s body, mixing with its muscles and organs. This process, called permineralization, reduced the contrast between bone and soft tissue, blurring the boundaries of its skeleton.But the exquisite preservation of the lizard’s exterior still yielded some key insights. Curiously, its legs were extremely tiny—even for its size. B. winhtini somewhat resembles a snake with gangly, misplaced hands awkwardly lashed to its sides. But Daza thinks this odd physique may have actually served the lizard in navigating the dense forest floor of Myanmar.
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“If you’re going to be small, you need a well-built body—otherwise you’ll be too fragile to survive these environments,” Daza explains. “If you live in the leaf litter, it’s a great locomotion strategy to stop using your legs”—which, if anything, might slow you down. In fact, B. winhtini’s slippery slide might have helped it better evade predators.B. winhtini stopped short of shedding its legs entirely, though: “They’re not running away all the time,” Daza explains. “They can use their limbs to stabilize their bodies… if they’re resting, foraging, [or] eating insects.”Despite its puny limbs, the amber anguimorph boasted quite the tail. Though a couple chunks of it have been lost to time, Daza believes this appendage made up half the lizard’s total length of 1.5 inches, acting as a rudder as B. winhtini undulated through fallen foliage.More intensive imaging methods might have yielded more information about the lizard’s mysterious heritage, but such techniques can often be destructive to the quality of amber. Because it’s currently a one-of-a-kind find, B. winhtini is too precious to pick at—so its full story remains shrouded in mystery.
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The combination of resin-secreting trees and the rich, nurturing environment of the tropics have made Myanmar a goldmine—or ambermine—for the study of ancient life. To entirely entomb even the teeniest of tropical lizards, Cretaceous trees were probably belching up a lot of soft, sticky amber, explains McCoy. With so much free-flowing resin, this little lizard may yet find a friend.“I think there’s definitely a chance we’ll find more specimens,” McCoy says.Though don’t expect clones of this mini-lizard to be walking the earth anytime soon: Contrary to what Jurassic Park might have you believe, <a href="https://www.pbs.org/wgbh/nova/video/jurassic-worlds-wrong-about-dna">DNA is far too fragile</a> to <a href="https://www.livescience.com/23861-fossil-dna-half-life.html">survive 100 million years</a>—even in the most perfectly preserved of amber prisons.Endnote: The original fossil will reside in Switzerland in a private collection. However, Daza and his team 3D-printed replicas, blown up to 10 times the specimen’s original size. The replicas will be publicly accessible at Florida’s Museum of Natural History and Harvard’s Museum of Comparative Zoology.

It may not have lived large, but in death, this never-before-seen Cretaceous reptile survived many millennia immortalized in amber.

Women planting in a rice paddy in the Kancheepuram district of Tamil Nadu, India. Photo Credit: McKay Savage, Wikimedia Commons

The Planet’s Getting Warmer. Can Plants Take the Heat?

As the planet’s thermostat <a href="https://www.smithsonianmag.com/smart-news/world-was-just-issued-12-year-ultimatum-climate-change-180970489/?no-cache">ticks steadily upwards</a>, life forms around the world may be in grave danger—and plants like rice are no exception. Already, global rice yields have <a href="http://www.pnas.org/content/114/35/9326">taken a hit</a> from rising temperatures. If the upward creep in heat continues, declines in this starchy staple could imperil the 3.5 billion people around the world who rely on rice for over 20% of their daily caloric intake.Today, in the journal PNAS, researchers <a href="http://www.pnas.org/lookup/doi/10.1073/pnas.1807988115">report</a> that rice plants are sensitive to the damaging effects of high heat even in the short term. Brief exposures to sweltering temperatures unraveled plant cells’ messenger RNA—a critical molecular envoy that ferries the instructions contained within DNA to the cell’s protein-producing factories—cuing the messages up for destruction. Though the rice eventually recovered, the new finding underscores just how sensitive plants may be to the hazards of a fast-warming world.
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With each degree-Celsius increase in average global temperature, rice crop yields fall by <a href="http://www.pnas.org/content/114/35/9326">about 3%</a>. And as the planet warms and <a href="http://www.un.org/en/development/desa/news/population/2015-report.html">the human population expands</a>, the gap between supply and demand for this staple crop continues to widen. But while these trends are clear at a macroscopic level, the inner workings of plant cells coping with toasty temperatures remain far less clear.To better understand heat tolerance in crops, a team of scientists led by <a href="http://www.personal.psu.edu/sma3/people.html">Zhao Su</a>, a plant biologist at Pennsylvania State University, heated cuttings of young rice shoots (Oryza sativa) to a temperature of 42º Celsius (nearly 108º Fahrenheit) for 10 minutes. Though temporary, the mini heat wave constituted a rapid 20º-Celsius shift upwards from room temperature—an escalation that’s “more than a human could ever withstand,” explains study author <a href="http://chem.psu.edu/directory/pcb5">Philip Bevilacqua</a>, an RNA chemist also at Pennsylvania State University.When the researchers analyzed the shoots’ cellular contents, they found that the temporary trauma had compromised the rice’s ability to relay genetic information through their messenger RNA, or mRNA.
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<figcaption>With every degree-Celsius increase in temperature, rice crop yields drop by over 3%. Photo Credit: Pixnio
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Plants, like humans, store their genetic information in the form of DNA. Contained within this molecular manuscript are all the necessary instructions for growth and survival—including all the cell’s contingency plans for emergencies or unanticipated changes in the surrounding environments. The DNA manual is extremely comprehensive, so cells access excerpts from it on an as-needed basis, making short-lived photocopies of the original text in the form of mRNA. Without mRNA, cells can’t receive the intel necessary to manufacture the building blocks necessary for life.But for such a critical piece of the cellular puzzle, mRNA is frustratingly fickle. Unlike DNA, which is stored in two strands that lock into each other like the halves of a zipper, the synthesis of mRNA creates an unwieldy single-stranded molecule. These open-faced strands can loop around and bind to themselves in a semblance of secure structure, but this makeshift jumble is inherently far less durable than that of double-stranded DNA.Because of mRNA’s infamous instability, the scientists reasoned it might be particularly susceptible to suffering at high temperatures. When they dosed the rice cells with a chemical marker that tags single-stranded mRNA molecules, Su and his colleagues discovered that heated plants contained higher proportions of unfurled mRNA compared to shoots lounging at room temperature. The head and tail ends of many mRNA strands appeared particularly fragile, accruing more of the incriminating chemical tags. In the heat of the moment, it seemed, these cellular messengers were melting.
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When the researchers probed the plants further, they discovered that several of the mRNAs slumping into single strands were being chewed up by a destructive machine called the exosome. The looser the mRNA, the more likely it was to be ghosted out of existence—implying that mRNA unfolding made the messages <a href="http://rstb.royalsocietypublishing.org/content/373/1762/20180160">more prone to annihilation</a>. As the rice shoots attempted to weather the warmth, their exosomes were disposing of cells’ hottest messes, along with the genetic information they carried.Luckily, the short spikes in temperature didn’t appear to put any of the rice plants permanently out of commission. Because the cells’ DNA remained intact, new mRNAs were eventually copied and redistributed as the rice recovered from the sizzling onslaught. But it took about 10 hours for the shoots’ mRNAs to fully reset—quite the price to pay for a 10-minute hot flash.Over a thousand mRNA transcripts, all carrying instructions from different genes, became more or less abundant after the rise in temperature. Some of them even appeared to code for proteins that control how certain stretches of DNA are photocopied into mRNA—which means the effects of heat stress could be even more widespread than they already appear.
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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/rice-1736909.width-990_8ekXdkD.jpg"/>
<figcaption>When subjected to just 10 minutes at a high temperature, messenger RNA in rice plants becomes unstable and is degraded by a molecular cleanup crew. Photo Credit: einszweifrei, Pixabay
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Until the researchers learn more, it’s unclear what exactly these molecular fluxes signify, explains <a href="https://www.danforthcenter.org/scientists-research/principal-investigators/ru-zhang">Ru Zhang</a>, a plant biologist at the Donald Danforth Plant Science Center who was not involved in the study. They could be adaptive, allowing the rice to acclimate to the warmth. Or they could be indicative of just how vulnerable plants’ internal infrastructure is to temperature changes of this magnitude. Either way, resources were likely being diverted away from normal growth.“The paper is an elegant piece of science,” says <a href="https://agronomy.unl.edu/cassman">Kenneth Cassman</a>, an expert in food security and agriculture at the University of Nebraska, Lincoln who did not participate in the new research. “It’s a significant advance in helping us understand how short term exposure to heat affects rice… and how a plant grows and yields.”However, 10 minutes under high heat in a laboratory environment isn’t the same as chronic exposure to, say, the gradual onset of global warming. According to Cassman, there may not be a ton of overlap in the processes that govern plants’ responses to long-term changes in temperature and to short exposures like the one in this study—but there are still several key instances in which the new findings may translate directly.
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For one, the changes associated with climate change affect <a href="http://science.sciencemag.org/content/305/5686/994">both averages and extremes</a> in temperature, so daily spikes in heat could involve a 108º-Fahrenheit stint in the sun. Additionally, crops like rice and maize that are grown in high densities often experience temporary spikes in sun exposure when winds disrupt the foliage, says study author <a href="http://bio.psu.edu/directory/sma3">Sarah Assmann</a>, a plant biologist at Pennsylvania State University. Given the vast changes that occurred in the rice plants after just a few minutes of heat, even the ephemeral passing of a cloud overhead could disrupt some of these cells’ internal functions.Additionally, the researchers’ findings will likely translate over to other vital crops, Cassman says. Ironically, he points out, because most (<a href="http://ricepedia.org/rice-as-a-crop/where-is-rice-grown">but not all</a>) rice is grown in standing water, it’s actually one of the few crops that are a bit buffered against rising temperatures. But much of the plant, including its shoots, is warmed by direct sunlight, and rice yields have still been <a href="http://www.pnas.org/content/114/35/9326">curbed</a> by <a href="http://www.pnas.org/content/101/27/9971">global warming</a>. This could prove even more ominous for the vast majority of cultivated plants that don't enjoy such liquid luxury, and remain especially vulnerable to surges of heat on dry land.Moving forward, Su, Bevilacqua, and Assmann hope to repeat their work in other strains of rice—including cultivars that have proven <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4052674/">hardy</a> in climes that tend to pack the heat. Comparing the responses of these different varieties to changes in temperature, along with the current findings, may help researchers target certain regions of plant genomes for manipulation in the future, Assmann explains, informing the production of more heat- and drought-resistant crops.
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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/Corncobs.width-990_D3amqUP.jpg"/>
<figcaption>Maize is another staple crop that will continue to suffer from rising temperatures. The molecular changes that occur in rice plants are likely to translate over to other plants. Photo Credit: Sam Fentress, Wikimedia Commons
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One possible intervention may already be apparent. It’s the sloppiest mRNAs (that is, those with particularly frayed heads and tails) that are especially susceptible to destruction, Bevilacqua explains. So genetic modifications that secure these ends—the molecular equivalent of clipping an aglet onto the end of a frazzled shoelace—might just increase their longevity.Even with exquisite knowledge of the coping mechanisms of plants in peril, however, there’s no guarantee a magic bullet will unveil itself, Cassman says. Plants have spent millennia adapting to heat, and researchers may not get much bang for their buck by trying to optimize their resilience further. If that’s the case, the ceiling on genetically engineering heat-resistant plants could be far lower than expected.But tinkering with the genes of crops is far from the only option, Bevilacqua says. “You can only go so far [with genetic engineering],” he adds. “Yes, it’s possible for us to intervene and help with plant production and response to these stresses as they increase. The bigger answer is to have policies to address and try to reverse climate change.”

Brief exposures to high temperatures compromise rice plants’ ability to relay genetic information.

Adult African clawed frogs (Xenopus laevis) usually develop spike-like structures at sites of limb amputation. But researchers can now equip these frogs with bioreactors that help them partially regenerate their hind legs. Photo Credit: TimVickers, Wikimedia Commons

A Progesterone-Pumping Device Helps Frogs Regenerate Lost Limbs

Somewhere along our evolutionary trajectory, we humans lost our regenerative powers. Sure, we can manage <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701258/">a hunk of liver here</a>, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5454966/">the tip of a finger there</a>—but in contrast to the <a href="https://www.pbs.org/wgbh/nova/article/saving-axolotls/">salamanders</a>, flatworms, and <a href="https://www.popularmechanics.com/science/animals/a27571/starfish-disease-science/">sea stars</a> of the world, the spontaneous remaking of entire organs and limbs eludes humankind.For biologist <a href="http://ase.tufts.edu/biology/labs/levin/">Michael Levin</a> of Tufts University, however, “lost” isn’t the same as “nonexistent.”Only a few million years separate humans from our closest regenerating relatives. If our animal ancestors built bone and tissue from scratch throughout adulthood, these superpowers may still lie buried within our own tissues, waiting to be reawakened. All it would take, says Levin, is the right signal.Now, Levin and his colleagues may have taken the next steps in pinpointing that very trigger by reviving these clandestine capabilities in African clawed frogs. Their work, <a href="https://www.cell.com/cell-reports/fulltext/S2211-1247(18)31573-0">published today</a> in the journal Cell Reports, kick-started the growth of partial but high-functioning hind legs in amphibian amputees after 24 hours of hormonal treatment. Though the work is still preliminary, such findings may someday inform researchers on the path to finding—and flipping—a similar switch in humans.
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Cut the tail off a tadpole, and <a href="https://www.nationalgeographic.com/science/phenomena/2013/01/13/tadpole-heal-thyself-vilified-chemicals-spur-regeneration/">another will take its place</a>. But even in the amphibian world, there are sobering consequences to growing up: If a mature frog loses a leg, the best it can hope for is a frail cartilaginous spike to take its place. This ability is technically regenerative—certainly far more than what any human could accomplish—but the resulting appendage does little for a creature that relies heavily on its hind limbs to navigate its aquatic environment.As the frog ages, its regenerative skills seem to go into hibernation—making it “a good stepping stone between animals that [fully] regenerate, like salamanders, and animals that don’t, like mammals,” Levin explains.To rouse regeneration from its slumber, the researchers first needed to identify the right molecular alarm. The ideal candidate, they reasoned, would be a powerful chemical cue that is both naturally produced by animal bodies and capable of directing a vast array of cellular functions—a winning combination that, for the researchers, pointed to progesterone.
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Every month, as a natural part of the female menstrual cycle, progesterone regenerates the entire endometrium, or lining of the uterus. “We thought, ‘It’s impossible that progesterone is only acting at this level,’” explains lead author <a href="http://sites.tufts.edu/celiaherrerarincon/">Celia Herrera-Rincon</a>, a neuroscientist at Tufts University.Progesterone wields far more power than simply preparing the uterus for pregnancy. Receptors for this hormone exist all over the bodies of both male and female mammals, and in the past several decades, researchers have shown it to be a potent catalyst for wound healing, promoting <a href="https://docplayer.net/74761056-Role-of-progesterone-in-peripheral-nerve-repair.html">nerve repair</a>, <a href="https://www.cell.com/developmental-cell/fulltext/S1534-5807(01)00064-8?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1534580701000648%3Fshowall%3Dtrue">bone remodeling</a>, and <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1524-475X.2008.00440.x">blood vessel formation</a>. If applied in the right place at the right time, progesterone could very well coax an injured limb onto a regenerative cascade.“Progesterone is very useful and safe,” explains <a href="https://www.popcouncil.org/research/expert/regine-sitruk-ware">Régine Sitruk-Ware</a>, a reproductive endocrinologist at the Population Council’s Center for Biomedical Research who did not participate in the new research. “It’s helpful for the uterus, but in many other layers of the body—in vessels, in bone, in the brain, and in the [nervous system] in general—progesterone has a positive, regenerative aspect.”
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To harness the power of progesterone, the researchers designed a silicon apparatus filled with a hydrating gel and stitched it onto <a href="https://www.sciencedaily.com/releases/2016/10/161019155533.htm">African clawed frogs</a> (Xenopus laevis) whose right hind legs had been amputated three hours prior. Some of the devices also contained a dose of progesterone, which was steadily fed to the wound site for 24 hours. When the day was up, the team carefully detached the device—and waited.Within a matter of weeks, the progesterone-treated frogs had a serious leg up on their peers. In the absence of the hormone, frog amputees produced the typical featureless rods, regardless of whether or not they’d been fitted with the apparatus. But the frogs hit with progesterone began to sprout bigger, more structured appendages. And nearly ten months out from the initial spark of progesterone, partial, paddle-like limbs had pushed their way out of the wound site.When the researchers inspected the burgeoning limbs more closely, they found that, unlike the simple, cartilaginous spikes of typical amputees, they seemed to have the form and patterning of true legs. The limbs were thick and full of new blood vessels, nerves, and bone, and were forming what looked like tentative knees: the beginnings of actual joints. These frogs’ legs weren’t just regenerating more than their untreated counterparts—they were regenerating better. It’s a phenomenon that regenerative biologist <a href="http://firm.uni-frankfurt.de/john-barker">John Barker</a> of the Frankfurt Initiative for Regenerative Medicine praises as “smart proliferation”: the ability to form order out of the chaos of growing, dividing cells.
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<figcaption>Amputation of adult frogs' hind limbs usually results in the formation of a cartilaginous "spike" (left). But attaching a device that feeds progesterone to the amputation site for just 24 hours stimulates the growth of a paddle-like structure (right). The dashed line indicates the plane of amputation. Photo Credit: Celia Herrera-Rincon, Tufts University
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“It was amazing that we were creating structures with only 24 hours of treatment,” Herrera-Rincon says. “I remember showing Mike [Levin] and being fascinated.”When the frogs got the chance to stretch their legs, the untreated, spike-toting regenerates proved to be feeble swimmers and spent more time loitering in place. Meanwhile, the animals that had worn the progesterone-dosing device glided merrily by, almost indistinguishable from their unamputated kin.Though the legs could function, the regeneration was far from complete. While the limb that appeared had clear features, the growth stopped abruptly before the frog’s hind digits would otherwise appear. And, importantly, not all the treated frogs responded to the same extent, indicating that the approach is unlikely to be a one-size-fits-all treatment. But for a first pass, Levin says, the amount of regeneration achieved was “really striking.”“If the person grew a limb like the frogs did, no one would say it was perfect,” says <a href="https://www.whitedlab.com/">Jessica Whited</a>, a regenerative biologist at Harvard University’s Brigham Regenerative Medicine Center who frequently collaborates with Levin’s lab, but was not involved in the newest finding. “But it’s important to demonstrate something that would be better than what grows naturally.”
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Levin and his team are currently tinkering with their cocktail of apparatus-administered drugs, as well as with the duration for which the device is worn after amputation. With just a few additions and adjustments, he says, the preliminary results are already looking good.“To rebuild any structure, you need to give the cells some signal about what they’re rebuilding,” Levin explains. “And progesterone [alone] gives an incomplete message.”The rest of this message, Whited adds, will involve a lot of fine-tuning. When limbs grow (and regrow) naturally, they rely on a suite of complex anatomical signals that both drive the production of new tissue and bone and tell it when and where to stop. But the domino effect likely still applies: The key will be finding the right recipe of chemicals to jumpstart the process, then sit back and let nature take its course.
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<figcaption>Deer antlers are mammalian appendages capable of repeated rounds of regeneration. Male deer (and female reindeer) shed and sprout their antlers anew each year. Credit: USFWS Mountain-Prairie, flickr
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“This isn’t ready for human trials… but it’s also not science fiction,” Levin says of the device. “I don’t think humans are barred from regeneration in any fundamental way.”We’re not exactly a hop, skip, and a jump away from regenerating limbs in people—even partial ones. Though frogs and humans share quite a few genes and basic anatomical structures, Barker explains, we’re still fundamentally very different creatures. But, even if the packaging varies from species to species, the basic toolkit of regeneration might translate across even fairly far-flung species. There are even <a href="/wgbh/nova/video/extreme-animal-weapons/">mammals that naturally regenerate</a>: Deer regularly <a href="https://www.sciencedirect.com/science/article/pii/S135727251400226X">regrow their antlers</a> well into adulthood—a process that, not-so-coincidentally, is also driven by sex hormones.Even as technology advances, it’s unclear if humans will ever regenerate as slickly as salamanders. But maybe these able-bodied amphibians are inching us just a bit closer: One small leap for a frog may someday mean one giant step for humankind.

Twenty-four hours of the hormone progesterone can kickstart over nine months of limb regeneration in amphibian amputees.

Engineers Shanhui Fan (left) and Zhen Chen (right) with their dual-action device, which simultaneously harvests solar energy and cools surfaces without the need for electricity. Photo Credit: Linda Cicero, Stanford News

The Forecast on Energy-Efficient Cooling Just Got a Bit Sunnier

As autumn gives way to winter in the northern hemisphere, it’s sometimes easy to forget that the planet is getting hotter. Air conditioners and electric fans account for <a href="https://www.iea.org/newsroom/news/2018/may/air-conditioning-use-emerges-as-one-of-the-key-drivers-of-global-electricity-dema.html">about 10 percent of global electricity consumption today</a>—and as average global temperatures continue to rise, the world’s reliance on air conditioners will likely more than triple by 2050.This has created a bit of a vicious cycle. Homes in the United States alone expel <a href="https://www.energy.gov/energysaver/home-cooling-systems/air-conditioning">over 100 million tons of carbon dioxide</a> into the atmosphere each year from AC alone, nudging temps further upwards—and prompting people around the world to seek even more solace in temperature-controlled buildings.But researchers are now developing tools that allow us to boot unwanted heat into outer space without using any of the power air conditioning requires. Today, in the journal Joule, a team from Stanford University takes the innovation <a href="https://www.cell.com/joule/fulltext/S2542-4351(18)30471-9">one step further</a> with a device that could not only keep us cool in the absence of air conditioning, but also simultaneously harness <a href="https://www.pbs.org/wgbh/nova/tech/how-solar-cell-works.html">solar power</a> to meet energy demands elsewhere in the grid.
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The cooling half of this new technology, pioneered by electrical engineer <a href="https://web.stanford.edu/group/fan/">Shanhui Fan</a> of Stanford University, takes advantage of the natural ability of all objects and organisms to emanate heat through radiation. Unlike conduction and convection—the other methods through which <a href="https://mass.pbslearningmedia.org/resource/lsps07-sci-phys-thermalenergy/thermal-energy-transfer/">thermal energy is transferred</a>—radiation doesn’t require direct contact or the movement of fluids to move heat from place to place: It simply emanates from all matter that’s at a temperature above absolute zero (or -459.67 degrees Fahrenheit… so, for all intents and purposes, let’s call it “all matter”). For example, radiation is responsible for the heat you feel wafting out from a toasty oven even when its door is shut.Through radiation, heat can be jettisoned spaceward—and if it clears the hurdle of the atmosphere, then it’s past the point of no return: Outer space is pretty much a vast, insatiable heat sink. Unfortunately, though, outbound radiation of most wavelengths doesn’t always make it that far. Some of it ricochets off water molecules in the atmosphere and boomerangs right back to Earth; another portion in the is absorbed and retained in the atmosphere by carbon dioxide and other greenhouse gases.But not all materials emit radiation at the same wavelength. If a surface emits radiation with a wavelength between eight and 13 micrometers, it hits a sweet spot that bypasses many of these atmospheric hurdles. By slipping through this mid-infrared “window,” heat can finally enter cold, cold space—allowing the radiating object to dip below the temperature of the surrounding air. Voilà: cooling achievement unlocked.
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Fan and his colleagues first exploited this window and its associated chill factor in 2014, with the design of a so-called radiative cooler. Because the device was engineered with silicon compounds and other materials that emit in the mid-infrared range, it was able to remain <a href="https://www.nature.com/articles/nature13883?foxtrotcallback=true">around 5 degrees Celsius (or 9 degrees Fahrenheit) below</a> ambient air temperatures while atop the roof of a building in sunny California. Two years later, Fan’s lab published a follow-up that used a similar setup to <a href="https://www.nature.com/articles/nenergy2017143">cool flowing water</a>—a breakthrough that, if scaled up appropriately, could reduce the reliance of air conditioning and refrigeration on electricity.For Fan, outer space is the ultimate untapped well of renewable energy. One of the most exciting potential applications of this technology involves speckling the world’s rooftops with radiative coolers. Unfortunately, this move could ruffle the feathers of those attempting to do the same with solar absorbers and solar cells, which typically colonize that same space to harvest energy from the Sun.At first glance, the two strategies seem incompatible: one hungers for heat, while the other is keen on keeping cool: Placing conventional radiative coolers and solar panels side-by-side could even reduce the efficiency of both processes. But as humankind struggles to curb carbon emissions, it’s pretty clear we need all the help we can get. Together with lead author <a href="https://sites.google.com/site/zchen0203/">Zhen Chen</a>, a mechanical engineer at the Southeast University of China, Fan assembled a team of researchers to engineer a peaceful coexistence between the two technologies.
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“The solar energy that’s coming into Earth must eventually come out of Earth,” Fan explains. “So these technologies are complementary: Solar energy harvesting is trying to benefit from the incoming flux of energy, while radiative cooling is trying to benefit from outgoing flux.”In fact, the spectrum of the Sun’s energy most relevant for a solar panel doesn’t actually overlap with the mid-infrared window—meaning that even if the two devices were stacked atop one another, they wouldn’t have to cancel each other out. To put this idea to the test, Chen, Fan, and their colleagues slid a silicon-based radiative cooler beneath a germanium solar absorber, which soaks in sunlight for the purposes of energy-efficient heating (not to be confused with a solar cell, which adds in the extra step of converting this energy into electricity). Unlike conventional solar absorbers, however, this particular panel is transparent to radiation in that mid-infrared range of eight to 13 micrometers. This allows the cooler to pass infrared heat through the solar absorber and eject it into space unimpeded.Importantly, the two layers of this device operate completely independently of each other. The solar absorber hoards heat—but none of this energy needs to be funneled to the radiative cooler below, which, by definition, works power-free. This means that the solar payload collected above can, theoretically, be routed elsewhere.
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<figcaption>The researchers' double-layered rooftop panel. On the bottom is a radiative cooler that emits heat in the mid-infrared range into outer space. On top is a solar absorber that is transparent in the aforementioned infrared range. Photo Credit: Linda Cicero, Stanford News
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While the two halves of this device aren’t interdependent, they can still benefit from each other’s company. Many conventional radiative coolers function best at night, out of the heat of the Sun; for efficient use in the daytime, the devices need <a href="https://www.nature.com/articles/nature13883?foxtrotcallback=true">highly reflective surfaces</a> capable of deflecting light. While this keeps the temperature down, it also wastes what could otherwise be a serious kick of solar power. With the solar panel on top sponging up sunlight, though, the cooler doesn’t need this reflective boost.Shielded by the solar panel, the temperature of the team’s radiative cooler plunged as low as 29 degrees Celsius (52 degrees Fahrenheit) below ambient temperature, while the absorber roasted at a pleasant 24 degrees Celsius (43 degrees Fahrenheit) above the surrounding air—an enormous differential. One immediate application, Chen says, has already revealed itself: The temperature gradient created by these two extremes could eventually be harnessed to power <a href="https://www.youtube.com/watch?v=p1woKh2mdVQ">a thermal engine</a>.Even more exciting to Chen and Fan is the idea of replacing the solar absorber half of their device with an electricity-generating solar cell. If this switch pans out, the dual-action technology could serve as a supplement to our conventional, electricity-sapping cooling methods while simultaneously supplying a source of renewable energy.“We’re trying to change how people view rooftops to harvest renewable energy,” Chen explains. “On hot summer days, you could continuously harvest electricity, and at the same time, you could use the device to cool down your house.”
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However, Chen doesn’t think radiative cooling will ever progress to the point of completely replacing air conditioning or refrigeration. Even the <a href="http://science.sciencemag.org/content/early/2017/02/08/science.aai7899">highest-efficiency coolers</a> would probably need to be scaled up to cover entire rooftops or more—probably an untenable engineering ask, especially given the costs of the materials the team used in their prototype. The mid-infrared window also bangs shut on cloudy or rainy days, making this technology the most literal of fair-weather friends. But, Chen explains, radiative cooling could still have its day in the Sun (on a small scale, at least) in arid climes or regions with inconsistent access to power. The researchers are also looking into rebuilding their apparatus with more cost-effective materials.In the meantime, there are still many technological roadblocks to clear. While the theory behind the methods is elegant, explains <a href="https://daedalus.caltech.edu/team-member/dr-emily-warmann/">Emily Warmann</a>, a mechanical engineer studying solar cells at the California Institute of Technology who did not participate in the study, “any practical implications are very, very far away.” Simple though they sound, the necessary tweaks to boost the device’s efficiency, or make the swap from solar absorber to solar cell, could very well compromise the panel’s critical infrared transparency.Furthermore, the prototype’s radiative cooler is sealed up in a vacuum chamber to minimize unwanted heat loss through conduction and convection. To function as an air conditioning or refrigeration alternative, as in their previous work, it would need access to water—but the exposure to the surrounding air would slash its cooling capabilities <a href="https://www.nature.com/articles/nenergy2017143">back down to about 5 degrees Celsius (9 degrees Fahrenheit) below ambient temperature</a>, as opposed to the 29 degrees Celsius (52 degrees Fahrenheit) achieved within the vacuum.
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Despite these obstacles, Chen, Fan, and their colleagues have demonstrated something new and important, says <a href="https://www.researchgate.net/scientific-contributions/2030818528_Mark_A_Nurge">Mark Nurge</a>, a physicist at NASA’s Applied Physics Lab who did not contribute to the new finding. For the first time, it’s clear from the one-two punch of this device that these two sources of renewable energy don’t have to jostle for space—and with radiative cooling on our side, even the sky is no longer the limit.“This is a creative idea,” says <a href="http://www.schlaucohenlab.com/">Gabriela Schlau-Cohen</a>, a chemist studying light harvesting at the Massachusetts Institute of Technology who was not involved in the study. “If we want to actually address our growing energy needs, we need to do it in a way that’s paradigm shifting. And that means ideas that are different than incremental improvements on our current structure.”

Scientists are pioneering technology that may someday cool buildings without electricity, while harvesting solar energy at the same time.

All infectious diseases may be seasonal, according to a new scientific report—which means that every season may now come with its own set of symptoms. Photo Credit: Valerii Tkachenko, Wikimedia Commons

It's Fall, Which Means It's Time for Gonorrhea

The transition from winter to spring signals the end of months of cold snaps, sweater weather, and <a href="https://www.pbs.org/wgbh/nova/article/llama-antibodies-flu-fighting/">flu season</a>. But even as the roads clear and flowers bloom anew, it may not yet be time to shelve your sick days for the year.According to <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1007327">a new article</a>, published today in the journal PLoS Pathogens, all infectious diseases may be seasonal—and there’s at least one for every time of the year.Study author <a href="https://www.mailman.columbia.edu/people/our-faculty/mem2352">Micaela Martinez</a>, an infectious disease ecologist at Columbia University’s Mailman School of Public Health, presents a compendium of 69 infectious diseases that run the gamut from rare to common, neglected to notorious, innocuous to deadly. Despite their differences, all the syndromes have one thing in common: They rise and fall with changing seasons.
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Martinez, a conservation ecologist by training, initially set out to track the seasonality of acute, or short-term, infections like influenza and chickenpox after noting similarities between the disease states of humans and wildlife. But as she began to compile a list of infectious diseases that tend to plague humans, Martinez found that the trend also held true for chronic, or long-term, diseases like gonorrhea and leprosy.“There’s documented seasonality for all infectious diseases, which is not what I was expecting,” Martinez explains. “It’s an even more widespread phenomenon than we thought.”A quick look at the infectious disease calendar paints quite the sobering picture. As autumn leaves turn from green to red, gonorrhea and yellow fever rear their ugly heads in some parts of the world. The winds of winter are <a href="https://www.popsci.com/flu-season-paid-sick-leave?src=SOC&amp;dom=fb&amp;linkId=57776260">famous for flu</a>, but also bring bouts of pneumonia. Refreshing springtime blooms breathe new life into outbreaks of chickenpox and salmonella. And last but certainly not least, summer months pack the heat with spikes in Lyme disease, polio, syphilis, tetanus, tuberculosis, and more.
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<figcaption>Female Aedes albopictus mosquitoes, which can carry yellow fever, dengue fever, and Chikungunya fever, are sensitive to seasonal changes. Ebbs and flows in their population can affect disease transmission. Photo Credit: FotoshopTofs, Pixabay
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Other diseases are a bit less finicky: They’ll take any period of natural warmth, spreading the joy over many months at a time—often in regions of the world that don’t experience four seasons of climactic change. For instance, Chagas disease, diphtheria, and genital herpes all flourish over both spring and summer, while their prevalence takes a welcome dip when temperatures fall. Other infectious diseases fare better during rainy seasons, or when climes are particularly dry.Though the diseases she linked together shared little in common, including even their seasons of prevalence, Martinez theorized there might be similar reasons driving their cyclic nature. To tease apart the connections, Martinez amassed data from 100 previously published studies, zeroing in on several factors that shape seasonality.For instance, environmental factors obviously come into play. Climate conditions such as temperature, humidity, and rainfall impact the wellbeing of infectious microbes, as well as the humans and wildlife they plague. In diseases that are ferried to humans via an insect vector like a <a href="https://www.smithsonianmag.com/science-nature/do-not-fear-drones-air-dropping-50000-mosquitoes-above-180970068/">mosquito</a> or fly, the seasonal ebb and flow of these pest populations may also play a role.
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The behaviors of hosts of disease, both human and wildlife, also appear to fluctuate from month to month. This has been infamously exemplified by congregations of kids in schools begetting measles outbreaks. But there’s also something to be learned, Martinez says, by studying flux in the habits of non-human animals, who go through bouts of seasonal breeding, territoriality, and migration, and how these changes affect the spread of disease. Humans may not be seasonal maters—at least, not to the same degree—but even a subtle shift, like an uptick in sex during the summer months, could spur outbreaks of <a href="https://sti.bmj.com/content/sextrans/54/6/433.full.pdf">gonorrhea</a>, <a href="https://sti.bmj.com/content/sextrans/54/6/433.full.pdf">genital herpes</a>, or <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0149401">syphilis</a>.“It’s not that we are vulnerable at a particular time of year and healthy at another,” Martinez explains. “We’re restructuring throughout the year. And the identity of the thing we’re vulnerable to changes with the seasons.”The idea that some infectious diseases are seasonal isn’t new, says <a href="https://med.stanford.edu/profiles/shanthi-kappagoda">Shanthi Kappagoda</a>, an infectious disease physician and epidemiologist at Stanford University who was not involved in Martinez’ work. However, Kappagoda adds, Martinez’ framework is unique in that it includes some infections that haven’t traditionally been considered seasonal—including several sexually-transmitted infections—and may change how clinicians and researchers approach future epidemics.
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<figcaption>As climate change progresses, increasingly warmer locales may favor the transmission of infectious diseases like cholera, or mosquito-borne infections. Photo Credit: Martijn Meijerink, Pexels
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According to Martinez, knowing when certain diseases are in season could help doctors quickly and effectively treat chronic infections that tend to flare up at certain times of the year, like herpes. With this sort of predictive power, patients may be able to minimize the amount of time they’re forced to deal with seasonal symptoms. The same line of thinking might even be applied to scheduling vaccines, which are ideally administered prior to the onset of an outbreak.Understanding the drivers of infectious diseases’ seasonality may also be helpful on much broader scales, including the <a href="https://www.pbs.org/wgbh/nova/article/disease-outbreaks/">forecasting of epidemics worldwide</a>, adds <a href="https://www.jhsph.edu/faculty/directory/profile/3546/amy-wesolowski">Amy Wesolowski</a>, an infectious disease epidemiologist at the Johns Hopkins Bloomberg School of Public Health who did not participate in the new analysis.
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Such global thinking is especially relevant in a rapidly changing world. As <a href="https://www.pbs.org/wgbh/nova/video/understanding-the-climate-clock/">climate change</a> progresses, the landscape of infectious diseases will shift, explains Kappagoda. Increasingly warmer locales may favor the transmission of summer-loving diseases like cholera. Humankind may also witness a boom in populations of insects like mosquitoes, which are likely to expand their habitats as temperatures climb, chauffeuring with them outbreaks of <a href="https://www.pbs.org/wgbh/nova/article/dogs-diagnose-malaria-socks/">malaria</a>, <a href="https://www.pbs.org/wgbh/nova/article/post-infection-symptoms/">West Nile virus</a>, and more. Additionally, human sensitivity to heat shouldn’t be underestimated in the context of infectious disease, Kappagoda points out: Climate change will continue to displace large populations of people, spurring the onset of epidemics.Whether we like it or not, the spread and severity of infectious diseases are inextricably tied to both biology and behavior—which, in turn, cycle with the seasons. According to Martinez, the implications of this go far beyond fingering a malady for all seasons; rather, these patterns could change how we view our own bodies… and give new meaning to the phrase, “feeling under the weather.”“This isn’t just about transmission—seasonality is also in the human body itself,” she explains. “There’s something happening in our bodies we don’t quite understand yet. Seasonality in infectious disease is just an enticing little piece of the puzzle.”

The flu isn&#x27;t alone: All infectious diseases might be seasonal, according to a new report.

The Cabbage tree emperor moth (Bunaea alcinoe) decorates its wings with tiny, sound-absorbing scales. By blocking echolocation, these scales lower the chances of the moth being pinpointed and eaten by a bat. Photo Credit: Bart Wursten, flickr

Moths Muffle Bat Sonar with Sound-Absorbing Wings

It’s not easy being deaf in the dark—especially when your greatest enemy is a master of sound.Such is the twilight plight of the humble cabbage tree emperor moth (Bunaea alcinoe): It’s all these umber underdogs can do to avoid becoming a hungry <a href="http://www.pbs.org/wnet/nature/group/mammals/bat/">bat’s</a> dinner. Bat sonar is so sensitive that these predators attain an impressive intimacy with their surroundings—one they manipulate to easily locate and devour the minute, wriggling bodies of their prey. But even moths that can’t hear their stalkers’ telltale screech aren’t as powerless as you might expect.Today, in the journal PNAS, researchers <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1810025115">report</a> that the wings of cabbage tree emperor moths are flecked with tiny scales capable of absorbing the sounds of echolocating bats, dampening reverberations that might give away their location. The evolution of this stealth-mode strategy may have helped moths evade detection by their nocturnal predators.
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Often dismissed as drab <a href="https://www.pbs.org/wgbh/nova/nature/journey-butterflies.html">butterfly</a> alternates or light-loving nuisances, moths might just be one of the most underappreciated members of the insect world. Like their butterfly relatives, moths are essential pollinators and sources of food, supporting diverse ecosystems worldwide. Even in the face of danger, the modest moth is mighty: In recent years, researchers have uncovered a dizzying array of anti-bat defenses in these little insects. Because bats rely heavily on sonar to navigate the world around them, much of the moth’s modus operandi is auditory. Some moths will produce their own ultrasonic clicks to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4443353/">jam bats’ sonar</a> or <a href="https://link.springer.com/article/10.1007%2Fs00359-014-0924-0">vocally advertise their toxicity</a>, while others have adopted a strategy of constant vigilance by <a href="https://academic.oup.com/bioscience/article/51/7/570/268256">evolving the insect equivalent of ears</a>, which are sensitive to the audio of approaching bats.However, one group of oddballs exhibits none of the aforementioned tricks of the trade—and it was these miscellaneous moths that piqued the interest of <a href="http://www.bristol.ac.uk/biology/people/marc-w-holderied/">Marc Holderied</a>, a sensory ecologist at the University of Bristol in the United Kingdom.<a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0027190">Previous research</a> had hinted that these mysterious moths, while effectively “deaf” to bats, were literally flying under the radar: They absorbed the sounds of sonar using the <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0027190">exquisite architecture</a> of tiny, leaf-shaped scales that decorate their <a href="https://www.jstor.org/stable/1539496?seq=1#page_scan_tab_contents">wings</a>. These scales might act like the auditory equivalent of an invisibility cloak, allowing moths to pass through bat territory neither seen nor heard. But no one had yet figured out exactly how these little scales were accomplishing such an acoustic feat.
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<figcaption>The Cape serotine (Neoromicia capensis) is a sub-Saharan species of bat that feasts on insects like moths, using echolocation to home in on its prey's location. Photo Credit: Bernard Dupont, flickr
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To puzzle out the mechanics of the muffling, Holderied and his colleagues, led by acoustician <a href="http://www.bristol.ac.uk/biology/people/zhiyuan-shen/overview.html">Zhiyuan Shen</a>, plucked individual scales from cabbage tree emperor moths and constructed 3D models of their structure to see how they would behave in the presence of sound waves.When bat sonar hits a typical object, some of the sound waves will ricochet off the surface and boomerang batward. This outcome is ideal for the bat, which can harvest the information contained in the echo and home in on its prey. All objects, however, have what’s called a resonant frequency, or a natural frequency at which they vibrate. (This is the phenomenon behind the common trope of opera singers shattering wine glasses—the sound hits the glass at its resonant frequency, causing the poor vessel to vibrate itself to pieces.) If incoming sonar meets its target at its resonant frequency, the energy of the sound wave can be converted into motion. This curbs the sound waves’ ability to reverberate and muddies the bat’s estimation of the vibrating object’s whereabouts.For this strategy to be viable for a moth in a bat’s crosshairs, the resonant frequency of its scales would need to overlap with the frequency of bat sonar, typically between 20 to 150 kilohertz. When the researchers analyzed their model scale, they found one resonant frequency. And then another. And then another. To Holderied’s amazement, an individual insect scale was capable of vibrating at not one, but three specific frequencies—28.4, 65.2, and 153.1 kilohertz—depending on how exactly the scale trembled in space.
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“They were perfectly spaced to cover the bat echolocation range,” Holderied explains. “At that moment, we know this wasn’t a coincidence: They’re there for a reason.”As a point of comparison, the researchers repeated their analysis with a modified scale resembling that of a butterfly, a close relative of the moth. Like moths, butterflies adorn their wings with scales—but because most butterflies are most active during the day, as a group, they probably have much less in the way of anti-bat defenses, Shen explains.Like the B. alcinoe model scale, the butterfly-like scale exhibited three resonant frequencies—but this time, they fell less cleanly within the relevant range of bat sonar, clocking in at 88.4, 150.9, and 406.0 kilohertz. It seemed that, under pressure from their bat predators, moths had embarked on this specific evolutionary trajectory alone.
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<figcaption>A single scale from the wing of a cabbage tree emperor moth (Bunaea alcinoe). Typical scales are less than 0.25 millimeters wide. Photo Credit: Marc W. Holderied and Zhiyuan Shen, University of Bristol
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But bats are not to be outdone. They wield a <a href="https://www.nature.com/articles/nature11664">high degree of control</a> <a href="http://www.pnas.org/content/114/41/10978">over the frequency</a> of their own sonar, meaning there’s a chance they could pinpoint gaps in the moth’s acoustic armor. However, not all moth scales are created equal, and every wing is dotted with units of different shapes and sizes, Holderied explains. With such diversity, B. alcinoe wings may stifle an even broader range of frequencies. It’s not yet clear exactly how much these moths compromise bat echolocation in a more natural context—but in the arms race between predator and prey, any amount of sound absorption could tip the scales in favor of Team Moth.Accordingly, one of the clearest next steps is to return to the field and see if the findings hold true for moths on the run from actual bats, says <a href="https://eeb.boisestate.edu/home/current-students/">Juliette Rubin</a>, a sensory ecologist at Boise State University who also studies anti-bat strategies in moths, but did not contribute to the newest finding. For instance, it will be important to test if sound-absorbing moths actually fall prey to bats less often than their not-so-covert cousins—or if shaving scales off B. alcinoe makes them more vulnerable to the hunt. After all, subtle sculpting of scales doesn’t guarantee that B. alcinoe can actually flummox an experienced, living predator. But if these wings are truly as functional as they seem, moths may just fly in the face of bats’ acoustic aptitude.“If the scales are really functioning to absorb sonar, this shows you the incredible adaptations that moths have made to bats,” says <a href="https://www.floridamuseum.ufl.edu/mcguire/kawahara/akito-kawahara/">Akito Kawahara</a>, a sensory ecologist at the Florida Museum of Natural History who did not participate in the research. “It really highlights the importance of bats in the nocturnal landscape and how much impact they have on insects.”
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The researchers are also currently investigating whether these scaly structures are present on other moths—especially those known to engage in other anti-bat antics. Doubling up on defenses could pay some serious dividends, but these adaptations often come with a cost. For instance, Holderied explains, soundproofing scales may have made moth wings heavier, potentially impeding flight.On the other hand, tinkering with the microstructure of a tiny scale is nothing compared to some of the evolutionary triumphs of some other moths—like growing a set of ears, explains biologist <a href="https://sites.google.com/site/cwrufoxlab/people">Jessica Fox</a>, who studies insect flight at Case Western Reserve University but was not involved in the new research.This is not to undersell the exquisite nature of these little scales. While humans continue to painstakingly construct more lightweight, effective resonant absorbers to soundproof buildings and conceal military operations, moths have executed a feat of engineering that’s eluded us for years. Evolution, it seems, operates on even the smallest of scales in the war waged between moth and bat.“Natural evolution and human engineering are converging on the same point,” Shen adds. “But nature is better than engineering.”

To shield themselves from bat echolocation, moths don an acoustic cloak of invisibility—using the sound-absorbing scales on their wings.

Four decades of community-based conservation in Brazil have increased the number of giant South American turtle hatchlings nine-fold along 1,500 kilometers of the Juruá River, a major tributary of the Amazon. Photo Credit: Camila Ferrara, Wildlife Conservation Society

Amazon Turtles Recovering, Thanks to Local Volunteers

Every year, as the late July waters ebb from the banks of the Brazilian Amazon, a bale of female<a href="https://www.arkive.org/giant-south-american-turtle/podocnemis-expansa/"> giant South American turtles</a> creeps shyly from the river’s edge. Here, they will burrow into the soft, speckled sand, excavating the pits in which they’ll lay their eggs. If the young are lucky, they’ll hatch just before the rains return to flood the river anew and amble toward the water, following <a href="http://www.hljournals.org/doi/abs/10.1655/HERPETOLOGICA-D-13-00050R2">the maternal calls</a> that beckon them home.But along portions of the Amazon’s Juruá River, most of these little turtles never make it out of their shells. Nesting areas on unprotected beaches remain vulnerable to raids by poachers, further imperiling a species already threatened by years of habitat destruction.In recent years, however, turtle populations have experienced a miraculous uptick, according to <a href="http://dx.doi.org/10.1038/s41893-018-0170-5">a new report</a> in the journal Nature Sustainability. The turtles’ recovery appears to have also buoyed beach biodiversity in these riverside habitats—and it’s all thanks to four decades of conservation efforts made by local communities.
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“Community engagement is an essential ingredient in wildlife and natural conservation,” says <a href="https://www.cpp.edu/~kconwaygomez/">Kristen Conway-Gómez</a>, a geographer and conservationist at California State Polytechnic University, Pomona, who did not participate in the research. “We can’t achieve [the same amount of] conservation without including local stakeholders.”Freshwater turtles of the Brazilian Amazon have long been sustainably harvested by indigenous peoples and remain a crucial aspect of traditional cultures. But the arrival of European settlers marked a turning point for these river populations, and foreign commercialization of the turtle trade quickly began to <a href="http://www.bioone.org/doi/abs/10.2744/CCB-0926.1?journalCode=ccab">take its toll</a> on local wildlife. During the Amazon rubber boom that began in the late 19th century, European colonists ravaged riverside habitats for natural resources, decimating fragile populations of turtles that once thrived in the waters. New legislation enacted by the Brazilian government, beginning in 1967, did little to curb poaching efforts. By the 1980s, P. expansa had found itself on the <a href="https://www.iucnredlist.org/species/17822/97397263">endangered species list</a>.“These river systems in the Amazon today are a pale shadow of what they were 150 years ago,” explains study author <a href="https://people.uea.ac.uk/en/persons/c-peres">Carlos Peres</a>, a conservation ecologist at the University of East Anglia in the United Kingdom. “P. expansa’s original habitat range has been contracted to perhaps 2 percent of what it used to be.”
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<figcaption>Due to centuries of over-exploitation, populations of the giant South American turtle (Podocnemis expansa) dwindled to concerning levels, particularly after the Amazon rubber boom in the late 19th century. Photo Credit: Priscila Miorando, Federal University of Western Pará
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But in the middle of the chaos, a small movement began to take root. In the mid-1900s, concerned Brazilian locals self-organized, recruiting volunteers to stake out turtle nesting beaches, or tabuleiros, to ward off poachers during breeding season. Today, several tabuleiros are protected by round-the-clock local surveillance for up to six months each year.This self-sustaining system has been in place for decades—but it wasn’t until recently that a team of researchers led by Peres and <a href="https://www.researchgate.net/profile/Joao_Campos-Silva2">João Campos-Silva</a> of the Federal University of Alagoas in Brazil finally quantified their impact on turtle viability.To track the wellbeing of Amazon turtle populations, the team collected 40 years of nesting data between 1977 and 2016—and it quickly became clear just how astoundingly successful the locals’ efforts had been. Four decades of community-based conservation had increased the number of P. expansa nests 11-fold along the Juruá River; the number of hatchlings had also increased nine-fold, averaging out to more than 70,000 additional hatchlings released on beaches each year.
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“This is a very important study,” says <a href="https://eohsi.rutgers.edu/eohsi-directory/name/joanna-burger/">Joanna Burger</a>, an ecologist and conservationist at Rutgers University who did not participate in the research. “There are so few long-term studies in conservation… so it’s hard to show that these work.”When the team compared wildlife inhabiting protected and unprotected beaches along a 1,500-kilometer (over 900-mile) stretch of the Juruá, they found that the locals’ vigilance had effectively deterred poachers from not only P. expansa nests, but also the burrows of their close relatives—yellow-spotted river turtles (Podocnemis unifilis) and six-tubercled river turtles (Podocnemis sextuberculata). While a staggering 99 percent of the 200 nests on unguarded beaches suffered poaching raids, only 2 percent of the over 2,000 nests on monitored beaches had been harvested. When the researchers took all local factors into account, they found that the number of years a beach had been protected was the most important contribution to the turtles’ reproductive success.
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<figcaption>Several freshwater turtle species, including the giant South American turtle (Podocnemis expansa), the yellow-spotted river turtle (Podocnemis unifilis), and the six-tubercled river turtle (Podocnemis sextuberculata), have been affected by human over-exploitation, but community-based efforts have brought populations back from the brink. Photo Credit: Camila Ferrara, Wildlife Conservation Society
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And the turtles weren’t the only beneficiaries of local generosity. The researchers were surprised to find that many diverse species, including other reptiles, birds, fish, and insects, were also thriving on protected beaches and in the waters they bordered—a striking contrast with the “deafening silence” of the unprotected beaches nearby, Peres explains. In this way, Campos-Silva says, the turtles were acting as a bit of an umbrella species, delivering collateral benefits to their neighbors.“The greatest contribution of this paper is all these positive benefits to [other] species,” explains <a href="https://bsc.ua.edu/profiles/jennifer-howeth/">Jennifer Howeth</a>, a conservation ecologist at the University of Alabama who did not contribute to the research. “From a conservation perspective, you’re getting a really good bang for your buck.”To round out their analysis of the program, the researchers interviewed beach guards who had participated in the efforts over the years. These results, unfortunately, were more sobering. While locals were enthusiastic about the recovery of biodiversity in the area, they expressed concerns about the dearth of monetary support and a lack of appreciation from government agencies for work that was harrowing, time-consuming, and often dangerous due to threats from particularly recalcitrant poachers.
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The sole compensation the guards receive is a monthly food hamper worth about $110, paid only during turtle breeding season. In spite of this, some of the most stalwart participants had been on the job for over 35 years, citing a moral obligation to continue the work they’d inherited from their parents and grandparents. “The guards are doing it out of love,” Campos-Silva says. “But we need a better solution for economic sustainability.”About 390 protected tabuleiros exist throughout the Brazilian Amazon. According to the researchers’ estimates, maintaining surveillance across all locales would incur an annual cost of about $833,000, a sum that will require a consistent, independent stream of financial support.In the meantime, however, Campos-Silva, Peres, and their colleagues hope that these early successes can inspire other conservation efforts worldwide—especially those lacking in funding or dedicated staff.
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<figcaption>Turtle conservation along the Juruá River has been almost entirely spearheaded by local volunteers in a labor of love. Guards monitor turtle breeding grounds 24/7 during the dry season for only a monthly food stipend, and some of the most devout individuals have been keeping watch for nearly four decades. Photo Credit: Joseph Hawes, Anglia Ruskin University
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But Conway-Gómez cautions that, while the statistics from the Juruá region’s conservation efforts are “striking,” it’s unclear how much—or if—they will be replicated in other communities around the world, where cultural resources and local enthusiasm may be less abundant. Future work will require tailoring each action plan to individual wildlife species and human communities and, as Howeth points out, identifying consistent sources of funding, management, and oversight.Once empowered with the right resources, local investment can be one of most critical aspects of conservation. A handful of passionate individuals might be all it takes to bring a species back from the brink.“In some ways, communities have better ways to do this work than outside biologists and conservationists,” Conway-Gómez adds. “It’s important to give them a place at the table.”

Forty years of community engagement has brought the freshwater turtles of Brazil back from the brink—but lack of funding may imperil conservation.

Katherine J. Wu

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