Research Highlights

Our pick of the latest scientific literature

  • Volume 550
  • Issue 7677
The Longnose gar (Lepisosteus osseus) is of great interest to researchers studying development.

The Longnose gar (Lepisosteus osseus) is of great interest to researchers studying development. Alex Mustard/NPL

Zoology

Head, trunk and in between

Understanding the origin of muscles that join head and trunk.

Vertebrates would look very different were it not for the evolution of the head and trunk into separate structures, and this differentiation is a subject of great interest in zoology.

Benjamin Naumann at Friedrich Schiller University in Jena, Germany, and his colleagues investigated the development of a muscle called the cucullaris, which spans the interface between the head and trunk in all vertebrates. They looked at its development in the longnose gar (Lepisosteus osseus). In fish phylogeny, gars sit near the base of the group of bony fish called ray-finned fishes. The team found that muscles previously identified as the cucullaris in these fish had been misidentified, and that the actual cucullaris develops later than the other muscles at the head–trunk interface. This is similar to how it develops in some tetrapods, and suggests that the muscle might have a common origin in all bony fish and tetrapod vertebrates, a subject of debate in the past.

The chemical make-up of this alabaster sculpture has revealed where its stone was quarried.

The chemical make-up of this alabaster sculpture has revealed where its stone was quarried. Wolfram Kloppmann/Louvre Museum, Sculptures Department

History

Tracing the origins of medieval sculptures using isotope fingerprints

Researchers track rock of fourteenth-century statue back to quarry in the French Alps.

Researchers have traced the origins of dozens of alabaster sculptures dating from the twelfth to the seventeenth centuries using chemical-isotope signatures.

Medieval trade routes are a mystery to historians because written records are rare. So Wolfram Kloppmann at the French Geological Survey in Orleans, France, and his colleagues analysed the isotopic composition of sulfur, oxygen and strontium in alabaster works of art from the period. They then matched these isotopic fingerprints with geographical locations.

They found three major sources of alabaster: central England, northern Spain and a previously little-known site in the French Alps. Alabaster from that quarry was used in a fourteenth-century sculpture depicting Christ carrying the Cross that now resides in the Louvre in Paris. The team’s results paint a picture of stiff competition between these sources at the time when this rock was a favourite with European sculptors.

A difference between the inclination of a star’s magnetic axis and its axis of rotation might switch on exoplanet volcanoes.

A difference between the inclination of a star’s magnetic axis and its axis of rotation might switch on exoplanet volcanoes. Frans Lanting/Mint Images/Getty

Planetary science

Induction heating could drive exoplanet volcanoes

Planets around TRAPPIST-1 could be disrupted by their star’s magnetic fields.

Powerful magnetic fields exerted by the ultra-cool dwarf star TRAPPIST-1 could trigger volcanoes to erupt on four of its seven known planets.

TRAPPIST-1 hosts several planets that might lie in the ‘habitable zone’, where liquid water could exist — therefore suggesting the potential for life.

But the star’s powerful magnetism would spell trouble for any possible extra-terrestrial life in the system, say Kristina Kislyakova of the Austrian Academy of Sciences in Graz, Austria, and her colleagues. If a star’s magnetic axis is inclined with respect to its axis of rotation, a nearby rocky planet will experience magnetic-flux changes as it orbits. This would heat the mantle of the planet, in the same way that an induction cooker warms a pan. The team’s modelling for the TRAPPIST-1 system found that this could cause volcanoes to erupt and potentially even turn part of the planet’s interior into a seething ocean of magma.

These fossils were discovered in summer 2012, and researchers worked for five years to unpick their significance.

These fossils were discovered in summer 2012, and researchers worked for five years to unpick their significance. H. Xu et al./Proc. Natl Acad. Sci. USA

Plant sciences

How the first trees grew so large

Remarkably well-preserved ancient trees show cellular anatomy from millions of years ago.

Cladoxylopsida were the first large trees to appear on Earth, arising almost 400 million years ago in the Devonian period. But how their trunks grew to reach sizes of up to a metre across has been unclear.

Hong-He Xu at the Chinese Academy of Sciences’ Nanjing Institute of Geology and Palaeontology, Christopher Berry at Cardiff University, UK, and their colleagues examined fossil tree trunks from China in which the cellular anatomy had been preserved. They found that hundreds of strands of water-carrying xylem cells formed a cylindrical trunk, with secondary growth of woody and soft tissue around individual strands. The trees would therefore have been able to reach large sizes by tearing and repairing the connections between individual strands during growth, the authors say. This growth strategy is unique, but has some similarities to that of modern palm trees.

Materials science

Controlling gas with the flip of a switch

A metal–organic framework can separate gas molecules that differ by just two hydrogen atoms.

Electric fields can be used to control the flow of gas through a membrane.

Porous materials known as metal–organic frameworks (MOFs) can be used to separate gas molecules of different sizes. But their scaffold-like structures, composed of metals linked by organic struts, are often flexible, and struggle to separate molecules whose sizes differ by only a small amount.

Jürgen Caro and Alexander Knebel at the Leibniz University of Hanover, Germany, and their colleagues investigated the effect of an electric field on a MOF called ZIF-8, made up of zinc ions and imidazolate (C3H3N2-) struts. They found that applying the field made a ZIF-8 membrane less permeable, allowing it to better sieve propane from propene — molecules that differ by just two hydrogen atoms.

X-ray studies suggested that this was due to the MOF’s crystal structure polarizing under the electric field and becoming more rigid, which barred the larger, propane molecules from passing through while permitting propene to pass. The reversible effect could be harnessed in a range of MOFs to create controllable materials for use in drug delivery and sensors, the authors suggest.

This 28,000-year-old mandible from a sabre-toothed cat was recovered from the North Sea. This 28,000-year-old mandible from a sabre-toothed cat was recovered from the North Sea.

Zoology

Sequencing reveals family history of sabre-toothed cats

Ancient beasts’ genomes suggest that two recognized species of Homotherium are actually one.

Sequencing of ancient DNA suggests that only one species of Homotherium, a sabre-toothed cat, roamed the Earth around 30,000 years ago.

Johanna Paijmans, at the University of Potsdam, Germany, and her colleagues sequenced the DNA of cell structures called mitochondria from three Homotherium specimens, two from over 50,000 and one from 28,000 years ago, and from the 11,000-year-old remains of a Smilodon, another sabre-toothed cat.

These partial genomes show major differences between the two lineages, and suggest that they split around 18 million years ago. However, the Homotherium samples showed little divergence, despite the two older ones being from North America and the other from Europe.

Currently, separate species are thought to have existed in the two regions up to the late Pleistocene. But the team suggests that these animals should all be considered one species: Homotherium latidens.

Divers surveyed fish, invertebrates and other animal life at sites across the globe. Divers surveyed fish, invertebrates and other animal life at sites across the globe.

Ecology

Unpicking patterns of global reef biodiversity

Data from divers show what lives where at different latitudes.

The diversity of life in the tropics is abundantly clear. But why more species live there than in colder climates is debated.

Graham Edgar at the University of Tasmania in Australia and his colleagues undertook standardized surveys of animals found at 2,406 reef sites across the globe. Overall species richness is at its highest in the ‘Coral Triangle’ between Australia and Southeast Asia, and declines outwards from there, they found. Looking only at latitude, richness peaks at 15° north and 15° south of the Equator. But at the site level, many more large, mobile invertebrate species are observed at high latitudes than are seen near the Equator. Species richness is highly correlated with the amount of coral reef in a given region.

The authors suggest that fish predation limits invertebrate diversity in the tropics, and that local temperatures and nutrient levels control abundance.

Chemistry

Polymer chains grow one ‘hairball’ at a time

A magnetic-tracking technique revealed that molecules added to a polymer exhibit ‘wait-and-jump’ behaviour.

Chain-growth polymerization is widely used for synthesizing long molecules, through the addition of building blocks called monomers to the end of a molecular chain.

A team led by Peng Chen, Geoffrey Coates and Fernando Escobedo of Cornell University in Ithaca, New York, has now observed the growth of an individual polymer as it gains monomers one at a time.

To follow this process, the researchers tethered magnetic particles to one end of polymers. They then used magnetic tweezers, which deploy magnetic fields to manipulate and image the particles, to track single monomers as they were inserted into the polymers. Chains, the team found, did not extend steadily, but instead jumped every few minutes by hundreds of nanometres — equivalent to the addition of thousands of monomers.

Simulations indicate that this ‘wait-and-jump’ behaviour is due to newly appended monomers becoming tangled and held together by weak interactions, forming an ‘entangled hairball’ that suddenly unravels. The researchers used a gentle magnetic force to keep the polymer extended and aligned as it grew. In the absence of this influence, such hairballs might be even more prevalent in polymer growth, they say.

Insects such as these are less plentiful in Germany than they used to be.

Insects such as these are less plentiful in Germany than they used to be. Agencja Fotograficzna Caro/Alamy

Zoology

Flying insects are disappearing from German skies

The country has lost three-quarters of its aerial insects since 1989.

The number of flying insects in German skies has fallen sharply over the past three decades.

Caspar Hallmann of Radboud University in Nijmegen, the Netherlands, and his colleagues have been deploying traps to capture aerial insects at 63 nature reserves in Germany over a 27-year period.

Most locations were sampled only once. In total, the team examined 96 separate combinations of year and site.

After correcting for seasonal changes and type of habitat, the researchers found a 6.1% annual decline in flying-insect biomass, and an overall decline of nearly 77% between 1989 and 2016. Declines were higher in summer months. Similar trends were seen in sites sampled more than once.

The authors say that this huge, unrecognized loss cannot be sufficiently explained by changes in weather, land use or habitat.

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