Research Highlights

Our pick of the latest scientific literature

  • Volume 575
  • Issue 7782
A bed of common mussels. Mytilus edulis in Little Fistral, Cornwall, UK.

Huge numbers of blue mussels (pictured) in France have died from a transmissible cancer that originated in a related species. Credit: Alamy


A cancer spreads worldwide, thanks to global shipping

A tumour affecting mussels in Chile and France is traced to a single Northern Hemisphere mussel of a separate species.

A contagious cancer affecting shellfish has crossed oceans — and species barriers — to threaten mussels in Europe and South America.

Transmissible tumours are rogue cell lineages that spread between individuals. Such tumours have been found in Tasmanian devils (Sarcophilus harrisii) and bivalves, including the bay mussel (Mytilus trossulus), which lives in the Northern Hemisphere.

Since 2014, a related species, the blue mussel (Mytilus edulis), has experienced mass die-offs in France. These events show signs of being caused by a transmissible tumour. A team led by Michael Metzger at the Pacific Northwest Research Institute in Seattle, Washington, sequenced DNA found in blue mussels from France and the Netherlands, and identified tumour cells with genetic markers characteristic of bay mussels.

The researchers also found that Chilean mussels (Mytilus chilensis), a species from Argentina and Chile, had tumours that were almost genetically identical to those afflicting the European blue mussels. The tumours originated in a single bay mussel and then spread to the South American and European mussel species — probably via international shipping vessels, the researchers suggest.

A woman smells a flower in the rose garden at the annual Chelsea flower show in London.

Four percent of left-handed women lack an olfactory bulb but can appreciate a flower’s perfume, according to analysis of data in a public repository. Credit: Dan Kitwood/Getty


The women who lack an odour-related brain area — and can still smell a rose

The olfactory bulb was considered crucial for a sense of smell, but a chance discovery challenges the dogma.

When the aroma of fresh coffee hits your nose, odour receptors send signals to a brain region called the olfactory bulb, which then transfers this information to other areas of the brain. But now researchers have stumbled upon people who can still enjoy coffee’s fragrance even though they lack an olfactory bulb.

Scientists had thought that people without olfactory bulbs could not detect odours. But as Tali Weiss and Noam Sobel at the Weizmann Institute of Science in Rehovot, Israel, and their colleagues reviewed brain scans of healthy, left-handed participants for a smell study, they found two women who seemed to lack olfactory bulbs but could still smell.

The team then analysed brain-scan data from more than 1,000 people, including 606 women, and found that roughly 0.6% of women and about 4% of left-handed women had no olfactory bulbs but did have a normal sense of smell.

How these women identify odours is unclear, but it’s possible that their neurons have wired into olfactory networks elsewhere in the brain, the researchers say.

An artist’s impression depicting the formation of a galaxy cluster in the early Universe

A galactic cluster (artist’s impression) takes shape in the early Universe. Analysis of a gas cloud from this period contradicts current thinking about the first stars. Credit: ESO/M. Kornmesser

Astronomy and astrophysics

Primordial gas cloud has thoroughly modern make-up

A cloud dating to the Universe’s early days hints that star formation had an early start.

One of the oldest clouds of intergalactic gas found so far has a surprisingly contemporary composition, suggesting that the first stars to form after the Big Bang lived and died more quickly than thought.

Early in the history of the Universe, gas clouds birthed the first galaxies and stars. But the details of this process remain mysterious.

While observing very bright objects called quasars, a team led by Eduardo Bañados at the Max Planck Institute for Astronomy in Heidelberg, Germany, stumbled on a peculiar cloud of gas that dates to just 850 million years after the Big Bang. Spectral analysis showed that the amounts of carbon and other elements in the cloud are much lower than those found in modern stars. This suggests that the cloud is made up of material from the early Universe.

But the ratios of these elements do not match the ratios that would be expected if the cloud contained remnants of the first generation of stars. Instead, the authors’ observations suggest that at least a second generation of stars had already come and gone, even at this early stage of cosmic growth.

The Whittier Fire burns in the mountains above above Goleta, California.

Flames flicker in the hills above Goleta, California. Non-native weeds infiltrating the state’s scrublands and woods have raised the risk of fire. Credit: Brian Stetson/Alamy

Environmental sciences

Rampaging weeds help to set the US landscape ablaze

Iconic landscapes of the western United States are more likely to burn if they are overrun by invasive grasses.

Invasion by non-native grasses sharply increases fire risk in a variety of ecosystems across the continental United States, from deciduous forest in the east to the deserts of the southwest.

Emily Fusco at the University of Massachusetts, Amherst, and her colleagues used government records, satellite fire data and computer models to analyse the impact of 12 species of non-native grasses on fire trends in 29 US ecological regions. The researchers then compared these patterns in invaded and uninvaded landscapes.

The results showed that fire had burned more of a habitat riddled with one of eight weed species than the same type of habitat without the invader. For example, flames had torched 2.3 times as much dry shrubland invaded by Schismus barbatus grass than dry shrubland free of this species. Of the eight fire-promoting weeds, six increased fire frequency in the ecosystems that they had invaded.

The authors suggest that the presence of invasive grasses should be considered more prominently in future land-management plans.

Ghost Forest in Neskowin, Oregon

The trees in this ‘ghost forest’ in Neskowin, Oregon, drowned when a massive earthquake in 1700 made the land subside. Researchers have modelled the motions of the fault involved in the quake. Credit: Getty

Solid Earth sciences

An epic earthquake’s backstory sends a warning

Scientists evaluate the seismic risk facing a portion of North America by comparing a centuries-old mega-quake with two recent events.

The great Cascadia earthquake of 1700 shook the coasts of what are now British Columbia, Washington and Oregon so violently that afterwards, entire forests stood below sea level. Now scientists have found similarities between the Cascadia event and other huge quakes that help to illuminate the seismic danger facing the region.

Erin Wirth and Arthur Frankel at the US Geological Survey in Seattle, Washington, developed a model to describe ground movement during the Cascadia quake, which is estimated to have been a magnitude 9 — as large as a 2011 earthquake in Tohoku, Japan that killed roughly 20,000 people. The team analysed three scenarios for the Cascadia fault’s motion to determine which could have led to the geologic changes created by the Cascadia quake.

The most accurate scenario exhibited features of the 2011 Japanese quake and a 2010 magnitude-8.8 quake in Maule, Chile. During both, parts of the Earth deep within the fault zone trembled at high frequencies, radiating energy that shook the ground above.

If the Cascadia fault were to generate a quake similar to the one in 1700, then officials might want to prepare for high-energy shaking in some areas near the fault.

Grey Wolf walking through snowy mountains

Predators such as grey wolves tend to roam greater distances than their prey, according to a broad study of terrestrial mammals. Credit: Janette Hill/Robert Harding/Getty

Animal behaviour

The animal that takes the crown for longest distance covered in one year

A grey wolf in Mongolia roamed more than 7,000 kilometres in a single year, but caribou boast the longest annual migration.

Which land animal has the longest migration? Biologists have long suspected that caribou journey the farthest on their annual round trip, but hard evidence was lacking.

Kyle Joly at the Gates of the Arctic National Park & Preserve in Fairbanks, Alaska, and an international team of researchers who track mammals decided to settle the question by pooling their own findings and data collected by other scientists. They found that caribou (Rangifer tarandus) do indeed migrate the farthest between their summer and winter ranges, with some herds covering more than 1,200 kilometres in a round trip. Caribou beat wildebeest, bison, pronghorns, Mongolian gazelles and Burchell’s zebras for the title of the mammal with the longest migration.

But the prize for most kilometres covered in a year went to another mammal: the grey wolf (Canis lupus). The absolute champion was a male from Mongolia that covered a jaw-dropping 7,247 km in a single year. In general, predators covered more ground than their prey.

Sadly, human manipulation of landscapes has broken or truncated many ancient migrations. The researchers call for the conservation of these epic animal journeys, as well as the species that undertake them.

A young girl waking her dad up from his nap

A night of inadequate sleep can trigger not only an overwhelming urge to nap, but also a rise in anxiety. Credit: Lynn Koenig/Getty


Sleep-deprived and anxious? This brain region helps to explain why

Too little shut-eye raises anxiety; deep sleep offers protection against it.

Inadequate sleep leads to changes in brain activity that are linked to anxiety.

In a laboratory study, Eti Ben Simon and Matthew Walker and their colleagues at the University of California, Berkeley, found that when healthy volunteers were kept awake for 24 hours, they had higher anxiety levels the next morning than they did after a full night’s sleep. In fact, when sleep-deprived, half of the study participants reported anxiety levels typically seen in people with clinical anxiety disorders. And online surveys completed by a larger number of volunteers showed that ordinary fluctuations in nightly sleep quality predict next-day anxiety levels.

The team also imaged the brains of the sleep-lab participants as they watched video clips designed to conjure up negative emotions. People who watched these videos after sleep deprivation showed less activity in the prefrontal cortex (PFC), an area involved in emotional control, than they did when they were well-rested. Those with the greatest drops in PFC activity reported the largest spikes in anxiety after an all-nighter.

More and higher-quality non-REM slow-wave sleep — often referred to as deep sleep — correlated with greater recovery of PFC activity and greater reductions in next-day anxiety.

See more Research Highlights