By Steve Connor, Science Editor One of the biggest studies ever undertaken into multiple sclerosis has identified 29 new genetic factors that are implicated in the development of the disease. The nature of the genes that have been linked with MS has demonstrated with a high degree of certainty that the root causes of the illness can be traced to the faulty functioning of the body's immune system, scientists said. Nearly 10,000 individuals with multiple sclerosis took part in the study and their genomes were scanned to find the genetic differences with the DNA of over 17,000 healthy people. The total number of genetic faults linked with the disease now amounts to 57. Alastair Compston, of the University of Cambridge, one of the lead authors of the study published in Nature, said there have been rival theories about what are the important factors implicated in triggering the disease, one of the most common neurological conditions affecting young adults. "Our research settles a long-standing debate on what happens first in the complex sequences of events that leads to disability in multiple sclerosis," he said. "This has important implications for future treatment strategies. It puts immunology right at the front end of the disease, absolutely." The study involved a relatively new technique called genome-wide scanning, which involves analysing the entire length of a patient's DNA for anomalies that appear not to exist in healthy people and could therefore be linked with the disease. Previous research had established that multiple sclerosis has a strong genetic component. ©independent.co.uk

Keyword: Multiple Sclerosis; Genes & Behavior
Link ID: 15664 - Posted: 08.11.2011

by Robert Krulwich OK, if you've got nothing else to do for one minute, let me mess with your head. Below, you will see two circles composed of parallelograms. There's a dot in the middle of the image. Focus on the dot. Move your head in, then move it out. Here is Pinna-Brelstaff Illusion. If you focus on the dot and move your head in, then move it out the circles spin. Weird, no? The circles seem to rotate. (Of course, they don't really rotate; if you focus on a single parallelogram, you can move your head in and out all day and that sucker won't move at all.) Something curious is going on. So I went to see an eye doctor (technically, he's a "visual science" professor, Ben Backus, at the State University of New York's College of Optometry) who agreed to explain to me why the circles seem to move. Yes, he said, what you are seeing is a lie ("illusion" is the polite word) but don't blame your lying eyes. Blame your lying brain. Copyright 2011 NPR

Keyword: Vision
Link ID: 15663 - Posted: 08.11.2011

By SINDYA N. BHANOO Male túngara frogs gather in shallow pools of water at night and let out long mating calls. Females visit these pools, listen to a few calls and then quickly pick mates. It’s a bit like speed dating. A male call consists of a whine followed by a series of grunts, or “chucks.” New research suggests that females judge males on these chucks — not the absolute number, but the ratio of one frog’s chucks to another. During the study in Panama, many female frogs seemed to prefer two chucks over a single chuck. But most did not show a preference between three chucks and two chucks. It’s a concept humans can relate to, said Karin Akre, an evolutionary biologist at the University of Texas at Austin who led the research. “If you have a pile of three oranges and four oranges, it’s pretty easy to see that one has more,” she said. “But it’s harder to tell the difference between 50 oranges versus 60 oranges, even though the absolute difference is greater.” The frogs are not alone at night; also lurking nearby are bats that prey on the frogs. Surprisingly, the researchers found that the bats use the same strategy as female frogs when selecting prey to single out. Like female frogs, they are drawn to males emitting more chucks, and make their determinations based on the ratio, rather than the absolute difference. © 2011 The New York Times Company

Keyword: Sexual Behavior; Hearing
Link ID: 15662 - Posted: 08.09.2011

By PERRI KLASS, M.D. Parents of children with autism often ask pediatricians like me about the cause of the condition, and parents-to-be often ask what they can do to reduce the risk. But although there is more research in this area than ever before, it sometimes feels as if it’s getting harder, not easier, to provide answers that do justice to the evidence and also offer practical guidance. Recent research has taught us more about the complexity of the genetics of autism, but the evidence also has suggested an important role for environmental exposures. It has become a very complicated picture: Genes matter, but we usually can’t tell how. Environmental exposures matter, but we usually don’t know which. In July, a study of autism in twins was published online in Archives of General Psychiatry. Researchers looked at almost 200 sets of twins in California. In each pair, one twin was autistic. The study sought to determine how likely the second twin was to have some form of autism. If autism was highly heritable, identical twins should have been far more likely to both have autism than fraternal twins. But the researchers found that fraternal twins were unexpectedly likely to both have autism. The implication is that something in their common gestational or early childhood experience may have contributed to this similarity. “The data definitely did surprise me,” said Dr. Joachim Hallmayer, the lead author of the study and an associate professor of psychiatry and behavioral sciences at Stanford University. “I expected the fraternal twin rates to be lower than what we found.” © 2011 The New York Times Company

Keyword: Autism; Genes & Behavior
Link ID: 15661 - Posted: 08.09.2011

By GINA KOLATA Does obesity spread like a virus through networks of friends and friends of friends? Do smoking, loneliness, happiness, depression and illegal drug use also proliferate through social networks? Over the past few years, a series of highly publicized studies by two researchers have concluded that these behaviors can be literally contagious — passed from person to person. And there was an important public health corollary, the researchers said: It should be possible to curb a behavior like obesity by focusing on small groups of people who would then influence their networks. But now those surprising conclusions have drawn heated criticism from other scientists who claim that the studies’ methodology was flawed and the original data completely inadequate to estimate the role that contagion might play in the spread of these behaviors. “I know that many professional statisticians felt it was all bunk from the word go,” said Russell Lyons, a mathematics professor at Indiana University, who recently published a scathing review. of the work on contagion of social behaviors. The researchers who published the original studies — Dr. Nicholas Christakis, a social scientist at Harvard, and James Fowler, a social scientist at the University of California, San Diego — say they are well aware of the limitations of their analyses but maintain that their conclusions are robust. “We have laid all our cards on the table,” Dr. Fowler said. “We have yet to see anyone who proposed a model that worked better than the one we used.” © 2011 The New York Times Company

Keyword: Obesity
Link ID: 15660 - Posted: 08.09.2011

By James Gallagher Health reporter, BBC News US scientists say they have "fundamentally transformed" the understanding of the genetics of schizophrenia. A report in the journal Nature Genetics showed that "fresh mutations" in DNA are involved in at least half of schizophrenia cases, when there is no family history of the illness. Researchers found mutations in 40 different genes. They say their findings explain the high number of cases around the world. Schizophrenia is quite common, it affects one in every 100 people during their lifetime. Genes play a part in the illness. A tenth of people with schizophrenia also have a parent with the condition. However, researchers now say there is a genetic role even in cases which have not been inherited. A person's DNA is not a perfect copy of their parents' genetic code - there are mutations when eggs and sperm are formed. A team at Columbia University Medical Center analysed the genetic code of 225 people, some with and some without the condition. They found mutations in 40 genes were linked to schizophrenia. Lead researcher Dr Maria Karayiorgou said: "The fact that the mutations are all from different genes is particularly fascinating. BBC © 2011

Keyword: Schizophrenia; Genes & Behavior
Link ID: 15659 - Posted: 08.09.2011

By Laura Sanders A common virus may slink into the brain through the nose. After setting up shop in people’s nasal mucus, human herpesvirus-6 may travel along olfactory cells right into the brain, researchers report online the week of August 8 in the Proceedings of the National Academy of Sciences. Most people’s first bout with HHV-6 comes at a tender age: It causes the common childhood infection roseola, marked by a chest rash and a high fever. “Everyone is exposed to this,” says study coauthor Steven Jacobson of the National Institute of Neurological Disorders and Stroke in Bethesda, Md. “You have it. I have it.” Despite its ubiquity, very little is known about the virus. HHV-6 may live in tonsils and shed in saliva, some studies suggest. And in some people (researchers don’t know how many), the virus can infect the brain, where some researchers believe it may contribute to neurological disorders such as multiple sclerosis, encephalitis and a form of epilepsy. Other viruses such as herpes simplex, influenza A and rabies can invade the brain by shooting through the nose, so Jacobson and his team wondered whether HHV-6 could do the same trick. The researchers found high levels of HHV-6 in the olfactory bulb, a smell-related part of the brain, in two of three autopsy brain samples. The team then looked at nose mucus and found the virus in 52 of 126 different samples. “We were surprised to find so much in the nasal mucus,” Jacobson says. © Society for Science & the Public 2000 - 2011

Keyword: Chemical Senses (Smell & Taste)
Link ID: 15658 - Posted: 08.09.2011

By Alexandra Witze There’s just no getting ahead when you’re a hobbit. Anthropologists are arguing yet again over whether a tiny 18,000-year-old Indonesian skull represents a separate species of little human cousins, or an ordinary Homo sapiens with an abnormally small head. New data compare the fossil to a large group of modern humans with microcephaly, a genetic condition that makes the head smaller than usual. Measurements of the hobbit skull suggest its proportions fall within the range of microcephalic Homo sapiens, researchers report August 8 in the Proceedings of the National Academy of Sciences. “Previously published papers that seemed to show that it can’t be a microcephalic are open to doubt,” says coauthor Ralph Holloway, an anthropologist at Columbia University in New York. The hobbit story began in 2003, when archaeologists unearthed the skull and other bones of a female hominid on the island of Flores. Her discoverers argued she represented a member of a human genus that had survived until relatively recently, and dubbed it Homo floresiensis. But some scientists charged that because the hobbit’s skull is so small, it might have just been a microcephalic Homo sapiens. To test that question, anthropologist Dean Falk of Florida State University in Tallahassee compared the skull’s internal dimensions to those of nine microcephalic humans and 10 normal humans. In a 2007 paper, she concluded the hobbit skull was still best assigned to its own species. © Society for Science & the Public 2000 - 2011

Keyword: Evolution
Link ID: 15657 - Posted: 08.09.2011

by Helen Fields Despite our wars and crime, humans tend to be nice. We bake for our neighbors, give directions to strangers, and donate money to far-off disaster victims. But does the same go for our closest cousin, the chimpanzee? A new study suggests that it does. People who study chimpanzees in the field have known for a long time that the apes console their comrades when they're upset and support each other in a fight. And when one chimp has a good hunting day and kills a nice, juicy monkey, it shares the meat with the other members of its group. But scientists have found that chimps don't share in lab experiments, creating a bit of a primatology mystery. For instance, when researchers gave captive chimps the opportunity to get rewards just for themselves or for both themselves and another chimpanzee from an apparatus with multiple interconnected trays, the apes were equally likely to choose the selfish and sharing options. Comparative psychologist Victoria Horner of Emory University in Atlanta thought she knew the reason why experiments didn't find sharing: the experimental setups other scientists used to test the chimps were just too confusing—"tables with pulley systems and whatnot." For one study, she says, "I had to read it several times before I understood the apparatus, and I'm a human." She thinks the chimps didn't understand how what they did affected their partner. With her colleagues at Emory, including renown primatologist Frans de Waal, Horner devised a new way to test chimps' generosity. "We did the same basic idea but from a more chimpy perspective," she says. In each experiment, two female chimps that live at the Yerkes National Primate Research Center in Lawrenceville, Georgia, were put in side-by-side rooms with a mesh-covered opening between them. Both chimps had been trained to "buy" food from the researchers with tokens, colored, 5-centimeter-long pieces of PVC pipe. © 2010 American Association for the Advancement of Science.

Keyword: Evolution; Emotions
Link ID: 15656 - Posted: 08.09.2011

Gwyneth Dickey Zakaib Margaret Gatz, a psychologist at the University of Southern California, Los Angeles, is investigating the causes of Alzheimer's disease. To that end, she has studied the health of more than 14,000 Swedish twins for more than 25 years. On 5 August, she will tell the annual convention of the American Psychological Association in Washington DC what the study has taught her about how to reduce risk for the disease. What first motivated you to study Alzheimer's disease? Before I studied aging, I was a clinical psychologist. I talked to older adults and their families, and it became clear to me that cognitive changes and memory problems were a big concern for a demographic that, at the time, was fairly neglected in terms of research. Then, when I was on a sabbatical in Stockholm, I had the opportunity to get involved with the Swedish Twin Registry, a large cohort study in which some researchers were looking at cognition. It became clear to me that some of the twins would develop dementia, and that this was a unique opportunity for a study. My lab has been working with the Swedish twins now since 1985. What does your research show? Somewhere in the ballpark of 70% of risk for Alzheimer's disease across a population is due to heredity. In each individual, there's some combination of genes and environment. But on average, genes have a greater influence than environment in explaining the disease. © 2011 Nature Publishing Group

Keyword: Alzheimers
Link ID: 15655 - Posted: 08.08.2011

By BENEDICT CAREY LEE’S SUMMIT, Mo. — The job was gone, the gun was loaded, and a voice was saying, “You’re a waste, give up now, do it now.” Mr. Holt and his wife, Patsy, who has been one of his main resources in his struggle with mental illness. It was a command, not a suggestion, and what mattered at that moment — a winter evening in 2000 — was not where the voice was coming from, but how assured it was, how persuasive. Losing his first decent job ever seemed like too much for Joe Holt to live with. It was time. “All I remember then is a knock on the bedroom door and my wife, Patsy, she sits down on the bed and hugs me, and I’m holding the gun in my left hand, down here, out of sight,” said Mr. Holt, 50, a computer consultant and entrepreneur who has a diagnosis of schizophrenia. “She says, ‘Joe, I know you feel like quitting, but what if tomorrow is the day you get what you want?’ And walks out. I sat there staring at that gun for an hour at least, and finally decided — never again. It can never be an option. Patsy deserves for me to be trying.” In recent years, researchers have begun talking about mental health care in the same way addiction specialists speak of recovery — the lifelong journey of self-treatment and discipline that guides substance abuse programs. The idea remains controversial: managing a severe mental illness is more complicated than simply avoiding certain behaviors. The journey has more mazes, fewer road signs. © 2011 The New York Times Company

Keyword: Schizophrenia
Link ID: 15654 - Posted: 08.08.2011

Sandrine Ceurstemont, video producer It looks like a typical face turned upside down (see video above). But keep watching as it's flipped right-side up and you'll probably be surprised by its unusual features. Produced by The Open University, the video is an example of a well-known illusion called the Thatcher effect. It was accidentally discovered by psychologist Peter Thompson in 1980, who later altered a photo of Margaret Thatcher to demonstrate how flipped features, like mouths or eyes, are difficult to detect once a face is inverted. But why does this arrangement trick our brain? It's typically thought that we make sense of what we see by comparing the overall configuration with a known mental map. Since we rarely see an inverted face, we are unlikely to know what to expect and so relate it to our model for upright faces. According to Gillian Rhodes and her team from University of Western Australia, we may not notice peculiar positioning of features because it's harder to detect facial expressions when a face is upside down. The team found that not all odd features are masked when a face is inverted. For example, they found that pulling a face or blackening a person's teeth was obvious whichever way a face was oriented. © Copyright Reed Business Information Ltd.

Keyword: Vision; Attention
Link ID: 15653 - Posted: 08.08.2011

by Linda Geddes It's what women have been telling men for decades: stimulating the vagina is not the same as stimulating the clitoris. Now brain scan data has added weight to their argument. The precise locations that correspond to the vagina, cervix and female nipples on the brain's sensory cortex have been mapped for the first time, proving that vaginal stimulation activates different brain regions to stimulation of the clitoris. The study also found a direct link between the nipples and the genitals, which may explain why some women can orgasm through nipple stimulation alone. The discoveries could ultimately help women who have suffered nerve damage in childbirth or disease. The sensory cortex is a strip of brain tissue positioned roughly under where the band between a pair of headphones sits. Across it, neurons linked to different body parts exchange information about the sensory information feeding into them. This is often depicted as the "sensory homunculus", a distorted image of a man stretched across the brain, with his genitals lying next to his feet (click here). The size of the body's parts show how much of the brain is dedicated to processing the sensory information from each body part. The diagram was first published in 1951 after experiments conducted during brain surgery performed while the patients were conscious: the surgeon electrically stimulated different regions of the patients' brains and the patients reported the parts of their bodies in which they felt sensation as a result. But all the subjects were men. Until recently, the position of female genitalia on the homunculus had only been guessed at. © Copyright Reed Business Information Ltd.

Keyword: Sexual Behavior; Brain imaging
Link ID: 15652 - Posted: 08.08.2011

By Laura Sanders Nerve cell communication gets better with use. A neuron’s electrical activity triggers other cells to come and slather on a protective coating that makes messages travel faster, a study published online August 4 in Science shows. Like rubber insulation around electrical wires, myelin wraps around message-sending axons, protecting and speeding electrical impulses. Specialized brain cells called oligodendrocytes wrap up to 150 layers of this insulation around a single axon. In this image, a single oligodendrocyte (green) wraps several axons (purple). The process begins when neurons fire off an electrical signal and the chemical messenger glutamate is released. Mouse neurons treated so they were unable to release glutamate had lower levels of myelin, Hiroaki Wake of the National Institute of Child Health and Human Development in Bethesda, Md., and colleagues found. When the team activated normal axons, boosting their glutamate production, oligodendrocytes produced more of the fatty proteins that make up the myelin coating. The results suggest one way that the brain quickly adapts and improves when a person practices new tasks such as playing the violin or juggling. © Society for Science & the Public 2000 - 2011

Keyword: Glia; Development of the Brain
Link ID: 15651 - Posted: 08.08.2011

By Steve Mirsky Parents often wonder what their little ones are absorbing from them. For example, my mother had a wonderful vocabulary. So it may be more than a family fable that when I was asked as a two-year-old whether I was wet, I allegedly responded, “No, I’m saturated.” Then again, my father has always tended to interpret things quite literally, which may explain why, a year or two later, my supposed response to the question of how my favorite record went was “’round and around and around.” (This all happened shortly after the invention of movable type, when music was literally pressed onto large vinyl disks that “turned” on what was fittingly called a turntable. For more on turntables, see this space in the June issue.) I was reminded of preposterously precocious utterances by tiny tykes during a brief talk that string theorist Brian Greene gave at the opening of the 2011 World Science Festival in New York City on June 1. Greene said he sometimes wondered about how much information small children pick up from standard dinner-table conversation in a given home. He revealed that he got some data to mull over when he hugged his three-year-old daughter and told her he loved her more than anything in the universe, to which she replied, “The universe or the multiverse?” Closer to home (well, my home at least), my seven-year-old grandnephew has often exhibited an interest in various science and math topics. He, like many preschoolers at the time, was deeply disappointed by the 2006 demotion of Pluto from the family of planets. So great was his grief then that when I asked him about Pluto’s fall, he only said, “I don’t want to talk about it.” More recently, he was a passenger when his grandfather exited a highway onto a cloverleaf that took them off their northern route toward the east, then south and then west onto the next road. With that maneuver complete, the kid said, “That was a 270-degree turn.” Which he either learned from his smart parents or from watching the X Games. © 2011 Scientific American,

Keyword: Development of the Brain; Intelligence
Link ID: 15650 - Posted: 08.08.2011

by Helen Fields Humans buy unripe bananas, then leave them on the kitchen counter. The tayra, a relative of the weasel native to Central and South America, appears to do much the same thing, picking unripe plantains and hiding them until they ripen, according to a new study. The authors speculate that tayras are showing a human-like capacity to plan for the future, which has previously been shown only in primates and birds. Biologist Fernando Soley was an undergraduate at the University of Costa Rica in 2004 when he first started thinking about tayras. He was studying poison dart frogs at La Selva Biological Station in northern Costa Rica, when he noticed a tayra—essentially a giant weasel with a bushy tail—approach a tree. "It climbed 4 meters high, went directly to a bromeliad [a plant growing in the tree], and came back down with a ripe plantain and ate it," Soley says. The trees in the forestry plantation where he was working are planted in neat rows, and it's easy for humans to get lost. Because the animal went straight to the plantain, he thought it couldn't have found it by chance. "I thought, wow, for sure this animal was the one that brought it there." A few years later, Soley came back for a closer look at the tayras, teaming up with Isaías Alvarado-Díaz, a self-taught biologist who lives near La Selva. Animals don't spend much time in the forestry plantation, so Soley thought tayras might hide their fruit there to keep it safe from prying snouts. The duo set up an Easter egg hunt for fruit thieves to find out if the tayras were doing a good job. "We hid pieces of banana, which pretty much tastes and smells very similar to plantains, in the forest and in the plantation, and after 2 days we went to count them," he says. Animals found fewer bananas in trees than on the ground, and fewer in the plantation than in the forest. That means hiding plantains in the plantation and up in tree is a smart move by tayras that don't want other animals to find their treasures. © 2010 American Association for the Advancement of Science

Keyword: Learning & Memory; Intelligence
Link ID: 15649 - Posted: 08.08.2011

David Cyranoski Mu-ming Poo leads a double life. For three weeks every month, he works in a cramped, cluttered office at the University of California, Berkeley. Looking drab in his dark-green pullover, olive trousers and black Adidas sports shoes, the 62-year-old neuroscientist slumps slightly in his chair. In the adjoining laboratory, half a dozen postdoctoral researchers, expected to work independently, go quietly about their business. Cut to Shanghai, China, where Poo spends the remaining quarter of his time. In the director's office at the Institute of Neurosciences (ION), he sports a pressed, light-blue shirt neatly tucked into belted trousers (same trainers). With few books and papers about, the room seems more spacious than its Californian counterpart; mangoes and other fruit in a bowl provide a tasteful flourish. Here, Poo supervises only one postdoctoral researcher, but a dozen chattering graduate students are stuffed into an office, waiting for the hour that he sets aside for each one during his whirlwind visits. Poo sits straighter, talks faster and seems more alert, alive — younger, even. As stimulating as he finds his research in the United States, where he is a member of the National Academy of Sciences, Poo finds a sense of mission in China. "It's more exciting, exhilarating here," he says. "They need me. I feel it's the best use of my life." China is alive with possibilities in science, but realizing them is a complicated affair. The country's fondness for speed — for short-term achievements and, increasingly, short-term profits — has worked relatively well in the chemical and physical sciences and in large-scale genomics, where researchers can systematically tick off the chemical compounds or genetic sequences that they have produced (see 'Eastern promise'). © 2011 Nature Publishing Group,

Keyword: Miscellaneous
Link ID: 15648 - Posted: 08.04.2011

By Victoria Gill Science reporter, BBC Nature The flamboyant "booming" display of the threatened Houbara bustard is linked to the rate at which the birds age A large, flamboyant bird has given biologists an insight into the relationship between sex and ageing. The male Houbara bustard has striking ornamental feathers that it displays while running around and "booming" to attract a mate. As scientists report in Ecology Letters, birds that indulge in more of these sexual displays age faster. The more "showy" males experienced earlier age-related declines in the quality of their sperm. The team used 10-years-worth of data on the sexual behaviour and fertility of more than 1,700 North African Houbara bustards that were bred by conservationists in Missour, Morocco. "The birds are a threatened species, and the data was collected as part of an ongoing conservation programme aimed at increasing their numbers in the wild," explained lead researcher Brian Preston, a scientist based at the University of Burgundy, France. The scientists measured how much time each male spent carrying out its elaborate display, and compared this to changes in its fertility that are associated with ageing. BBC © 2011

Keyword: Sexual Behavior; Evolution
Link ID: 15647 - Posted: 08.04.2011

by Frank Swain We need to talk about how the digital world might be changing our brains, says the neuroscientist and former director of the UK's Royal Institution You think that digital technology is having an impact on our brains. How do you respond to those who say there's no evidence for this? When people say there is no evidence, you can turn that back and say, what kind of evidence would you imagine there would be? Are we going to have to wait for 20 years and see that people are different from previous generations? Sometimes you can't just go into a lab and get the evidence overnight. I think there are enough pointers that we should be talking about this rather than stressing about not being able to replicate things in a lab instantly. So what evidence is there? There is lots of evidence, for example, the recent paper "Microstructure abnormalities in adolescents with internet addiction disorder" in the journal PLoS One. We know the human brain can change and the environment can change it. There is an increase in people with autistic spectrum disorders. There are issues with happy-slapping, the rise in the appeal of Twitter - I think these show that people's attitude to each other and themselves is changing. Anything else? There's a recent review by the cognitive scientist Daphne Bavelier in the high-impact journal Neuron, in which she says that this is a given, that the brain will change. She also reviews evidence showing there's a change in violence, distraction and addiction in children, linked to the pervasion of technology. © Copyright Reed Business Information Ltd.

Keyword: Attention
Link ID: 15646 - Posted: 08.04.2011

by Daniel Strain Agatha Christie, meet your tiniest villain yet: the African crested rat (Lophiomys imhausi). Dogs that try to grab a bite of this spiky-haired East African rodent, more closely related to lemmings or voles than true street rats, often wind up violently ill or even dead. Now, scientists have discovered the secret to the crested rat's fatal kiss: A poison once used by African hunters to kill elephants. When cornered, crested rats don't run or hide like a normal rodent. Instead, they twist to the side and arch their backs, parting their long, gray outer coats, to reveal black-and-white bands that run like racing stripes down their flanks. Like a hornet's yellow-and-black rear or a rattlesnake's rattle, these stripes seem to tell predators one thing: Back off. The rats' defensive postures are fearsome, but they don't explain the trails of sick dogs left in their wakes. Researchers suspected that the rodents were harboring poison, but they didn't know how. In the new study, Fritz Vollrath, an evolutionary biologist at the University of Oxford in the United Kingdom, and colleagues have turned Miss Marple and solved the mystery. Crested rats, it turns out, don't make their own poison; they gather it. The team's first clue was observing a captive crested rat diligently gnaw on pieces of bark from the African tree Acokanthera schimperi, also called the arrow poison tree. The animal would then "slather" its short hairs in fibrous spit. That bark carries large amounts of ouabain, a chemical that overstimulates heart muscle, similar to the poison curare, commonly obtained from South American plants. East African hunters once boiled down the bark to coat poisoned arrows for taking down elephants and other big game. © 2010 American Association for the Advancement of Science.

Keyword: Neurotoxins; Aggression
Link ID: 15645 - Posted: 08.04.2011