Field of Science


Actual Top Ten Animals of 2013

Not so much a popularity contest as an altitude contest.

10: Himalayan Jumping Spider

The fuzzy and springy Euophrys omnisuperstes lives on the world's highest mountains. It's been found 6,700 meters (a little over four miles) high on Mount Everest. Some birds can fly at higher altitudes, but the spider lives there full-time, apparently subsisting on unlucky insects carried up to it by the wind.

9, 8: Iranian Space Monkeys

Twice this year, Iran announced that it had successfully sent a monkey on a sub-orbital rocket flight. The trips allegedly happened in January and December, both reaching heights of 120 kilometers (75 miles) before safely returning their rhesus macaque-nauts to Earth. But the Associated Press pointed out that the launches couldn't be confirmed by outside sources, and that one post-launch photo showed an entirely different monkey than pre-launch.

7, 6, 5, 4, 3: Russian Rocket Zoo

On April 19 of this year, a Soyuz rocket took off for space carrying a capsule full of animals. Called Bion-M1, the capsule held mice, mongolian gerbils, geckos, fish, and snails. The mice were shared between Russian scientists and NASA, whose researchers would study the effects of low gravity on cell growth, blood flow, joint movement, and sperm motility, among other body functions. The mission orbited Earth for 30 days.

NASA writes, "All of the mice that Russian scientists had shared with their U.S. colleagues returned from space in good health." The Russian scientists must have kept the dead ones for themselves, then, because 29 out of the 45 mice didn't survive. All 8 gerbils perished too, along with the fish. There appeared to have been technical problems with the systems built to feed and keep the animals alive onboard.

2, 1: Imaginary Mars Rock Animals

"NASA Curiosity Rover spots iguana on Mars," declared a Fox News headline in November. It was actually a rock shaped vaguely like a lizard. But someone from a website called UFO Sightings Daily was calling it an "animal" and doing news interviews. Back in May, the same paranormal website had announced the discovery of a "Mars rat" in another one of the rover's photos. It was, of course, also a rock.

Will any Earth animals travel farther from the planet's surface in 2014? If they do, here's hoping they fare better than a Mongolian gerbil.

Honorable mention for effort: NASA launchpad frog.

Why It's Nearly Impossible to Castrate a Hippo

Chances are you've never wondered how difficult it is to remove the testes of a hippopotamus. Other people have been thinking hard about it, though, because in fact it's almost impossible.

Before sitting down to emasculate a common hippopotamus, Hippopotamus amphibius, it would be reasonable to ask why. They're a threatened species, so usually conservationists try to make more baby hippos—not fewer. But in zoos, hippos turn out to be prolific baby-makers. Females can live for 40 years and may birth 25 calves in that time. This would be great news in the wild, but zookeepers don't always have someplace to store a new two-ton animal.

Male hippos can also be aggressive toward each other, at least while they have all their man parts. For both of these reasons, zoos may want to have their male hippos fixed. But there are a few factors working against them, explains a new paper in the journal Theriogenology (that's reproductive science for vets) by an international group of authors.

The first challenge is that hippopotamuses hide their genitals. The testes are inside the body, instead of outside in a scrotum. (Other mammals in the internal-testes club, since you asked, include the armadillo, sloth, whale, and platypus.) This makes the hippo's testes totally invisible from the outside. Combined with a penis that the paper's authors describe as "discreet," it means it's hard to tell males from females at a distance.

Another problem is that testes aren't in the same place from one hippo to the next, and they may "retract" even farther during surgery. Hippopotamuses are also difficult to safely put to sleep. "In the past, hippopotamus anesthesia has been fraught with serious complications," the authors explain.

After moving past the anesthesia problem (they used an apparently safer blend of drugs, delivered via a dart to the hippo's ear), the researchers turned to the anatomical problems. Their answer was ultrasound. Once they had positioned the animal, they used ultrasound imaging to find the testes—then used it again after cutting into the hippo, if the testis they were looking for had scooted farther away from them.

Even after finding the sneaky organs, the procedure wasn't simple. The depth of the testes' hiding places varied by as much as 16 inches from one hippo to the next. Everything had to be done deep inside the animal's body, making it hard to see what was going on. "Grasping the testicle with forceps proved laborious" in most of the animals, the authors write. They also mention using a "two-handed technique" and "moderate traction." The whole hour-and-a-half procedure, based on a method for castrating horses, is described in detail for anyone who wants to try it themselves.

All ten hippos in the study were successfully castrated, though one died shortly afterward, following a complication from a unknown pre-existing condition. Over the next six months, the authors checked in with the zoos housing the hippos to see whether their behavior or interaction with other animals had changed. There were four cases where zoos wanted their hippos fixed to ease aggression between males; in all four, the problem seemed better. (One zoo, though, reported that castrated males were harassed more by females.) Overall, the authors think their technique will help zoos take better care of their hippos.

The final challenge to hippopotamus surgery—what should be a challenge, anyway—is that the animals spend most of their time in a pool of water packed with feces. The animals in the study lowered their stitched-up bellies into this infectious slurry as soon as they had a chance. Yet all of them healed from surgery without trouble. Hippos in general seem to be especially good healers, the authors write.

A possible explanation for the animals' healing superpower is the "red sweat" or "blood sweat" that oozes from their skin. It's not really sweat and it doesn't contain blood, though it is red. The pigments in this skin secretion have been found to absorb UV light, making the "sweat" a potential sunscreen. The pigments can also keep bacteria from growing. So a built-in antibiotic may be what keeps hippos from getting infections after they tussle and bite each other (or after meddling vets come and cut out their manhood). However the red sweat works, it shows that a hippo's secrets don't end with the location of his testicles.

Images: Charlesjsharp (via Wikimedia Commons); drawings by Eva Polsterer (from Walzer et al.).

Walzer C, Petit T, Stalder GL, Horowitz I, Saragusty J, & Hermes R (2013). Surgical castration of the male common hippopotamus (Hippopotamus amphibius). Theriogenology PMID: 24246424

Spider Acts Like Ruthless Carnivore, Is Really Flexitarian

Even deadly predators crave a salad sometimes. Certain orb-weaver spiders—apparent full-time carnivores who eat by trapping prey, covering it with digestive juices, and then slurping it down like an insect smoothie—have been secretly taking their meals with a plant-based side dish. Namely, pollen.

Orb weavers are a family of spiders common all across the world; they're the ones that weave the classic concentric-circle webs you see in picture books. Earlier studies have shown that those webs can collect a lot of pollen on their sticky strands, and that the spiders are willing to eat pollen in the lab. Benjamin Eggs, a graduate student at the University of Bern in Switzerland, and ecologist Dirk Sanders studied two kinds of orb weavers to see what truth there was to this rumor.

For the first part of the experiment, Eggs gathered 20 young Aculepeira ceropegia spiders from outdoors in the spring and brought them into the lab. He coaxed each spider to build its nest inside a cardboard box, where he supplied it with several fruit flies per week. Eggs also sprinkled half the spiderwebs with birch pollen, as they might be in the wild.

After a month, Eggs broke down the spiders' bodies and examined the carbon and nitrogen isotopes inside them. Isotopes, if it's been a while since your last chemistry class, are different forms of the same element. For example, most carbon atoms in the world have 6 protons plus 6 neutrons in their nuclei, making them carbon-12. But a small percentage of carbon atoms, called carbon-13, have an extra neutron. Animals incorporate the atoms they eat into their bodies. So by comparing the ratio of lighter to heavier isotopes in spiders' bodies to the signature ratios of their various foods, the researchers could see what the spiders were eating.

In the lab, orb weavers supplied with pollen had a different isotope ratio than their neighbors who only received fruit flies. This told Eggs that his spiders were, in fact, eating the pollen. But would they do it in the wild?

He returned outdoors and gathered young Araneus diadematus spiders, another orb-weaver species, from the trees. He used nets and bug vacuums to gather as many other insects from the area as possible—the spiders' potential prey. And he collected samples of pollen from neighboring trees.

Eggs analyzed the carbon and nitrogen isotopes in the outdoor spiders, along with all the insects and pollen that might be on their menu. Based on those ratios, he calculated that pollen made up 25 percent of the orb weavers' diet.

It's convenient for orb weavers to eat pollen, because they frequently dismantle and eat their webs in order to recycle the silk proteins. As long as they're at it, they may as well suck down the vegetables trapped there. Eggs points out, though, that the pollen grains he found in his study are too big for spiders to swallow accidentally. So his orb weavers must have deliberately eaten pollen grains by first covering them in digestive enzymes, then slurping them up.

Eating pollen might be most practical in the spring, when young spiders have just hatched and built webs, but insects are still hard to find. The spiders in this study were all juveniles. Yet Eggs, who carried out this research for his undergraduate thesis, thinks there's no reason adult spiders wouldn't eat pollen too. He says, "The anatomy of araneids does not change dramatically when they reach maturity." (He adds intriguingly, "Exception: genitals.")

It's even possible that other kinds of spiders nibble on pollen too. "There is evidence that other web-building spiders like the sheet weavers (Linyphiidae) also feed on pollen," Eggs says, "although they don’t eat their own web." Every diet needs a cheat day, after all.

Photo by Dirk Sanders.

Eggs B, & Sanders D (2013). Herbivory in spiders: the importance of pollen for orb-weavers. PloS one, 8 (11) PMID: 24312430

Higher Altitude Protects Teens from Concussions

The human brain is a vulnerable thing, perched in its peanut shell on top of our walking, stumbling bodies. Humans who enjoy collision-heavy pastimes—say, tackle sports—put their brains in particular danger. And when it comes to concussions, young people are at even more risk than adults. Yet kids who play at at higher altitudes seem to be safer than their peers. The reason, hidden somewhere in the brain's squishy dynamics, might help protect kids and adults who are smashing into each other everywhere.

You don't have to travel to Denver's Mile High stadium for your body to start responding to altitude. "Relatively small changes in altitude can have significant changes upon the physiology of the body," say Gregory Myer and David Smith, both in the sports medicine department at Cincinnati Children's Hospital Medical Center. (The coauthors responded to my email jointly.)

At just 600 feet above sea level, the authors point out, oxygen in the atmosphere has already dropped from 21 percent to 20 percent. Your body notices this slight change and adjusts. One measure it takes, upon noticing there's less oxygen available than usual, is to send a little more blood to your brain. "This leads to a slight filling up of the brain space," Myer and Smith say. Your brain ends up squeezed just a tad more tightly into your head.

Wherever you are, if you get suddenly knocked on the head, your brain will ricochet around inside your skull's fluids. In actual scientific terms, it "sloshes." The delicate brain squishes and twists, and hosts of neurons fire all at once. You may black out. Afterward, you might have memory loss, confusion, nausea, dizziness, and other symptoms that can last for days or months. The looser, stretchier blood vessels in the brains of people under age 20 may explain why they're at even greater risk.

Concussions might be prevented if the skull could keep the brain from sloshing by holding onto it a little tighter—as it does at higher altitudes. To find out whether this works, Myer, Smith and their colleagues used data from the National High School Sports-Related Injury Surveillance System. Run by the University of Colorado, Denver, this study collects data on injuries from high schools across the country.

The authors looked at nearly 6,000 concussions from about 500 schools. The concussed kids were athletes in all kinds of sports, at schools ranging from sea level to 6,900 feet. When the researchers divided student athletes into those living above and below the median altitude—which was 600 feet—they saw a significant difference in concussions. Across all sports, kids at higher altitudes had a 31 percent lower risk of concussion. Among football players only, the results were essentially the same: a 30 percent lower risk at higher altitude.

It's an intriguing difference. As sports organizations and the public learn more about chronic traumatic encephalopathy (CTE) and the long-term risks for athletes with head injuries, the quest to prevent concussions is growing more urgent. High schoolers, though, don't travel to play like professional athletes do. Could some of their lower risk have to do with changes in their bodies that happen over a lifetime of living at a certain altitude? "Visiting altitude will begin creating a tighter fit the minute you arrive," Myer and Smith say. However, adjustment happens over the long term too. "Everyone is likely different in how quickly they respond [to altitude] and how protection occurs for them," the authors say. "This is why we are working to evaluate technologies that can give this same protection whether you are in Denver or Miami." They'll be looking next at adults and professional athletes to try to find answers.

One hint comes from an earlier study David Smith performed on rats. While wearing a collar that slightly squeezed their jugular veins, the rats were hit hard on the head. The collar seemed to make rats less vulnerable to concussion, apparently because more blood was in their heads, squeezing their brains more tightly and preventing sloshing. This all sounds pretty unpleasant for the rats, but Myer and Smith insist that "the technologies we are studying are no more risky than yawning or even the act of lying down."

Animals like woodpeckers and head-ramming sheep manage to protect their brains from damage, the researchers point out. So why can't we? Of course, in our case the head ramming is in the name of fun. But there might be ways to safeguard our brains, like these animals do, from the inside out.

Image: Rocky Mountain High School in Colorado, by Paul L. Dineen (via Wikimedia Commons)

David W. Smith, Gregory D. Myer, Dustin W. Currie, R. Dawn Comstock, Joseph F. Clark, & Julian E. Bailes (2013). Altitude Modulates Concussion Incidence: Implications for Optimizing Brain Compliance to Prevent Brain Injury in Athletes. Orthopaedic Journal of Sports Medicine DOI: 10.1177/2325967113511588

Laughter Is OK Medicine, Unless It Kills You

Careful with the bedside banter, doctors. Before you put on your best Patch Adams impression, you might want to consider whether your attempts at humor will ease your patient's discomfort or give him a protruding hernia.

That's the conclusion of a review paper in the Christmas issue of BMJ that asks the jolly question of whether laughter can kill. The two authors, R. E. Ferner of the University of Birmingham and J. K. Aronson of Oxford University—no JK-ing, those are his real initials—take a tongue-in-cheek approach. They even give their research question an acronym: MIRTH (Methodical Investigation of Risibility, Therapeutic and Harmful).

Ferner and Aronson scoured medical literature for studies having to do with laughter. After "excluding papers on the Caribbean sponge Prosuberites laughlini and with authors called Laughing, Laughter, Laughton, or McLaughlin," they were left with three categories of study. One had to do with the benefits of laughter, one with its dangers, and the third with medical conditions that have laughter as a symptom.

Let's hear the bad news first. Laughter, according to various researchers, can lead to syncope (fainting), arrhythmia, and cardiac rupture. In asthmatics, laughing can trigger an attack. Laughing can even cause pneumothorax, a collapsed lung. People with cataplexy, a rare condition tied to narcolepsy, may suddenly lose all their muscle strength and collapse during a fit of laughter. An especially good laugh can make a person's hernia protrude, or dislocate someone's jaw.

Among the more pedestrian dangers, breathing in sharply when you start to laugh can make you choke. Laughing in someone's face can spread germs. And, of course, there's the danger of pee coming out when you laugh, which doctors call "giggle incontinence."

The authors also gathered a list of about three dozen medical conditions that have been reported—commonly or not—to cause laughter. These include epilepsy, brain tumors, multiple sclerosis, and kuru (a disease you are unlikely to contract unless you're a practicing cannibal).

Now for the good news. Laughter may increase your pain tolerance, reduce stiffness in the walls of your arteries, and even lower your risk of a heart attack. In patients with chronic obstructive pulmonary disease (COPD), laughter can improve lung function. Fifteen minutes of laughter reportedly burns 40 calories, which fitness-wise makes it similar to a very slow walk (or, according to Fitness magazine, barbecuing.)

Most strangely, one study used clowns to try to (indirectly) get women pregnant. Immediately after undergoing IVF, women were subjected to 12 to 15 minutes of entertainment by "a clown, dressed as a chef de cuisine." Among these women, 36 percent became pregnant, compared to just 20 percent in a control group.

Perhaps aspiring clowns themselves, the authors can't resist throwing in a few puns of their own: "Laughing fit to burst can cause cardiac rupture." "Perhaps surgical patients derive no advantage from being in stitches." "It remains to be seen whether...sick jokes make you ill, [or] dry wit causes dehydration." I'll give them the benefit of the doubt and assume that, knowing the potentially serious side effects of laughter, they chose to spare their audience the risk.

Image: Urban Combing (Ultrastar175g) (via Flickr)

R E Ferner, & J K Aronson (2013). Laughter and MIRTH (Methodical Investigation of Risibility, Therapeutic and Harmful): narrative synthesis. BMJ DOI: 10.1136/bmj.f7274

Newly Discovered Flower Makes Fake Pollen to Fool Bees

"I was certain it was something new when I saw it," says Chris Martine of the bush tomato species he discovered in the Australian outback. It's a scrappy, spiny shrub with crinkly purple flowers that thrives on fire. It also uses treachery to survive, disguising its female flowers with fake male parts and even fake pollen.

A botanist and biodiversity scientist at Bucknell University, Martine explains that the new plant "was on the radar of a few local botanists as being an oddball." Martine had been studying related species for a decade, so when his lab analyzed this plant's DNA, he recognized that it was something different. He went to Australia to document the species in person and dubbed it Solanum cowiei after botanist Ian Cowie at the Northern Territory Herbarium, who first introduced him to the plant.

The diverse Solanum genus includes plants ranging from potatoes and tomatoes to eggplant and nightshade. The Australian bush tomatoes that Martine studies grow little fruits that can be edible or quite poisonous, depending on the species.

Martine discovered that compared to its relatives, S. cowiei is especially well adapted to the fires that sometimes sweep through its habitat. The plants live in large groups of clones tied together by underground root systems. In an area that had recently been burned clear, Martine found S. cowiei plants springing up and blooming while other species lagged behind. This means that after a fire, these plants have a competitive edge over all their neighbors in getting to pollinators.

The new species's method of reaching those pollinators is a weird one. S. cowiei grows separate male and female flowers, and like about a dozen of its close relatives, it disguises the female flowers with fake male parts and pollen. Under an electron microscope, the false pollen grains look like brand-new tennis balls. Real pollen grains are closer to old ping-pong balls, with large dents or grooves on their surface—these are the weak spots where a narrow tube may later burst out of the wall of the pollen grain, carrying the plant's sperm to an egg.

Why bother with the ruse? Solanum flowers don't have any attractive fragrance to lure their pollinators, or nectar for insects or birds to drink while they're dusted with pollen. Instead, these plants rely on pollinators that want to eat the pollen itself. Certain foraging bees use pollen to feed their young, Martine says. "So if you want one of these bees to visit your flowers, you have to have to have the visual cue of the anthers," a flower's male parts. "And if you want them to come back to flowers like yours again, you have to give them some reward to take away."

Martine and his collaborators are now studying whether this fake pollen is any better or worse for young bees to eat than the real stuff. "Is there a difference in what they are getting?" he says. "Can they tell?"

The "oddball" bush tomato isn't the only plant Martine finds intriguing. He produces an online video series called "Plants Are Cool, Too!" ("Can an animal make its own food? No! Can an animal feed the whole world? No!" the theme song declares.) Martine started this series after working with kids who were interested in science and realizing that they knew a lot about animals, but not so much about plants. People browsing online are more likely to encounter a cute cat video, after all, than one about cattails. So he started putting together episodes that highlight some of the "coolest" plants, along with the botanists who study them.

The next full episode should be out in January, he says, and it includes an especially cool moment: a new species of mustard plant being discovered. "Our guest expert looked down during shooting and said, 'Hey, wait a minute,'" he says. "I don't know how often new species are discovered while a camera is running, but it can't be very common."

Photo by Kym Brennan.

Christopher T. Martine, David E. Symon, & Elizabeth C. Evans (2013). A new cryptically dioecious species of bush tomato (Solanum) from the Northern Territory, Australia. PhytoKeys DOI: 10.3897/phytokeys.30.6003

Leaping Land Fish Has Perfect Camouflage, Is Not a Hoax

You might never spot them if not for the jumping. On the coast of Guam, Pacific leaping blennies blend in perfectly with the rocks they live on, their limbless bodies maintaining a sleek profile. But the creatures give themselves away when they coil their tails to one side and shoot like a spring from rock to rock. These unsettling animals are fish that live on land. How they pull it off could give us hints about the evolution of our first earthbound ancestors.

Terry Ord, an evolutionary ecologist at the University of New South Wales, calls the Pacific leaping blenny "an extraordinary animal." It lives its adult life out of water, hopping between rocks and breathing through its skin as well as gills. It relies on splashes from waves to stay wet, but it rarely—or never—goes for a swim.

Even though the coast of Guam teems with leaping blennies, Ord says, "we know surprisingly little about this land fish." Ord and his graduate student Courtney Morgans investigated one mysterious feature: the fish's conveniently rock-like coloration. Without being so well camouflaged, could the blennies have ever made their first leap onto land?

Morgans and Ord traveled around the periphery of Guam and visited five different blenny populations. At each site, they took photographs of the fish and their background rocks. (The blennies aren't always stone-colored; during courtship, males darken to a charcoal hue while females fade nearly to white. Both sexes can flash a bright-red fin on their backs that they normally keep hidden. But the researchers kept a close eye on their subjects during the experiment to make sure they didn't change colors.)

Computer analysis of the photos showed that the blennies' normal skin color is a perfect match to the rocks they live on. Some birds use UV light, which the researchers didn't analyze, to find their prey. But for most of the hungry lizards and crabs patrolling Guam, the blennies should blend right in to the rocks.

To find out how well this camouflage really protects leaping blennies, Morgans and Ord set up 70 fake fish as bait. They molded plasticine blenny bodies with realistic coloration and anchored them to spots around the island with fishing line. Some fake blennies sat on the rocks, while others were on the sand, where they don't blend in as well.

After three days, Morgans and Ord returned to their fake fish. If the props were nicked, punctured, or had bites taken out of them, the scientists assumed predators had come by. They saw that predators attacked blennies on the sand much more often than those on the rocks.

So their coloration seems to be crucial to the leaping blennies' survival on shore. The scientists think that in this regard, the fish may have just been lucky. When they compared the Pacific leaping blenny to 12 closely related blenny species, they found that all the relatives have similar coloration. (Some of these relatives also spend time out of water, but the Pacific leaping blenny is the only one to live on land full-time.) If the ancestor to all these species had the same rocky skin color, then it was well prepared to wriggle out of the ocean and start a new life on land.

That doesn't mean the transition was easy. Blennies also had to evolve a way to breathe air through their skin, like frogs do. Their tail-jumping trick is helpful too, letting the legless fish propel themselves through their habitat. "Obviously moving about on land is critical," Ord says. (You can watch them leaping in the video below, from his lab's YouTube channel.)

Ord says this freak-show fish actually has a lot to tell us about evolution. For one thing, it demonstrates the kinds of adaptations an animal can make after it transitions to a new home. It also speaks to our own ancestry. "In the late Devonian, fish made the first transition onto land, and from that event evolved all of the land vertebrates we now have in the world," he says. The land fish represent a "snapshot of one of the most important evolutionary events in our history." Our ancestors may have looked equally ridiculous as they floundered on land—but like the leaping blenny, they were going places.

Image: Courtney Morgans, UNSW

Courtney L. Morgans, & Terry J. Ord (2013). Natural selection in novel environments: predation selects for background matching in the body colour of a land fish. Animal Behaviour DOI: 10.1016/j.anbehav.2013.09.027

Turtle Moms Choose Their Babies' Genders by Where They Build Their Nests

If turtles had realtors, their motto would also be "Location, location, location!"—but not because they care about a scenic vista. The spot a mother turtle chooses to dig her nest determines whether her young will be males or females. This might even be the most important factor in her decision.

A female painted turtle (Chrysemys picta) is not an over-involved parent. She digs a hole in the dirt, lays a batch of eggs there, and buries them. Then she returns to her freshwater life without giving the nest another thought. The eggs incubate and develop under the soil while the summer wears on. Hatchlings finally chip their way free in the late summer or early fall, but in cooler parts of North America they don't leave the nest right away; they stay hunkered down with their siblings to hibernate until the following spring.

Sometime in the middle of the summer, a significant event happens inside each buried egg: the developing turtle becomes male or female. Its sex hasn't been determined by its genes like ours is. Instead, as with many other reptiles, the temperature in the nest tilts the egg toward one sex or the other. Cooler nests produce males and warmer ones make females. If the nest stays within a narrow temperature range, hatchlings of both sexes will crawl out at the end of the season.

Timothy Mitchell, a Ph.D. student in ecology at Iowa State University, studies a population of painted turtles living in northwestern Illinois. These particular turtles have been under close watch by scientists for more than two decades, but it hasn't become clear whether turtle moms are active in determining their hatchlings' sex—do they choose nest sites that will best balance the sex ratio of their eggs? To find out, Mitchell set up a kind of nest-building competition between himself and the mother reptiles.

Mitchell scoped out 20 nests in his study site, a forested area near the Mississippi River. Right after the mothers left their nests behind, he went in and dug the eggs up. Then he tucked the eggs into artificial, Styrofoam-box nests. Half the eggs from each batch went into a box right next to where their mother had left them, buried at the same depth to create a controlled replica of the original nest. The other half went into a box at a site Mitchell selected at random.

(How do you randomly place a turtle nest? Mitchell used a random number generator to choose a distance away from the original nest, up to 30 meters. Then he flung a pencil in the air and walked in whatever direction in was pointing when it fell. If the resulting location was, say, in the Mississippi, he tried again.)

Just before they were due to hatch, the eggs were dug up and brought to a lab. Mitchell monitored their hatching and then returned the tiny turtles to their artificial nests for hibernation (along with a sprinkling of eggshells, as if the turtles had been there the whole time). He checked on the baby turtles once more in the spring.

Temperature sensors hidden in the nests revealed that sites chosen by turtle moms were a little warmer than Mitchell's randomly selected ones. This meant they were more open to the sun; nests that were shaded by vegetation were cooler.

Between the original nest sites and the random ones, there was no difference in the number of eggs that survived all the way through hatching and hibernation. But there was a major difference in sex ratio: while the turtle moms' nest sites produced roughly equal numbers of boy and girl turtles, the hatchlings from Mitchell's randomly placed nests were about 80 percent male.

"This strongly suggests this process of sex ratio selection is influencing where Mom chooses to nest," Mitchell says, "as opposed to selection to have eggs survive."

Wherever she builds her nest within this forest, a painted turtle mother can be assured that her young will survive equally well. But it's in her best interest to keep the sex ratio balanced. In the long term, turtles that tend to build male-heavy or female-heavy nests will lose out when the population swings in that direction, because young turtles of the opposite sex will then have better mating prospects.

A warming climate is a threat to any species whose sex ratios depend on the temperature. But if female turtles are savvy enough to leave their eggs in exactly the right sex-balancing spot, should we stop worrying about them? "That is still the big question in the field!" Mitchell says. He thinks moms' choice of nest sites will be a crucial part of how this species responds to climate change. But many other factors will matter too, like the fragmentation of the turtles' habitat and how the climate affects their predators. Turtle moms today know how to build a perfect nest for their offspring , but that balance may be as fragile as eggshells.

Image: Timothy Mitchell.

Timothy S. Mitchell, Jessica A. Maciel, & Fredric J. Janzen (2013). Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination? Proceedings of the Royal Society B DOI: 10.1098/rspb.2013.2460

Cooler Than Your Environmental Club: An Interview with My Little Sister about the Adirondack Youth Climate Summit

Teenagers who want to cause a disruption don't have to ride a skateboard anymore; these days they can do it on a bike generator. Earlier this November a crowd of students came together in Upstate New York to share ideas about greening their schools and addressing climate change on a small and large scale.  My youngest sister, Leigh, is a senior in high school and was at the conference for her second year. I asked her what they did there, and she told me about energy efficiency, celeriac soup, and how her generation is going to do things differently. (I never did get a straight answer about some Facebook photos, though.)


Hi Leigh! So who attends the Adirondack Youth Climate Summit?

There were about 150 students representing 27 colleges and high schools around New York, mostly from the Adirondack region. Each school could send 5 to 6 students along with a teacher chaperone. Students at my school had to write an essay explaining why they wanted to go to the summit and what interest they had in climate change. (Most students I talked to were shocked that my school had been so selective because their schools just brought their entire environmental club.)

By the way, I hope email is OK. Would I have more generational cred with you right now if I were conducting this interview via SnapChat or something?

I have to say, I much prefer the transfer of information through text bubbles containing less than 140 characters attached to a picture I can only view for 10 seconds on a 4-inch screen...but I guess this will do.

What kinds of workshops did you go to?

I got to attend three different workshops of my choice on the first day, splitting up with my school group so that we could cover more ground. I attended the three that were geared towards successfully sustaining a school garden and implementing younger students into climate action, because that's what I've been focused on at school the past couple years. The rest of my team attended workshops about composting, green teams, energy efficiency, biofuels, and recycling.

I hear the food was a highlight.

The food was absolutely delicious! All the meals and snacks were provided by local farms and vendors. They had vegetarian, vegan and gluten-free options, and Ben & Jerry's (a major sponsor of the summit) provided ice cream the second day. I caught myself enjoying kale chips and even tried parsnip and celeriac for the first time in a delicious soup that a Culinary Arts professor from Paul Smith's College made. (See recipe below.)

As weird as it sounds, I think the presence of wholesome, fresh, unprocessed food really boosted everyone's brain power for a few days.

And there were speakers too?

Brian Stillwell of Alliance for Climate Education kicked off the summit with a catchy, motivating presentation about climate change and the science behind it, followed by Brother Yusef Burgess of Youth Ed-Venture and the Children & Nature Network, who spoke about using the power of nature to transform and educate youth. Later in the afternoon Dr. Susan Powers, the Associate Director for Sustainability at Clarkson University, presented to us the outcomes of climate change in both our best and worst case scenarios.

Mark and Kristin Kimball, who own Essex Farm in the Adirondacks, hosted the dance party, fed us freshly harvested carrots, and encouraged our generation to be the driving force of the climate movement—and, more importantly, to have fun doing it. They made the point that these days, things like smoking cigarettes or dumping gasoline into a lake are considered "socially unacceptable," but that took time. Now, it is our time to make not caring about the environment be socially unacceptable.

Was it valuable just interacting with the other kids there, from different kinds of schools? Were you learning and getting ideas from each other?

YES. The second day, there was a 2-hour poster session where all the schools displayed posters of their current "green" efforts and plans for the future. I had a chance to talk to so many different schools and share ideas about outdoors clubs, gardening problems, recycling efforts and cafeteria food. I had conversations with a high school that was having trouble even starting an environmental club due to the lack of support from administration, and on the other end of the spectrum, I talked to a school that had livestock and taught all their science classes on a farm.

We also had the amazing opportunity to Skype with Finland, where they were holding a similar youth climate summit modeled after ours in the Adirondacks. Despite the sound lag and language barrier, it was still inspiring to see that kids our age halfway around the globe are facing the same problems we are.

It looks like you guys had a lot of fun at this dance party. In your Facebook photos I observed electric guitar, someone crowdsurfing, a guy in a sailor hat juggling fire, and what appeared to be people using ropes to move a large rock. Are these the elements of a good party for the young environmentalist crowd?

I think these are the elements of any good party, actually. Moving the rock could have been a metaphor for how teamwork can move the world or something, but it was really just for the fun of moving a rock. We were told that our generation will make it through this difficult time in climate change only if we have fun in the process.

What sorts of ideas or projects did you bring back from the summit to use at school?

The second day of the summit, all the teams were given 2 hours to create their school's "Climate Action Plan" and a detailed timeline to present to the rest of the schools at the end of the day. Our team decided to focus on 4 major projects in the coming year: improving the school garden, building a bike generator for the lobby, holding a bi-annual school-wide locker clean-out to donate gently used school supplies and teach proper recycling, and finding places to cut the school's phantom energy usage (a.k.a. the wattage used by electronics when they're turned off but still plugged in).

You may not know this, but back when I was at your school I belonged to an "environmental club" too. This meant that a couple of us would go to all the classrooms after school and pull trash out of the blue bins, because otherwise the maintenance guys refused to recycle. Is it fair to say things have come a long way?

Simply put, yes. We have a recycling bin in every classroom, our cafeteria serves vegetables from a number of local farms, quarterly grades and comments are now only available online, our drinking fountains are now water-bottle filling stations, and we have a garden that brings vegetables to the salad bar. We have solar panels on one building and another LEED-qualified building, with another one in the construction phase.

I think we're also a little cooler than your environmental club, because now we are the "Green Avengers," equipped with a logo and a Facebook page.

Are you optimistic about climate change? Do you come back from an event like this feeling like you're part of a group of people who will actually make a difference, whether it's through school-level projects now, or after college as policy makers? Or are we pretty much screwed?

Both times going to the summit I came back incredibly high in motivation, but I knew if I didn't write down all my ideas and get acting quickly, I would lose my energy. Spending time around so many like-minded people definitely makes me excited to get out there and make change.

It also reminds me we have to be able to work on our own and not rely on the work of others because that's part of the attitude that brought us to this predicament in the first place. As Dr. Powers told us, even in the earth's "best-case scenario," we'll still experience rising global temperatures. It's just up to my generation to slow the acceleration of carbon dioxide emissions and provide the optimistic attitude.

Celeriac and Parsnip Soup
Yields 18-24 servings (reduce if you're not feeding a youth summit)

5 pounds cubed celeriac root
5 pounds chopped parsnip
6 tablespoons olive oil
15 cups vegetable stock
1 bundle thyme
1/2 teaspoon salt
1/2 teaspoon ground black pepper

Preheat the over to 400°F. Toss the celeriac and parsnip with the olive oil. Arrange the vegetables in a single layer on a foil-covered baking sheet. Roast them 35-45 minutes, flipping once, until they are tender and golden brown. Combine the caramelized vegetables with the stock and other ingredients in a pot over medium-high heat. After bringing to a boil, let the soup simmer for 15 minutes. Put all the food through a blender or food processor until smooth and serve hot.

Images: The Wild Center (top); Leigh Preston (bottom).

The Shambulance: Put Down the Bananas! There's No Such Thing as a Mono Meal

The Shambulance is an occasional series addressing bogus products and overhyped health claims. The chief tactical officer onboard is Steven Swoap.

While you're enjoying a full Thanksgiving plate this Thursday, you might take a moment to be thankful that your meal isn't a single melon with a spoon stuck in it. Or a stack of plain lettuce. People who eat "mono meals" insist that having only one type of raw fruit or vegetable per mealtime makes their digestive process more natural and virtuous. In reality, it just takes the fun out of salad.

Not to be confused with the noodle soup eaten by college students who are sick with mono, a mono meal is something eaten by healthy people who can afford to buy a lot of produce every week. It's an especially orthodox version of the "high carb raw vegan" diet—or maybe it's a sect of the "80/10/10" diet (which dictates that 80 percent of one's calories should come from carbs, and 10 percent each from fat and protein).

However the eating style evolved, Buzzfeed recently claimed mono meals are a "new diet trend." While it's hard to tell how many mono mealers are out there—they're hardly mainstream—it's true you can search Instagram, Pinterest or Twitter and find photographs of people's thirteen-tangerine breakfasts with a side of hashtags (#801010 #monomeal #fruit!).

An especially zealous group of high-carb raw vegans populates a website called 30 Bananas a Day, although some of them choose to eat their fruits and veggies mixed together, rather than individually. (I spent some time on this site looking for answers about what motivates the mono diet, and instead found several surreal items: a claim that the flavor of raw okra is delicious; a suggestion to blend dates into "dateorade"; a GIF of someone's stomach bloating and un-bloating, mesmerizingly.)

Other sites are more explicit about the point of mono-ing your meals. It's all about simplifying digestion, they say. "If too much activity is happening in the digestive tract," according to Carla Golden Wellness, "enzymes can cancel each other out causing food to rot...With so many different kinds of foods going in at one sitting, our body can get VERY tired trying to sort out the different enzymes and digestion times for all these various foods."

When I sent these claims to Steven Swoap, a physiologist at Williams College, he was pretty efficient about tearing them down.

"You can't have too much activity in the digestive tract," he says flatly. Our bodies use different enzymes to digest proteins, carbohydrates and fats, and "there is no canceling each other out." These processes have evolved to happen at the same time with no stress to our organs—not the stomach or intestine, where digestion occurs, and not the pancreas, which cranks out the enzymes. "The pancreas multi-tasks as well as the best of them," Swoap says.

Mono meal advocates say it's healthier to make things easy on your digestive system by eating just one thing. "When only one food is eaten at a time at a meal, the process of digestion is made to be extremely efficient," says the website Nature's Pilgrim. "The body must only focus on breaking down and absorbing one particular compound."

"Not only is this garbage, it can actually be critically wrong," Swoap counters. Eating a heap of bananas for dinner doesn't make digestion happen faster—and we wouldn't want it to. "Nutritionists agree that taking a longer time is much better for you," he says. Absorbing carbohydrates quickly causes a spike in blood sugar, followed by a spike in insulin. The more sharply a meal raises your blood sugar, the higher its "glycemic index" (GI), a score given by nutritionists.

A plain baked potato, for instance, has a high GI because we can very easily break down its starches into sugars and absorb them. But there's a way to slow things down and avoid the blood sugar spike: add some fat or protein. A dollop of sour cream or butter slashes the GI of that baked potato.

So a mono mealer's goal of mainlining carbs is actually a bad idea. Eating a lot of high-GI foods has been linked to diabetes and heart disease. Luckily, though, a pile of fruit doesn't fit the bill.

"If you each just one naturally occurring food (like a banana or a green pepper or a cucumber)," Swoap says, "this is inherently a meal that is mixed—mixed with carbs, protein, and fats." Every living cell contains fats in its outer membrane and proteins that drive its activities. Additionally, something like an apple or banana has plenty of fiber that slows down your body's absorption of its sugars.

That pile of kiwi fruits, then, won't make anybody's digestion quicker or cleaner than usual. And that's a good thing; your body is happier with slow-and-steady. (A meal that does have a high glycemic index? Juice.)

If you enjoy cantaloupe or plain vegetables enough to eat them exclusively for your meal, it probably won't hurt you. If you really enjoy them, you might become like 30 Bananas a Day user Jared Six. "I have NEVER enjoyed the taste of food more than I do now after 6 months of eating this way," he gushes. "People look at me like there is something seriously wrong for me for being so happy eating something like a meal of just lettuce."

Just make sure those 30 bananas a day don't turn into 36 bananas in one sitting, because that's enough to cause dangerously high potassium levels in your blood—something for which you won't feel thankful.

Image: Elaine Vigneault (via Flickr)

Bees Can Smell How Much Sex Their Queen Has Had

Just because girl talk between bees is wordless doesn't mean it lacks for intimate details. When sister honey bees gather around their queen, they can tell from her pheromones whether she's mated—and how much. What they learn may determine whether they let her live.

The queen honey bee doesn't do much day-to-day ruling, but she does lay nearly every egg in the hive. Her daughters become worker bees, who keep the colony running. Pheromones that the queen and the workers emit—then spread through the hive as they touch antennae and clamber over each other's bodies—carry the signals that maintain order. Among other laws, the queen's pheromones tell workers not to lay eggs of their own.

When the queen's egg-laying prowess starts to fade, though, her workers will replace her without sentimentality. They prepare special queen egg chambers and feed royal jelly to the chosen larvae (who will battle once they emerge, leaving only one queen standing). Then the workers sting the old queen to death. "It can take up to 6 weeks for the new queen to produce a new cohort of workers," says Elina Niño, an entomologist at Pennsylvania State University. So the process harms the hive's productivity, in addition to the dispatched queen herself.

Along with colleagues at North Carolina State University (where she worked at the time) and Tel Aviv University, Niño investigated whether the queen honey bee is honest when she sends pheromone messages to her workers. If the queen could fake the pheromones that say she's in great shape, it would keep her colony loyal for longer. To find the answer, the researchers set about artificially inseminating some bees.

New queens mate just once in their lives, in a sex spree that involves lots of males (called drones). They store all that sperm and use it, a little bit at a time, to fertilize the eggs they lay for their remaining years. The scientists gathered groups of queen bees who had not yet mated with any drones. Then they simulated sex in several ways: Some queens had a needle inserted into them to mimic the physical aspect of mating. Some received actual semen (mixed from the contributions of multiple bachelor bees), in either a large or small volume. Others were pumped with a large or small volume of salt water.

Several days later, the unfortunate queens were offed. The researchers extracted the contents of two pheromone glands, one at a queen bee's mouth and the other near her stinger. Chemical analysis showed that in the pheromones from the bees' back ends, there was a difference between queens who'd been inseminated (or faux-inseminated) and those whose insides were still empty. The pheromones from the jaw gland seemed to carry even more specific information: each group of queens (inseminated for real or with salt water, holding a large or a small volume of whatever it was) had a distinct chemical signature.

But how would worker bees respond to these signals? The scientists put their pheromone extracts onto glass plates and set them down by groups of worker bees. They hoped to take advantage of a bee behavior called the "retinue," in which workers cluster around a queen while licking her and touching her with their antennae.

The worker bees treated the pheromone puddles like real queens. But not all queens were equal. The researchers saw that workers were most attracted to pheromones from queens who were full of semen, rather than salt water. They also preferred pheromones from queens with a larger volume of semen stuffed inside of them.

"Colonies headed by multiply mated queens are more productive, more resistant to diseases and more likely to overwinter successfully," Niño says. In other words, queens that have mated with lots of drones produce hives that are healthier, because they're more genetically diverse. So it would benefit worker bees to be able to sniff out their queen's sexual history and "act accordingly," Niño says. This might mean ousting a queen who hasn't gotten around much, and gambling on a new queen instead.

For beekeepers, the results add new importance to having a healthy queen. Just because a queen is laying eggs, Niño points out, doesn't mean she can keep her subjects loyal. Workers that don't like the smell of their queen's pheromones, perhaps because she hasn't mated with an adequate number of drones, may execute her. Beekeepers who want to avoid that drama should make sure their queen has plenty of partners—because when she talks to her workers about her sexual past, she won't be able to lie.

Image: by Dude-K (via Flickr)

Niño EL, Malka O, Hefetz A, Tarpy DR, & Grozinger CM (2013). Chemical Profiles of Two Pheromone Glands Are Differentially Regulated by Distinct Mating Factors in Honey Bee Queens (Apis mellifera L.). PloS one, 8 (11) PMID: 24236028

You Might Have Outgrown Synesthesia as a Kid

Feeling smug because your normal brain doesn't insist on coloring all its 2's blue and M's purple? Not so fast: you might have been a child synesthete. Some elementary schoolers have associations between colors and letters or numbers that fade as they age. Others' associations expand to take over the whole alphabet, leading them toward a rainbow-hued adult life.

Studying kids with synesthesia is tricky, because first you have to find them—and at a young age, kids don't know the word, or that their perceptions aren't standard. University of Edinburgh psychologist Julia Simner screened 615 kids for synesthesia back in 2009. Starting with six- and seven-year-olds, Simner and her coauthors sat the kids in front of a computer screen and told them to play a game: they'd see a letter or number next to a set of colors, as above, and should choose the "best" color for each one.

After the computer ran through every letter and numeral in random order, it paused for several seconds, then did the entire test a second time. Forty-seven of the kids were significantly consistent in their choices between the two tests—which meant either that they were synesthetic, or that they had a good memory for colors they'd picked at random. The moment of truth came a year later, when those 47 kids sat down and took the test again. People with synesthesia should be consistent not only over a few minutes, but over years. That's because it's not really a test of memory for them; color is simply a quality that a letter or number has, like being even or a consonant. (For rarer types of synesthesia, people might experience colors with sounds, or tastes with words.)

In 2009, Simner found eight girls and boys who passed her tests. For a new study published in Frontiers in Human Neuroscience, Simner and coauthor Angela Bain returned to these patient elementary schoolers—now 10 or 11 years old—and did the test a third time.

They wondered whether any kids' synesthesia would have faded over the intervening years. Anecdotally, some adults say they remember having synesthesia as a child and growing out of it. The researchers started with not just their eight synesthetes, but 39 of the kids who had been classified as near misses in the first go-around—they had been consistent over 10 seconds, perhaps, but not over a year, or their performance had been just shy of statistically significant. Another 40 average kids served as controls.

This time, six kids passed the test. They were consistent both within two trials and compared to their original tests four years earlier. On testing day, these synesthetes made consistent color choices for about 26 out of the 36 letters and numerals they saw. Non-synesthetes were consistent for only 6 or 7.

Five of the children were from the original batch of synesthetes, and the sixth had been a near miss originally. The other three original synesthetes were no longer significantly outperforming their peers in choosing consistent colors. This may be evidence of "synesthetic demise," the authors write.

Young synesthetes losing their colors over time would fit with a popular theory about synesthesia, which says that it comes from an overly connected brain. "All very young children have hyper-connected brains," Simner says; the neurons branch out indiscriminately between different areas. As we grow, the unneeded connections are pruned away, a process that continues throughout childhood. "It may be that synesthetes escape the pruning, so to speak," Simner says. All kids might start out with some degree of synesthesia, which fades away with normal development.

It's also possible, Simner says, that the "near-miss" kids actually had synesthesia that was developing more slowly than their peers'. She found that synesthetes add more and more colored characters to their rosters as they age. When synesthetes were six or seven years old, they had consistent colors for only about a third of letters and numbers. In another year that number had risen to almost half, and at age 10 or 11 over 70% of letters and numbers had fixed colors. Adult synesthetes have consistent colors for 80 to 100% of letters and numbers.

So for people who don't lose their synesthesia as they age, it becomes steadily more consistent. Now that Simner's subjects are 14 and 15 years old, she says, "we very much hope" to test them again. The teenagers may be happy to learn that at least one thing about their lives is becoming less chaotic.

Image: Simner & Bain 2013.

Julia Simner, & Angela E. Bain (2013). A longitudinal study of grapheme-color synesthesia in childhood: 6/7 years to 10/11 years. Frontiers in Human Neuroscience DOI: 10.3389/fnhum.2013.00603

Citizen Scientists Dig Up the Truth about Decomposing Dung

The amount of cow dung plopped into the world every day is almost unthinkable, but Tomas Roslin is thinking about it.

"We can regard it as either an immense waste problem or an enormous ecosystem service," he says. He means that what starts out as a turd in a field turns into a wealth of nutrients for plants—assuming it can make its way below ground. So understanding how dung gets broken down can help us ensure an ecosystem is running smoothly. To address such a messy, large-scale question, Roslin recruited a big mess of young volunteers.

Roslin is an ecologist at the University of Helsinki, and he found his citizen scientists through the Finnish 4H Federation. In all, 79 volunteers signed up, ranging from 10 to 27 years old (most were under 20). They agreed to sample 82 cattle farms that spanned Finland nearly from end to end.

From each farm, the volunteers collected 20 liters of "fresh dung" in late spring or early summer. They divided their dung into 15 pats (using an official dung measurer that had been provided to them) and put the pats back onto cow pastures. Some of the manmade cow patties were left open to the air, while others were covered with cages of coarse or fine mesh to keep out certain insects.

Roslin and his coauthors were especially interested in large dung beetles called dor beetles. In some cases they prevented dor beetles from burying the dung (as the beetles enjoy doing) by putting mesh underneath the patty, and in other cases a full wire cage kept dor beetles from getting into the dung at all. Smaller insects were kept out with finer mesh cages, and earthworms were blocked from the dung by putting a layer of cloth underneath it.

Volunteers weighed the dung piles periodically over the next two months to see how much was left of them. As the summer went on, the patties dried out and were broken down by whatever insects could reach them, as well as by microbes that couldn't be kept out. (Only 73 farms were left in the final analysis, since a few sites were lost to "lack of sufficient commitment by the volunteer" and others to "cows trampling on the experimental pats.")

The results showed that 13 percent of dung decomposition is done by insects. Microbes and rainstorms take care of the rest. The farther north you are in Finland, the more slowly your dung will disappear, perhaps because cooler weather slows bacterial growth.

Each added barrier around the dung made it decompose a little more slowly, showing that all the groups of insects were helping to break it down. But the biggest contribution came from dor beetles. This was in line with what previous, small-scale research had shown—but his network of citizen scientists let Roslin confirm that dor beetles are equally important all across Finland.

It matters because "our dor beetles are not doing that well," Roslin says. Out of three species in Finland, one has gone regionally extinct and another is on the decline. Knowing how important the dor beetle is to healthy farms gives Finland more reason to keep it alive.

Additionally, Roslin says, "just figuring out the basics of how the system works" is critical. In the United States, most cattle waste goes into manure lagoons, where beetles or ecosystems don't really enter the equation. But when waste is returned to the soil, Roslin says, "we need to understand who is behind it." He points out that cattle were initially brought to Northern Europe in part to fertilize the fields.

"We love citizen science," Roslin declares. He and his lab have previously organized citizen investigations of dung beetles and gall-wasps, and they're now working with volunteers to study the hermit beetle Osmoderma barnabita. "The volunteers involved have come to appreciate completely new aspects of their own environment," he says.

There are some drawback to the approach, of course —experiments have to be kept simple, and sometimes a volunteer loses interest or flattens a cow patty. But by pairing small-scale lab research with large citizen projects, Roslin says, "we have managed to collect scientific data sets unachievable by relying on professional biologists."

Riikka Kaartinen, Bess Hardwick, & Tomas Roslin (2013). Using citizen scientists to measure an ecosystem service nationwide. Ecology DOI: 10.1890/12-1165.1

Images: top Timo Marttila/Satakunnan Kansa; bottom Riikka Kaartinen.

Found: A Rotten-Smell Button in the Brain

Window or aisle? Hamburger or hot dog? Bouquet of flowers or rotting flesh? Not all your preferences are up to you—some have been hammered into your genes by evolution.

If you're an average human, you avoid the smell of decay. It signals unsafe food and the threat of infection or disease. Other animals run toward the stench of a stale carcass, maybe because they're flies and it signals a place to lay their eggs.

Whether they love it or hate it, animals identify the scent of rot from two signature molecules. German doctor Ludwig Brieger discovered these molecules in the late 1900s; in English, they're rather cutely named "cadaverine" and "putrescine." Bacteria create the two culprits by breaking down down amino acids in animal bodies. Not solely the sign of a rotting carcass, cadaverine and putrescine also show up in urine and bad breath.

Despite the importance of these smells (or avoiding these smells) in animals' lives, no one had found receptors for these molecules—that is, the locks to which the molecules are keys. Scent receptors are attached to one end of a neuron inside the nose (or whichever body part an animal smells with); when a certain chemical wafts up the nose and latches onto the receptor, a signal travels along the neuron to the brain at the other end. Researchers at the University of Cologne in Germany and Harvard University think they've found one of those receptors for rot.

The authors, led by the University of Cologne's Ashiq Hussain, studied zebrafish, which are commonly used to model the sense of smell in vertebrates. First they checked to make sure zebrafish respond to the smell of decay. When they put putrescine and cadaverine into a tank, zebrafish swam to the other end, showing they feel the same way we do about these smells. When the authors plugged the zebrafishes' little nostrils with glue, the fish were no longer bothered by the odor.

The researchers searched for a receptor in a family of proteins called TAARs (trace amine-associated receptors). Related receptors in rodents are thought to detect other unpleasant odors that come from living things. Zebrafish make 112 different kinds of these receptors, but the molecules that attach to them hadn't been found yet.

After testing 93 smelly chemicals on representative zebrafish TAARs, the authors found a match: cadaverine turns on a receptor called TAAR13c. But could the receptor detect cadaverine in real life, and not only when it was dripped on in purified form by a scientist? To test it, the researchers used an extract of dead fish. When exposed to liquid made from a recently deceased zebrafish, the receptors didn't respond. Liquid from a week-old, rotten fish carcass, though, easily activated the receptor—even when diluted to 1 part in 1,000.

Finding a receptor for cadaverine means scientists now understand a little bit more about how the vertebrate brain responds to awful smells. The receptor protein itself "will not be similar in humans, because mammals do not have close relatives of this zebrafish receptor," says Sigrun Korsching, the paper's senior author. Still, she adds, "There are very few cases where you can show activation of a single receptor leads to a behavioral response." Studying how the zebrafish's neurons respond to cadaverine could lead to a better understanding of how animals process all kinds of odors, whether they enjoy them or not.

Image: by Bill Gracey (via Flickr)

Ashiq Hussain, Luis R. Saraiva, David M. Ferrero, Gaurav Ahuja, Venkatesh S. Krishna, Stephen D. Liberles, & Sigrun I. Korsching (2013). High-affinity olfactory receptor for the death-associated odor cadaverine. PNAS DOI: 10.1073/pnas.1318596110

Note: This post has been edited from an earlier version.

Fungus-Farming Beetles Start Tending Their Crop as Babies

Inside the stems of Japanese bamboo plants, tiny farmers are working in secret. They tend to their crop of fungus, growing it in plump white clusters on their walls for eating, all while sealed safely away from the rest of the world. They begin farming the day they hatch—and when they retire, tuck some of their crop into their pockets to pass on to the next generation.

The farmer is Doubledaya bucculenta, a species of lizard beetle. Many social insects (those that live in colonies) are well-known farmers. Leafcutter ants, for example, cut up all those leaves to feed to their own fungus crop. But farming in nonsocial insects, like the loner lizard beetles, is more mysterious.

Wataru Toki of the University of Tokyo has been gradually uncovering the farming habits of D. buccalenta. Last year, Toki and other researchers announced that the beetle grows a certain kind of yeast (which is a fungus) inside bamboo plants. Each spring, female beetles come to bamboo stems, chew a hole through their hard walls, drop a single egg inside, and then seal the cavity back up. Bamboo stems have hollow sections separated by solid nodes. Inside this protected home, the egg hatches into a larva. The walls of its home end up covered in white fungus, which the larva eats.

Once it's grown into an adult, the beetle chews its way back out of the bamboo and into the world. But female beetles, the researchers found, carry a little bit of their yeast crop with them. They store it in a kind of pocket built into the ends of their abdomens. Is this stash somehow passed on to the next generation of eggs?

To find the answer, Toki and others carried out a number of experiments, including slicing bamboo stalks in half and videotaping the egg-laying process from the inside. After the mother beetle hacks into the plant (she has an asymmetrical head, which Toki suspects somehow helps her crack the tough bamboo), she turns around and sticks an organ called her ovipositor through the hole. She extrudes a single long, tubular egg, then makes several squeezing motions with her ovipositor before sealing the hole back up with bamboo fibers.

This squeezing action seems to deliver the yeast from the mother's pocket into the bamboo plant. The researchers found yeast cells concentrated on the end of the egg and at the sealed-up bamboo hole. Left alone, this yeast can grow into a meager colony. But when the egg hatches, the larva emerges from the yeasty end of the egg and begins to wriggle around its home. Soon, lush yeast colonies sprout in its path.

In other words, "The larvae actively spread the yeast," Toki says. Mothers pass down the crop to their offspring, and larvae start nurturing it as soon as they hatch. For the beetles, farming is a family business.

Toki says it's still not known how mother beetles collect yeast in their pockets. "However, it is clear that they get the yeast before they leave the home—bamboo cavity—where they grew up." Next, Toki hopes to figure out how D. buccalenta prevents other microorganisms from invading its yeast farms. They may not be social, but the beetles have plenty to tell us.

Image: Toki et al.

Wataru Toki, Yukiko Takahashi, & Katsumi Togashi (2013). Fungal Garden Making inside Bamboos by a Non-Social Fungus-Growing Beetle. PLOS ONE DOI: 10.1371/journal.pone.0079515