- Frog Bladders Hunt and Remove Foreign Objects
- Crab Nebula’s Violent Outbursts Shock Astronomers
- The Desperate Battle Against Killer Bat Plague
- Doubts Brew About NASA’s New Arsenic Life
- Republican Congressmen Crowdsource Attack on Science
- X Particle Explains Dark Matter and Antimatter at the Same Time
Posted: 08 Dec 2010 11:46 AM PST
A bizarre discovery shows some frogs and toads can grow their bladders around objects lodged deep within their bodies, ultimately peeing them out.
Zoologists from Australia's Charles Darwin University discovered the oddity after implanting frogs with tiny radio transmitters, which inexplicably migrated to the bladder. They describe their findings in an upcoming issue of Biology Letters.
"This is an extraordinary evolutionary trick," said Rick Shine, an evolutionary ecologist at the University of Sydney who wasn't involved in the study. "It wouldn't surprise me if we continue to find this ability in other animals. Natural selection has had a few hundred million years to solve tough problems organisms encounter."
Christopher Tracy and his team came across the amphibian ability while studying heat regulation in Australian green tree frogs. The team implanted tiny radio transmitters deep in the amphibians' peritoneal cavity, which lies just outside the peritoneum — a membrane containing the major organs of most animals.
After a few weeks of living in the wild, however, about 75 percent of the frogs' transmitters were found in their bladders. Tracy and his colleagues also found some on the ground without any signs of frog death, including being eaten by a predator, disease or other explanations.
"We thought there was a more mundane explanation until we started retrieving transmitters in frogs, and they were in the bladder," Tracy said. "At that point we connected the dots."
Back in the lab, Tracy's team put their hypothesis to the test. They enlisted five green tree frogs and five cane toads, implanting small inert beads in each the same way they implanted the radio transmitters. Each tree frog expelled its bead within 23 days. One cane toad also gave its bead the boot, and the beads in the other four toads had migrated to their bladders.
To unravel the secrets of the process, the zoologists implanted beads in 31 more cane toads, toxic amphibians native to South America but introduced to northeastern Australia in 1935 to control beetle infestations. (Since then, Shine says, the toads have become invasive and poisoned populations of large predators such as pythons. As a result, ecologists now closely track their numbers and behavior.)
Toads dissected on sequential days revealed that the bladder grew a thin offshoot of cells to surround the bead, which later developed into mature, bladder-like tissue and merged with the organ's main cavity. From there, they "floated freely in the urine" and were peed out if near the bladder's opening.
"It could be a fluke of nature, but we've thought of many stories where this makes some sort of adaptive sense," Tracy said. "Frogs and toads have pretty thin skins and are clumsy when they hop, so it's not hard to imagine them landing on something that pierces the skin. They also don't chew on insects they eat, so the hard parts could poke through their digestive systems."
The intestines of humans and other animals, including sharks, reef fish, crocodiles and snakes, are already known to enshroud and expel foreign debris. But the handiwork of amphibious bladders was previously unheard of.
"As far as we can tell, this is a completely different mechanism than what's seen in other animals. We're still in early stages of figuring out what's going on," Tracy said. "It may be going on in other amphibians as well."
When a snake eats, its digestive system occupies most of the creature's body cavity, Shines says, so it makes sense that the reptiles would use that organ to remove strange objects. Likewise, bladders take up most frogs' and toads' internal real estate.
"Frogs have a terrible problem with water loss, so one of their insurance policies is to have very large bladders, used as a kind of water reserve," Shine said. "It's a very plausible place you could slip an object to get rid of it."
Implanted radio transmitters have been a popular method to follow these creatures' populations, but Shine and Tracy don't think the latest wrinkle in the device's efficacy should put a hold on their use.
"It's not a terrible problem. We will have to be more cautious in interpreting telemetry data," he said. "But there may be modified ways to put in a transmitter so that it won't be removed from the body."
Carl G. Meyer, a marine biologist at the Hawaii Institute of Marine Biology, agrees.
"We have long-term data from large numbers of sharks and large reef fishes, indicating the majority of animals retain their implants despite a natural ability to expel foreign objects from the body cavity," Meyer wrote in an e-mail to Wired.com.
Smaller animals such as reef fish, however, may be better at removing debris, and thus more likely to skew population data.
"We need to run additional controlled experiments to determine whether this is in fact the case," he wrote.
Images: 1) A cane toad, also known as Rhinella marina. Credit: Flickr/Sam Fraser-Smith 2) An Australian green tree frog, also known as Litoria caerulea. Credit: Chris Tracy
Posted: 08 Dec 2010 09:55 AM PST
HEIDELBERG, Germany — Astronomers consider the Crab nebula one of the steadiest sources of high-energy radiation in the universe. Radiation from the supernova remnant is believed to be so constant that astronomers use it as a standard candle with which to measure the energetic radiation of other astronomical sources.
That's why researchers are astounded that two spacecraft recently recorded giant gamma-ray hiccups from the Crab, the remnants of a stellar explosion 6,500 light-years from Earth that was observed by humans in 1054. The intensity of the Crab's gamma-ray radiation suddenly became two to three times stronger for three days beginning September 19, scientists with the Italian Space Agency's AGILE telescope reported in a September 22 Astronomical Telegram, an e-mail communication. Researchers with Fermi's Gamma-ray Space Telescope found an even larger increase over roughly the same time period, they reported in a telegram on the following day. Both teams also announced they had found evidence of previous flares — the AGILE telescope recorded an outburst in the fall of 2007 while the Fermi team spotted one in February 2009.
The suspected source of the energetic flares, along with steadier radiation emanating from the nebula, is blizzards of electrons spat out by the Crab's pulsar — the rapidly rotating, exploded cinder of a star that lies at the very center of the Crab nebula. But figuring out exactly how the electrons got revved up to energies of at least 1015 electron volts — the most energetic charged particles ever associated with a distinct astrophysical object — for so short a time has astronomers at the biannual Texas Symposium on Relativistic Astrophysics, held this year in Heidelberg, Germany, scratching their heads and searching for new models.
Finding the flares "was a shock," said AGILE team member Marco Tavani of the INAF-IASF in Rome and the University of Rome Tor Vergata, who spoke about the findings at the meeting on December 6 and 7. In fact, when his team first noticed a sudden, short-lived rise in gamma-ray emissions from the Crab in the fall of 2007, soon after AGILE was launched, the researchers didn't believe it. Only when the craft recorded the 2010 outburst was the team convinced enough to go public with both findings. "If you say a steady source like the Crab is variable and it's not true, you burn yourself for life," Tavani said at the meeting.
Fermi researcher Rolf Buehler of the SLAC National Accelerator Laboratory in Menlo Park, Calif., joined Tavani in a hastily convened session on December 6, not part of the scheduled program, to discuss variable sources of energetic radiation in the Milky Way. Tavani and Buehler declined to talk to reporters because both of their teams have submitted their findings to Science.
In a widely accepted model, the stage is set for any kind of gamma-ray emissions — steady or short-lived — when electrons hurled from the Crab's central pulsar encounter strong magnetic fields in the surrounding debris. The electrons gyrate around the magnetic fields and get revved up to energies high enough to emit gammas.
But the Crab's recently detected outbursts would seem to pose problems for that acceleration model. The brevity of the flares indicates that the electrons couldn't have gyrated long enough to produce the energetic radiation, Buehler noted. Another problem: Because electrons accelerated to very high energies lose that energy quickly, the nebula's magnetic field might have to be three to 10 times stronger — 3 to 10 milliGauss — than is commonly assumed. (By comparison, Earth's surface magnetic field is about 500 milliGauss.)
The short duration suggests the gamma rays originate in a relatively small part of the inner nebula. Buehler suggested that the pulsar's own electric field helped accelerate the electrons in the inner part of the nebula to energies high enough to emit the gammas.
Wlodek Bednarek and a colleague from the University of Lodz in Poland offered another explanation. In a paper posted at www.arXiv.org on November 19 (http://arxiv.org/abs/1011.4176), they suggest that the pulsar's wind of charged particles rams into and compresses the magnetic field in the nebula. As the disrupted field snaps like a rubber band and reconfigures itself, it unleashes an enormous amount of energy that accelerates the electrons, the researchers propose.
As researchers puzzle over the details, astronomers are also trying to pinpoint the exact region from which the September outburst originated. As revealed in visible light and X- ray images, the nebula contains a complex array of wisps and jets. A series of portraits taken by the Chandra X-ray Observatory beginning a few weeks after the September flare shows that the base of one of the jets has brightened. This might be where the gamma-ray flare originated, says Tavani.
Figuring out the riddle presented by the Crab nebula is likely to shed new light on the nature of its pulsar, noted Jonathan Arons of the University of California, Berkeley. "All these particles come screaming out [of the pulsar] and get stopped in the nebula," which acts like the pulsar's catch basin, Arons said. "Studying what's going on in the inner nebula is as close as we can get to a laboratory experiment" to probe the pulsar, he added.
It may also help elucidate the physics of a host of other astronomical systems that feature a central compact object, Arons said. These include black holes whose jets of charged particles slam into surrounding interstellar space or collisions between clumps of material within such jets that are thought to create the most energetic explosions in the universe, events called gamma-ray bursts.
Image: A composite photograph of the Crab Nebula showing x-ray light (light blue), visible light (green and dark blue) and infrared light (red). Credit: NASA, ESA, CXC, JPL-Caltech, J. Hester and A. Loll (Arizona State Univ.), R. Gehrz (Univ. Minn.), and STScI
Posted: 08 Dec 2010 04:00 AM PST
It's a postcard October morning at Kentucky's Carter Caves state park. Sycamore and hickory have already turned orange, and the sun crests ancient Appalachian slopes against a cloudless sky. With Halloween a few days away, a life-sized Elvis dummy peeks out a visitor center window. Middle schoolers on a field trip are coming down one of the trails, preceded by their laughter.
The idyll is complete but for two details: All but two of the park's caves are permanently shut to the public, and in the parking lot are six researchers in Tyvek bodysuits and gloves, like extras from Outbreak.
The caves are closed, and bodysuits required, because of White Nose Syndrome, a bat-killing disease more virulent than any other disease in the known history of mammals. As the children walk to their bus, I wonder if they'll remember this morning as adults, and tell their own kids about a time when bats lived in caves. "What's wrong with the bats?" a girl asks, her tour guides having kept the day shadow-free. "They're sick," I say.
My answer isn't precisely correct. Had the girl asked Hazel Barton, a Northern Kentucky University microbiologist who's there to sample bat hair and skin, or Brooke Slack, a state bat biologist, she would have learned that Carter Caves' bats are being protected. White Nose Syndrome — WNS for short — hasn't yet reached Kentucky, but its march down the cave-riddled Appalachians passed within 100 miles of where we stand, putting us squarely on the battle's front lines.
At this point, it's a losing battle. Bats with noses dusted by the Geomyces destructans fungus that causes WNS were seen for the first time in early 2006, in upstate New York. One year later, biologists realized that WNS could kill bats in large numbers. By 2008, mortality in major New York and Vermont hibernacula, caves where tens and hundreds of thousands of bats had wintered, was more than 90 percent. Biologists wore gas masks against the stench of rotting bodies. Bones cracked like popcorn under their feet.
By the end of last winter, G. destructans was found in 14 states and two Canadian provinces, and at least a million bats were dead. In August, a high-profile Science study gave computationally modeled meaning to all those dead-bat piles. The little brown bat, more common than any other in North America, the furred star of most every attic and open-window encounter, so numerous as to be considered pests, would be extinct in 20 years in the eastern United States. If by some unexpected miracle WNS mortality dropped from over 90 percent to 5 percent, they might make it to the century's end.
That essential prognosis applies to at least three other cave-dwelling, hibernating bat species, and probably more, though one-by-one tabulations tend to obscure the potential of WNS to annihilate an entire manner of animal being. In sheer magnitude, WNS threatens to dwarf the demise of plains bison or passenger pigeons, the historical benchmarks of American animal collapse. The closest comparison is Chytridiomycosis, a fungal disease now scouring amphibians from much of the planet.
Yet even as the reality of WNS has emerged in the popular press, public and policy reaction has been muted. Awareness and concern exists, but at a fraction of what would likely be displayed if, say, half of America's waterfowl were about to vanish.
Bat conservationists tend to blame this on bats' unfair and untrue reputation as rabies-ridden, hair-tangling rodents. A more fundamental problem, however, is that bats are generally absent from everyday awareness. Most specialize in eating insects at night in the air, an ecological niche both staggeringly enormous and out of sight. Their taxonomic order, Chiroptera — more closely related to primates than rodents — contains more mammal species than any order except rodents, yet most people have never seen a bat up close.
Several thousand hibernate in the old saltpeter mine where Hazel Barton and Brooke Slack and their assistants go. At this point in the season, they'll fly out at night for a last few pre-winter meals. In the daytime they sleep, clinging to walls and cuddling for warmth and companionship.
Barton, a lifelong spelunker with rare expertise in cave microbiology, is interested in fungi that grow naturally on bat skin. By the glow of headlamps the researchers pluck bats from the ceiling with practiced efficiency, swabbing their skin and clipping tufts of hair from which fungal DNA will later be extracted. Slack examines the wings, looking for any signs of the dreaded disease.
This early in the season, it's extremely unlikely that G. destructans growth would be visible. But it's always possible that some spore-carrying survivor from one of West Virginia's WNS-afflicted colonies arrived this season, scars on its wings portending potential doom. The presence of G. destructans was confirmed in West Virginia's largest hibernacula last winter; it also reached Tennessee, Missouri and Oklahoma. Barton and Slack were sure it would reach Carter Caves, as well. Their fears survived for another season.
Despite the researchers' care, the bats start to wake, roused by noise and light and even the ambient temperature difference of our bodies. By the time Barton finishes, many are aloft, circling with the speed and agility of swallows. Their cries reverberate down the narrow hall. Others remain hanging, swaying every so slightly, just enough to make it feel like the walls are pulsing. It's as if the entire cave is alive.
As we hurry out, I ask Barton whether she thinks these bats will stay WNS-free, if they have a chance. Grimacing, she shakes her head.
Posted: 07 Dec 2010 04:00 PM PST
An arsenic-loving microbe found in a salty lake, which was touted last week as a potentially new form of life, is under heavy fire from the scientific community.
The microbe, a bacteria called GFAJ-1, can apparently use arsenic instead of phosphorous to build its DNA, a trick no other life form has ever managed.
A team of astrobiologists pulled the bacteria from Mono Lake in eastern California and starved it of phosphate, the molecule most organisms prefer for building their DNA backbones, while force-feeding it arsenate, the analogous form of arsenic.
The bacteria continued to grow despite the poisonous diet, prompting the researchers to assert that the microbes had successfully swapped arsenic for phosphorous. The team, led by NASA astrobiologist Felisa Wolfe-Simon, published their results in Science Dec. 2, accompanied by a very excited NASA press conference.
But other biologists started raising red flags almost immediately, questioning the methods the team used to purify the DNA and asking why the researchers skipped certain tests.
"It seems much more likely that the arsenic they're seeing is contaminating arsenic that's going along for the ride," biologist Rosie Redfield of the University of British Columbia told Wired.com.
Redfield posted a biting critique Dec. 4 on her research blog. As of today, the post has received more than 40,000 hits.
She points out that the team didn't properly clean their DNA before or after running it through a standard device for separating DNA and RNA from other molecules, a technique called gel electrophoresis.
Cleaning the samples would require "a little kit that costs $2 and takes 10 minutes, and then you have pure DNA that you can analyze," Redfield said. The researchers used this method elsewhere in the paper, but not in the critical experiment that was supposed to show arsenic was incorporated into the bacteria's DNA.
"That's just asking for contamination problems," she said. The arsenic they found could have been hanging around in the gel, not in the cells, she added. "It's as if they wanted to find arsenic, so they didn't take a lot of trouble to make sure they didn't find it by mistake."
The NASA team immersed the DNA in water, where arsenic compounds quickly fall apart. If the DNA was really built from arsenate, it should have broken into pieces, Bradley wrote. But it didn't. That suggests the molecules were still using stronger phosphate to hold themselves together.
A thorough review on Slate.com by science writer Carl Zimmer raises a host of other problems with the paper. Zimmer spoke with nearly a dozen outside experts for the story (and more for ongoing updates on his blog), nearly all of whom think the NASA team failed to support their claims.
A similar story by Alla Katsnelson on Nature's news site points out the arsenate-eating microbes appear fat and bloated, a possible sign that they are sequestering toxic substances. Rather than continuing to grow in number and thrive, the bacteria could have been getting fatter as they stored up just enough energy for survival.
The authors of the original paper have so far declined to respond to these criticisms, at least to journalists. A NASA spokesperson also publicly dismissed blog-based critiques, saying any discussion should be confined to scientific journals.
"That's kind of sleazy given how they cooperated with all the media hype before the paper was published," Redfield said.
But senior author Ronald Oremland of the U.S. Geological Survey spoke to an audience of scientists at the Carnegie Institution in Washington, DC Dec. 7, which was streamed live over NASA TV. Apparently against his own policy, Oremland fielded several questions about specific tests the team could have performed on the microbes.
Most of them, he said, were "certainly worth doing" and "an area for future work."
"There's a laundry list of things," he said. "We can't do everything."
Oremland also indirectly addressed the backlash in the blogs.
"I'm not surprised by pushback from the scientific community and bloggers. That's part of the process," he said. "But those are arguments about how many angels on the head of a pin. The only way this is going to get settled is if people reproduce these experiments on their own."
Redfield agrees that more studies are needed, and that the best place for scientific back-and-forth is in peer-reviewed journals.
"But putting it out just so people can comment on it directly is also extremely valuable," she said. Scientists have always discussed their work in non-peer-reviewed channels, such as letters or conferences, she notes. "It's just working faster and better now because we have things like blogs. That just lets the science be so much more powerful. In a lot of ways this is how science is supposed to work."
Image: The bloated microbes that may just be storing arsenic, not using it in their DNA. Science/AAAS
Posted: 07 Dec 2010 12:35 PM PST
Under the auspices of keeping federal spending under control, Republican congressmen have launched yet another attack on the basic scientific research that could lead to useful, potentially job-creating discoveries.
House majority leader Eric Cantor (R-Virginia) announced last week that the YouCut Citizen Review, a crowdsourcing tool for identifying "wasteful spending that should be cut," would make its very first target the National Science Foundation.
One would expect science-targeting politicians to have learned caution from Sarah Palin's fruit-fly debacle, in which the 2008 vice presidential candidate mocked the methodology of research into neurological disorders like Down syndrome and autism, both of which afflict members of her family.
But in a video introduction to the YouCut review, Rep. Adrian Smith (R-Nebraska), a member of the House Committee on Science and Technology, pulls rank on peer review.
"Help us identify grants that are wasteful or that you don't think are a good use of taxpayer dollars," he asks, mentioning "university academics [who] received a $750,000 grant to develop computer models to analyze the on-field contributions of soccer players" and "scientists [who] received $1.2 million to model the sound of objects breaking for use by the videogame and movie industry."
Soccer, it turns out, happened to be a useful model for Northwestern University researchers trying to develop a framework for evaluating individual contributions to organizational success. Their work may enable better long-distance group collaboration, helping people in rural areas — like, say, Smith's district of Nebraska — compete against big-city companies.
As for the videogame modeling, it's the work of Cornell University researchers developing algorithms for simulating sounds in real time. Even though it's possible to realistically model the physics of splashing water or breaking glass, sonic modeling isn't nearly so developed. Figuring it out would "transform how sound is computed in interactive virtual environments," say the researchers.
It's not hard to imagine noncommercial applications for immersive computer simulations, but it certainly would help videogame and movie makers and potentially create jobs in those fields. Smith, whose district has received $8.27 billion in farm subsidies since 1995, ought to applaud when government spending helps create jobs.
Video: Eric Cantor/YouTube.
Posted: 07 Dec 2010 11:29 AM PST
A new hypothetical particle could solve two cosmic mysteries at once: what dark matter is made of, and why there's enough matter for us to exist at all.
"We know you have to have these two ingredients to the universe, both atoms and dark matter," said physicist Kris Sigurdson of the University of British Columbia, coauthor of a paper describing the new particle. "Since you know you need those ingredients anyway, it seems like a natural thing to try to explain them from the same mechanism."
Cosmologists think the same amount of matter and antimatter should have been created in the Big Bang, and particles and antiparticles immediately started colliding and extinguishing each other. But the fact that stars, planets and physicists exist now is proof that that's not what happened.
"If matter and antimatter were created in equal amounts in the early universe, they would all have annihilated [each other]," said theoretical physicist Sean Tulin of the Canadian physics institute TRIUMF. "There has to be some asymmetry that was left over."
Together with physicists Hooman Davoudiasl at Brookhaven National Lab and David Morrissey of TRIUMF, Tulin and Sigurdson suggest a way to solve the problem of missing antimatter: Hide it away as dark matter. The details are published in the Nov. 19 Physical Review Letters.
"If our theory is right, it would tell you what dark matter is," Tulin said.
Most of what we know about dark matter is that it is mysterious stuff that makes up a quarter of the energy density of the universe, but refuses to interact with regular matter except through gravity.
The most popular candidate for dark matter is a theoretical weakly interacting massive particle, or WIMP, that connects only with the weak nuclear force and gravity, making it undetectable by eyes, radios and telescopes at all wavelengths. Based on current theories, WIMPs are expected to be about 100 times as massive as a proton, and to be their own antiparticle — whenever two WIMPs meet up in space, they annihilate each other.
The new theoretical particle "is completely different from the WIMP idea," Tulin said. The proposed particle, named simply "X," has a separate antiparticle called "anti-X." Equal amounts of X and anti-X were created in the Big Bang, and then decayed to lighter particles. Each X decayed into either a neutron or two dark-matter particles, called Y and Φ. Every anti-X converted to an anti-neutron or some anti-dark matter.
But the hypothetical X particle would rather decay into ordinary matter than dark matter, so it produced more neutrons than dark matter. Anti-X preferred decaying into anti-dark matter, and so produced more of it.
After all the particles and anti-particles that could find each other collided and eliminated each other, the universe was left with some extra neutrons and a corresponding number of extra anti-dark matter particles.
"The protons and neutrons can't annihilate completely with their antiparticles, because there's not enough to annihilate with," Tulin said. "The same story happens in the hidden sector as well…. Some dark matter can't annihilate with anything. So you're left with some extra dark matter in the universe."
Conveniently, this picture could explain another particle-physics puzzle: why there is only five times more dark matter than regular matter in the universe. To physicists, five is a really small number. If dark matter and regular matter didn't spring from similar origins, there's no reason why there should be roughly the same amount of both of them.
But in the new model, there should be the same absolute number of regular-matter particles and dark-matter particles left after all the particles that can destroy each other are gone. If the dark-matter particles each have a mass between two and three times the proton's mass, then the universe ends up with five times more dark matter than regular matter.
"That's why the light stuff, the visible matter that we all know and love and are used to, is in exact balance with the excess in the dark matter," Sigurdson said. He compares the balance to a yin-yang: "You end up with a little bit more matter and a little bit more antimatter, but they're in exact compensation with each other."
The signatures of this new form of dark matter could be detected by existing experiments. In this model, dark matter doesn't interact with regular matter very often — but it can happen. A dark-matter particle can sometimes smack into a proton or a neutron and destroy it, creating a signature similar to a proton decaying.
Proton decay isn't allowed by the standard model of particle physics, but some theories that go beyond the standard model allow it. An enormous underground tank of water in Japan, called SuperKamiokande, was designed to look for the decaying protons, but has so far found nothing. If physicists at SuperKamiokande went back through their data and looked at slightly different energies, they may be able to find traces of dark matter.
"It's a pretty novel idea," said astroparticle physicist Subir Sarkar of the University of Oxford, who has suggested detecting a different possible form of dark matter by observing its buildup in the sun. The signature of dark matter destroying protons "can be easily tested by the even bigger proposed underground detectors" planned to be built somewhere in Europe.
"This is only the beginning," Sigurdson said. "There's other puzzles out there in particle physics, and we'd like to connect as many of those as possible."
Image: Physicists paddle around the Super Kamiokande detector in a rubber raft as it fills with water. The detector was designed to hunt neutrinos and decaying protons, but could catch the signatures of Particle X. Credit: Kamioka Observatory, ICRR (Institute for Cosmic Ray Research),The University of Tokyo.
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