Science Headlines for December 3, 2008

Particulate Emissions From Laser Printers

Do laser printers emit pathogenic toner particles into the air? Some people are convinced that they do. As a result, this topic is the subject of public controversy. Researchers have now investigated what particles the printers really do release into the air.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

Training Doesn't Reduce Avalanche Risk When Skiing, Study Shows

A new study of backcountry ski habits finds training has little impact on risk of being caught in an avalanche, and Americans have higher avalanche risk than Canadians.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

New Strategy For Broad Spectrum Anti-viral Drugs Developed

Bavituximab, a newly developed anti-viral drug shows promise as a new strategy to fight viral diseases, including potential bioterrorism agents.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

Mini Heart Attacks Lessen Damage From Major Ones

Researchers have discovered one potential mechanism by which briefly cutting off, then restoring, blood flow prior to a heart attack lessens the damage caused. The work could lead to new drugs that provide protection ahead of heart attacks, and may help to prevent damage caused as US heart surgeons temporarily cut off blood flow 450,000 times each year to perform coronary artery bypass graft surgeries.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

Gene Mutation May Cause Immature Lungs In Newborns

Scientists have identified a gene critical to lung maturation in newborns and the production of surfactant, which lines lung tissues and prevents the lungs from collapsing. Scientists deleted the Foxm1 gene in embryonic mice. Lungs in the mice did not fully mature and the mice died shortly after birth from respiratory distress.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

Sun's Magnetic Field May Impact Weather And Climate: Sun Cycle Can Predict Rainfall Fluctuations

The sun's magnetic field may have a significant impact on weather and climatic parameters in Australia and other countries in the northern and southern hemispheres. Droughts are related to the solar magnetic phases and not the greenhouse effect, according to new research.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 7:00 pm

Bio-inspired Wing Design To Revolutionize Aircraft Flight

It's a bird, it's a plane, it's ... both! While aircraft have always borne a resemblance to their feathered counterparts in the sky, new research is bringing the two even closer together.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 4:00 pm

Gene Which Protects Against Lung Cancer Identified

Scientists have identified a gene that protects the body from lung cancer. The research has found that the tumour suppressor gene, LIMD1, is responsible for protecting the body from developing lung cancer — paving the way for possible new treatments and early screening techniques.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 4:00 pm

Evidence From Dirty Teeth: Ancient Peruvians Ate Well

Starch grains preserved on human teeth reveal that ancient Peruvians ate a variety of cultivated crops including squash, beans, peanuts and pacay. Starch grain analysis of human dental remains should prove to be a powerful means to directly study ancient diets.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 4:00 pm

Researchers Call For Fragile X Testing Throughout The Lifespan

Researchers urge physicians to test for mutations of the fragile X gene in patients of all ages. That's because, after decades of research, it is clear that mutations in this gene cause a range of diseases, including neurodevelopmental delays and autism in children, infertility in women and neurodegenerative disease in older adults.
Source: ScienceDaily: Latest Science News | 3 Dec 2008 | 4:00 pm

GM exec: bankruptcy not an option for industry (AP)

AP - A top executive of General Motors Corp. said Wednesday bankruptcy isn't a viable option, as the United Auto Workers braced for a decision on contract concessions to the endangered Big Three.

Source: Yahoo! News: Science News | 3 Dec 2008 | 1:26 pm

Invisible Lights on Mars Mapped

Mars' ultraviolet auroral lights have been mapped for the first time.
Source: Livescience.com | 3 Dec 2008 | 1:18 pm

Huge Sun Shield Built for Space Telescope

A tennis-court-sized sun shield will keep the James Webb Space telescope chilled to perfection in space.
Source: Livescience.com | 3 Dec 2008 | 1:15 pm

Sea's pollution hotspots 'missed'

Large sources of pollution to the Baltic Sea have been missed by existing monitoring efforts, according to a Swedish study.
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 12:56 pm

The Energy Debates: Solar Energy at Home (LiveScience.com)

LiveScience.com - Editor's Note: "The Energy Debates" is a LiveScience series about the pros, cons, policy debates, myths and facts related to various alternative energy ideas. We invite you to join the debate by commenting directly on each article. The Facts Imagine never paying another electric bill. Solar energy could make this a reality. Solar electric systems employ photovoltaic cells to convert sunlight into electricity, while solar water heaters use solar collector panels to warm up water. ...
Source: Yahoo! News: Science News | 3 Dec 2008 | 12:36 pm

Swedish researchers create body-swap illusion

WASHINGTON (Reuters) - Researchers using closed-circuit televisions to create an illusion have made volunteers virtually swap bodies, even making women believe they were in a man's body and vice-versa.

Source: Reuters: Science News | 3 Dec 2008 | 12:27 pm

The Energy Debates: Solar Energy at Home

The Energy Debates is a LiveScience series about the pros, cons, policy debates, myths and facts related to various alternative energy ideas.
Source: Livescience.com | 3 Dec 2008 | 12:27 pm

Activists vows to protect whales from Japanese (AP)

AP - The leader of a militant conservation group that has skirmished violently with Japanese whalers said Wednesday he will not retreat from confrontation during his bid to stop this season's hunt in Antarctic waters.

Source: Yahoo! News: Science News | 3 Dec 2008 | 12:25 pm

Darwin public holiday

Surely no denizen of the Science Blog could disagree with the notion of celebrating the life and works of Charles Darwin with a public holiday - unless perhaps you think some other scientist would be more deserving.

If Darwin is your man then tell Gordon Brown by signing this petition on the Number 10 website.

Here's why Ian Roberts of the Watford Area Humanists set it up:

Charles Darwin was a truly remarkable scientist. His work on evolution deserves to be honoured in some way. Making his birthday (12th February) a bank holiday would be a simple way of doing this.

Regular evolution-related CIF blogger and general top bloke Adam Rutherford has made this suggestion before, although I'm not sure he got as far as setting up a petition.

Public holiday or not, 2009 will be a huge year for fans of the bearded one. In celebration of his 200th birthday and the 150th anniversary of publication of On The Origin of Species, Darwin Day alone has 72 events scheduled in 15 different countries.

The British Council's Darwin Now project has a packed schedule, the Natural History in London has a major exhibition about Darwin's life and there is a project to recreate the voyage of the Beagle.

And there are more Darwin bicentenary related goodies on the Guardian's site here.

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Source: Science | guardian.co.uk | 3 Dec 2008 | 10:32 am

Multitasking canola: A California miracle crop? (AP)

AP - A hardy but pedestrian plant is doing triple duty in California's agricultural heartland.

Source: Yahoo! News: Science News | 3 Dec 2008 | 10:15 am

Doctor performs amputation in DR Congo by text

A British doctor volunteering in DR Congo performs a life-saving amputation using text message instructions from a colleague.
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 10:13 am

Rocket company sells discount rides to space

CAPE CANAVERAL, Florida (Reuters) - The space tourism race heated up on Tuesday when a second company began offering tickets for suborbital rides at less than half the price of competitor Virgin Galactic's.

Source: Reuters: Science News | 3 Dec 2008 | 7:58 am

Ancient insect imprint found in Massachusetts

NORTH ATTLEBORO, Massachusetts (Reuters) - U.S. researchers say they have discovered what appears to be the oldest imprint of a prehistoric insect, made while the dragonfly-like creature was still alive.

Source: Reuters: Science News | 3 Dec 2008 | 7:52 am

River recovery 'dampened by rain'

Research by a university finds that wet weather is preventing rivers from overcoming the effects of acid rain.
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 7:18 am

Bird flu makes mallards thin, study finds

WASHINGTON (Reuters) - Avian flu viruses make mallard ducks thinner than other ducks, a finding that implies they do not spread the germs over long distances, researchers reported Tuesday.

Source: Reuters: Science News | 3 Dec 2008 | 1:55 am

Body swap research shows that self is a trick of the mind

Brain scientists have succeeded in fooling people into thinking they are inside the body of another person or a plastic dummy.

The out-of-body experience - which is surprisingly easy to induce - will help researchers to understand how the human brain constructs a sense of physical self. The research may also lead to practical applications such as more intuitive remote control of robots, treatments for phantom limb pain in amputee patients and possible treatments for anorexia.

The research follows a related study from the same group last year in which the scientists convinced volunteers that they were having an out-of-body experience. It was the first time it had been done in the lab and showed that the intensely spiritual experiences that patients sometimes have while on the operating table, for instance, can have a scientific explanation.

"We are interested in how normal perception works, how we recognise our own body. And we do that by studying these perceptual illusions," said Dr Henrik Ehrsson at the Karolinska Institute in Sweden. "Critically it depends on the visual perspective and the so-called multisensory integration or the combination of visual signals and tactile signals."

In the new study Ehrsson and his colleague, Valeria Petkova, attached two cameras to the head of a dummy. These were hooked up to two small screens placed in front of their subjects' eyes. This gave the illusion that the person was looking through the mannequin's eyes. For example, when they looked down they saw the dummy's body and not their own.

To create the illusion of occupying the dummy's body, the team stroked the abdomen of the subject and the dummy at the same time while the subject watched the stroking via the cameras on the dummy's head. As a result, subjects reported a strong feeling that the dummy's body was their own. The technique is similar to the "rubber hand illusion", in which a subject can be convinced that a rubber hand is his or her own, but this is the first time the illusion has been extended to a whole body.

The illusion was so convincing that when the researchers threatened the dummy with a knife they recorded an increase in the subject's skin conductance response - the indicator of stress that polygraph lie detector tests rely on. "This shows how easy it is to change the brain's perception of the physical self," said Ehrsson, who led the project. "By manipulating sensory impressions, it's possible to fool the self not only out of its body but into other bodies too."

Things got even weirder when the researchers dispensed with the dummy and put the cameras on the head of another person. After carrying out the same double stroking routine the subjects were convinced that they were occupying another person's body. The illusion persisted even when the other person came over and shook the subject's hand, producing the sensation of the subject feeling as if they were shaking hands with themselves.

The researchers plan to use the out-of-body illusion to try to treat amputee patients that experience phantom limb pain in the arm or leg they have lost. "We have begun to realise that there could be a link between pain perception and the feeling of ownership of the body," said Ehrsson.

Another potential angle for research is body image in patients with anorexia. These people become obsessed with reducing their own weight even when they become dangerously thin. "Possibly this approach could be used for new diagnostic tools and maybe therapeutic tools to train people better to recognise their actual body size," he said.

Another application is in remotely operated robots, for example in nuclear power plants or surgery. "The hope is to elicit a full-blown illusion that you are the robot," said Ehrsson.

The results are reported today in the journal PLoS One.

guardian.co.uk © Guardian News & Media Limited 2008 | Use of this content is subject to our Terms & Conditions | More Feeds

Source: Science | guardian.co.uk | 3 Dec 2008 | 1:09 am

Lasius neglectus ants threaten UK gardens

An ant species that forms huge supercolonies and infests gardens and parks is marching rapidly across Europe and will soon invade the UK, according to entomologists who are monitoring its spread.

The colonies can swell to 10 or 100 times the size of those of common garden ants and scientists warn that they can cause significant damage to plants.

"When I saw this ant for the first time, I simply could not believe there could be so many garden ants in the same lawn," says Prof Jacobus Boomsma at the University of Copenhagen, one of its co-discoverers almost 20 years ago.

"We reckon it's only a matter of time before [it invades the UK]."

The invasive garden ant or Lasius neglectus was first identified in 1990 when it was found infesting an entire neighbourhood in Budapest, Hungary.

"This ant basically looks like the garden ant that everybody knows, so you don't really become suspicious if you see a few of those crawling around because they are everywhere," he said. It has since become a major pest in central Europe and has spread as far as Jena in Germany, Ghent in Belgium and Warsaw in Poland.

Boomsma and his team think it is moved around by the horticultural trade because it hides inside plant pots. "That is the most reasonable hypothesis for how these ants get transported because the ants themselves have lost the ability to fly so they are very poor disbursers," he said.

In research published today in the journal PLoS One, the team used genetic techniques to work out where the ants originated and what makes them so successful at taking over new regions. One reason is that they are able to form super-colonies.

The ants occupy many interconnected nests with many queens. Because they are related, the ants in these nests do not show territorial aggression. When they reach new locations the parasites that usually keep the ants in check are no longer there, so they are able to expand their colonies rapidly.

"We found that invasive garden ants developed from species in the Black Sea region that have natural populations with small networks of interconnected nests with many queens that mate underground and don't fly.

"It is now becoming clear that rather many ant species share this lifestyle, so it is no surprise that a number of them have become invasive pests with giant super-colonies based on the same principles," said Dr Sylvia Cremer, at the University of Regensburg.

Dr Jes Pedersen, a co-author at the University of Copenhagen, said: "The future will therefore see many more ants become invasive, so it is about time we understand their biology. This study is a major step in that direction."

Much of the damage that the invasive garden ant causes is connected with the herds of aphids that it tends. The ants have a symbiotic relationship with the aphids in which the aphids provide sugary food while the ants provide protection from predators.

With the ants around, aphid populations expand to large numbers causing damage to plants and releasing sticky secretions that create a mess on parked cars. Because the ant colonies are so large they can cause a nuisance by invading homes and spoiling food.

Invasive ants have caused much more significant damage in other countries. The imported red fire ant, which has a nasty sting, causes $750m (£500m) of damage in the US each year to crops and livestock. The Argentine ant has spread along 6,000km of coastline in southern Europe, exterminating many local insects.

guardian.co.uk © Guardian News & Media Limited 2008 | Use of this content is subject to our Terms & Conditions | More Feeds

Source: Science | guardian.co.uk | 3 Dec 2008 | 1:07 am

Ant invader knocks on UK's door

A recently identified ant which wipes out native species is finding new homes in northern Europe.
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 1:06 am

Brilliant future

"Crown jewel" of European science to get upgrade
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 1:04 am

Surgeon carries out amputation by text

A British surgeon volunteering in the Democratic Republic of Congo saved the life of a teenage boy by amputating his shoulder using instructions texted by a colleague in London.

David Nott, 52, a general and vascular surgeon at Chelsea and Westminster hospital, was working with the charity Médecins sans Frontières (MSF) in the town of Rutshuru when he came across the badly injured 16-year-old in October.

The teenager's left arm had been so badly damaged - either in an accident or as a result of the fighting between Congolese and rebel troops - that it had already had to be amputated. But the flesh and bone that remained had become badly infected and gangrenous.

"He was dying" said Nott. "He had about two or three days to live."

The doctor realised the boy's best chance of survival was a forequarter amputation which requires the surgeon to remove the collar bone and shoulder blade. The only problem was that it was an operation Nott had never performed. But he remembered that one of his colleagues at home had carried out the procedure.

"I texted him and he texted back step-by-step instructions," he said.

"Even then I had to think long and hard about whether it was right to leave a young boy with only one arm in the middle of this fighting.

"But in the end he would have died without it, so I took a deep breath and followed the instructions to the letter."

Such an operation, if performed in the UK, would require careful planning with every sort of modern medical product on hand if things went wrong.

But in Congo Nott had just one pint of blood and an elementary operating theatre.

Despite the basic conditions, the operation was a success and the teenager made a full recovery.

More than 5 million people have been killed in Congo since the early 1990s when the Rwandan genocide spread into what was then Zaire.

guardian.co.uk © Guardian News & Media Limited 2008 | Use of this content is subject to our Terms & Conditions | More Feeds

Source: Science | guardian.co.uk | 3 Dec 2008 | 12:39 am

In pictures

Bangladeshis send climate change message
Source: BBC News | Science & Environment | UK Edition | 3 Dec 2008 | 12:23 am

Spacewatch

The ISS (International Space Station) has been making some spectacular transits across our evening sky of late, even accompanied by the shuttle Endeavour between its undocking last Friday and its touchdown in California on Sunday. Our predictions cover the station's best passes before it shifts too far to the W next week for it to be seen from Britain. Asterisks flag the directions in which it disappears into eclipse.

Endeavour's mission accomplished much, including repairs to some solar power arrays and numerous DIY activities. It may be remembered for the slip that left a tool bag drifting away into space. That bag, about the size of a small backpack, is surprisingly easy to spot providing we have adequate predictions and a well aimed pair of binoculars. It is now far from the ISS, slowly falling because of atmospheric drag, and should burn up as it re-enters sometime next summer by my calculations.

guardian.co.uk © Guardian News & Media Limited 2008 | Use of this content is subject to our Terms & Conditions | More Feeds

Source: Science | guardian.co.uk | 3 Dec 2008 | 12:07 am

How to Use Neuroscience to Become Your Avatar

Research subjects fitted with goggles that stream video from cameras strapped to another person (or mannequin) can experience that body as their own, neuroscientists say.

And not just in a fluffy, philosophical way: the subjects experienced measurable physiological changes, as reported in the open-access journal Public Library of Science.

The paper's authors argue that their work could prove important for future human-robot collaborations — and give hope to those dreaming of uploading their brains after the Singularity. What the researchers have found, they say, is a method for allowing humans to better inhabit non-flesh-and-blood consciousness.

"The present findings could have groundbreaking industrial and clinical applications" write neuroscientists Valeria I. Petkova and H. Henrik Ehrsson of the Karolinska Institutet in Stockholm. "Experiencing 'becoming' a humanoid robot in tele-robotics and feeling ownership of simulated bodies in virtual reality applications would probably enhance user control, realism, and the feeling of 'presence.'"

The gaming industry is already taking steps down that road with Mirror's Edge, which lets players see other parts of their virtual body in motion producing a sensation real enough to induce carsickness.

While the research might be biological, the ability to make headway on this centuries-old problem is technological. The development of light-weight head-mounted displays that are capable of displaying real-time video is the key advance in creating this curious body-swapping illusion. The research follows a slate of publications by the same Swedish group and another European team on generating out-of-body experiences using video and virtual reality tools.

"These experiments have demonstrated how remarkably easy it is to 'move' a human centre of awareness from one body to another," they write. "This speaks directly to the classical question of the relationship between human consciousness and the body, which has been discussed by philosophers, psychologists, and theologians for centuries."

Taken together, they show how our Stone Age brains — and the bodily boundaries they are used to — can be confused by technology that has outpaced our evolutionary development. In particular, Ehrsson has said that his previous work using displays and live camera feeds indicate that our brains are tuned to believe what our eyes tell us is our body.

"The first-person visual perspective is critically important for the in-body experience," Ehrsson told the BBC. "In other words, we feel that our self is located where the eyes are."

In the first experiment, the research subject put on the augmented reality glasses and was told to look down. At the same time, video was beamed into the glasses' displays from a camera attached to the head of a mannequin. In short, the study participant was looking in the direction of his or her own stomach, but actually seeing the stomach of the mannequin.

At that moment, the person conducting the experiment would rub both the stomach of the mannequin and of the research subject. Subjects reported that they felt as if they were feeling the touch on the mannequin.

After a minute of this touching, the researchers threatened the abdomen of the mannequin with a knife while administering a common physiological stress test. The test measured a jump in the physiological stress the subject's were undergoing, which the researchers said implied that they had taken psychological ownership of the mannequin.

In a separate set of experiments, people shook hands with another person for two minutes while seeing the view from a camera attached to the other person's head. Incredibly, the study's participants experienced more stress when the other person's hand was threatened with a knife than when his or her own were.

These experiments provide even more evidence for the argument that Ehrsson has been making for several years. Vision — not just tactile sense — plays a major role in our sense of where our bodies end and the environment begins.

"Thus, the matching of multisensory and motor signals from the first person perspective is sufficient to create a full sense of ownership of one's own entire body," the authors conclude. "This conclusion certainly contrasts with the traditional textbook wisdom which emphasises that body perception is a direct result of bottom-up processing of afferent signals from muscles, joints and skin."

Citation:

"If I Were You: Perceptual Illusion of Body Swapping" by Valeria I. Petkova, H. Henrik Ehrsson. Public Library of Science One: doi: 10.1371/journal.pone.0003832

See Also:

WiSci 2.0: Alexis Madrigal's Twitter , Google Reader feed, and webpage; Wired Science on Facebook.

Source: Wired: Wired Science | 3 Dec 2008 | 12:01 am

Russians Track Troubled U.S. Spy Satellite (SPACE.com)

SPACE.com - Even in the vacuum of outer space, it's hard to keep the sound of a secret quiet.
Source: Yahoo! News: Science News | 2 Dec 2008 | 11:46 pm

Cuba ready to authorize GM corn crop: scientists

HAVANA (Reuters) - Cuba could soon authorize the planting of 124 acres of genetically-modified corn for the first time to help reduce its dependence on costly food imports, Cuban scientists said on Tuesday.

Source: Reuters: Science News | 2 Dec 2008 | 11:10 pm

Cuba ready to authorize GM corn crop: scientists (Reuters)

Reuters - Cuba could soon authorize the planting of 124 acres of genetically-modified corn for the first time to help reduce its dependence on costly food imports, Cuban scientists said on Tuesday.
Source: Yahoo! News: Science News | 2 Dec 2008 | 11:10 pm

Socket Survey: Many Don't Know About Light Bulb Phase Out

78 percent of Americans do not know of the federal legislation to phase out incandescent light bulbs.
Source: Livescience.com | 2 Dec 2008 | 9:37 pm

Body-swap illusion tricks mind in new study (AP)

AP - Shaking hands with yourself is an amusing out-of-body experience. The illusion of having your stomach slashed with a kitchen knife, not so much. Both sensations, however, felt real to most participants in a Swedish science project exploring how people can be tricked into the false perception of owning another body.

Source: Yahoo! News: Science News | 2 Dec 2008 | 9:22 pm

Brazil aims to repair ports destroyed by floods (AP)

AP - Brazil is committed to quickly repairing key ports damaged in massive floods in order to recoup millions of dollars in daily losses to the economy, a government official said Tuesday.

Source: Yahoo! News: Science News | 2 Dec 2008 | 9:19 pm

S. Africa Takes Stage at Climate Talks

World leaders get down to business at the annual U.N. climate convention.
Source: Discovery News Top Stories : Discovery Channel | 2 Dec 2008 | 9:15 pm

Odd Comet Possibly from Another Star System

New chemical analyses suggest a comet may have been flung into the solar system from afar.
Source: Livescience.com | 2 Dec 2008 | 8:21 pm

Antarctica Has More Species than Galapagos

An inventory of Antarctic islands animals reveals more known species than in the Galapagos.
Source: Livescience.com | 2 Dec 2008 | 8:17 pm

Brain Waves Shed Light on Autism

Imaging reveals autistic children may experience delay when processing sounds.
Source: Discovery News Top Stories : Discovery Channel | 2 Dec 2008 | 7:49 pm

Ancient insect imprint found in Massachusetts (Reuters)

Reuters - U.S. researchers say they have discovered what appears to be the oldest imprint of a prehistoric insect, made while the dragonfly-like creature was still alive.

Source: Yahoo! News: Science News | 2 Dec 2008 | 7:36 pm

Harbour seals' decline 'alarming'

Marine biologists are baffled by a dramatic decline in numbers of harbour - or common - seals from UK shores.
Source: BBC News | Science & Environment | UK Edition | 2 Dec 2008 | 7:28 pm

Oatmeal and OJ: Breakfast of Champions?

So say the makers of oatmeal and orange juice in their marginally legitimate study.
Source: Livescience.com | 2 Dec 2008 | 6:58 pm

Hacking Salmon's Mental Compass to Save Endangered Fish

One of the animal kingdom's enduring mysteries — the sea-spanning return of salmon to their home stream — may be explained by in-brain GPS systems calibrated to Earth's magnetic field.

Scientists hope to program the navigation systems of captive salmon to help the species survive in the wild. If they can figure out how to mimic the magnetic signature of a stream, they can train fish to go there when released.

As hatchlings, says University of North Carolina biologist Ken Lohmann, the fish are biologically imprinted with local geomagnetic coordinates. Years later, they sense subtle variations in the intensity and angle of Earthly magnetism that guide them home from thousands of miles away.

"What we've done is to present a new theory in terms of how these animals find their way back home," said Lohmann. "If it turns out to be true, it could be a powerful conservation tool for establishing them in places where they once lived and are now extinct."

Lohmann's theory, published Monday in the Proceedings of the National Academy of Sciences, has not been proven, but scientists call it a compelling piece of an incomplete migratory puzzle. Though salmon follow chemical scents from river mouths to birth streams, how they first find the rivers remains unknown.

Whatever their origin, those homing mechanisms once guided now-unimaginable migratory runs. Late into the 19th century, salmon packed northern coastal rivers so densely that people told stories about using them as a bridge. Six species of salmon — chinook, chum, coho, pink and sockeye in the west, and the Atlantic salmon in the east — supported indigenous tribes and eventually European settlers. Fish not caught by people or bears died after mating, and nutrients released by their decomposing bodies nourished entire inland ecosystems.

In the 20th century, overfishing, pollution, dams and mismanagement produced dramatic declines in wild salmon populations. Most of the species are now threatened or endangered. Rivers host tiny fractions of their historical numbers. But even these remnant populations still support fisheries and could, perhaps, flourish again. If Lohmann is right about salmon navigation, he wants to adjust it, programming newborn fish raised in captivity to colonize now-deserted waters.

"We would set up a large magnetic-coil system that lets us dial in the precise magnetic field that we want," he said. "Then we could take fish from a location where they still survive, raise them in the magnetic field of the tanks, and see if they go to the new river."

Lohmann bases the machine on one he built to test sensitivity in sea turtles, whose migratory patterns also follow a magnetic map. In the turtle experiment, when suspended in a water-filled tank and tricked with false magnetic fields, they changed swimming direction, swiveling like compass needles next to a screwdriver.

The salmon tank is set in a scaffold of wire-wrapped lumber. By adjusting the wiring configuration and the current passing through it, Lohmann thinks he could imitate a target river's geomagnetic identity.

Lohmann's system is still hypothetical, as is the explanation itself. But researchers say it's not far-fetched: Juvenile salmon have proven sensitive to magnetism. "There is good experimental support for the use of the individual cues," said Marcel Holyoak, a population dynamics expert at the University of California at Davis. "It is an entirely reasonable idea."

As for how the salmon physically navigate with magnetism, results are preliminary but promising. One possibility is specialized cells containing particles of magnetite pulled from the environment, which form neurological compasses inside their foreheads. Another possible mechanism, said Lohmann, are chemical reactions that occur on the surface of some animal eyes. These could produce an overlay of shifting colors or spots that change according to gaze direction.

Magnetism is also a more plausible force than smell over oceanic distances. "I just can't imagine how, for salmon, river water would be detectable so far away from the mouth of the river," said University of Montana salmon ecologist Jack Stanford. "Combined with an olfactory signal near the coastline," he said, magnetism "makes perfect sense."

But Stanford warned against quick fixes for the wrong problem. The real problem threatening wild salmon is artificially raised fish intended to sustain open-sea fisheries, he said. These are genetically different from native salmon strains, and threaten to replace them. "Getting back to fresh water is not the issue. It's how they're able to grow and survive in the face of a massive onslaught of human-cultured fish," said Stanford.

Salmon conservation aside, however, Lohmann's hypothesis remains intriguing.

"It is always fascinating to see animals with little brains performing complex tasks ... that we are unable to perform without the use of complex technical devices like GPS systems," wrote University of California at Irvine biophysicist Thorsten Ritz in an e-mail. "Maybe we can learn a trick or two from them."

Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea turtles [PNAS] (Not yet online)

Images: 1,2. Sockeye salmon/Washington University 3,5. Geomagnetic field maps/PNAS 4. Prototype marine magnetic field simulator/Kenneth Lohmann

See Also:

Google Earth Reveals Sixth Sense of Cattle, Deer

WiSci 2.0: Brandon Keim's Twitter stream and Del.icio.us feed; Wired Science on Facebook.

Source: Wired: Wired Science | 2 Dec 2008 | 6:40 pm

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