- Clever Crows Use Tools in New Way
- Toxic Oceans May Have Poisoned Early Animals
- Moon and Space Station Eclipse the Sun
- Ancient Birds Clobbered Rivals With Clubbed Wings
- Nanoparticles in Sewage Sludge May End Up in the Food Chain
- Galactic Smashups Leave Giant Black Holes Hungry
- Junk-Food–Valuing Brain Cells Pinpointed
Posted: 05 Jan 2011 01:44 PM PST
With the simple act of using twigs to poke a rubber spider, New Caledonian crows may have become the first birds to join an exclusive cognitive class.
Using tools in multiple ways, and not just to get food, was once considered a singularly human ability. Then chimpanzees, other primates and elephants proved able. But if flexible tool use wasn't uniquely human, it did seem limited to mammals.
"There is no species of bird that has been recorded using tools for more than one function," said zoologist Joanna Wimpenny of the University of Sheffield.
The new findings, published in December in Animal Cognition, are still preliminary, but "we really think they suggest very strongly that they're using tools for a different function," she said.
Wimpenny led the study while in the lab of Alex Kacelnik, a University of Oxford zoologist who specializes in New Caledonian crow cognition.
While crows are generally clever creatures, New Caledonians are the genus' valedictorians. Having evolved in a region rich in tree-boring grubs but devoid of woodpeckers, they use twigs to pry insects from wood.
That alone is a special behavior, and New Caledonians have refined it, choosing their twigs carefully and even demonstrating what's known as sequential tool use — using twigs to obtain twigs that would allow them to obtain food.
Sequential tool use in particular is considered a possible sign of high-level cognitive powers: understanding causality, analogizing, planning. Whether the birds in fact possess these powers, or happen to be instinctively good at a narrow range of tasks, is inconclusive, but flexible tool use would suggest something more than simple instinct.
"If tools are employed flexibly and for a variety of innovative purposes, then conventional combinations of inherited predispositions and associative learning are challenged and interesting questions emerge," wrote the researchers.
To study this more rigorously, 10 of the birds were presented with a variety of objects, from a Frisbee and a Hawaiian bracelet to a rubber spider and rubber snake.
Again and again, the crows used twigs to poke the objects. While the researchers note that the birds may have been searching for food, they acted very differently than while foraging.
"It's very difficult to know exactly why they would use tools to contact objects, but we think the most plausible explanation is not that they saw them as a food source," said Wimpenny.
It's now up to other researchers to replicate the findings and identify a purpose. And should New Caledonian crows be found using tools in yet another context, "the evidence would be accumulating that tool use is flexible, and indicative of more general intelligence mechanisms," Wimpenny said.
As for crows in other parts of the world, only New Caledonians are known to make tools in their natural habitat. "But in terms of general cognitive processes, the speed of learning and innovation, general problem-solving mechanisms, I think they're pretty uniform," said Wimpenny. "The crow that you might see out in your garden, might have the same abilities."
Images & Video: A New Caledonian crow uses a stick to investigate a rubber spider./Jo Wimpenny.
Citation: "New Caledonian crows use tools for non-foraging activities." By Joanna H. Wimpenny, Alexander A. S. Weir, Alex Kacelnik. Animal Cognition, online publication, December 23, 2010.
Posted: 05 Jan 2011 12:43 PM PST
Soon after complex animals made their first great strides onto the stage of life, the oceans brewed up a toxic chemical mix that put the brakes on evolutionary innovation, suggests a paper in the Jan. 6 Nature.
The culprits? Too little oxygen and too much sulfur dissolved in coastal waters, reports a team led by geochemist Benjamin Gill of Harvard University. Ancient creatures such as trilobites and brachiopods could not cope with the changes, and many of them went extinct.
The "remarkable" new data is the first to link a changing ocean environment to some of the extinctions that took place between about 490 million and 520 million years ago, says Graham Shields-Zhou, a geologist at University College London, who was not on the research team.
Perhaps not surprisingly, marine creatures are exquisitely sensitive to their surroundings, suffocating when oxygen levels drop. Other big extinctions, like one that occurred around 400 million years ago and another around 250 million years ago, have also been blamed on low levels of oceanic oxygen. But the more ancient extinctions studied by Gill, which took place in the later part of the Cambrian period, are of particular interest because they came soon after the "Cambrian explosion" in which animals blossomed in biodiversity.
Gill's team decided to look at a specific subset of Cambrian extinctions that began 499 million years ago and lasted for 2 million to 4 million years. Other researchers had proposed that low oxygen levels — a condition known as anoxia — could be involved. But no one had marshaled enough evidence to prove that. Gill and his colleagues are the first to look at sulfur along with other elements, to piece together a complete picture of what was happening in the oceans. High levels of sulfur can kill marine creatures.
The researchers traveled the globe to collect rock samples of the proper age from Nevada, Utah, Missouri, Australia and Sweden. By analyzing sulfur and carbon isotopes — different forms of an element that vary in atomic mass — the scientists could track changes such as sediment being buried on the ocean bottom, a process that alters chemistry in the waters above.
The amount of carbon in the rocks, as compared to the amount of sulfur, could only have come about if the water were low in oxygen and high in the sulfide form of sulfur, the team reports. Today, a similar environment can be found in the oxygen-starved Black Sea, says Gill.
Most of the toxic waters would have shoaled up along the coasts, where the majority of animals lived. Overall, the new data suggest how pulses of rising and falling oxygen and sulfur could have repeatedly devastated marine ecosystems, says Shields.
Although the researchers think the Cambrian oceans were toxic, they don't know why. "What we're looking at is the aftermath of the crime scene," says Gill. "We don't have the cause for why the oceans suddenly went anoxic."
His team plans to broaden the search to see if some of the other late-Cambrian extinctions could also be linked to toxic oceans.
Poisonous waters could even have been the norm through much of the planet's history, adds Isabel Montañez, a geologist at the University of California, Davis. The new work, she says, "begs the question as to whether ocean anoxic events were a recurrent theme in the oceans that hosted Earth's early metazoan life."
Image: A reconstruction of the Cambrian ocean as it was 500 million years ago. Credit: Wikipedia/Ron Blakey
Posted: 05 Jan 2011 10:45 AM PST
Tuesday morning's partial solar eclipse produced a gorgeous crescent sunrise in Europe, Africa and Asia as the moon blocked most of the sun's disk. But for a split second, the sun was also partially blocked by another satellite: the International Space Station.
French astrophotographer Thierry Legault traveled to Oman to snap this mind-blowing photo of the sun, moon and space station all lined up. The space station took just 0.86 seconds to cross the sun.
Image: Thierry Legault
Posted: 05 Jan 2011 09:45 AM PST
By Mark Brown, Wired UK
Paleontologists at Yale University have discovered that a prehistoric bird with club-like bludgeons for hands likely used its powerful wings to beat up monkeys, snakes and other predators.
The fowl, named Xenicibis xympithecus, lived in Jamaica about 10,000 years ago, and was first discovered in the 1970s. The flightless bird was about the size of a chicken, with a long beak and legs. So far, so ibis.
But instead of small hands, this ancient bird sported thick, curved hand bones, like two baseball bats, hinged at the wrist joint.
The team at Yale analyzed new wing bones from the Xenicibis, and found evidence of combat in fractured hand bones and broken arm bones, giving evidence that his bird could deal extreme force when clobbering each other with their specialized wings.
And, outside of Xenicibis-on-Xenicibis battles, it would have proved especially useful for a small, flightless creature in a land teeming with deadly predators. The bird might have used its flail-like bones to club animals such as the Jamaican yellow boa, a small extinct monkey and over a dozen birds of prey.
"No animal has ever evolved anything quite like this," said Nicholas Longrich of Yale University's Department of Geology and Geophysics, who led the research. "We don't know of any other species that uses its body like a flail. It's the most specialized weaponry of any bird I've ever seen."
Nowadays, modern ibises don't have these remarkable weaponized arms, but still use their wings to pound away at foes, after grabbing an opponent with their sizable beak. No other bird features such highly powerful weaponry, though some birds do still pack a small arsenal: the spur-winged goose, for example, has a bony knob on its arm to deal extra damage in disputes.
Images: Courtesy of Nicholas Longrich. 1) Illustration of two Xenicibis xympithecus birds fighting. 2) A skeletal reconstruction of Xenicibis xympithecus. 3) An extinct ibis' wing bone structure (top) compared to a modern American white ibis'.
Posted: 05 Jan 2011 09:00 AM PST
Plants and microbes can absorb nano-sized synthetic particles that magnify in concentration within predators up the food chain, according to two new studies.
Nanoparticles can be made of countless different materials, and their safety isn't well-understood. Yet the minuscule specks are infused into hundreds of consumer products ranging from transparent suncreens to odor-eating socks.
From there, they can wash down drains, ultimately ending up in the sewage sludge of wastewater treatment plants. About 3 million tons of dried-out sludge is subsequently mixed into agricultural soil each year.
"We wanted to look into the possibility of nanoparticles getting into the food chain in this way," said environmental toxicologist Paul Bertsch of the University of Kentucky. "What we found really surprised us."
Synthetic nanoparticles are about 1 to 100 nanometers in size (as small as some viruses) and made of silver, titanium dioxide, zinc oxide and other substances. By virtue of their small size and stability, they can nullify odors, prevent food spoilage and absorb harmful ultraviolet radiation, among other feats.
But knowledge about their impacts to the environment is still in a state of infancy, Bertsch said.
To explore nanoparticle absorption in the food chain, Bertsch's team raised tobacco plants in a hydroponic greenhouse. While the plants grew, the team added super-stable gold nanoparticles to the water to mimic consumer nanoparticles in wastewater sludge.
Gold nanoparticles built up in tobacco leaf tissue, and tobacco hornworms that ate the plants accumulated concentrations of the nanomaterials about 6 to 12 times higher than in the plant.
"We expected [nanoparticles] to accumulate, but not biomagnify like that," said Bertsch, co-author of the Dec. 3 study in Environmental Science & Technology.
Predatory microbes in a separate study, published Dec. 19 in Nature Nanotechnology, also built up concentrated levels of cadmium selenide nanoparticles after eating smaller microbes that ingested them.
"For me, it's really interesting to see two different models using two different nanoparticles arrive at conclusions reinforcing each other," said Patricia Holden, an environmental microbiologist at University of California, Santa Barbara who co-authored the microbe-based study.
At least five government agencies (EPA, FDA, NIH, NIOSH and NIST) host efforts to investigate nanotechnology's risks to health and the environment, and their funding is increasing each year. And while heavy metals and other toxins in sludge are federally regulated, manmade nanoparticles are not. That may be cause concern as farms increasingly mix sludge into their soils, where nanoparticles may build up over time.
"At this point, the science right now is not saying 'stop using nanoparticles,'" said David Holbrook, a chemical engineer at NIST who wasn't involved in either study. Holbrook said the new research is important and creates new avenues for nanotechnology safety research. "We've got to continue this kind of work," he said.
There's some evidence that nanoparticles are toxic under lab-controlled conditions, Bertsch said, but realistically assessing risks to health and the environment demands more advanced models. He and other scientists are already collaborating on an experiment at Cranfield Univeristy in England that will use the institution's wastewater stream to gauge nanoparticle effects on earthworms and nematodes.
"I expect the results may not be as dramatic," Bertsch said. "But so far, the jury is still out on safety."
Image: A tobacco hornworm. Credit: Flickr/cbede
Posted: 05 Jan 2011 07:46 AM PST
Colliding galaxies don't shake up enough food to feed enormous black holes lurking in their centers. A new study suggests that less violent events, like gravitational disturbances within the galaxy, are probably black holes' primary source of fuel.
Almost every galaxy is centered on a supermassive black hole hundreds of millions of times more massive than the sun. Some of them, like the black hole at the center of the Milky Way, are relatively docile. But others draw a huge, hot disk of gas that glows white-hot just before it vanishes forever. These disks, called active galactic nuclei, can outshine the rest of the host galaxy.
Astronomers have suspected for decades that these ravenous black holes get their fuel from major mergers between two large galaxies. In all the chaos of a galactic pile-up, plenty of gas should get funneled toward the center and gobbled up, astronomers reasoned. Simulations have found that black holes and galaxies grow together. Some observations even suggested that galaxies with active galactic nuclei were slightly distorted, a sign of a recent collision.
"It's totally intuitive," said astrophysicist Knud Jahnke of the Max-Planck Institute for Astrophysics in Germany, a coauthor of the new study. "But it was a gut-feeling idea. In court you would say there was some circumstantial evidence for it, but no proof."
Earlier studies looked only at galaxies with the brightest active nuclei, which could have biased their results, Jahnke said. They also didn't compare active galaxies to those with quiet black holes.
In a paper to appear in the Jan. 10 Astrophysical Journal, Jahnke and colleagues selected galaxies from the COSMOS dataset, the largest continuous galaxy survey the Hubble Space Telescope has ever completed. The survey covered an area of the sky 10 times the size of the full moon, and found hundreds of thousands of galaxies.
The team chose 140 active galactic nuclei, or AGNs, by selecting galaxies that emit a lot of X-rays, which can pierce the galactic gas and dust that might otherwise block the nuclei from view. They then chose more than 1,200 inactive galaxies at the same distance and brightness levels to ensure all images were of the same quality.
Next, the astronomers checked the galaxies for the subtle signs of a recent galactic collision, such as a warped disk or a trailing tail of stars. Jahnke and nine other astronomers examined each galaxy by eye, a low-tech but reliable method of picking out galaxy shapes.
"There's no magic algorithm that will tell you if a galaxy is merging," said Mauricio Cisternas, a graduate student at the Max-Planck Institute and lead author of the paper. "The human brain is much better at these things than any algorithm you could write."
The human galaxy sorters didn't always agree on which galaxies were merger survivors, but they all found merging galaxies are no more likely to aggressively feed black holes at their hearts than ordinary galaxies. At least 75 percent of the active galaxies get their fuel somewhere else.
"We don't observe more mergers in the AGN host galaxies," Cisternas said. "From there it's straightforward to infer that mergers are not triggering AGNs, and are not responsible for black-hole fueling."
Instead, black holes could be fed by smaller mergers, like a large galaxy gobbing a smaller one. Or perhaps a series of gravitational disturbances, which Jahnke calls an "angular momentum transport chain," could ferry fuel to the black hole over great distances.
"This is a significant step forward," said galaxy astronomer Romeel Davé of the University of Arizona, who was not involved in the new study. "The fact that we can do this now is unique and new. This represents a significant addition to the literature for sure."
There are two caveats, though. One is that black holes could start feeding long after a merger, when the galaxy's shape has smoothed out. Cisternas and Jahnke said that's unlikely, however, because so many of their galaxies had prominent spiral shapes, and mergers tend to destroy a galaxy's spiral forever. But Davé is not so sure.
"Just because one sees spiral structure does not mean that you don't have merger activity," he said.
The second is that the new study used galaxies whose light is 8 billion years old when it reaches Earth. Galaxies farther away than that are too fuzzy to see, but black holes were growing fastest about 10 billion years ago. That's when mergers may still have been an important source of food, Davé said.
An ongoing survey with Hubble's new Wide-Field Camera 3 could see further and resolve the question.
"That sort of information will be coming down the line fairly soon," Davé said.
Image: A sample of the galaxies studied; sorted based on whether they show no signs of a recent merger (top row), minor signs (middle) or major disruptions (bottom). The black spot in the center of each galaxy ensured that the test was blind. The team blocked out the bright nuclei from active galaxies and added a spot to galaxies with dim centers, so the sorters couldn't tell which was which. Credit: NASA, ESA, M. Cisternas (Max-Planck Institute for Astronomy)
Posted: 05 Jan 2011 04:00 AM PST
Individual human brain cells can be savvy shoppers, tuning their behavior to precisely reflect the worth of a candy bar, finds a study published January 5 in The Journal of Neuroscience.
Evaluating objects is "something we all do on a moment-to-moment basis," says study coauthor Rick Jenison of the University of Wisconsin–Madison, but just how the human brain tallies up value isn't clear.
To eavesdrop on the discerning human brain, Jenison and his team took advantage of a rare opportunity: human volunteers who are undergoing a procedure that uses electrodes to pinpoint the origin of severe seizures. As a by-product, these electrodes can also listen to the activity rates of single neurons in the amygdalae — a pair of almond-shaped structures located on each side of the brain — as the volunteers assessed the value of junk food.
Experiments with monkeys and rats have shown that amygdala neurons play a role in evaluating objects, but getting precise value estimates from an animal is nearly impossible. In contrast, human volunteers can easily assign exact values to objects and communicate that information to researchers.
"In this study, you can get humans to tell you how much they value something," says neurophysiologist Jonathan Wallis of the University of California, Berkeley. "You're not just getting, 'Its good,' or 'It's bad.' You're getting a precise estimate of how good it is, or how bad it is."
After the electrodes were in place, three participants viewed pictures of 50 different kinds of junk food, ranging from chocolate-chip cookies to M&M's to salty chips. The participants viewed each image for one second, and then came up with a subjective value rating of the snack by bidding amounts between zero and three dollars for the item.
The system was designed to reflect personalized tastes. "With different people, it's quite idiosyncratic in terms of what they like and dislike," Jenison says. "The real goal here is to get them to give us an honest bid of what they value the food item to be."
Throughout the experiment, electrodes caught the activity of single neurons in the volunteers' amygdalae. Of the 51 neurons that the researchers tracked in the three volunteers, 16 performed in lockstep with the value of the food item, changing their activity in a predictable way as the value increased. As the value (and corresponding bid) went up, some of these neurons' activity went up too. Others showed an inverse relationship, with their activity declining as the value increased.
Neuroscientist Daeyeol Lee of Yale University says that along with other studies, the new work "expands the role of the amygdala," a region that is traditionally associated with fear. Lee cautions that due to the necessity of working with human volunteers who have electrodes implanted in their heads, the sample size is inherently small, precluding many repetitions of the experiment. "The opportunity is limited, but it's a really, really exciting opportunity."
Next, Jenison and his team are testing how these neurons respond to foods that some people find disgusting, such as oyster juice and liver pâté. They are also examining how these neurons behave when a person decides between two objects.
Image: Neurons at 100X magnification. Credit: Flickr/thelunch_box
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