HOW MUCH MOSQUITOES LIKE YOUR TASTE DEPENDS ON YOUR GENES

NEW RESEARCH COULD LEAD TO MORE EFFECTIVE REPELLENTS

Female A. aegypti mosquito

Credit: G. Mandela Fernández-Grandon et al, 2015

For many people, warmer weather means more days spent in the sun and long evenings outdoors. It also means mosquito bites. Even if you’re one of the lucky people that receives relatively few, you’ve probably noticed that not all people get bitten with the same frequency. And while frequent bites might simply be a nuisance for some, it could mean a much higher incidence of nasty diseases such as malaria, dengue andchikungunya in some parts of the world. According to a new study published in PLOS One, your genes have a lot to do with that.

Past studies have found that female mosquitoes—the ones that suck your blood—have strong preferences for people based on the chemicals they emit, otherwise known as their odor, which is heavily influenced by genes. So for this study, the researchers from the London School of Hygiene and Tropical Medicine wanted to test the role of genes more directly. They selected 18 pairs of identical twins and 19 pairs of non-identical female twins to see the variations in how much mosquitoes were attracted to them (the women were all post-menopausal to ensure that their menstrual cycles didn’t affect the outcomes). They found that the identical twins attracted mosquitoes at much more similar levels than the non-identical twins.

The researchers haven’t pinpointed which genes in particular draw in the most mosquitoes. But they hope that a better understanding of why mosquitoes are drawn to some people more than others could lead to more effective repellents in the future.

SCIENTISTS CAN TRICK YOU INTO THINKING YOU’RE INVISIBLE

THE ILLUSION COULD ONE DAY HELP PEOPLE CONQUER THEIR FEARS

Bringing Hogwarts to Life

Staffan Larsson

Ph.D. student Zakaryah Abdulkarim, M.D., shows how to create the illusion of invisibility in the lab.

It looks like Muggles have finally caught up with the wizarding world. Neuroscientists from Sweden’s Karolinska Institutet gave 125 study participants the illusion of being invisible.

The researchers described the invisibility illusion in the journal Scientific Reports. For the experiment, a participant stands and wears a head-mounted display, which plays a real-time video feed from a camera pointed down at an empty space nearby. So when the participant looks down, she sees an empty space instead of her body. The scientist touches various locations on the participant’s body with a large paintbrush. At the same time, with a paintbrush in his opposite hand, he imitates these motions in mid-air beneath the camera. The participant simultaneously feels the brush poke and sees the brush poking into empty space. The trick leads to a Harry Potter-like sensation of invisibility. Off to Hagrid’s!

Arvid Guterstam, the lead author of the study, explains in a press release, “Within less than a minute, the majority of the participants started to transfer the sensation of touch to the portion of empty space where they saw the paintbrush move and experienced an invisible body in that position.”

To test how well the illusion worked, the researchers made stabbing motions with a knife toward the empty space that represented the invisible body. When participants were under the spell of the illusion, they perceived these jabs as threats to their invisible bodies, and their sweat and heart rates were elevated. But when the illusion was broken--for instance, when the brushstrokes they felt and those they saw weren't in sync--they weren't unnerved by the knife.

Interestingly, the illusion of being invisible changed participants' responses during stressful situations. The researchers positioned the participants in front of a virtual audience of strangers, measuring their heart rate and self-reported stress levels. Unsurprisingly, participants were less stressed when they thought they were invisible.

So basically, pretending you’re invisible seems to be a more effective way to handle stage fright than imagining everyone in their underwear.

Looking ahead, the researchers hope to find out what else an illusion of invisibility might affect. This study might be useful for social anxiety disorder therapies or to examine decision-making. The study’s principal investigator Henrik Ehrsson says, “Follow-up studies should also investigate whether the feeling of invisibility affects moral decision-making, to ensure that future invisibility cloaking does not make us lose our sense of right and wrong, which Plato asserted over two millennia ago.”

Freshly Eaten Snake Makes Amazing Escape—Find Out How

Newly published photographs show a snake fleeing from the belly of another.

The lucky snake crawls out of the mouth of a larger snake in 2011.
PHOTOGRAPH BY DICK MULDER

A snake remarkably escaped from a larger snake that swallowed it whole on theGreek island of Corfu, according to recently published photographs.

In 2011, the wild reptile, a Dahl's whip snake (Platyceps najadum), wriggled its way to freedom after being eaten by a four-lined snake (Elaphe quatuorlineata), which was in turn killed by a pet cat. (The four-lined snake, a type of large rat snake, is common in Greece.)

(Also see "Pictures: How a Python Can Swallow a Crocodile.")

The cat's owner, Dutch national Dick Mulder, caught the event on camera at his Corfu home after he retrieved the dead snake from his garden.

"My wife, who didn't like the idea of a dead snake on her veranda, screeched that the snake wasn't dead—she saw it moving," he said in an email. "I reassured her that it was really dead," Mulder recalled—until he took a closer look.

"I went to grab my camera, and by the time I came back I saw the head of a small snake," he said. (Get National Geographic's tips on photographing wildlife.)

The whip snake eventually struggled free and slithered back to the wild, apparently unharmed.

"As far as I know it avoided its savior, Demon the Cat," Mulder quipped.

Slippery Business

Andrew Gray, curator of herpetology at Manchester Museum in the U.K., first reported the bizarre incident in January on his blog.

Gray, an expert on the snakes of Corfu, said the smaller snake's escape was rare. He knows of only one other example of a snake getting away after becoming another's last meal—in that case, the reptile wriggled from the wound of a snake that was shot by hunters.

It's also unusual in that the whip snake managed to exit from the dead snake's mouth, given snakes generally swallow their prey head first. (See "Giant Python Meals That Went Bust.")

It's easier for snakes to start with their prey's head, "particularly rodents that have legs that can get in the way," Gray said.

That said, "this was a small snake, so it was probably eaten any which way," he added.

And if the whip snake did need to perform a U-turn inside its predator's belly in order to escape, Gray reckons it would have been "small enough and agile enough to perform that trick."

How'd It Survive?

Agile or not, how could a snake survive inside another? The only answer is that the bigger snake had just eaten its prey before the cat intervened, Gray added. (See "5 of Nature's Wildest Animal Showdowns.")

Otherwise, he said, the effects of the larger snake's digestive fluids would have been fatal to the smaller snake—a likelier cause of death than either suffocation or crushing through constriction, given the prey snake's slender build.

The eaten snake was also fortunate to be preyed on by a four-lined snake—it's the largest snake native to Europe without a venomous bite.

Overall, then, this is one very lucky snake—all thanks to a cat. As the animal with nine lives, perhaps it could afford to share one.

Woolly Mammoth DNA Successfully Spliced Into Elephant Cells

A group of researchers are getting closer to bringing the extinct woolly mammoth back to life. Geneticist George Church’s lab at Harvard University successfully copied genes from frozen woolly mammoths and pasted them into the genome of an Asian elephant.

Using a DNA editing tool called CRISPR, the scientists spliced genes for the mammoths’ small ears, subcutaneous fat, and hair length and color into the DNA of elephant skin cells. The tissue cultures represent the first time woolly mammoth genes have been functional since the species went extinct around 4,000 years ago.

The research has not yet been peer-reviewed or published in a scientific journal “because there is more work to do,” Church told the U.K.’s Sunday Times, “but we plan to do so.”

The work is part of an effort to bring extinct species back from the dead, a process called “de-extinction”. The recent breakthrough shows that one proposed de-extinction method--which involves splicing genes from extinct animals into the genomes of their living relatives--just might work. But don't believe the headlines suggesting woolly mammoth cloning is just around the corner. Church explained to Popular Science that there’s a lot more research to be done.

“Just making a DNA change isn’t that meaningful,” says Church. “We want to read out the phenotypes.” To do that, the team needs to figure out how to take the flat hybrid cells from a petri dish and coax them into becoming specialized tissues--such as blood cells or liver organoids--then test to see if they behave properly. For example, do the mammoth hair genes lead to hair that's the right color, length, and woolliness?

If those tests go well, the team hopes to turn the elephant/mammoth skin cells into hybrid embryos that can be grown in artificial wombs, devices that allow for pregnancies outside of an animal's uterus. Artificial wombs are pretty speculative at this point, but the alternative--implanting the hybrids into the wombs of female elephants--is unsavory to animal rights activists as well as geneticists. “It’s going to be more humane and easier if we can set up hundreds of [embryos] in an incubator and run tests,” says Church.

If they can get the hybrid creatures to survive, the project's first goal will be to engineer an elephant that can survive in cold temperatures. The team thinks that expanding the elephant’s range into colder climates could help keep it away from humans and the conflicts that are threatening to make Asian and African elephants extinct. Later, after the engineered elephants gain a foothold, Church says the team will try to revive the mammoths by integrating higher amounts of mammoth DNA into the hybrids.

Of course, it's possible the mammoth genome will never be completely reconstructed, and the creatures will only remain elephant/mammoth hybrids. But if it looks like a mammoth and fulfills the same ecological functions as a mammoth, is it a mammoth? What even is a mammoth, anyway?

2,000 Snow Geese Die in Possible Avian Cholera Outbreak

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Hibernators Stretch After Long Winter's Nap: Photos

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Wildlife officials in Idaho are investigating a suspected avian cholera outbreak that took the lives of about 2,000 migrating snow geese.

The geese, which were journeying from the U.S. Southwest and Mexico toward Northern Alaska nesting grounds, were found at the state's at Mud Lake and Market Lake wildlife management areas, near Terreton.

Test results have not yet confirmed the deaths were the result of avian cholera, but officials said the symptoms seen in the downed birds point to the deadly bacteria.

VIDEO: Why Birds Are Always Flying into Things

"Outbreaks of avian cholera have occurred sporadically in the region over the past few decades," explained Idaho Upper Snake Regional Supervisor Steve Schmidt, in a press release. "The important thing is to quickly collect as many of the carcasses as possible, to prevent other birds from feeding on the infected birds."

For that reason, the carcasses of the animals have been collected and the plan is to incinerate them. Officials said about 20 eagles were seen near the Mud Lake carcasses, but due to a delayed incubation of the disease, they can't be sure whether or not the birds have been infected.

Officials stressed that while humans are not at high risk from the bacteria that causes avian cholera, residents should not handle any dead birds, as that could accidentally spread the disease to other wildlife.

HOW BIG WOULD A METEORITE HAVE TO BE TO WIPE OUT ALL HUMAN LIFE?

SHORT ANSWER: 60 MILES WIDE, GIVE OR TAKE

INCOMING

ILLUSTRATION BY JASON SCHNEIDER

IT WOULD TAKE A REALLY BIG SPACE ROCK TO KNOCK US ALL OUT.

WHEN IT COMES TO METEORITES, THE BIGGER THEY ARE, THE MORE HAVOC THEY GENERALLY WREAK. IN 1997, UNIVERSITY OF COLORADO GEOSCIENTIST BRIAN TOON AND COLLEAGUES PREDICTED THE AFTERMATH OF METEORITE IMPACTS OF VARIOUS SIZES. THEY FOUND THAT A SPACE ROCK HALF A MILE WIDE WOULD PRODUCE AN EXPLOSION THAT RELEASES THE ENERGY EQUIVALENT OF UP TO 100,000 MILLION TONS (MT) OF TNT. THAT’S ENOUGH TO CAUSE WIDESPREAD BLAST DAMAGE AND EARTHQUAKES, BUT NOTHING TOO OUT OF LINE WITH MANY NATURAL DISASTERS IN THE MODERN AGE. ONCE A COLLISION EXCEEDS THE 100,000 MT THRESHOLD, YOU’RE LOOKING AT A CATASTROPHE LARGER THAN ANY IN HUMAN HISTORY. A METEORITE A MILE IN DIAMETER MIGHT SEND ENOUGH PULVERIZED ROCK INTO THE STRATOSPHERE TO BLOCK OUT SUNLIGHT AND CAUSE GLOBAL COOLING.

THE OBJECT THAT KILLED OFF THE DINOSAURS WAS PROBABLY SEVEN OR EIGHT MILES WIDE, SAYS JAY MELOSH, A PLANETARY PHYSICIST AT PURDUE UNIVERSITY. ITS IMPACT WOULD HAVE EJECTED A DUST PLUME THAT SPREAD CLEAR AROUND THE PLANET AND RAINED BLAZING-HOT ON TO FORESTS, IGNITING THEM. “THE DINOSAURS PROBABLY BROILED TO DEATH,” HE SAYS.

SUCH A COLLISION TODAY WOULD KILL BILLIONS OF PEOPLE. THOSE WHO DIDN’T PERISH IN THE INITIAL BLAST OR THE FIRES THAT FOLLOWED WOULD FACE LONG ODDS OF FINDING SUSTENANCE. “PEOPLE ARE GOING TO STARVE TO DEATH,” TOON SAYS. STILL, A FEW WOULD LIKELY WEATHER THE APOCALYPTIC STORM. “PROBABLY SOME FISHERMEN IN COSTA RICA,” HE OFFERS. “PEOPLE NEAR THE OCEANS WHO MANAGED TO HIDE OUT AND FISH WHEN THE FIRES STARTED.”

FOR A COLLISION TO OBLITERATE THE HUMAN RACE ALTOGETHER, TOON ESTIMATES IT WOULD TAKE A 60-MILE-WIDE METEORITE. HE SAYS, “THAT WOULD INCINERATE EVERYBODY.”

Why Do Butterflies Have Such Vibrant Colors and Patterns?

Colors give butterflies camouflage, which helps them avoid hungry predators.

The sheen of these gold chrysalides offers a shield of camouflage for paper kite butterflies growing inside them.

 

Ask a social butterfly where she got that great dress, and she'll say, "This old thing?" and then tell you its entire history.

Ask an actual butterfly about its colorful attire, and things get a lot more complicated.

Our Weird Animal Question of the Week comes to us from National Geographic's own Angie McPherson, a volunteer at the Smithsonian Butterfly Garden in Washington, D.C.'s National Museum of Natural History. She asked, "Why does the paper kite butterfly create a gold chrysalis?" (See "New Golden Bat Adds to Animals With the Midas Touch.")

The paper kite butterfly, native to Asia, is light yellow or off-white with an elaborate pattern of swooping black lines and dots. But its chrysalis—a hard case that protects the caterpillar during its final transformation into a butterfly—is a shiny, golden hue.

It's unknown why the chrysalis itself is gold, but its shininess helps camouflage the developing butterfly, says Katy Prudic, a biologist at Oregon State University in Corvallis.

In particular, the sheen is "disruptive" to potential predators—it makes the chrysalis "hard to detect in a complicated background," Prudic says. A hungry bird may even think it looks like a drop of water.

"Sitting Duck"

Camouflage is crucial to chrysalides: Because growing butterflies are unable to move and in danger of being eaten or parasitized, "they're a sitting duck," Prudic notes.

The giant swallowtail is another example of chrysalis camo. In that species, the chrysalis resembles part of the tree on which it hangs—or it looks a bit snakelike, depending on the vantage point. (Watch video: Growing Up Butterfly.)

This species' caterpillar has some tricks up its sleeve: It can resemble bird droppings but can also look like a tiny snake at a later stage of development.

The monarch butterfly chrysalis has what appear to be gold dots and threads, which help the developing insect blend in with leaves.

Color Advantage

Adult butterflies also use color to their advantage—not only to blend in but also to warn.

For instance, the adult monarch sports a bright orange color and distinctive pattern, a red flag to potential predators that it's distasteful and toxic.

Another species called the viceroy has even evolved to mimic the monarch's appearance so that predators keep their distance, according to Prudic. (Related:"Butterflies Can Evolve New Colors Amazingly Fast.")

A particularly impressive dual use of color, she adds, is seen in the blue morphobutterfly of the Central and South American rain forests.

The brilliant blue of the morpho butterfly helps the insect communicate with others of its kind. 
PHOTOGRAPH BY CHRISTIAN RICHTER, WESTEND61/CORBIS

This insect's strikingly blue wing color "is used to communicate among butterflies, so they'll display it when they're courting or mating," she says.

Underneath the wing is a dull brown decorated with fantastic eyespots, whichalarm and confuse predators.

More Than Meets the Eye

As for how we humans perceive those brilliant butterfly colors, it depends. Some color we see is the insect's true pigment, and some is structural, or the way light reflects off a surface.

When you see blue, purple, or white on a butterfly, that's a structural color, while orange, yellow, and black are pigment, Prudic says.

"The nanostructure of the chitin, or wing scale," Prudic says, "affects what light is reflected and how it's reflected." (Related: "Pictures: Butterfly Wing Colors Imaged in 3-D.")

This is what makes butterfly wings iridescent—the quality that makes them change color according to the angle from which you look at them, Prudic says.

Caterpillar Diet

McPherson also asked us what paper kite caterpillars eat to turn the chrysalis golden.

The diet of the caterpillar doesn't affect the hue of the paper kite chrysalis, though it does affect the chrysalis color of other species, Prudic says.

Plant-derived chemicals called flavonoids—which differ in leaves, flowers, and seeds—can influence chrysalis color.

The zebra swallowtail, for example, feeds on the leaves of plants of the  Asimina family—and has a leaf-green chrysalis.