Science & Technology


Poisonous frogs evolve to sing longer and louder

Devil Frog
© Pete Oxford/NaturePL
Hear my song: but you'll regret it if you eat me.
He's sexy and he knows it. The little devil frog is noisy in pursuit of a partner, and doesn't care who hears him.

The little devil frog's fearlessness in the face of hungry predators could be down to his toxicity. The little devil, Oophaga sylvatica, is a member of the dendrobatid group of poisonous frogs. His bright colours warn predators that he is unsafe to eat, which Juan Santos of the University of British Columbia in Vancouver, Canada, believes has allowed the evolution of more flamboyant mating calls.

Santos and his colleagues examined the calls, colourings and toxicity of 170 species of frog, including the little devil. They found a strong relationship between the volume of a frog's call and its aposematism - markings that warn of its toxicity. In general, the more toxic a frog, the brighter and more noticeable it is - and the louder and more rapidly it sings (Proceedings of the Royal Society B). Non-toxic frogs are camouflaged and call from less exposed perches, says Santos.

"Females can have a significant effect on the selection of the most noisy males, given that predators will avoid these aposematic individuals," says Santos.

Myelin vital for learning new practical skills

© Sarah Jolly, UCl
Image shows the complex shape of individual oligodendrocytes (OLs) and myelin in adult mice injected with tamoxifen.
New evidence of myelin's essential role in learning and retaining new practical skills, such as playing a musical instrument, has been uncovered by UCL research. Myelin is a fatty substance that insulates the brain's wiring and is a major constituent of 'white matter'. It is produced by the brain and spinal cord into early adulthood as it is needed for many developmental processes, and although earlier studies of human white matter hinted at its involvement in skill learning, this is the first time it has been confirmed experimentally.

The study in mice, published in Science today, shows that new myelin must be made each time a skill is learned later in life and the structure of the brain's white matter changes during new practical activities by increasing the number of myelin-producing cells. Furthermore, the team say once a new skill has been learnt, it is retained even after myelin production stops. These discoveries could prove important in finding ways to stimulate and improve learning, and in understanding myelin's involvement in other brain processes, such as in cognition.

For a child to learn to walk or an adult to master a new skill such as juggling, new brain circuit activity is needed and new connections are made across large distances and at high speeds between different parts of the brain and spinal cord. For this, electrical signals fire between neurons connected by "axons" -- thread-like extensions of their outer surfaces which can be viewed as the 'wire' in the electric circuit. When new signals fire repeatedly along axons, the connections between the neurons strengthen, making them easier to fire in the same pattern in future. Neighbouring myelin-producing cells called oligodendrocytes (OLs) recognise the repeating signal and wrap myelin around the active circuit wiring. It is this activity-driven insulation that the team identified as essential for learning.

Brain's compass relies on geometric relationships, say researchers

© Penn News
Each of the virtual museums in the study was visually distinct, but had the same layout and geometry.
The brain has a complex system for keeping track of which direction you are facing as you move about; remembering how to get from one place to another would otherwise be impossible. Researchers from the University of Pennsylvania have now shown how the brain anchors this mental compass.

Their findings provide a neurological basis for something that psychologists have long observed about navigational behavior: people use geometrical relationships to orient themselves.

The research, which is related to the work that won this year's Nobel Prize in Physiology or Medicine, adds new dimensions to our understanding of spatial memory and how it helps us to build memories of events.

The study was led by Russell Epstein, a professor of psychology in Penn's School of Arts & Sciences, and Steven Marchette, a postdoctoral fellow in Epstein's lab. Also contributing to the study were lab members Lindsay Vass, a graduate student, and Jack Ryan, a research specialist.

It was published in Nature Neuroscience.

Could designer viruses be the new antibiotic?

© Credit: Graham Beards/Wikimedia Commons
Bacteria under attack by a flock of bacteriophages.
Bacterial infections remain a major threat to human and animal health. Worse still, the catalogue of useful antibiotics is shrinking as pathogens build up resistance to these drugs. There are few promising new drugs in the pipeline, but they may not prove to be enough. Multi-resistant organisms - also called "superbugs" - are on the rise and many predict a gloomy future if nothing is done to fight back.

The answer, some believe, may lie in using engineered bacteriophages - a type of viruses that infects bacteria. Two recent studies, both published in the journal Nature Biotechnology, show a promising alternative to small-molecule drugs that are the mainstay of antibiotics today.

Physicists develop model of ammonite' coiled spiral shell

© Henrich Harder/Wikipedia
Ammonites as they would appear in life
Ammonites are a group of extinct cephalopod mollusks with ribbed spiral shells. They are exceptionally diverse and well known to fossil lovers. Régis Chirat, researcher at the Laboratoire de Géologie de Lyon: Terre, Planètes et Environnement (CNRS/Université Claude Bernard Lyon 1/ENS de Lyon), and two colleagues from the Mathematical Institute at the University of Oxford have developed the first biomechanical model explaining how these shells form and why they are so diverse. Their approach provides new paths for interpreting the evolution of ammonites and nautili, their smooth-shelled distant "cousins" that still populate the Indian and Pacific oceans. This work has just been published on the website of the Journal of Theoretical Biology.

ammonite shell
© Derek Moulton, Alain Goriely and Régis Chirat
The mechanical model predicts the correlations observed between rib frequency and amplitude and the shell's general shape in ammonites (blue morphological space) and nautili (red morphological space) The 3D-views produced by the model are juxtaposed with fossil specimens, ammonites and nautili, that have a similar shape. The ribs tend to disappear for the broadly open shell shapes that have characterized nautili for almost 200 million years. W = expansion rate D = coiling tightness
The shape of living organisms evolves over time. The questions raised by this transformation have led to the emergence of theories of evolution. To understand how biological shapes change over a geological time scale, researchers have recently begun to investigate how they are generated during an individual's development and growth: this is known as morphogenesis. Due to the exceptional diversity of their shell shapes and patterns (particularly the ribs), ammonites have been widely studied from the point of view of evolution but the mechanisms underlying the coiled spirals were unknown until now. Researchers therefore attempted to elucidate the evolution of these shapes without knowing how they had emerged.

Régis Chirat and his team have developed a model that explains the morphogenesis of these shells. By using mathematical equations to describe how the shell is secreted by ammonite and grows, they have demonstrated the existence of mechanical forces specific to developing mollusks. These forces depend on the physical properties of the biological tissues and on the geometry of the shell. They cause mechanical oscillations at the edge of the shell that generate ribs, a sort of ornamental pattern on the spiral.
Solar Flares

The Sun's atmosphere is hotter than its surface, says NASA

© NASA, Lockheed Martin Solar & Astrophysics Laboratory
NASA’s Solar Dynamics Observatory provided the outer image of a coronal mass ejection on May 9, 2014. The IRIS spacecraft.
NASA's Interface Region Imaging Spectrograph (IRIS) has provided scientists with five new findings into how the sun's atmosphere, or corona, is heated far hotter than its surface, what causes the sun's constant outflow of particles called the solar wind, and what mechanisms accelerate particles that power solar flares.

The new information will help researchers better understand how our nearest star transfers energy through its atmosphere and track the dynamic solar activity that can impact technological infrastructure in space and on Earth. Details of the findings appear in the current edition of Science.

"These findings reveal a region of the sun more complicated than previously thought," said Jeff Newmark, interim director for the Heliophysics Division at NASA Headquarters in Washington. "Combining IRIS data with observations from other Heliophysics missions is enabling breakthroughs in our understanding of the sun and its interactions with the solar system."
Bizarro Earth

Four San Francisco fault lines have built up enough seismic strain to unleash destructive earthquakes

northern california fault lines

San Francisco Bay Area earthquake faults are drawn in red.
With several faults slicing through the San Francisco Bay Area, forecasting the next deadly earthquake becomes a question of when and where, not if.

Now researchers propose that four faults have built up enough seismic strain (stored energy) to unleash destructive earthquakes, according to a study published today (Oct. 13) in the Bulletin of the Seismological Society of America.

The quartet includes the Hayward Fault, the Rodgers Creek Fault, the Green Valley Fault and the Calaveras Fault. While all are smaller pieces of California's San Andreas Fault system, which is more than 800 miles (1,300 kilometers) long, the four faults are a serious threat because they directly underlie cities.

Dinosaurs may have been heavy, wet breathers

© Corbis
Illustration of the Cretaceous pachycephalosaur Stegoceras.
The first ever reconstruction of how dinosaurs breathed finds that these long-extinct animals used each heavy, mucous-moistened breath to smell their surroundings and to cool their brains.

The study, published in the Anatomical Record, helps to explain why most non-avian dinosaurs had such long snouts. It also adds another dimension of life to these prehistoric animals, the last of which took its final breath around 65 million years ago.

Lead author Jason Bourke and his team used plant-eating Stegoceras as a model dinosaur since it had a particularly bony skull with fossilized bones in its nasal region still in place.

MAVEN spacecraft finds oxygen and hydrogen in Mars' atmosphere

© NASA/Univ. of Colorado
These are two views of Mars' escaping atmospheric gases -- oxygen and hydrogen -- obtained by MAVEN's Imaging Ultraviolet Spectrograph.
Early results from NASA's recently arrived MAVEN Mars spacecraft show an extensive, tenuous cloud of hydrogen surrounding the Red Planet, the result of water breaking down in the atmosphere, scientists said Tuesday.

MAVEN, an acronym for Mars Atmosphere and Volatile Evolution, arrived on Sept. 21 to help answer questions about what caused a planet that was once warm and wet to turn into the cold, dry desert that appears today.

Construction secrets of a galactic metropolis

APEX reveals hidden star formation in protocluster

© ESO/M. Kornmesser
This artist's impression depicts the formation of a galaxy cluster in the early Universe.
Galaxy clusters are the largest objects in the Universe held together by gravity but their formation is not well understood. The Spiderweb Galaxy (formally known as MRC 1138-2621) and its surroundings have been studied for twenty years, using ESO and other telescopes2, and is thought to be one of the best examples of a protocluster in the process of assembly, more than ten billion years ago.

But Helmut Dannerbauer (University of Vienna, Austria) and his team strongly suspected that the story was far from complete. They wanted to probe the dark side of star formation and find out how much of the star formation taking place in the Spiderweb Galaxy cluster was hidden from view behind dust.

The team used the LABOCA camera on the APEX telescope in Chile to make 40 hours of observations of the Spiderweb Cluster at millimeter wavelengths - wavelengths of light that are long enough to peer right through most of the thick dust clouds. LABOCA has a wide field and is the perfect instrument for this survey.

Carlos De Breuck (APEX project scientist at ESO, and a co-author of the new study) emphasizes: "This is one of the deepest observations ever made with APEX and pushes the technology to its limits - as well as the endurance of the staff working at the high-altitude APEX site, 5050 meters above sea level."