Chapter 9. Hearing, Vestibular Perception, Taste, and Smell
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By Michael Price Doctors and soldiers could soon place their trust in an unusual ally: the mouse. Scientists have genetically engineered mice to be ultrasensitive to specific smells, paving the way for animals that are “tuned” to sniff out land mines or chemical signatures of diseases like Parkinson’s and Alzheimer’s. Trained rats and dogs have long been used to detect the telltale smell of TNT in land mines, and research suggests that dogs can smell the trace chemical signals of low blood sugar or certain types of cancer. Mice also have powerful sniffers: They sport about 1200 genes dedicated to odorant receptors, cellular sensors that react to a scent’s chemical signature. That’s a few hundred less than rats and about the same as dogs. (Humans have a paltry 350.) Paul Feinstein wants to upgrade the mouse’s already sensitive nose. For the last decade, the neurobiologist at Hunter College in New York City has been studying how odorant receptors form on the surface of neurons within the olfactory system. During development, each olfactory neuron specializes to express a single odorant receptor, which binds to chemicals in the air to detect a specific odor. In other words, each olfactory neuron has a singular receptor that senses a particular smell. Normally, there is an even distribution of receptors throughout the system, so each receptor can be found in about 0.1% of mouse neurons. Feinstein wondered if he could make the mouse’s nose pay more attention to particular scents by making certain odorant receptors more numerous. He and colleagues developed a string of DNA that, when injected into the nucleus of a fertilized mouse egg, appears to make olfactory neurons more likely to develop one particular odorant receptor than the others. This receptor, called M71, detects acetophenone, a chemical that smells like jasmine. When the team added four or more copies of the DNA sequence to a mouse egg, a full 1% of neurons carried it—10 times more than normal. © 2016 American Association for the Advancement of Science.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 22412 - Posted: 07.08.2016
By Patrick Monahan Birds are perhaps best known for their bright colors, aerial prowess, and melodic songs. But research presented in Austin last week at the Evolution Conference shows that bacteria have granted some birds another important attribute: stink. Having long taken a back seat to sight and sound, scent is becoming more and more recognized as an important sense for songbirds, and dark-eyed juncos (Junco hyemalis, pictured) are no stranger to it. When these common birds clean their feathers—or preen—they spread pungent oil from their “preen glands” all over their bodies. The act is important for enticing mates: Three of the gland’s smelly chemicals are found in very different quantities in the two sexes, and males with a more masculine musk end up with more offspring. Females with a more feminine scent profile are more successful, too. But juncos likely aren’t making their perfume alone: Lots of those preen gland chemicals are naturally made by bacteria. And new work is making the bird-bacteria link even more firm. When researchers inject antibiotics into the juncos’ preen glands, the concentrations of three smelly molecules tend to decrease—the same three molecules that juncos find sexy in the right proportions, Danielle Whittaker of Michigan State University in East Lansing told attendees. So it seems like juncos may actually be picking mates based on their bacterial—rather than self-produced—body odor, a first for birds. © 2016 American Association for the Advancement of Science.
By REUTERS SINGAPORE — Phones or watches may be smart enough to detect sound, light, motion, touch, direction, acceleration and even the weather, but they can't smell. That's created a technology bottleneck that companies have spent more than a decade trying to fill. Most have failed. A powerful portable electronic nose, says Redg Snodgrass, a venture capitalist funding hardware start-ups, would open up new horizons for health, food, personal hygiene and even security. Imagine, he says, being able to analyze what someone has eaten or drunk based on the chemicals they emit; detect disease early via an app; or smell the fear in a potential terrorist. "Smell," he says, "is an important piece" of the puzzle. It's not through lack of trying. Aborted projects and failed companies litter the aroma-sensing landscape. But that's not stopping newcomers from trying. Like Tristan Rousselle's Grenoble-based Aryballe Technologies, which recently showed off a prototype of NeOse, a hand-held device he says will initially detect up to 50 common odors. "It's a risky project. There are simpler things to do in life," he says candidly. The problem, says David Edwards, a chemical engineer at Harvard University, is that unlike light and sound, scent is not energy, but mass. "It's a very different kind of signal," he says. That means each smell requires a different kind of sensor, making devices bulky and limited in what they can do. The aroma of coffee, for example, consists of more than 600 components. France's Alpha MOS was first to build electronic noses for limited industrial use, but its foray into developing a smaller model that would do more has run aground. Within a year of unveiling a prototype for a device that would allow smartphones to detect and analyze smells, the website of its U.S.-based arm Boyd Sense has gone dark. Neither company responded to emails requesting comment. © 2016 The New York Times Company
Keyword: Chemical Senses (Smell & Taste)
Link ID: 22354 - Posted: 06.24.2016
By Brian Platzer It started in 2010 when I smoked pot for the first time since college. It was cheap, gristly weed I’d had in my freezer for nearly six years, but four hours after taking one hit I was still so dizzy I couldn’t stand up without holding on to the furniture. The next day I was still dizzy, and the next, and the next, but it tapered off gradually until about a month later I was mostly fine. Over the following year I got married, started teaching seventh and eighth grade, and began work on a novel. Every week or so the disequilibrium sneaked up on me. The feeling was one of disorientation as much as dizziness, with some cloudy vision, light nausea and the sensation of being overwhelmed by my surroundings. During one eighth-grade English class, when I turned around to write on the blackboard, I stumbled and couldn’t stabilize myself. I fell in front of my students and was too disoriented to stand. My students stared at me slumped on the floor until I mustered enough focus to climb up to a chair and did my best to laugh it off. I was only 29, but my father had had a benign brain tumor around the same age, so I had a brain scan. My brain appeared to be fine. A neurologist recommended I see an ear, nose and throat specialist. A technician flooded my ear canal with water to see if my acoustic nerve reacted properly. The doctor suspected either benign positional vertigo (dizziness caused by a small piece of bonelike calcium stuck in the inner ear) or Ménière’s disease (which leads to dizziness from pressure). Unfortunately, the test showed my inner ear was most likely fine. But just as the marijuana had triggered the dizziness the year before, the test itself catalyzed the dizziness now. In spite of the negative results, doctors still believed I had an inner ear problem. They prescribed exercises to unblock crystals, and salt pills and then prednisone to fight Ménière’s disease. All this took months, and I continued to be dizzy, all day, every day. It felt as though I woke up every morning having already drunk a dozen beers — some days, depending on how active and stressful my day was, it felt like much more. Most days ended with me in tears. © 2016 The New York Times Company
By C. CLAIBORNE RAY Insects have an odor-sensing system that is roughly analogous to that of vertebrates, according to “The Neurobiology of Olfaction,” a survey published in 2010. Different species have varying numbers of odor receptors, special molecules that are attuned to specific odor molecules. Genes govern the production of each kind of receptor; the more genes, the more kinds of receptor. A big difference with insects is that their olfactory receptors are basically external, often within hairlike groups of cells, called sensilla, on the antennas, not inside a collection organ like a nose. Sign Up for the Science Times Newsletter Every week, we'll bring you stories that capture the wonders of the human body, nature and the cosmos. The odorant molecules encounter odorant-binding proteins, assumed to guide them to the long receptor nerve cells, called axons. Electrical signals are sent along the axons. The axons are usually connected to specific processing centers in the brain called glomeruli, held in a region called the antennal lobe. There the signals are analyzed. Depending on the nature, quantity and timing of the odor signals received, still other cells appear to excite or inhibit reactions. Exactly how the reaction system works is not yet fully understood. The Florida carpenter ant and the Indian jumping ant both have wide-ranging abilities to sense odors, with more than 400 genes to make different odor receptors, a 2012 study found. The fruit fly has only 61. The research also found marked differences in the smelling ability of the sexes, with the female ants well ahead. © 2016 The New York Times Company
By Anahad O'Connor The federal government’s decision to update food labels last month marked a sea change for consumers: For the first time, beginning in 2018, nutrition labels will be required to list a breakdown of both the total sugars and the added sugars in packaged foods. But is sugar really that bad for you? And is the sugar added to foods really more harmful than the sugars found naturally in foods? We spoke with some top scientists who study sugar and its effects on metabolic health to help answer some common questions about sugar. Here’s what they had to say. Why are food labels being revised? The shift came after years of urging by many nutrition experts, who say that excess sugar is a primary cause of obesity and heart disease, the leading killer of Americans. Many in the food industry opposed the emphasis on added sugars, arguing that the focus should be on calories rather than sugar. They say that highlighting added sugar on labels is unscientific, and that the sugar that occurs naturally in foods like fruits and vegetables is essentially no different than the sugar commonly added to packaged foods. But scientists say it is not that simple. So, is added sugar different from the naturally occurring sugar in food? It depends. Most sugars are essentially combinations of two molecules, glucose and fructose, in different ratios. The sugar in a fresh apple, for instance, is generally the same as the table sugar that might be added to homemade apple pie. Both are known technically as sucrose, and they are broken down in the intestine into glucose and fructose. Glucose can be metabolized by any cell in the body. But fructose is handled almost exclusively by the liver. “Once you get to that point, the liver doesn’t know whether it came from fruit or not,” said Kimber Stanhope, a researcher at the University of California, Davis, who studies the effects of sugar on health. © 2016 The New York Times Company
Meghan Rosen SALT LAKE CITY — In the Indian Ocean off the coast of Sri Lanka, pygmy blue whales are changing their tune — and they might be doing it on purpose. From 2002 to 2012, the frequency of one part of the whales’ calls steadily fell, marine bioacoustician Jennifer Miksis-Olds reported May 25 at a meeting of the Acoustical Society of America. But unexpectedly, another part of the whales’ call stayed the same, she found. “I’ve never seen results like this before,” says marine bioacoustician Leanna Matthews of Syracuse University in New York, who was not involved with the work. Miksis-Olds’ findings add a new twist to current theories about blue whale vocalizations and spark all sorts of questions about what the animals are doing, Matthews said. “It’s a huge mystery.” Over the last 40 to 50 years, the calls of blue whales around the world have been getting deeper. Researchers have reported frequency drops in blue whale populations from the Arctic Ocean to the North Pacific. Some researchers think that blue whales are just getting bigger, said Miksis-Olds, of the University of New Hampshire in Durham. Whaling isn’t as common as it used to be, so whales have been able to grow larger — and larger whales have deeper calls. Another theory blames whales’ changing calls on an increasingly noisy ocean. Whales could be automatically adjusting their calls to be heard better, kind of like a person raising their voice to speak at a party, she said. If the whales were just getting bigger, you’d expect all components of the calls to be deeper, said acoustics researcher Pasquale Bottalico at Michigan State University in East Lansing. But the new data don’t support that, he said. © Society for Science & the Public 2000 - 2016. A
Amy McDermott Giant pandas have better ears than people — and polar bears. Pandas can hear surprisingly high frequencies, conservation biologist Megan Owen of the San Diego Zoo and colleagues report in the April Global Ecology and Conservation. The scientists played a range of tones for five zoo pandas trained to nose a target in response to sound. Training, which took three to six months for each animal, demanded serious focus and patience, says Owen, who called the effort “a lot to ask of a bear.” Both males and females heard into the range of a “silent” ultrasonic dog whistle. Polar bears, the only other bears scientists have tested, are less sensitive to sounds at or above 14 kilohertz. Researchers still don’t know why pandas have ultrasonic hearing. The bears are a vocal bunch, but their chirps and other calls have never been recorded at ultrasonic levels, Owen says. Great hearing may be a holdover from the bears’ ancient past. Citations M.A. Owen et al. Hearing sensitivity in context: Conservation implications for a highly vocal endangered species. Global Ecology and Conservation. Vol. 6, April 2016, p. 121. doi: 10.1016/j.gecco.2016.02.007. © Society for Science & the Public 2000 - 2016.
Link ID: 22269 - Posted: 06.01.2016
by Helen Thompson In hunting down delicious fish, Flipper may have a secret weapon: snot. Dolphins emit a series of quick, high-frequency sounds — probably by forcing air over tissues in the nasal passage — to find and track potential prey. “It’s kind of like making a raspberry,” says Aaron Thode of the Scripps Institution of Oceanography in San Diego. Thode and colleagues tweaked a human speech modeling technique to reproduce dolphin sounds and discern the intricacies of their unique style of sound production. He presented the results on May 24 in Salt Lake City at the annual meeting of the Acoustical Society of America. Dolphin chirps have two parts: a thump and a ring. Their model worked on the assumption that lumps of tissue bumping together produce the thump, and those tissues pulling apart produce the ring. But to match the high frequencies of live bottlenose dolphins, the researchers had to make the surfaces of those tissues sticky. That suggests that mucus lining the nasal passage tissue is crucial to dolphin sonar. The vocal model also successfully mimicked whistling noises used to communicate with other dolphins and faulty clicks that probably result from inadequate snot. Such techniques could be adapted to study sound production or echolocation in sperm whales and other dolphin relatives. © Society for Science & the Public 2000 - 2016.
Link ID: 22244 - Posted: 05.25.2016
“I understand how the appearance and texture of food can change the experience,” says food writer and Great British Bake Off finalist Tamal Ray, “but I never really considered how the other senses might have a role to play.” An anaesthetist by day, Ray is best-known for creating spectacular tiered cakes and using a syringe to inject extra, syrupy deliciousness into them. Which is why we introduced him to Oxford psychologist Charles Spence and chef Jozef Youssef – and turned what they taught him about the science of taste into the video above. Part mad professor, part bon vivant, Spence has spent the past 15 years discovering that little of how we experience flavour is to do with our taste buds – smell, vision, touch and even sound dictate how we perceive flavours. Youssef, meanwhile, sharpened his culinary skills at the Fat Duck, the Connaught and the Dorchester, before starting experimental dining outfit Kitchen Theory, where he applies science to meals that play with the multisensory experience of eating. When Spence started studying the sensory science behind flavour perception, it was a deeply unfashionable subject. “There’s some ancient Roman notion that eating and drinking involve lower senses,” he says, “not higher, rational senses like hearing and vision.” Now, the fruits of the research field he calls “gastrophysics” can be seen everywhere from the world’s top restaurants to airline food, via progressive hospital kitchens and multisensory cocktail bars. Spence heads the Crossmodal Research Laboratory at the University of Oxford. “Crossmodal”, in this context, means the investigation of how all the senses interact. Although we’re often unaware of it, when it comes to flavour perception, we all have synaesthesia. That is, our senses intermingle so that our brains combine shapes, textures, colours and even sounds with corresponding tastes.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 22239 - Posted: 05.23.2016
By Linda Zajac For nearly 65 million years, bats and tiger moths have been locked in an aerial arms race: Bats echolocate to detect and capture tiger moths, and tiger moths evade them with flight maneuvers and their own ultrasonic sounds. Scientists have long wondered why certain species emit these high-frequency clicks that sound like rapid squeaks from a creaky floorboard. Does the sound jam bat sonar or does it warn bats that the moths are toxic? To find out, scientists collected two types of tiger moths: red-headed moths (pictured above) and Martin’s lichen moths. They then removed the soundmaking organs from some of the insects. In a grassy field in Arizona they set up infrared video cameras, ultrasonic microphones, and ultraviolet lights, the last of which they used to attract bats. In darkness, they released one tiger moth at a time and recorded the moth-bat interactions. They found that the moths rarely produced ultrasonic clicks fast enough to jam bat sonar. They also discovered that without sound organs, 64% of the red-headed moths and 94% of the Martin’s lichen moths were captured and spit out. Together, these findings reported late last month in PLOS ONE suggest that instead of jamming sonar like some tiger moths, these species act tough, flexing their soundmaking organs to warn predators of their toxin. © 2016 American Association for the Advancement of Science
Scientists have outwitted the crafty rat with a stimulating new formula that puts sex on the brain. A team at Simon Fraser University in Burnaby, B.C., has developed a rat trap that combines synthetic sex pheromones, food scents and baby rat sounds to lure rodents to their deaths. The bait has proven 10 times more powerful than traditional traps and could be commercialized in about two years, said principal investigator Gerhard Gries. "Rats are really intelligent, and in order to manipulate them you have to be intelligent as well, and do that in a way that addresses their needs," said Gries, a communication ecologist in the department of biological sciences. "It smells delicious, it smells like rat and it sounds like rat." Research outlining the pheromone component of the control tactic was published last week in the international edition of the German peer-reviewed online journal Angewandte Chemie, which translates to "Applied Chemistry." The research on the use of baby rat sounds was published recently in the journal Pest Management Science. Gries worked for several years with research associates Stephen Takacs and Regine Gries, his wife, to develop the three-pronged extermination technique. Humans have waged war against the pests for more than 10,000 years, said Gerhard Gries, noting they spread disease, reduce agricultural crop yields and threaten endangered animal species. But rats are quick learners that have evolved to avoid traps, a behaviour called "neophobia," he said. ©2016 CBC/Radio-Canada.
By C. CLAIBORNE RAY Q. Why do we become desensitized to a perfume we are wearing while others can still smell it? A. Ceasing to smell one’s perfume after continuous exposure while casual passers-by can still smell it is just one example of a phenomenon called olfactory adaptation or odor fatigue. After some time without exposure, sensitivity is usually restored. A similar weakening of odor signals with continued exposure also takes place in animals other than humans, and researchers often rely on animal studies to try to understand the cellular and molecular bases for the condition. It has been suggested that odor fatigue is useful because it enables animals to sort out the signals of a new odor from the background noise of continuous odors. It may also enable them to sense when an odor grows stronger. Studies published in the journal Science in 2002 pinpointed a chemical that seems to act as a gatekeeper for neurons involved in smell, opening and closing their electric signal channels. Genetically engineered mice that did not produce the substance, a protein called CNGA4, had profoundly impaired olfactory adaptation. A separate test-tube study found similar changes on a cellular level, with the signal channels remaining open when CNGA4 was absent. email@example.com © 2016 The New York Times Company
Keyword: Chemical Senses (Smell & Taste)
Link ID: 22042 - Posted: 03.29.2016
Anxious people perceive the world differently. An anxious brain appears to process sounds in an altered way, ramping up the expectation that something bad – or good – might happen. There’s no doubt that some degree of anxiety is vital for survival. When we learn that something is dangerous, we generalise that memory to apply the same warning signal to other, similar situations to avoid getting into trouble. If you’re bitten by a large, aggressive dog, for instance, it makes sense to feel slightly anxious around similar dogs. “It’s better to be safe than sorry,” says Rony Paz at the Weizmann Institute of Science in Rehovot, Israel. The trouble begins when this process becomes exaggerated. In the dog bite example, a person who went on to become anxious around all dogs, even small ones, would be described as overgeneralising. Overgeneralisation is thought to play a role in post-traumatic stress disorder and general anxiety disorder, a condition characterised by anxiety about many situations, leaving people in a state of near-constant restlessness. A study carried out by Paz suggests that overgeneralisation is not limited to anxious thoughts and memories – for such people the same process seems to affect their perception of the world. © Copyright Reed Business Information Ltd.
By Roni Caryn Rabin Does long-term use of artificial sweeteners cause weight gain or contribute to metabolic syndrome? Scientists are still scratching their heads over this question. Artificial, or nonnutritive, sweeteners have no calories and are often used as diet aids. But while some well-designed trials have found that those randomly assigned to drink artificially sweetened beverages gained less weight than those given sugar-sweetened drinks, large population studies suggest that frequent consumption of artificial sweeteners may be linked with unanticipated consequences, including weight gain. A large study that followed a diverse group of 6,814 Americans ages 45 to 84 for at least five years found that those who drank diet soda at least once a day were at 67 percent greater risk of developing Type 2 diabetes than those who didn’t consume diet drinks, regardless of whether they gained weight or not, and at 36 percent greater risk of metabolic syndrome, which can be a precursor to heart disease, stroke and diabetes. Another large study that followed thousands of residents of San Antonio, Tex., for 10 years found those who drank more than 21 servings of diet drinks a week were at twice the risk of becoming overweight or obese, and the more diet soda people drank, the greater the risk. These large observational trials do not prove cause and effect, however, and may reflect the fact that people who are gaining weight may be most likely to drink a lot of diet soda. Dr. John Fernstrom, a University of Pittsburgh professor who is also a paid consultant to Ajinomoto, a maker of aspartame, reviewed the evidence on nonnutritive sweeteners and concluded that the evidence linking them to metabolic problems was “not compelling.” © 2016 The New York Times Company
By NATALIE ANGIER Whether to enliven a commute, relax in the evening or drown out the buzz of a neighbor’s recreational drone, Americans listen to music nearly four hours a day. In international surveys, people consistently rank music as one of life’s supreme sources of pleasure and emotional power. We marry to music, graduate to music, mourn to music. Every culture ever studied has been found to make music, and among the oldest artistic objects known are slender flutes carved from mammoth bone some 43,000 years ago — 24,000 years before the cave paintings of Lascaux. Given the antiquity, universality and deep popularity of music, many researchers had long assumed that the human brain must be equipped with some sort of music room, a distinctive piece of cortical architecture dedicated to detecting and interpreting the dulcet signals of song. Yet for years, scientists failed to find any clear evidence of a music-specific domain through conventional brain-scanning technology, and the quest to understand the neural basis of a quintessential human passion foundered. Now researchers at the Massachusetts Institute of Technology have devised a radical new approach to brain imaging that reveals what past studies had missed. By mathematically analyzing scans of the auditory cortex and grouping clusters of brain cells with similar activation patterns, the scientists have identified neural pathways that react almost exclusively to the sound of music — any music. It may be Bach, bluegrass, hip-hop, big band, sitar or Julie Andrews. A listener may relish the sampled genre or revile it. No matter. When a musical passage is played, a distinct set of neurons tucked inside a furrow of a listener’s auditory cortex will fire in response. Other sounds, by contrast — a dog barking, a car skidding, a toilet flushing — leave the musical circuits unmoved. Nancy Kanwisher and Josh H. McDermott, professors of neuroscience at M.I.T., and their postdoctoral colleague Sam Norman-Haignere reported their results in the journal Neuron. The findings offer researchers a new tool for exploring the contours of human musicality. © 2016 The New York Times Company
By RACHEL NUWER For all the havoc that zebra mussels, Asian carp, round gobies and dozens of other alien species have wrought on the Great Lakes, those waters have never known a foe like the sea lamprey. The vampirelike parasites cost many millions each year in depleted fisheries and eradication efforts. Wildlife managers have long used lampricide — the lamprey version of pesticide — with mixed results. Now, an innovative control program seeks to improve on that method by using pheromones to trick the bloodsuckers into voluntarily corralling themselves in designated areas, to then be trapped or poisoned. But achieving this depends on cracking the fish’s olfactory language. “The broad goal is to understand how this animal makes decisions,” said Michael Wagner, a fish ecologist at Michigan State University. “Then, we want to use that understanding to guide lampreys’ movements by manipulating the landscape of fear and opportunity.” Lampreys look like the stuff of horror films: a slithering, tubular body topped with a suction-cup mouth ringed with row upon row of hooked yellow teeth. With this mouth, a sea lamprey anchors to its fish prey and uses its rasping tongue to drill into the victim’s flesh. It remains there for up to a month, feeding on blood and body fluids. Even if a fish survives the attack, the gaping wound left behind often results in death. In their natural ranges, lampreys are important components of food webs. The problems begin only when they shift from native to invader. Sea lampreys slipped into Lake Ontario through the Erie Canal in the mid-19th century, and then made it past Niagara Falls around 1919 with the renovation of the Welland Canal. In the lakes, lampreys found a utopia: no predators, and bountiful prey that had no natural defenses against their voracious appetites. Biological disaster ensued. © 2016 The New York Times Company
Keyword: Chemical Senses (Smell & Taste)
Link ID: 21869 - Posted: 02.08.2016
by Bethany Brookshire Unless you’re in the middle of biting into a delicious Reuben sandwich, you might forget that taste is one of the fundamental senses. “It’s required for our enjoyment of food,” explains Emily Liman, a taste researcher at the University of Southern California in Los Angeles. “Without taste … people stop eating. They don’t enjoy their food.” A life without the sweet jolt of sugar or the savory delights of umami seems, well, tasteless. When you put that mouthwatering combination of corned beef, Swiss cheese, Thousand Island dressing, sauerkraut and rye in your mouth, the chemicals in the sandwich stimulate taste buds on your tongue and soft palate. Those taste buds connect to the ends of nerve fibers extending delicately into the mouth. Those nerve fibers are the ends of cells located in the geniculate ganglion, a ball of cells nestled up against the ear canal on the side of your head. From there, taste sensations head toward the brain. Chemical messengers bridge the gap between the taste bud and the end of the nerve fiber. But what chemical is involved depends on the type of cell within the bud. There are three types of taste cells (imaginatively titled I, II and III). Type I is not well-understood, but it may be a kind of support cell for other taste cells. Type II, in contrast, is better known. These taste cells sense the slight bitterness of the rye seeds, the sweet edge of the Thousand Island dressing and the savory umami of the beef. They pass that delightful message on using the chemical ATP. © Society for Science & the Public 2000 - 2016
By SINDYA N. BHANOO Climate change may affect wood rats in the Mojave Desert in a most unusual way. A new study finds that warmer weather reduces their ability to tolerate toxins in the creosote bush, which they rely on for sustenance. The consequences may be dire for the wood rats. “There’s not much more they can eat out there,” said Patrice Kurnath, a biologist at the University of Utah and one of the study’s authors. She and her colleagues reported their findings in Proceedings of the Royal Society B: Biological Sciences. The leaves of the creosote bush contain a resin full of toxic compounds. They are known to cause kidney cysts and liver failure in laboratory rats. Wild wood rats, however, generally tolerate the poisons. Ms. Kurnath and her colleagues monitored the wood rats as they ate the leaves in warmer temperatures — around 83 degrees Fahrenheit. Although highs in the Mojave can reach the 80s and 90s during the summer, much of the year is cooler. The rats became less tolerant of the toxins and began to lose weight. The reason may have to do with how the liver functions in warmer weather, Ms. Kurnath said. The liver is the body’s primary detoxifying organ. When a mammalian liver is active, it increases internal body temperature. “In warmer weather, maybe you’re not producing huge amounts of heat and you’re not breaking down the toxins,” Ms. Kurnath said. © 2016 The New York Times Company
By Elizabeth Pennisi PACIFIC GROVE, CALIFORNIA—Bats have an uncanny ability to track and eat insects on the fly with incredible accuracy. But some moths make these agile mammals miss their mark. Tiger moths, for example, emit ultrasonic clicks that jam bat radar. Now, scientists have shown that hawk moths (above) and other species have also evolved this behavior. The nocturnal insects—which are toxic to bats—issue an ultrasonic “warning” whenever a bat is near. After a few nibbles, the bat learns to avoid the noxious species altogether. The researchers shot high-speed videos of bat chases in eight countries over 4 years. Their studies found that moths with an intact sound-producing apparatus—typically located at the tip of the genitals—were spared, whereas those silenced by the researchers were readily caught. As the video shows, when the moths hear the bat’s clicks intensifying as it homes in, they emit their own signal, causing the bat to veer off at the last second. It could be that, like the tiger moths, the hawk moths are jamming the bat’s signal. But, because most moth signals are not the right type to interfere with the bat’s, the researchers say it’s more likely that the bat recognizes the signal and avoids the target on its own. Presenting here last week at a meeting of the American Society of Naturalists, the researchers say this signaling ability has evolved three times in hawk moths and about a dozen more times overall among other moths. © 2016 American Association for the Advancement of Science
Link ID: 21810 - Posted: 01.23.2016