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Grasshoppers' terror outlives them

Grasshoppers' terror outlives them

Carcasses of jumpy insects taint soil

Terrified insects can haunt their homeland after they die. Chemical remnants of fear in the rotting corpses of grasshoppers slow the decomposition of dead grass and other debris important for fertilizing new plant growth, a new study finds.

Spiders that frighten grasshoppers may thus play an unrecognized role in shaping ecosystems, adding a menacing presence that both cows the predators’ prey and suppresses the local vegetation, researchers report in the June 15Science.

A team working at Yale spookedMelanoplus femurrubrumgrasshoppers by raising them in cages with Pisaurina mira spiders. The arachnids’ mouth parts had been glued shut, so they could scare but not kill the hapless insects. Stress boosts a grasshopper’s metabolism and appetite for carbon-rich carbohydrates. So compared with insects living in predator-free cages, grasshoppers cohabitating with eight-legged horrors were made of more carbon and less nitrogen.

That change in composition proved to be problematic for soil microbes, which need nitrogen to break down plant litter. When the researchers added the carcasses of once-fearful grasshoppers to dirt, microbial activity dropped by 62 percent in the lab and 19 percent in plots of land outdoors.

By : Haiderzai

Diet sodas may confuse brain's 'calorie counter'

Diet sodas may confuse brain's 'calorie counter'

Sugar-free drinks may make sweet-detecting circuits numb to the real stuff

By baffling the brain, saccharin and other sugar-free sweeteners — key weapons in the war on obesity — may paradoxically foster overeating.

At some level, the brain can sense a difference between sugar and no-calorie sweeteners, several studies have demonstrated. Using brain imaging, San Diego researchers now show that the brain processes sweet flavors differently depending on whether a person regularly consumes diet soft drinks.

“This idea that there could be fundamental differences in how people respond to sweet tastes based on their experience with diet sodas is not something that has gotten much attention,” says Susan Swithers of Purdue University in West Lafayette, Ind. A key finding, she says: Brains of diet soda drinkers “don’t differentiate very well between sucrose and saccharin.”

Erin Green and Claire Murphy of the University of California, San Diego and San Diego State University recruited 24 healthy young adults for a battery of brain imaging tests. Half reported regularly drinking sugar-free beverages, usually at least once a day. The rest seldom if ever consumed such drinks. While the brain scans were underway, the researchers pumped small amounts of saccharin- or sugar-sweetened water in random order into each recruit’s mouth as the volunteer rated the tastes.

Both the diet soda drinkers and the nondrinkers rated each sweetener about equally pleasant and intense, Green and Murphy report in an upcoming Physiology & Behavior. But which brain regions lit up while making those judgments differed sharply based on who regularly consumed diet drinks.

Certain affected brain regions are associated with offering a pleasurable feedback or reward in response to desirable sensations. And compared with those who don't drink diet soda, the diet soda drinkers “demonstrated more widespread activation to both saccharin and sucrose in reward processing brain regions,” the researchers say.

One of the strongest links seen was diminishing activation of an area known as the caudate head as a recruit’s diet soda consumption climbed. This area is associated with the food motivation and reward system. Green and Murphy also point out that decreased activation of this brain region has been linked with elevated risk of obesity.

The new findings may help explain an oft-observed association between diet soda consumption and weight gain, the researchers say. Once fooled, the brain’s sweet sensors can no longer provide a reliable gauge of energy consumption.

It’s something Swithers’ group demonstrated two years ago in rats. Animals that always received a saccharin-sweetened yogurt learned to modulate their food intake to account for the sweetener’s failure to deliver calories. But animals that alternately got saccharin- and sugar-sweetened yogurts blimped out, gaining substantially more body fat.

“The brain normally uses a learned relationship between sweet taste and the delivery of calories to help it regulate food intake,” Swithers explains. But when a sweet food unreliably delivers bonus calories, the brain “suddenly has no idea what to expect.” Confused, she says, this regulator of food intake learns to ignore sweet tastes in its predictions of a food’s energy content.

By : Haiderzai

Calcium offers clues in mass extinction

Calcium offers clues in mass extinction
Ocean acidification during Permian period may have caused the Great Dying

New clues in a mass murder that took place 252 million years ago points to a suspect: Ocean acidification may have driven the largest extinction of animals the world has ever seen.

Carbon dioxide belched out by volcanic eruptions during the Permian period could have caused the oceans’ chemistry to change. That’s worrisome because CO2 levels are rising today — thanks to the burning of fossil fuels — and pushing down seawater pH, researchers report online June 8 in Geology.

“The worst biodiversity catastrophe we've had in the history of animal life appears to have been associated with ocean acidification and other kinds of environmental changes we anticipate in the coming centuries,” says Jonathan Payne, a paleobiologist at Stanford University. “It’s a useful comparison point to have in mind as we think about the future of the modern oceans.”

The Great Dying at the end of the Permian period 252 million years ago wiped out most animal species, with marine critters hit hardest. Popular explanations include an upwelling of deep, oxygen-poor waters that suffocated life near the surface, or perhaps huge eruptions in Siberia that warmed and acidified oceans.

To distinguish between those scenarios, Payne and colleagues examined minerals in marine sediments and in fossilized, toothlike parts from prehistoric creatures that looked like eels. The minerals, made from calcium that had once been dissolved in seawater, had higher proportions of a lighter form of the element after about 250 million years ago, the researchers found.

A world warmed by volcanic eruptions would have increased levels of this light calcium isotope, the researchers’ simulations suggest. More intense rains would have flushed calcium into the ocean by eroding rocks on land, which tend to be made of the light calcium. Seawater that soaked up carbon dioxide and became more acidic would have stunted the productivity of organisms that pull calcium out of the water, allowing it to build up in the ocean.

Other lines of evidence corroborate this story. Previous studies have found that not only calcium but also carbon tends to get lighter in limestone that was formed after the extinction, a shift that could also be explained by more erosion on land. And acidified oceans would have made life particularly difficult for thick-shelled creatures, which died out in droves during the extinction.

But Paul Wignall, a paleontologist at the University of Leeds in England, says the records are too crude to reveal the timing of the calcium shift. The light calcium could have come from the shells of creatures wiped out by other means.

“I suspect what their data really record is that a lot of skeletal invertebrates died out,” says Wignall. “They've recorded an effect, not the cause.”

The new calcium records also don’t reveal how strongly the oceans acidified. One recent simulation (SN: 10/8/11, p. 10) claimed a huge, devastating drop in pH would have been possible. But an unpublished simulation from Lee Kump, a geoscientist at Penn State, suggests that any changes in water chemistry were too gradual and mild to do significant damage.

“The notion that ocean acidification led to the extinction is still a viable one and perhaps even the leading explanation,” says Kump. “But the calcium isotopes aren’t the nail in the coffin."

By : Haiderzai

Science News

European cave art gets older

Ancient illustrations in northern Spain date to more than 40,000 years ago

Red disks, hand stencils and club-shaped drawings lining the walls of several Stone Age caves in Spain were painted so long ago that Neandertals might have been their makers, say researchers armed with a high-powered method for dating ancient stone.

Scientists have struggled for more than a century to determine the ages of Europe’s striking Stone Age cave paintings. A new rock-dating technique, which uses bits of mineralized stone to estimate minimum and maximum ages of ancient paintings, finds that European cave art started earlier than researchers have assumed — at least 40,800 years ago, say archaeologist Alistair Pike of the University of Bristol in England and his colleagues.

Pike’s team presents its findings in the June 15 Science.

Previous age estimates were based on stylistic comparisons of drawings in different caves and radiocarbon dates for ancient pigments containing charcoal or other organic material. That research indicated that people began creating cave paintings in Europe possibly 36,000 years ago. Some researchers suspect thatHomo sapiens made rapid advances in symbolic thinking around that time.

New evidence of European cave art’s early origin fits a scenario in which wall drawings and other symbolic behaviors extend far back in the Stone Age (SN: 8/13/11, p. 22). People may have begun cave painting either before or shortly after entering Europe as early as 45,000 years ago (SN Online: 11/2/11), Pike suggests. Or perhaps Neandertals that already inhabited Europe drew on cave walls before their evolutionary cousins arrived, he says.

“If cave painting started before the arrival of modern humans, it would mean that hand stencils on cave walls are outlines of Neandertals’ hands,” Pike says. “We will need to date more examples to see if this is the case.”

Neandertals died out around 30,000 years ago. Many cave paintings in the new study date to no more than 21,000 years ago, clearly marking them as creations of H. sapiens.

Only small pigment scrapings have been radiocarbon dated to reduce damage to Stone Age artworks. Such tiny samples magnify the distorting effects of contamination on radiocarbon age estimates. Scientists also can’t be sure that charcoal in ancient pigments isn’t considerably older than the rock art being dated.

For the new study, Pike’s team employed a technique called uranium-series dating to analyze thin mineral deposits that had formed over or under parts of 50 paintings and engravings in 11 Spanish caves. Uranium incorporated into the minerals at the time of formation decays into a form of radioactive thorium at a known rate, allowing researchers to calculate its age.

Uranium-series technology “is certainly our only hope at present for dating engravings and inorganic pigments,” says Paul Bahn, an independent archaeologist and cave-art investigator in Hull, England.

“Neandertals were capable of producing cave art, and these new dates make it probable that cave art does go back to the Neandertal period,” Bahn holds.

Data from Pike’s team show that cave art in Europe was created over a longer period than previously assumed, comments archaeologist Daniel Richter of the University of Bayreuth, Germany, a specialist in dating methods. Richter suspects that modern humans crafted these earliest cave paintings, because no evidence exists that Neandertals were involved.

Two dating studies at a German cave, one led by Richter and another by archaeologist Thomas Higham of the University of Oxford in England, place painted shapes, bone figurines and other artifacts often associated with modern humans at about 42,500 years ago. Those studies employed radiocarbon dating and a method to estimate the time since artifacts were exposed to a Stone Age fire, but not uranium-series dating.

“I think it is far more likely that all of the art at European sites was made by modern humans, although it’s possible that a Neandertal hand was involved,” Higham says.

Northern Spain’s earliest cave art consists of red dots, disks, lines and hand stencils, Pike says. Drawings of animals and mythical creatures in the region’s caves appear starting around 30,000 years ago, indicating that artistic styles became more complex over time.

Pike’s team identified Europe’s oldest known wall painting at El Castillo cave, where several chambers contain more than 100 illustrations. One of several large red disks dates to at least 40,800 years ago. A nearby hand stencil was made at least 37,300 years ago, the researchers say; dozens of other disks and hand stencils on the same wall probably come from the same period.

Artistic activity at El Castillo continued for nearly 20,000 years. A red disk in another chamber was painted between 36,000 and 34,100 years ago, and a black outline of an animal dates to at least 22,600 years ago.

A club-shaped symbol in a decorated chamber at Altamira cave dates to at least 35,600 years ago, about 10,000 years before previous estimates of when painting started at the site. Dates for other Altamira drawings suggest that the cave hosted ancient illustrators over a span of more than 20,000 years.