default

New antibody attacks 99% of HIV strains

HIVImage copyright
SPL

Scientists have engineered an antibody that attacks 99% of HIV strains and can prevent infection in primates.

It is built to attack three critical parts of the virus – making it harder for HIV to resist its effects.

The work is a collaboration between the US National Institutes of Health and the pharmaceutical company Sanofi.

The International Aids Society said it was an “exciting breakthrough”. Human trials will start in 2018 to see if it can prevent or treat infection.

Our bodies struggle to fight HIV because of the virus’ incredible ability to mutate and change its appearance.

These varieties of HIV – or strains – in a single patient are comparable to those of influenza during a worldwide flu season.

So the immune system finds itself in a fight against an insurmountable number of strains of HIV.

Super-antibodies

But after years of infection, a small number of patients develop powerful weapons called “broadly neutralising antibodies” that attack something fundamental to HIV and can kill large swathes of HIV strains.

Researchers have been trying to use broadly neutralising antibodies as a way to treat HIV, or prevent infection in the first place.

The study, published in the journal Science, combines three such antibodies into an even more powerful “tri-specific antibody”.

Dr Gary Nabel, the chief scientific officer at Sanofi and one of the report authors, told the BBC News website: “They are more potent and have greater breadth than any single naturally occurring antibody that’s been discovered.”

The best naturally occurring antibodies will target 90% of HIV strains.

“We’re getting 99% coverage, and getting coverage at very low concentrations of the antibody,” said Dr Nabel.

Experiments on 24 monkeys showed none of those given the tri-specific antibody developed an infection when they were later injected with the virus.

Dr Nabel said: “It was quite an impressive degree of protection.”

The work included scientists at Harvard Medical School, The Scripps Research Institute, and the Massachusetts Institute of Technology.

‘Exciting’

Clinical trials to test the antibody in people will start next year.

Prof Linda-Gail Bekker, the president of the International Aids Society, told the BBC: “This paper reports an exciting breakthrough.

“These super-engineered antibodies seem to go beyond the natural and could have more applications than we have imagined to date.

“It’s early days yet, and as a scientist I look forward to seeing the first trials get off the ground in 2018.

“As a doctor in Africa, I feel the urgency to confirm these findings in humans as soon as possible.”

Dr Anthony Fauci, the director of the US National Institute of Allergy and Infectious Diseases, said it was an intriguing approach.

He added: “Combinations of antibodies that each bind to a distinct site on HIV may best overcome the defences of the virus in the effort to achieve effective antibody-based treatment and prevention.”

Follow James on Twitter.

Article source: http://www.bbc.co.uk/news/health-41351159

default

Birds ‘churring’ is a sign isles’ shipwreck rats dying out

Shiant IslandsImage copyright
JJM/Geograph

Image caption

The Shiant Islands could be declared free of non-native black rats next year

The calls of a small seabird have been recorded for the first time on a group of islands in The Minch.

Conservationists hope the sound of storm petrels’ “churring” is an indication that an effort to eradicate rats on the Shiant Islands is working.

The black rats are not native to the islands off Lewis and are thought to be the descendants of rats that came ashore from shipwrecks in the 1900s.

Storm petrels are not found where there are rats, which eat their eggs.

Media captionStorm petrels were recorded for the first time on the islands in the summer

On the Shiants, colonies of puffins, razorbills and guillemots have been in decline, while Manx shearwaters and until now storm petrels have not been found at all.

RSPB Scotland, Scottish Natural Heritage and the Nicolson family, which owns the islands, secured funding to start the rat eradication work in 2015.

They hope it will be possible to declare the islands rat-free next March.

Storm petrels, which are slightly bigger than a sparrow, had been seen flying past the Shiants.

To encourage them to breed on the islands, conservationists played the sound of their calls from a loud speaker.

This summer, real storm petrels’ churring was heard and the birds seen at a burrow by conservationists using night vision equipment.

Image copyright
Ed Marshall/RSPB Images

Image caption

Conservationists say storm petrels are vulnerable to rats

Dr Charlie Main, senior project manager for the Shiant Isles Recovery Project, said: “The churring of a storm petrel is very distinctive and we’re delighted that it’s been recorded on the Shiants this summer.

“While we are still some way off the islands being officially declared rat-free, these calls indicate that all the biosecurity work we’re doing to keep these islands predator-free and make them ideal breeding sites for seabirds is paying off.”

She added: “The long-term aim is to allow a breeding colony of storm petrels to establish at the Shiants.”

Dr Andrew Douse, policy and advice manager in ornithology at Scottish Natural Heritage, said the first recording of the birds was “very welcome”.

He said: “Storm petrels only occur on islands without rats, which means that they are very vulnerable to the effects that arise from invasive species such as these.

“The Shiants are an ideal breeding location for storm petrels and hopefully they will go on to become an important stronghold for this species.”

Image copyright
Jac Volbeda/Geograph

Image caption

The islands lie just off the coast of Lewis in the Minch

Article source: http://www.bbc.co.uk/news/uk-scotland-highlands-islands-41347336

default

Big Antarctic iceberg edges out to sea

A-68Image copyright
Copernicus Sentinel data (2017)

Image caption

Widening gap: The picture contains data gathered on 13 and 16 September

The giant berg A-68 looks finally to be on the move.

Recent weeks have seen it shuffle back and forth next to the Antarctic ice shelf from which it broke away.

But the latest satellite imagery now indicates the near-6,000 sq km block is swinging out into the Weddell Sea.

A wide stretch of clear water has opened up between the berg’s southern end and the remaining Larsen shelf structure, suggesting A-68 is set to swing around and head north.

  • A-68 iceberg opens up clear water
  • Giant iceberg splits from Antarctic
  • Iceberg ‘doodles’ trace climate history
  • Antarctica’s troublesome ‘hairdryer winds’
  • The graveyard of giant icebergs

This is the direction the Weddell currents should take the iceberg.

Polar experts expect the trillion-tonne block to essentially bump along the shelf edge until it reaches the great eastward movement of ocean water known as the Antarctic Circumpolar Current.

This would then export what is one of the largest bergs ever recorded out into the South Atlantic.

How far A-68 actually gets along this predicted path is anyone’s guess, however. The berg already shows evidence of fragmentation at its edges.

These bits – they carry the designation A-68b, A-68c, etc – all still float close to their parent. But in time they will get separated, and it is entirely possible that big segments with deep keels could get anchored in shallow waters and become semi-permanent “ice islands”.

A-68 calved during mid-winter and it required radar satellites – such as Europe’s Sentinel-1 spacecraft – with their unique ability to pierce cloud and darkness to keep track of developments.

With the return now to longer days in the Antarctic, opportunities are increasingly opening up for high-resolution optical satellites to take a close look at the state of the berg.

And new imagery from the Spanish Deimos-2 spacecraft shows how the initial sharp edges of the block’s northern-western corner have been lost.

Image copyright
Deimos Imaging, an UrtheCast Company

Scientists are not just looking at the berg; they also continue to monitor the Larsen Ice Shelf.

They are checking to see if its behaviour has changed since the calving.

The shelf is the floating protrusion of glaciers coming off the Antarctic landmass, and the ejection of such a large section of its structure could potentially trigger further fracturing or a change in the speed of ice flow.

So far, however, there is little evidence of either.

When A-68 moves clear of its birth position it will reveal seafloor that probably has not been free of ice cover for 120,000 years – during the peak of the last warm phase in Earth’s history known as the Eemian.

The area has already gained protected status from the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

This gives scientists priority access and keeps fisheries activity at bay for a minimum of two years.

Previous research in locations uncovered by departing bergs has found new species.

Expeditions to visit A-68 this coming Antarctic summer season are in the planning stage.

Article source: http://www.bbc.co.uk/news/science-environment-41366504

default

Ancient DNA sheds light on African history

Mount HoraImage copyright
Jessica Thompson

Image caption

Burials at Mount Hora in Malawi yielded DNA used in the study

DNA from ancient remains has been used to reconstruct thousands of years of population history in Africa.

Researchers sequenced the genomes of 16 individuals who lived between 8,000 and 1,000 years ago.

The data shows how the invention and spread of farming had a major impact on the genes of people in Africa – just as it did in Europe and Asia.

The findings are published in the journal Cell.

The results suggest that populations related to the indigenous people of southern Africa had a wider distribution in the past.

This southern African-like genetic background is found in hunter-gatherers from Malawi and Tanzania in the east of the continent. These hunters lived between 8,100 and 1,400 years ago.

But the later spread of farmers from western Africa had a major impact on the genetic make-up of people in surrounding regions.

Further DNA analysis revealed the hunter-gatherers in eastern Africa had mixed extensively with the incoming farmers.

The researchers estimate that the mixing occurred between 800 and 400 years ago.

The study also found possible evidence of migration into Africa from the Middle East. About 38% of the ancestry of a 3,100-year-old livestock herder from Tanzania was related to ancient farmers from the Levant region.

“These results document a prehistoric population landscape that we didn’t know about,” said co-author Pontus Skoglund, from Harvard Medical School, US.

“They document how farmer and herder migrations swept through eastern and southern Africa.”

The researchers also found tentative evidence of adaptive evolution – changes driven by environmental pressure – for genes involved in taste in the ancient individuals. These taste receptors are known to be important for detecting and learning to avoid poisonous plants.

Article source: http://www.bbc.co.uk/news/science-environment-41348087

default

Plant-eating dinosaurs ‘strayed from veggie diet’

Herbivorous dinosaursImage copyright
Science Photo Library

Image caption

Duck-billed dinosaurs may have been tempted away from a vegetarian diet

The idea of plant-eating dinosaurs having a strict vegetarian diet has been called into question.

New evidence suggests that some dinosaurs snacked on shellfish and insects as well as plant food.

A study of fossilised droppings indicates duck-billed dinosaurs dined on crabs at certain times of the year.

Fossil remains of dinosaur dinners is rare, so this pescatarian diet may have been overlooked in the past.

The popular perception of what dinosaurs ate was simplistic, said Dr Karen Chin of the University of Colorado, Boulder, US, who led the research.

“Plant-eating dinosaurs had more complex diets than we assumed that they had, and these diets included feeding on some animals, including at least crustaceans, and this was more like diets of modern plant-eating birds,” she told BBC News.

When the first dinosaur discoveries were made in the 1850s, some species were labelled plant-eaters because their teeth resembled those of living plant-eating mammals such as rhinos.

The new evidence comes from an area of southern Utah that is regarded as a treasure trove of fossils from the Late Cretaceous Period, when dinosaurs were coming to the end of their reign.

Image copyright
Science Photo Library

Image caption

The hadrosaurs were duck-billed dinosaurs that flourished some 80-65 million years ago

Fossilised dinosaur droppings found on the Kaiparowits Plateau give new insights into what was on the menu for dinosaurs.

Fragments of shell and other remains show they consumed crustaceans such as crabs, which likely sheltered in rotting wood.

The dinosaurs probably actively hunted for crustaceans and insects in a “woody stew” rather than swallowing them accidently, the researchers said.

Animal products may have been a vital source of protein, particularly when they were about to lay their eggs.

Plant guzzlers

“This find really breaks the mould for what we expect a plant-eating dinosaur to do,” said Dr Steve Brusatte of the University of Edinburgh, UK, who was not connected with the study.

“We think of them as these multi-tonne plant guzzlers, but some of them also indulged in other types of food.

“And I guess we shouldn’t be too shocked because that’s true of many plant eaters today, they’ll ingest other stuff, sometimes accidentally, sometimes to supplement their diet with other nutrients.”

The droppings were left by dinosaurs some 75 million years ago on what would then have been a landscape dotted with rivers and ponds.

Duckbilled dinosaurs were common in the area at the time. The bones and teeth of the reptiles suggest they spent most of their time on land, though close to freshwater, feeding on tough plants such as ferns and conifers.

The discovery, detailed in the journal Scientific Reports suggests other plant-eating dinosaurs may have in fact been omnivorous.

“We’ll just have to find more evidence and we’re always on the look out for that,” said Dr Chin.

Follow Helen on Twitter.

Article source: http://www.bbc.co.uk/news/science-environment-41341231

default

Neanderthal brains ‘grew more slowly’

Skeleton of the Neanderthal boy recovered from the El Sidrn cave (Asturias, Spain).Image copyright
Joan Costa

Image caption

The skeleton of a boy that shattered our view of Neanderthal brain development

A new study shows that Neanderthal brains developed more slowly than ours.

An analysis of a Neanderthal child’s skeleton suggests that its brain was still developing at a time when the brains of modern human children are fully formed.

This is further evidence that this now extinct human was not more brutish and primitive than our species.

The research has been published in the journal Science.

Until now it had been thought that we were the only species whose brains develop slowly. Unlike other apes and more primitive humans modern humans have an extended period of childhood lasting several years.

This is because it takes time and energy to develop our large brain. Previous studies of Neanderthal remains indicated that they developed more quickly than modern humans – suggesting that their brains might be less sophisticated.

But a team led by Prof Antonio Rosas of the Museum of Natural Sciences in Madrid found that if anything, Neanderthal brains may develop more slowly than ours.

“It was a surprise,” he told BBC News. “When we started the study we were expecting something similar to the previous studies,” he told BBC News.

Image copyright
Paleoanthropology Group MNCN-CSIC]

Image caption

The remains were discovered inside the El Sidrón cave in Asturias, Spain.

Prof Rosas and his team believe they are right and the previous studies are wrong because for the first time they were able to study a relatively complete skeleton of a child at a crucial stage in their development.

It was of a boy who was nearly seven-and-a-half years old when he died found in the 49,000-year-old site of El Sidrón, in Spain.

The boy’s remains are exceptionally well-preserved and include a mix of baby and adult teeth, which enabled the team to accurately determine his age.

This brain is estimated to have been 87.5% of the size of an average adult Neanderthal brain upon death, whereas a modern humans child the same age would have on average a brain that was 95% the size of an adults.

The researchers also found that reveals that some of the small bones forming the boy’s back bone were not fused. In modern humans, these bones tend to fuse by the time children reach the age of six.

Image copyright
Joan Costa

Image caption

The researchers were surprised to discover that Neanderthal brains develop more slowly

According to Prof Rosas, the finding shows that Neanderthals were similar to our us.

The brutish primitive picture of Neanderthals is an old one. In the last few years there has been growing evidence to suggest that they were a human species with some small differences. Now we can say that the way their growth pattern is similar to ours too”.

The finding raises the intriguing possibility that the Neanderthals’ slightly slower brain development may mean that their brains may have been more advanced than ours. But Prof Rosas prefers a more prosaic interpretation.

“Neanderthals have a larger brain and larger body and so it is logical to think that the brain of the Neanderthal continues to grow for a little longer to allow their brains and bodies to get to their adult size”

Before this finding scientists believed that modern humans were the slowest growing species. Now we know that Neanderthals took slightly longer, suggesting that both species inherited this growth pattern from a now extinct common ancestor.

Follow Pallab on Twitter

Article source: http://www.bbc.co.uk/news/science-environment-41351019

default

Neolithic Orkney rivalries detailed in new study

Ring of BrodgarImage copyright
Colin Richards / UHI

Image caption

Ring of Brodgar is a famous Orkney site

Rivalries in Orkney more than 4,500 years ago led to competition between communities including over how people were buried, according to new research.

Scientists were able to gather much more precise estimates of the timing and duration of events in the period around 3200-2500 BC by examining more than 600 radiocarbon dates.

The study challenges many previously-held ideas about Neolithic Orkney.

The study has been published in the journal Antiquity.

It was led by Prof Alex Bayliss from Historic England, with Prof Colin Richards of the University of the Highlands and Islands in Kirkwall as co-author. It is part of a wider project called The Times of Their Lives.

Ritual clues

The study concludes that seemingly rapid changes in settlements and monuments indicate that there were rivalries and tension between social groups.

This was played out in how they buried their dead and in their communal gatherings and rituals.

The study covered famous Orkney sites including Skara Brae and Maeshowe.


Key dates indicated by the study

  • Orkney was probably first colonised in 3600 BC
  • Settlement peaked in the period 3100-2900 BC
  • There was a phase of decline 2800-2600 BC, measured by the number of stone houses in use
  • Settlement resumed in 2600-2300 BC, and it could have been about this time that the Ring of Brodgar itself was erected.

Prof Bayliss said: “This study shows that new statistical analysis of the large numbers of radiocarbon dates that are now available in British archaeology really changes what we can know about our pasts.

“People in the Neolithic made choices, just like us, about all sorts of things – where to live, how to bury their dead, how to farm, where and when to gather together – and those choices are just beginning to come into view through archaeology.

“It’s an exciting time to be an archaeological scientist.”

Image copyright
Colin Richards / UHI

Prof Richards said: “Our study shows how much remains to be discovered in Orkney about the Neolithic period, even though it may appear well known.”

Prof Alasdair Whittle of Cardiff University is the lead investigator for The Times of Their Lives.

Prof Whittle said: “Visitors come from all over the world to admire the wonderfully preserved archaeological remains of Orkney, in what may seem a timeless setting.

“Our study underlines that the Neolithic past was often rapidly changing, and that what may appear to us to be enduring monuments were in fact part of a dynamic historical context.”

Article source: http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-41319168

default

Owls hold secret to ageless ears

Barn owlImage copyright
Getty Images

Image caption

Barn owls rely on their hearing to hunt

Barn owls keep their acute sense of hearing into old age, scientists have discovered.

Previously, starlings have been found to have this ability, suggesting birds are protected from age-related hearing loss.

Understanding more about the “ageless ears” of barn owls could help develop new treatments for human hearing problems.

Birds are able to naturally repair damage to the inner ear.

Georg Klump of the University of Oldenburg, Germany, a researcher on the study, said owls keep their hearing into very old age.

“Birds can repair their ears like (humans) can repair a wound,” he said. “Humans cannot re-grow the sensory cells of the ears but birds can do this.”

It appears that humans lost these regenerative abilities at some point in evolution. Like all mammals, people commonly suffer from hearing loss in old age.

By the age of 65, humans can expect to lose more than 30 dB in sensitivity at high frequencies.

Commenting on the study, Dr Stefan Heller of Stanford University School of Medicine, said work was underway to investigate differences between birds and mammals.

“To truly utilise this knowledge, we need to conduct comparative studies of birds and mammals that aim to find the differences in regenerative capacity, a topic that is actively pursued by a number of laboratories worldwide,” he said.

The research, published in the journal, Royal Society Proceedings B, was carried out on seven captive barn owls.

The birds were trained to fly to a perch to receive a food reward in response to sounds.

Even the oldest owl, which reached the ripe old age of 23, showed no signs of age-related hearing loss.

Barn owls typically only live to the age of three or four in the wild. The birds rely on their hearing to hunt prey at night.

Follow Helen on Twitter.

Article source: http://www.bbc.co.uk/news/science-environment-41325339

default

UK strikes research deal with US in run-up to Brexit

UK US FlagImage copyright
Fredex8

The UK and US have reached a deal to develop a special relationship for science.

An agreement between the two countries aims to make it easier for researchers to travel, collaborate and share facilities.

US science bodies are said to be “eager” to take advantage of research opportunities lost because of Brexit.

The deal is part of government efforts to develop research collaborations outside the EU.

BBC News revealed earlier this year when the deal was being negotiated that the aim was to develop a legal framework to allow a freer flow of people, research grants and tariff-free exchange of equipment between the two countries.

Possible strategic areas of collaboration include:

  • synthetic biology
  • information technology
  • GM research

Image copyright
SANGER CENTRE

Image caption

America and Britain were key partners on the project to decode the human genome

The agreement, signed by the Science Minister Jo Johnson and his US counterparts, states that national laws will “seek to facilitate” freer movement of people and scientific equipment.

Speaking in Washington, Mr Johnson said that the deal would help to ensure that the UK would maintain its global lead in many areas of research.

“Our continued collaboration with the US on science and innovation is beneficial to both of our nations, and through this agreement we are sharing expertise to enhance our understanding of many important topics that have the potential to be world changing,” the minister added.

The impetus for the deal came following the UK referendum result to leave the European Union. British universities, in collaboration with small businesses, receive £850m in research grants each year from membership of the EU’s research programmes. EU membership also makes it easy to form collaborations.

There are fears that much of the funding and collaborative work with EU scientists will be in jeopardy once the UK leaves the EU, despite recent assurances from the Brexit Secretary, David Davis, that his aim is to foster even closer scientific relationships with the EU.

Prof Venki Ramakrishnan, president of the Royal Society, welcomed the deal with the US but remains concerned that Mr Davis’ aspiration to have closer collaboration with the EU lacks any detail on how to achieve his aim.

“This agreement sends a welcome message that UK science remains outward looking. International research collaboration allows the rapid exchange of new ideas and expertise and it also allows us to address problems that no one country can on its own. It is an essential part of modern science,” he said.

Image copyright
NSF/LIGO

Image caption

A wider partnership could give UK researchers even more access to US facilities

British researchers are being encouraged to foster links with other nations. While most if not all research leaders are still dismayed by the referendum result – some are beginning to see advantages for greater collaboration with the US.

For example, there is scope for greater freedom in research in synthetic biology and information technology because biotechnology and privacy regulation is less restrictive outside the EU.

For their part, US science bodies see Brexit as an opportunity for them. US research leaders are anxious that American research groups fill any shortfall left by the UK’s departure from the EU, rather than their rivals in India and China.

Mr Johnson announced that the government had pledged £65m to participate in a US-based and led international project to learn more about sub-atomic particles called neutrinos. He said he hoped it would be the first of many more UK research collaborations with the US.

Media captionPallab Ghosh looks at how the neutrino beam would be fired underground

The so-called Dune project involves 150 scientists from 10 UK universities participating in a US-led effort involving 1,000 scientists from 30 countries.

The UK was likely to participate in Dune before the referendum result, but the project received greater support from ministers subsequently because it fitted well with the government’s narrative to reassure the British scientific community that Brexit would free them to take up new opportunities outside the EU.

Echoing that message Sir Mark Walport, currently the government’s chief scientific adviser and soon to be chief executive of UK Research and Innovation, the body that will oversee funding of civil government research, said that the agreement sent a “clear signal that UK researchers are outward looking and ready to work with the best talent wherever that may be”.

“UK Research and Innovation is looking forward to extending partnerships in science and innovation around the world,” he added.

Follow Pallab on Twitter

Article source: http://www.bbc.co.uk/news/science-environment-41340971

default

Outwitted

HouseflyImage copyright
Science Photo Library

Try to swat a fly and it will soon become clear that they’re faster than you. Much faster. But how on Earth do these tiny creatures – with their minuscule brains – outwit us so easily?

You’ve probably pondered it after chasing a fly around your house and flailing your shoe with repeated, unsuccessful swats. How does it move so fast? Can it read my mind?

It was the question put to the BBC World Service CrowdScience team for our most recent episode addressing the apparent super powers of tiny animals. The answer is that, compared with you and me, flies essentially see the world in slow motion.

To illustrate this, have a look at a clock with a ticking hand. As a human, you see the clock ticking at a particular speed. But for a turtle it would appear to be ticking at twice that speed. For most fly species, each tick would drag by about four times more slowly. In effect, the speed of time differs depending on your species.

This happens because animals see the world around them like a continuous video. But in reality, they piece together images sent from the eyes to the brain in distinct flashes a set number of times per second. Humans average 60 flashes per second, turtles 15, and flies 250.

It’s all relative

The speed at which those images are processed by the brain is called the “flicker fusion rate”. In general, the smaller the species, the faster its critical flicker fusion rate – and flies, in particular, put us to shame.

Professor Roger Hardie, from the University of Cambridge, investigates how flies’ eyes work, and he has an experiment to determine their flicker fusion rate.

Image copyright
SPL

Image caption

“How d’ya like them apples?” For flies, time drags more slowly than for people

“The flicker fusion rate is simply how fast a light has to be turning on and off before it’s perceived or seen as just a continuous light” says Prof Hardie.

Roger inserts tiny glass electrodes into the living light sensitive cells of their eyes – photoreceptors – before flashing LED lights at faster and faster speeds. Each flash of the LED produces a tiny electrical current in the photoreceptors that a computer can graph onto a screen. Tests reveal the fastest fly records distinct responses to flickering up to 400 times per second, more than six times faster than our own rate.

The fastest vision of all is found in a species literally called a “killer fly”. It’s a tiny predatory species found in Europe that catches other flies out of the air with super-fast reactions. In her “fly lab” at Cambridge University, Dr Paloma Gonzales-Bellido demonstrates the killer flies’ hunting behaviour by releasing fruit fly prey into a special filming box with a female killer fly.

Media captionSome flies see six times faster than us, catching prey in mid-air in less than a second.

Paloma records the behaviour at 1,000 frames per second using slow motion video cameras with a recording buffer. The attached computer constantly saves the video, over-writing itself every twelve seconds. When the fly moves, Paloma clicks a button to permanently save the last 12 seconds.

“Our reaction time is so slow that if we were to stop it when we think something is happening it would have happened already,” says Dr Gonzales-Bellido. Essentially, we can’t even click a button before the behaviour has happened, it’s that fast.

Fly vs fly

With the killer flies and their prey in the filming box, initially the killer fly just sat around motionless, but as one of the fruit flies flew about 7cm above it, there was a flash of movement and suddenly the killer fly was at the bottom of the box chomping into the quivering fruit fly.

Only looking at the slowed-down footage on the computer did it become clear what happened; the killer fly took off, circled the fruit fly three times as it tried to grab it repeatedly, before succeeding in capturing the elusive fruit fly with its front legs.

The whole behaviour from take-off to landing took just one second. It appears as a flash to our eyes, so conversely, the swatting hand of a human must appear at a snail’s pace.

Image copyright
Other

Image caption

The killer fly’s eyes contain many more mitochondria than in the eyes of other fly species

Image caption

Paloma Gonzales-Bellido uses a special filming box to study killer flies

To enable this incredible speed of the killer fly, which is faster even than other fly species, the light-detecting cells in the killer fly eyes contain many more mitochondria (the “batteries” of biological cells) than are present in the same cells of other flies.

These are the batteries of the cell, so the speedy vision must take more energy than slow vision, explaining why all eyes aren’t just set to the highest flicker fusion rate.

The carnivorous diet of the killer fly provides the large amounts of energy it needs to power these high-energy cells. But even if we had the same number of mitochondria in the cells or our own eyes, we wouldn’t have the same vision speed because flies’ light-sensitive cells have a totally different design to those of vertebrates.

Behind the structural differences in the eyes of flies is their evolutionary origin. Arthropods and vertebrates, the groups holding flies and humans, evolved their eyes entirely separately around 700-750 million years ago.

String theory

Flies’ eyes evolved to pick up light with a series of tiny string-like structures that lie horizontal to the path that light travels through the eye. These structures react to light mechanically whereas vertebrates have long tube-like cells facing the light, with chemicals that react to light at the base.

This structure in the fly eye is something Roger studies in his lab. “It’s more sensitive in terms of being able to give a large signal to the tiniest amount of light and it can also respond faster than the rods and cones in the vertebrate eye,” he explains.

Image caption

Roger Hardie studies the structure of the fly visual system

There are a few reasons for this higher sensitivity, but what Prof Hardie discovered is that they respond mechanically to light, as opposed to chemically as in cones and rods.

Mechanical responses enable faster neural signals. On top of that, there’s a limit to the speed at which neural impulses can travel and the smaller nerve distances from fly eye to fly brain speeds up processing compared to larger vertebrates.

Some vertebrates experience much faster vision than our own. Whether the species is able to fly seems to correlate with faster vision, as does being small. This may be because small flying animals have to react so quickly during flight to avoid approaching obstacles.

‘Slow motion swats’

The fastest vision of all is found in species that catch flies in the air.

Back with vertebrates, when investigating the vision of the pied flycatcher, a small perching bird that catches flies in flight, scientists at Uppsala University in Sweden discovered that it was able to identify a light flashing on and off 146 times per second from a continuous light source.

The birds were trained to associate a flashing light source with a tasty treat, and would accurately identify the flashing light up to this rate, placing their flicker fusion rate at 146. That’s about twice the rate humans can see but still not as fast as the average fly.

This means the birds, like flies, experience each tick of the clock more slowly than humans.

There is an evolutionary pressure on the flycatchers to experience the ticking hand of the clock as slowly as possible in order to outwit their speedy prey. Over evolutionary time, birds that experienced ‘slower ticking’ could react faster to their prey, allowing them to eat more, raise more chicks and pass this speedy vision to future generations.

The flies that have been chased by the fast-sighted birds will be evolving faster reactions to get away. Creating an evolutionary arms race that has gone on longer even than the existence of birds. Prey flies have been evolving faster vision and reactions to escape predatory flies like the killer fly since they evolved flight.

Next time you try inanely to swat a fly, try not to be so disheartened. Your lumbering, slow motion swats are being thwarted by hundreds of millions of years of natural selection letting the flies watch your attempts in slow motion.

Between you and the fly, time, it seems, is relative.

Listen to ‘CrowdScience’ on the BBC World Service, the programme whose listeners inspired this article, and send your science questions to ‘CrowdScience@bbc.co.uk’ :

Article source: http://www.bbc.co.uk/news/science-environment-41284065

© Warren Fyfe
CyberChimps