Research Highlights

Our pick of the latest scientific literature

Illustration of Cretoxyrhina attacking Pteranodon

A shark from the age of the dinosaurs terminates the flight of a winged reptile called a pterosaur (artist’s illustration). Credit: Mark Witton, D. Hone <i>et al.</i>/<i>PeerJ</i>

Palaeontology

A ‘Ginsu shark’ lost a tooth in its Cretaceous dinner

Some 85 million years ago, an apex predator chomped on a flying reptile.

Graceful winged reptiles known as pterosaurs ruled the skies for millions of years while dinosaurs roamed the Earth. But aerial prowess could not keep one unfortunate pterosaur from the jaws of a predator known as the Ginsu shark.

The pterosaur in question was a Pteranodon, a fish-eater that soared over the sea on wings that measured as much as 7.25 metres from tip to tip. The shark was Cretoxyrhina mantelli, a fearsome and now-extinct predator nicknamed for the similarity between its teeth and the blades of a popular brand of knife. Examining a museum display of a Pteranodon skeleton dated to about 85 million years ago, David Hone of Queen Mary University of London and his colleagues identified an object wedged in one of the skeleton’s neck vertebrae as a tooth from a C. mantelli. The tooth’s size indicates that the shark measured roughly 2.5 metres long.

The shark may have snatched a Pteranodon bobbing on the waves. But Pteranodon carcasses would probably have floated for long periods, which would also have allowed the shark to scavenge its reptilian repast, the authors say.

A snow covered crater on Mauna Kea, Hawaii

A crater on Hawaii’s Mauna Kea, a 4,200-metre-tall volcanic peak that shelters patches of frozen soil on its slopes even in the summer. Credit: Getty

Climate sciences

Why a palm-fringed Pacific island harbours pools of ice

Hawaiian peaks host icy pockets year-round, but the cold spots are at risk from climate change.

The island of Hawaii is renowned for its tropical climate, but the stony deserts on two of its volcanoes support unlikely patches of permanent ice.

Norbert Schörghofer at the University of Hawaii at Manoa in Honolulu and his colleagues gathered weather data from sites near the barren, rocky summits of Mauna Kea and Mauna Loa, Hawaii’s tallest volcanoes. Measurements at a crater high on Mauna Kea yielded the coldest temperature ever reported for the Hawaiian Islands: -20.3°C.

The researchers found that, despite the area’s relatively mild air temperatures, pools of exceptionally cold air sometimes form in the craters during still nights. This cold air is trapped between rocks, helping to preserve patches of ice and frozen soil in the craters.

Similar pooling and trapping of cold night air may also help to maintain ponds of ice found deep inside two caves on Mauna Loa. Evaporation of ice from the ponds’ surfaces removes significant amounts of latent heat. But the ice ponds are showing signs of thawing and will probably vanish as the climate warms.

Patient derived organoids

Tumours-in-a-dish include cancer cells (magenta) and immune cells (yellow) with nuclei in blue. The cultures originated from human tumours of the lung (left), kidney (middle) and skin. Credit: J. T. Neal <i>et al.</i>/<i>Cell</i>

Cancer

Mini-tumours tell of immune cells’ role in cancer

3D cultures detail the complex relationship between a tumour and its environment.

3D cultures of cancer cells can reveal not only what happens inside a tumour, but also how the tumour is influenced by nearby immune cells.

Researchers use clumps of cultured cells called organoids to study cancer, but the organoids developed so far do not fully capture the effects of the immune cells surrounding a tumour. Calvin Kuo at Stanford University in California and his colleagues devised a technique to grow organoids from patient samples while preserving more of the architecture of the original tumour — including some of the immune cells embedded in it — than previous methods have done.

The researchers generated cultures from more than 100 human tumours and assessed gene activity and other characteristics from thousands of individual cells in four of them. In two additional samples, the team found that the composition of the immune-cell community in an organoid resembled that of the parent tumour, suggesting that the organoids are high-fidelity models of actual cancers.

Cancer drugs that activate immune cells killed some of the organoids, suggesting that those cultures included functional immune cells.

Osteocyte bone cell surrounded by bone tissue

A bone cell called an osteocyte (red; artificially coloured) is nestled in bone tissue. Osteoctyes host a newly discovered receptor for a hormone called irisin. Credit: Steve Gschmeissner/SPL

Metabolism

A molecule that helps the ‘exercise hormone’ do its work

Receptor identified on bone cells binds to compound secreted by muscles.

A hormone that muscles release in greater amounts during exercise binds to bone cells, and could help new bone cells to take the place of old ones.

Some studies have linked certain types of physical activity to increased bone mass and protection against age-related bone loss. Previous research had suggested that an exercise-related hormone called irisin might be involved in this effect, but the receptor for irisin had not been identified.

Bruce Spiegelman at the Dana-Farber Cancer Institute in Boston, Massachusetts, and his colleagues found that irisin binds to a receptor on fat tissue and on the surface of osteocytes, which are the predominant type of cell in bone.

When applied to cultured osteocytes, irisin helped to protect the cells against certain types of cellular damage. Mice that received irisin injections showed elevated levels of sclerostin, an important regulator of the process by which old bone cells break down and are replaced by new ones.

The team’s discovery of a receptor for irisin could help scientists to uncover the molecule’s effects on bone and other tissues, and might lead to the development of therapies for bone diseases.

Paracas ceramic pot

This South American ceramic vessel was embellished with mineral-based pigments in the 3rd to 6th centuries BC. Credit: age fotostock/Alamy

Archaeology

Reptile urine used as paint in ancient Peru

Snake waste the probable source of white colour on pottery from first millennium BC.

Some of the most striking ceramics known from prehistoric South America are decorated with a pigment derived from reptile urine.

The Paracas culture, which flourished along the Pacific coast of what is now Peru in the first millennium BC, is known for its colourful, intricately detailed textiles and pottery. Dawn Kriss, then at the American Museum of Natural History in New York City, and her colleagues set out to research the ancient artists’ techniques. They analysed the chemical components of the paint on more than a dozen Paracas ceramics, including bowls and vases.

The team found that the white paint (pictured below) on two fragments of pottery contained uric acid, which is a component of urine, and white particles. Similar particles previously recovered from African rock art have been identified as originating from snake urine. Blue paint on the fragments included urine and indigo.

Paracas ceramic shark with blue and white pigment

Credit: Dawn Kriss/American Museum of Natural History (41.2/8345 AMNH)

The urine used by the South American artists might also have come from snakes, which are commonly depicted on Paracas textiles and ceramics.

Dracula ant striking a termite

A Dracula ant uses its record-setting mandibles — the pincer-like appendages on its face — to body slam a termite. Credit: <a href="https://www.youtube.com/antlab" data-track="click" data-label="https://www.youtube.com/antlab" data-track-category="body text link">Ant Lab</a>

Animal behaviour

Dracula ant’s powerful pincers snap shut at record speed

Fangs are feeble next to the fastest appendages in the animal world.

An insect dubbed the Dracula ant is a speed champion among animals: it snaps its front pincers shut in less than 1/5,000 of the time it takes to blink.

Trap-jaw ants (Odontomachus), mantis shrimp and other creatures have evolved appendages that move with lightning swiftness. These species achieve high speeds using a spring-loaded system similar to a catapult. But Dracula ants — in the genus Mystrium, and so called because they sometimes feed on the blood of their young — press their two front pincers together before slipping them past each other like a finger snap.

Fredrick Larabee at the National Museum of Natural History in Washington, DC, and colleagues investigated this mechanism using computer models and high-speed videos. The researchers found that the ant’s front appendages, unlike those of most other ants, can bow inwards when the pincer tips press against each other, generating a spring-like tension. When one pincer slips under the other, this tension releases, propelling the pincers shut at 90 metres per second — faster than a bullet train, and the fastest-known speed for an animal appendage.

View of the clocks (purple foreground) with screens showing sub-programmes that control various parts of the clocks (background)

This atomic clock (foreground), shown with control screens, was part of a network designed to test a theory on the nature of dark matter. Credit: Nicolaus Copernicus Univ.

Applied physics

The search for dark matter that runs on time

A far-flung network of atomic clocks could hunt for defects in the fabric of space-time.

Highly precise atomic clocks from three different continents have been recruited in the search for dark matter.

Most of the matter in the Universe is unaccounted for — it seems to exert a gravitational pull on other objects, but emits no light. One theory proposes that this dark matter is actually an artefact of inconsistencies that formed in the fabric of space-time as the early Universe cooled. If Earth passed through one of these ‘topological defects’, the strength of interactions among elementary charged particles would briefly shift. That would momentarily disturb the inner workings of extremely precise atomic clocks, enabling scientists to detect the defect.

To create a clock network, Michał Zawada at Nicolaus Copernicus University in Toruń, Poland, and his colleagues combined timing data from four atomic clocks in the United States, Europe and Japan. A topological defect would show up as a shift in the frequencies of the lasers and atoms that the clocks use to keep time, with a different shift for each clock. In tests, this arrangement was two orders of magnitude more sensitive to such shifts than networks of Global Positioning System satellites.

A larger network would allow for testing of the topological-defect theory and other dark-matter candidates, the authors write.

Adult Egyptian fruit bat appearing to smile as it flies out of its' cave to forage

Egyptian fruit bats that roost together host the same fur bacteria, which may help group members to recognize one another by smell. Credit: Jens Rydell

Microbiome

How snuggling close affects bats’ microbiome

Members of a bat colony pass fur bacteria to each other.

Egyptian fruit bats share the microbes living in their fur with their neighbours.

Colonies of the Egyptian fruit bat (Rousettus aegyptiacus) include several dozen to many thousands of animals. The bats hang from cave ceilings in tightly packed, noisy masses, which sometimes erupt into squabbles, complete with screeching and cuffing.

Yossi Yovel at Tel Aviv University and his colleagues studied ten bats from a captive colony and four from a wild colony. For 13 weeks, the researchers collected weekly samples of the bats’ fur and gut secretions, and analysed them for bacteria.

The bacteria in the gut differed between individual bats. However, colony members tended to have the same combination of bacterial species in their fur, probably because the bats share fur bacteria by touching one another.

The mix of bacterial species on the animals’ pelts changed over time, suggesting that the bat’s microbiome is influenced by the environment, the authors say.

Researchers working on apparatus

Researchers Jacklyn Gates and Kenneth Gregorich install the FIONA device used to size up several superheavy elements. Credit: Marilyn Chung/Lawrence Berkeley National Laboratory

Atomic and molecular physics

How to measure a superheavy atom

Researchers derive the masses of nihonium and moscovium using a new direct technique.

Physicists have taken the first direct measurements of the mass number — the total number of protons and neutrons in an atomic nucleus — of the superheavy elements nihonium and moscovium.

Jacklyn Gates of the Lawrence Berkeley National Laboratory in California and her colleagues used a small-particle accelerator to shoot calcium ions at a target of americium, element 95. These collisions produced nuclei of nihonium and moscovium atoms (elements 113 and 115), at a rate of about one per day. The team built a device that separated the newly created nuclei according to their mass-to-charge ratios.

The nuclei then lodged themselves in a silicon detector and underwent a chain of nuclear decays, emitting charged particles in the process. By tracking these charged particles, the researchers could pinpoint a nucleus's location. That location was dictated by the nucleus's mass-to-charge ratio, which allowed the team to extrapolate from a nucleus’s position on the detector to its mass number, which in turn is closely related to an atom’s mass.

The results validated more indirect techniques commonly used to estimate superheavy masses.

Winding view of Elwha river, site of the former Lake Mills, south of the Glines Canyon Dam in 2012.

A lake in Washington state has been replaced by the free-flowing River Elwha, which was unleashed by a dam-removal project some two decades in the making. Chris Wilson/WP via Getty

Geophysics

River bounces back after world’s largest-ever dam removal

The Elwha River quickly cleared itself of debris after dams’ demolition.

Freed from two large dams, a small river in Washington state has efficiently flushed vast amounts of mud, sand and gravel towards the sea.

In the world’s largest dam-removal project so far, two obsolete barriers on the Elwha River — the 32-metre-tall Elwha Dam and the 64-metre-high Glines Canyon Dam — were dismantled between 2011 and 2014 to restore the river’s flow from source to mouth. Amy East at the US Geological Survey in Santa Cruz, California, and her team monitored river flow and topography before, during and after the dams’ removal.

The release of some 20 million tonnes of sediment that had been trapped in the reservoirs behind the dams substantially altered the shape of the river, filling pools and creating new sandbanks. But the major disturbance lasted no more than five months; by the end of that time, most of the debris reached the river’s mouth at the Strait of Juan de Fuca.

Rivers of sufficient stream power seem to be able to cope with large dam removals without serious harm, the authors conclude.

A gecko running across water

A gecko uses a complex series of movements to splash across a laboratory tank. Credit: Pauline Jennings

Biophysics

Geckos slap their feet and swish their tails to race over water

Slender lizards can speed across a body of water faster than a young alligator can swim.

Geckos zoom over water using a unique combination of undulation, water-slapping and other motions.

Small, lightweight insects can glide atop water thanks to surface tension, a cohesive force between water molecules. Some larger creatures, such as the basilisk lizard (Basiliscus basiliscus), run across water by vigorously slapping the surface with their limbs.

Jasmine Nirody at the Rockefeller University in New York City, Robert Full at the University of California, Berkeley, and their colleagues found that geckos (Hemidactylus platyurus) rely on a complex mix of mechanisms. Geckos use basilisk-like slapping and stroking movements, creating underwater air pockets that propel them. Lifting their heads and chests out of the water reduces drag, and wriggling their bodies and submerged tails from side to side generates thrust. Surface tension also seems to give the animals a boost; when the researchers halved the surface tension of water using detergent, geckos slowed by 58% compared to controls.

The geckos could sprint across water at an average speed of around 62 centimetres per second. That’s faster than the swimming speed of young alligators.

Microglial white blood cell

A microglial cell (artificially coloured). These cells destroy pathogens in the brain and secrete compounds that stimulate an immune response. Credit: Steve Gschmeissner/SPL

Neuroscience

The cells that help cancer drugs to cloud the mind

Microglial cells, which provide immune protection to the nervous system, might have a role in the cognitive impairment known as ‘chemobrain’.

Neurological difficulties induced by some cancer treatments might stem from nervous-system cells called microglia, which promote inflammation.

Some chemotherapies cause a lasting condition known as ‘chemobrain’, which is marked by deficiencies in attention, information processing and fine motor skills. Michelle Monje at Stanford University in California, and her colleagues found that children and young adults treated with a chemotherapy called methotrexate had fewer oligodendrocyte-lineage cells — cells that help to form the crucial insulation around neurons — in their brains than those who had not been exposed to the drug.

Similarly, mice exposed to methotrexate had fewer of these cells than untreated controls. Six months after methotrexate treatment, these mice struggled to distinguish between novel and familiar objects. They also had increased numbers of active microglia.

After exposing the mice to chemotherapy, researchers gave the animals a drug that reduced the numbers of their microglia. This reversed methotrexate’s negative effects on both oligodendrocyte-lineage cells and the animals’ ability to discriminate between novel and familiar objects.

Human red blood cell infected with the malarial parasite

The malaria parasite (blue) infects a red blood cell. Infection of blood cells triggers symptoms such as fever and chills. Credit: Mordun Scientific Ltd/SPL/Getty

Drug discovery

Almost half a million mosquitoes are drafted to fight malaria

High-volume tests identify nearly 6,000 molecules that prevent the malaria parasite from multiplying in the liver.

An assembly-line-style test found thousands of compounds that hold promise for halting the malaria parasite’s spread through the body.

When an infected mosquito bites a human, it injects spore-like forms of the malaria-causing Plasmodium parasite, which travel to the liver and multiply. Symptoms emerge only after the parasites invade the bloodstream and proliferate.

In a search for therapies that confine this parasite to the liver, a team led by Elizabeth Winzeler at the University of California, San Diego, in La Jolla painstakingly dissected Plasmodium parasites from nearly half a million mosquitoes. The scientists added the parasites to liver cells mixed with a variety of chemical compounds, and then monitored the parasites’ fate.

Out of more than 500,000 compounds, almost 6,000 efficiently quashed the pathogen’s growth, most without seriously damaging liver cells. Further tests could yield drugs that prevent runaway infection without the logistical difficulties — such as storage in a cold environment — posed by conventional vaccines.

Neptune

An unusual storm on Neptune is seen as several white streaks in this view from the Hubble Space Telescope. Credit: E. Molter et al./Icarus

Planetary science

Epic storm roils a tranquil region of Neptune

Amateur astronomers help to track a disturbance in the icy planet’s atmosphere.

A storm wider than Mars tore across Neptune’s equator in 2017 — the first tempest observed in the giant planet’s midsection, which tends to sport a cloudless sky.

Astronomers have observed several colossal dark spots between Neptune’s equator and its poles. These blemishes, such as the Earth-sized Great Dark Spot seen in 1989, are storms that propel atmospheric gases upwards, producing bright clouds.

In June of 2017, Edward Molter at the University of California, Berkeley, and his colleagues spotted a roughly 8,500-kilometre-wide storm on Neptune. Unlike previous systems, this one was at the planet’s equator and lacked a dark spot. The scientists, along with amateur astronomers that they recruited, imaged the storm's massive cloud for about seven months until it dissipated.

Photo analyses and computer models indicated that the cloudy storm drifted eastward at more than 200 metres per second, roughly three times faster than a category-5 hurricane on Earth. The researchers conclude that the cloud formed either from rising gases or from moist gases that became trapped at Neptune’s equator and drifted east with the planet’s rotation.

Micrograph of Influenza A particles

Influenza particles (artificially coloured) swap the proteins on their surfaces with ease. Credit: Eye of Science/SPL

Cell biology

Flu virus is a master shape-shifter

Cells infected with the versatile pathogen churn out viral particles with many different shapes.

An influenza virus infecting a single cell can produce offspring with a wide variety of shapes, maximizing the virus’s chance of escaping attack by antiviral therapies.

Antibodies and vaccines target proteins on the surface of a viral cell. But the flu virus can quickly swap out one set of proteins for another, making the virus notoriously difficult to track and treat.

Michael Vahey at Washington University in St Louis, Missouri, and Daniel Fletcher at the University of California, Berkeley, developed a strain of the flu virus and attached fluorescent markers of a specific colour to each type of the virus’s surface proteins. The researchers infected cells with this virus and allowed it to replicate for one generation — this ensured there was not enough time for significant genetic mutation to occur. The cells produced viral particles with a vast assortment of marker combinations, suggesting that the virus can assemble different structures without undergoing genetic mutations.

New antiviral therapies could be designed to target more than one surface protein and thus more effectively treat the flu virus, the authors say.

Lonesome George, a century-old tortoise

The giant tortoise known as Lonesome George, who died in 2012 at a tortoise breeding centre in the Galapagos Islands, was the last survivor of his species. Credit: Jad Davenport/NGC

Genetics

Genome of ‘Lonesome George’ reveals a tortoise’s secrets to long life

Blood from the world’s only remaining Pinta Giant tortoise yields clues about the genetic underpinnings of longevity.

The Galapagos Islands tortoise named Lonesome George was the last member of his species when he died in 2012 at an estimated age of more than 100 years. But he lives on through his genome sequence, which hints at the genetic factors underlying the extraordinary longevity of his kind.

A team led by Carlos López-Otín at the University of Oviedo in Spain and Adalgisa Caccone at Yale University in New Haven, Connecticut, sequenced and analysed DNA from George — who for roughly 40 years was the only known living specimen of the Pinta Giant tortoise (Chelonoidis abingdonii). The researchers also analysed the genome of another giant tortoise species, the Aldabra giant tortoise (Aldabrachelys gigantea), which is native to the Aldabra Atoll in the Indian Ocean.

The team compared George’s genome with those of other reptiles, including small-bodied and shorter-lived turtle species. Their analysis showed that the giant tortoise lineages had genetic variants linked to DNA repair, inflammation control and cancer resistance — factors that could help explain how some of Lonesome George’s luckier relatives lived for nearly two centuries.

See also: ‘The secrets of Lonesome George

Transient upstream reservoir

This waterway in northern Canada contained mercury; levels were especially high downstream of the landslide-like feature. Credit: K. A. St. Pierre et al./Environ. Sci. Technol.

Environmental sciences

Mercury levels skyrocket thanks to Arctic warm up

Thawing permafrost dumps potentially toxic metal into waterways.

Large amounts of mercury could soon be released from frozen ground that will thaw as the Arctic warms.

When long-frozen ground called permafrost starts to thaw, this sometimes triggers the collapse of sloping land above bodies of water. The resulting landslide-like features, or ‘thaw slumps’, can release large amounts of sediment into waterways.

Kyra St. Pierre at the University of Alberta in Edmonton, Canada, and her team determined mercury concentrations in waterways close to thaw slumps in Canada’s Northwest Territories. Mercury levels downstream of the slumps were up to two orders of magnitude higher than upstream levels, reaching the highest concentrations ever measured in otherwise uncontaminated sites in Arctic Canada.

The team estimates that across the Arctic region, climate warming and the resulting expansion of thaw slumps could spark the release of almost 90,000 tonnes of mercury — 5% of all mercury currently stored in northern permafrost soils.

A synthetic synapse on a human structure model

A synthetic version (transparent rectangle) of the junction between a neuron and a muscle is shown on a model of a human hand. Credit: Y. Lee et al.

Synthetic biology

Light pulses prod artificial muscle into action

An optical signal triggers mechanical motion thanks to a nerve junction constructed in the laboratory.

A device inspired by the body’s network of nerve cells could enable wireless control of artificial muscles and prostheses.

When a neuron commands a muscle to contract, the message travels through a junction called a synapse. The development of a synthetic system that mimics the activity of neurons and synapses to control artificial muscles would be a fundamental step for bio-inspired robotics, but such a system has proved challenging to create.

Tae-Woo Lee at Seoul National University and Zhenan Bao at Stanford University in California and their colleagues designed a synthetic synapse equipped with a light detector, which allows researchers to control the device with light pulses. The synapse converts these light signals into electrical impulses that can trigger movement of an artificial muscle made from a strip of polymer material. In tests, varying the rate of light pulses helped to control the strip’s flexion.

This approach is similar to optogenetic techniques, which genetically modify neurons to render them sensitive to light, the authors write.

Indian farmers walk across their parched paddy field

Farmers walk across their drought-ravaged fields in India. Climate change raises the odds of droughts that are paired with severe heat. Credit: STR/AFP/Getty

Climate change

A warning of future years both hot and dry

A double whammy of heat and aridity is now more likely to strike regions around the globe.

Global warming has doubled the probability that in any given year, some regions of our planet will be both hotter and dryer than they’ve been on average.

Most research into future heat waves, droughts and other extreme events investigates the likelihood of only one such event at a time. Ali Sarhadi at Stanford University in California and his colleagues wanted to determine the odds of multiple extreme events occurring at once.

They compared global temperatures stretching back to 1931 with conditions predicted by climate models. The team found that the odds of a particular region being both hotter and drier in one year than the historical average are much higher today than they were before.

Worryingly, the chances are also higher that multiple important agricultural regions will suffer exceptional heat and drought at the same time. Compared with data from the period before 1980, the odds have more than tripled that China and India will experience both extremes in the same year.

The risk of these events occurring simultaneously will fall if greenhouse-gas emission cuts, such as those outlined in the recent Paris climate accord, are implemented.

Fragment of Endmesolithic pottery with foodcrust

An ancient clay cooking pot was encrusted with food remnants that included proteins found in fish eggs. Credit: A. Shevchenko <i>et al.</i>

Proteomics

Prehistoric Europeans feasted on caviar

Pottery fragments hint at how ancient cooks prepared the fishy delicacy.

Gunk on a prehistoric cooking pot reveals that 6,000 years ago, people had already discovered the delights of caviar.

The early connoisseurs were hunter-gatherers camped by a now-vanished lake. Excavations at the site, located in modern Germany, have yielded prehistoric fishing nets, canoe fragments and bits of pottery. To determine what was on the menu, Anna Shevchenko at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany, and her colleagues examined pieces of a sturdy clay cooking vessel dated to about 4000 BC.

Proteins on the clay matched those of the common carp (Cyprinus carpio). Several of those proteins are common in fish eggs; other proteins present suggest that the pot also held fish flesh. The authors say that the ancient diners may have prepared their delicacy by poaching roe in fish broth or water, using leaves to cover the pot.