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.