Inkfish

Rare Blooms

2012-06-01T10:02:00.001-05:00

John pauses with his cursor over a photo of a dark yellow flower. He seems to be debating whether to say something. "I call this one the penis orchid," he admits.

I see it. The Coryanthes bears a bulbous, upright projection, behind which is a bucket-shaped area filled with fluid. Male euglossine bees tumble into the bucket while trying to collect the orchid's fragrance, which they use like a cologne to make themselves more attractive to females. As a male bee repeatedly falls into and crawls back out of these buckets, he unwittingly pollinates the flowers.

It's a great story, but the flower's endowment might be distracting to the middle- and high-schoolers who read the magazine I edit. "Yeah," I tell him, "my photo editor will never let that fly."

I'm visiting my friend John Osterhagen to research an article for kids about orchids. John works for an insurance company by day, but returns home to an apartment bursting with orchid plants. There are eighty or so, living in his bedroom on rows of shelves and windowsills, under special lamps or misting devices. John's cat, Keiko, likes to chew the leaves of just one plant, so he keeps it tucked in his farthest corner.

Flowers aren't John's only self-admittedly strange hobby. He loves early music, origami, and coloring with Crayolas. But none of his other hobbies lives and breathes in his home with him. "People say in the orchid world that you 'get the bug,'" he says. A few fussy but handsome potted plants become shelves full of exotic hybrids and a membership to the Orchid Society. "It's as if the orchids themselves are manipulating you."

John also has the bug for orchid taxonomy, which is always changing as genetic studies revise the family trees guessed at by past centuries' naturalists. He rattles off genus names: Paphiopedilum, Phragmipedium, Bulbophyllum. Sometimes a genus becomes empty and abandoned as taxonomists shift all its species into different groups. John keeps up on the research and edits Wikipedia pages where he can.

The magazine story I'm working on is about deception. Orchids thrive on lying. Some grow petals that look precisely like the back of a female bee or beetle or wasp; a male of the targeted species will try his hardest to mate with the unresponsive flower part while the orchid quietly glues its pollen onto his head. Other species trap their pollinators in well-like petals that can only be exited through a tunnel rigged with pollen. There are orchids that mimic other flowers to attract the pollinators that drink their nectar. (Most orchids don't make nectar, the usual lure for insects, at all.) Those that seek to attract carrion flies mimic rotting meat, emitting a stink from masses of gut-colored petals decorated with maggoty white streaks.

John shows me examples on his computer and on his shelves while Keiko paces around our ankles. A petite epiphytic orchid—a species that lives on trees with its roots dangling into the air—has bloomed just in time for me to see it. He points into the innards of another flower, where I can barely make out the trap door flanked with pollen blobs.

And he points out several species that bear a speckled pattern around their centers, as if a breeze has generously dusted them with their own pollen. In reality, the pollen is waiting elsewhere in a large mass to be attached to a pollinator. John has a strong suspicion that the speckles are another kind of deception, meant to attract insects that eat pollen. "I don't know whether it's been studied academically," he says.

The flowers bloom infrequently and on their own schedules, most often around December or January. Even after putting so much effort into dressing up for a pollinator, they seem not to care whether they get pollinated at all. John says he sometimes gets up in the morning to find that an orchid has tossed a new, perfectly formed blossom to the ground overnight.

The whole family of Orchidaceae, in fact, can appear bent on self-destruction. They grow slowly, sometimes taking years to reach maturity. They're "insanely specialized to their pollinators," many wagering all their future generations on a visit from a single species. If pollinated, they produce seeds that are nearly microscopic. And those seeds can't sprout unless they happen to cross paths with a fungus that will enter into a symbiotic relationship and provide the nutrients the orchid needs. "It seems like the odds are stacked against them," John says.

Yet orchids are some of the most successful plants in the world. There are around 25,000 species, living on every continent except Antarctica and in nearly every kind of climate. They're either the largest or second-largest flowering plant family that exists, depending who does the counting.

The secret to their world dominance may be genetic. During the orchid's evolution, master genes that control the organization of the flower were duplicated. This gave the plant a huge amount of freedom to mutate. New flower shapes emerged to fill thousands, then tens of thousands, of ecological niches.

John doesn't breed his plants. With their expected pollinators never showing up, and John declining to pollinate them by hand, he says they're "the world's most sexually frustrated orchids."

But he does see plenty of mutants. The orchid tendency to create genetic monsters manifests even in his apartment. John shows me a plant that grows flowers with four parts instead of six, and another that has piles of unnecessary petals, "like a Frankenstein flower." He has a plant that can't keep its flowers' lips (the modified petals at the front and center) straight from its other petals. After the mottled fuchsia flowers open, the lips try to turn into petals while the petals start to curl like lips. In a photo, another flower grows an extra petal straight from its center, like an arm coming out of its face.

Orchid growers keep track of individual plants with an elaborate naming system that traces each plant's family history. Thanks to the finickiness of orchid growth, many of these species can't be cloned like other plants can. So their incarnations on John's shelves are one of a kind.

Whether they grow flawless blossoms or freaks, "that particular plant is unique in the whole world," he says. "Like a human."

All images by John Osterhagen. Top to bottom: An orchidarium; Paphiopedilum venustum (a Himalayan species species with a pattern that, John notes, looks like a brain); Jumellea comorense (native to the Comoros Islands in the Indian Ocean); and Dendrobium Negro (a hybrid of Southeast Asian Denbrobium species).

Flowers Use Velcro Cells to Keep Bees from Blowing Away

2012-05-29T09:57:00.000-05:00

When a pollinator is at your front steps about to come in for a drink of nectar, you'd be foolish to let a gust of wind blow her away. That's why most flowers have installed velcro doormats. Pointy cells give their petals an extra-grippy surface that encourages bees, even in the middle of a windstorm, to stop and stay a while.

Flowers such as roses, tomatoes, and petunias have cone-shaped cells in the surface of their petals. In fact, about 80 percent of flowers with traditional petals have these conical cells, says University of Cambridge plant scientist Beverley Glover. The cones make a flower's color appear more vibrant by focusing sunlight onto pigment held in the center of the cell. They also help bees latch on. Since the cells are about the same size as the tiny claws on bees' feet, the claws slide in between the cones for a tight grip.

Previous research has shown that conical cells help bumblebees get the nectar out of snapdragons. These flowers keep their goods hidden inside what looks like a hinged door (or apparently, if you're the person who named this flower, a dragon's mouth). Snapdragons with pointed petal cells let bees comfortably land, pry open the door, and drink the nectar. When bees visit mutant snapdragons with flat petal cells, they struggle to maintain their grip.

But snapdragons, with their elaborate structure, are an unusual case. So Glover's team set out to see what conical cells are doing in simpler flowers. They started with the ordinary petunia.

When the team presented bumblebees with both standard petunias and mutant (flat-celled) petunias, the bees preferred to visit the more velcro-esque flowers. The difference in color between the two purple flowers was too slight for a bee's eyes to detect, so something else about the conical cells must have been attracting them.

To find the attractive quality in grippy petunia petals, the researchers swapped their standard petunias for a grippy petunia that's unattractive. This genetic mutant has the usual cone-shaped cells, but a much darker purple color that makes the flower difficult for bees to see. Now the bees preferred the flat-celled flowers, since they were easier to find and fly to.

Then the team created a little wind to see whether it gave the upper hand back to cone-celled flowers. Or rather, they created the appearance of wind by placing their petunias on a laboratory shaking machine. This device has a platform that jostles its contents around, keeping tubes and beakers of things well-mixed during experiments. When loaded up with petunias, it waved the flowers as if they were outside in a stiff breeze. (To add to the illusion, the shaker was covered with green tissue paper.)

At first, the bees still flew to the lighter-colored flowers with flat cells. But over the course of the 100 flower visits researchers let each bee make, the bees learned to favor the conical-celled flowers, even though they were still harder to see. By the end of the experiment, bees flew to these flowers a majority of the time.

Not only do conical cells help bees grip flowers, but they become even more important when those flowers are moving. The bumblebees' desire for a comfy place to wedge their feet overcame their dislike of difficult-to-see colors.

If pointed cells on your petals is so great, why do flowers such as lilies, tulips, and magnolias have flat cells instead? Glover says this is a question she's still trying to answer. "In a couple of plant groups we've been studying, we do think we see an association between switching to moth or bird pollination and losing your conical cells," she wrote in an email. If your pollinator is an insect or hummingbird that hovers over you rather than landing, there may be no advantage to keeping a sticky doormat.

Another possibility is that slippery-petaled flowers encourage bees to ignore the doorstep altogether and fly straight in the window. In flowers such as the flat-celled woody nightshade, Glover says, "the bee grasps the anthers and vibrates them to get the pollen out." But, she adds, "we don't have data to support this idea yet." When it comes to pollination etiquette, we're still learning the rules.

Alcorn, K., Whitney, H., & Glover, B. (2012). Flower movement increases pollinator preference for flowers with better grip Functional Ecology DOI: 10.1111/j.1365-2435.2012.02009.x

Images: Bee on flower by Martin Cathrae/Flickr; experimental diagram by Alcorn et al.

Octopuses Host a Masterclass on Hiding

2012-05-25T10:00:00.000-05:00

When you're surrounded by an ocean full of potential predators, the best way to avoid seeing the inside of one's stomach is to make sure none of them see you in the first place. Octopuses and some other cephalopods are experts at camouflage, manipulating the colors and textures of their skin to hide in plain sight. But their strategy, it turns out, has nothing to do with disappearing into the background.

To learn the camouflaging secrets of the masters, researchers led by Noam Josef at Ben-Gurion University of the Negev in Israel went scuba diving. On reefs in the Red Sea and Tyrrhenian Sea, they snapped pictures of two octopus species (Octopus cyanea and O. vulgaris) whenever they saw an individual hiding—crouched low and motionless for a minute or longer.

For the pictures to work in the team's digital image analysis, they had to be sunlit just so and taken from directly above. Over three years, they captured just 11 photos that fit their criteria. "These images are a bit hard to get," Josef said in an email. Not to mention the challenge of finding a camouflaged octopus in the first place.

Hint: Look for the coral with tentacles.

Each bird's-eye, or rather shark's-eye, photo was converted to a grayscale image. Researchers selected a rectangle showing the pattern on the octopus's mantle (the part that's not tentacles). Then a software algorithm compared the mantle sample to rectangles from everywhere else in the photo, shifting the frame one pixel at a time and searching for a match.

The best matches to the octopuses' camouflage patterns were not to be found in the gravely ground beneath them. Instead, 10 out of the 11 octopuses had clearly mimicked a specific object nearby. They played coral, rock, weird sand blob, or algae patch.

View this picture larger and you'll see that one coral has eyes on top.

A camouflaged animal's best strategy depends on the viewpoint of its predators. Many fish have light-colored bellies that blend in with the sky when seen from below. Certain pygmy sharks take this trick a step further and emit a blue glow from their undersides. When viewed from above, fishes' darker-colored backs vanish into the background of the ocean.

An octopus sitting on a reef has to worry about big fish hunting from above, as well as moray eels and other predators that creep up from the sides. Since these enemies approaching from different angles will see the octopus framed against different backdrops, maybe it makes sense for the octopus to forgo blending in altogether. It's stuck being obvious, so it may as well pose as an obvious object that's less edible.

"Sometimes octopuses make an honest mistake and simply become conspicuous" by camouflaging, Josef says. "However, in a complex environment like the coral reef, acquiring key features of an object may serve the octopus better than just matching the general look of the reef." You can see a few of those convincing key details in the photos above, where octopuses have contorted themselves into the knobby branches of a coral or a shell's striped ridges.

Scientists have discovered some of the specialized cells in octopus skin that help them pull off their elaborate imitations—pigment holders, reflectors, light scatterers. But Josef says there are still more questions than answers: "What visual cues are used by these animals? How do octopuses match their colors even though they're colorblind?" (Yes. Colorblind.) "What information is transmitted from the eye to the brain? And what does an octopus really see?"

We're still "far from understanding" the camouflaging act of the octopus, Josef says. We'll have to keep hunting for scraps of information the cunning cephalopods let slip. That is, assuming we can find them first.

Josef, N., Amodio, P., Fiorito, G., & Shashar, N. (2012). Camouflaging in a Complex Environment—Octopuses Use Specific Features of Their Surroundings for Background Matching PLoS ONE, 7 (5) DOI: 10.1371/journal.pone.0037579

Images: Top, Ms. Keren Levy. Middle and bottom, Mr. Zvika (Ziggy) Livnat.

Having a Water Bottle for a Mom Not Ideal

2012-05-21T14:06:00.000-05:00

In the wild, young rhesus macaques can reasonably expect not to have their mothers replaced by kitchen props. The monkeys depend on their moms to nurse them and tote them through tree branches while they're small, just like other primates. But a laboratory experiment in Maryland took these babies from their mothers and had them raised alone or in groups of their peers. The monkeys' strange infancies had physical and mental effects that lasted into adulthood.

At the National Institute of Child Health and Human Development (part of the National Institutes of Health), rhesus macaques born between 2002 and 2007 were randomly assigned to one of three groups. The lucky first group got to stay with their mothers, who kept their young close by while living in a large cage with other monkeys.

The rest of the young monkeys were taken from their mothers and reared by humans in a nursery for their first five weeks of life. Then, if they were in the second experimental group, they were put into a cage with three other monkeys of the same age. The four peers were left to "raise" each other, Lord of the Flies style.

The final group of monkeys, after being nursed by humans for five weeks, spent two hours a day in these same peer cages. During the remaining 22 hours, they lived alone in a cage with a "surrogate mother." The name is a bit of an insult to primate intelligence, though, since researchers describe this object as "effectively a terry cloth-covered hot water bottle hanging from the top of the cage."

By the end of their first year of life, all the juvenile monkeys had been moved from their experimental cages into one social group. Now the researchers, led by Gabriella Conti at the University of Chicago, began to collect data on the monkeys' health. Over the years of the study, they watched 231 rhesus macaques grow up in this bizarre daycare system. Even though the monkeys all ended up living together, their disparate childhoods left a mark.

The first clear effect was illness. Male monkeys that had been raised by a "surrogate" got sick nearly twice as often as mother-raised or peer-raised monkeys, even though by this time in their lives they all shared the same living conditions. Nearly every surrogate-raised male monkey had an illness at some point during the study.

Female monkeys that had been raised by peers, rather than by a real or fake mother, were more likely to have wounds and bald patches once they were living in the large group. Since these females displayed more aggressive behavior, the researchers think they may have been starting fights with the other monkeys. Their aggression may have goaded other monkeys into biting them and pulling their hair out.

And across all the groups taken away from their mothers—male and female, peer-raised and surrogate-raised—monkeys were more likely to have repetitive habits called stereotypies. In the zoo, a stereotypy such as pacing or swimming in circles suggests that an animal is in distress. In humans, stereotypies can be a symptom of autism. Habits displayed by the rhesus monkeys in this study included "digit sucking (the most frequent behavior), pacing, head tossing, self-grasping, saluting, spinning, rocking, circling, and swinging."

Some of the difference between monkeys raised by their mothers and the rest could be due to breastfeeding, Conti points out. But the increased illness in male monkeys was limited to the surrogate-mom group; the peer-raised monkeys, despite also missing out on breastfeeding, didn't have extra illnesses. And although all motherless monkey groups showed an increase in stereotypy, the effect was greatest in surrogate-raised males. This suggests that even if formula feeding causes some of the health effects seen here, it can't account for all of them.

The not-shocking conclusion is that monkeys need their moms to develop normally. Being raised parentless seems to make them less able to cope with infections or social stressors later in life. It's something to consider for research centers or zoos raising animals without their mothers. Even if the young have been orphaned or abandoned, there may be ways for human keepers to mitigate the damage.

Conti is an economist, though, and she's more interested in another primate: humans. She compares the rhesus research to studies of human children raised without either of their parents. These studies have found mental and physical health effects in children in Romanian orphanages, for example, or Israeli kibbutzim (where kids were raised communally). As smart and independent as we are, we're still primates who need someone to haul us through the tree branches when we're young.

Gabriella Conti, Christopher Hansman, James J. Heckman, Matthew F. X. Novak, Angela Ruggiero, & Stephen J. Suomi (2012). Primate evidence on the late health effects of early-life adversity PNAS : 10.1073/pnas.1205340109

Image: Baby Japanese macaque by Nemo's great uncle/Flickr

The Secret to Success Is Giant-Jawed Snake Babies

2012-05-18T09:52:00.001-05:00

When coming face-to-face with a wriggling, freshly born pile of poisonous snakes, most of us wouldn't linger for a close look. But it was by looking into these living linguini platters that one biologist found a new answer to an old question: Why does island life make animals such freak shows?

Some big-bodied species shrink when they move from the mainland to an island habitat, a phenomenon that's created pygmy sloths, miniature mammoths, and possibly even a dwarf hominid that's now extinct. Some small-bodied species, meanwhile, grow enormous on islands. This category includes a 3-inch-long earwig, various ungainly and flightless birds, and a giant rat (living on Flores, the same island where the miniature people were, unfortunately for them).

Scientists have explained these fun-house transformations with a lack of resources on an island (keeping animals smaller) or a lack of predators (allowing them to grow bigger). Other factors, such as distance to the mainland or one sex's preference for extreme traits in a mate, could be at work too.

French researcher Fabien Aubret wondered whether scrutinizing the sizes of adult animals was making scientists miss another important variable: the size of babies. A newborn animal that can't find its first meal will quickly exit the gene pool. In snakes, this could be a simple matter of not being able to get one's mouth all the way around one's prey to swallow it.

Aubret studied twelve populations of tiger snakes, some living on mainland Australia or Tasmania and others on nearby islands. Among the island exiles, some groups have grown giant--up to 1.5 meters long, rather than the usual 0.8 or 0.9 meters--while others have shrunk. Most of the island populations were stranded by rising seas six to ten thousand years ago, leaving them with a different selection of prey animals than on the mainland.

Armed with a measuring tape, Aubret asked whether the changes the snakes' bodies have undergone since then can be entirely explained by the need for newborns to get their jaws around a meal. Tiger snake mothers give birth to live young rather than laying eggs, popping out a dozen or more at a time. On the mainland, these snakes and their parents swallow frogs for most of their meals. But on the islands, their prey can range from little lizards to large nesting seabirds.

Aubret captured almost 600 adult snakes from the various populations, measuring their length and weight before releasing all of them except the pregnant females. When the tangles of baby snakes emerged, he monitored the newborns' sizes for six months while feeding them a standard diet. For each study site, he calculated the average weight and circumference of animals on the prey buffet. (Weight because first a snake must subdue the unfortunate gecko or skink, and circumference because the animal must fit down the gullet.)

The size of baby snakes from each site--and the size of their jaws--was closely tied to the weight and circumference of the prey animals available there. Baby snakes from sites with large prey also grew faster.

Aubret says the pressure on newborn snakes to swallow available prey might be the only explanation necessary for the various body sizes tiger snakes have evolved on different islands. Adult body size, though of course it's related to the size of newborns, might be mainly irrelevant.

This gives biologists a new clue to the puzzle of how island life makes animals shrink or grow. While they wrap their heads around that, the tiger snakes will continue to wrap their own heads around any slow-moving animal that fits.

Fabien Aubret (2012). Body-Size Evolution on Islands: Are Adult Size Variations in Tiger Snakes a Nonadaptive Consequence of Selection on Birth Size? The American Naturalist, 169 (6)

Image: Not actually a tiger snake, by batwrangler/Flickr

Memory-Improving Gene Tied to PTSD

2012-05-15T10:03:00.001-05:00

A superior visual memory is the best friend of artists and competitive card memorizers. But to people who've lived through traumatic events, it might be the enemy.

Researchers in Switzerland and Germany guessed that people with a better memory might be more susceptible to post-traumatic stress disorder, their minds clinging stubbornly to horrific events in the past. But studying the memories of people living with a mental illness is difficult, since the disorder itself might affect their memory. So when the researchers went on a hunt for genes that are linked to both memory and PTSD, they began in a healthy population.

A group of more than 700 Swiss young adults, free of any mental illness, participated in the first part of the study. They viewed several dozen pictures that were meant to elicit either a positive emotional response, a negative emotional response, or a neutral one. After being distracted for 10 minutes, they were given a surprise quiz on how many of the pictures they could recall.

The subjects's DNA underwent testing too. The researchers checked 2,005 individual spots in each person's genes called SNPs (pronounced "snips"). These are bits of DNA that vary across a population, such that some people might have a T nucleotide where others have a G, for example. All of the 2,005 SNPs the researchers checked had to do with certain multitasking molecules called protein kinases that seem to be involved in memory formation.

Out of the 2,005 gene variants in this haystack, one needle emerged: a bit of DNA that was significantly linked to subjects' performance on the memory test. There are two versions (or alleles) of the gene in question, which makes a molecule called PKC alpha. People with one of these alleles--an A rather than a G--remembered more of the pictures they'd seen. Although researchers were especially interested in their subjects' recall of emotionally negative pictures, the effect seemed to extend to positive and neutral ones as well.

Brain scans showed a difference inside the heads of these high-performing memorizers. Subjects with A alleles had more activity in parts of the prefrontal cortex while looking at the negative images. These same regions, the authors say, have been linked to emotional memory storage in other studies.

Now that the researchers had found a gene of interest, they could study it in some actual traumatized people. They turned to a group of 347 Rwandan refugees who fled their country during the civil war. After being interviewed thoroughly, 134 of the refugees were found to meet criteria for post-traumatic stress disorder. Rwandans who had the better-memory gene variant from the first part of the study were more likely to be in the PTSD group. They were also more likely to have the symptom of reliving a traumatic memory over and and over.

Among the healthy Swiss population, the better-memory A allele was more common than the worse-memory G allele. But among the Rwandan refugees, the opposite was true: The better-memory gene variant was the rare one. If it were more common, PTSD symptoms might have been even more frequent among the displaced Rwandans.

The genetics of mental illness are tricky to untangle, and what merits a diagnosis in one culture might be normal in another. Studies such as this one, though, could reveal who's most at risk for certain symptoms. And if scientists can figure out how exactly the genes in question are acting in the brain, we might see new drugs that can treat some of these symptoms--or prevent people's memories from turning against them in the first place.

de Quervain, D., Kolassa, I., Ackermann, S., Aerni, A., Boesiger, P., Demougin, P., Elbert, T., Ertl, V., Gschwind, L., Hadziselimovic, N., Hanser, E., Heck, A., Hieber, P., Huynh, K., Klarhofer, M., Luechinger, R., Rasch, B., Scheffler, K., Spalek, K., Stippich, C., Vogler, C., Vukojevic, V., Stetak, A., & Papassotiropoulos, A. (2012). PKC is genetically linked to memory capacity in healthy subjects and to risk for posttraumatic stress disorder in genocide survivors Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1200857109

Image: Virginia Guard Public Affairs/Flickr

In the Spring, Bat Moms Choose Girls

2012-05-11T09:41:00.000-05:00

Naturally a mother bat is happy to welcome into the world a bouncing baby whatever, as long as it has all its fingers and toe-claws. But she also wants her little one to have every advantage she can give it. So when spring comes early, big brown bats prefer to keep their female embryos. Unwanted males are reabsorbed into their mothers' bodies as if they never existed.

University of Calgary biologist Robert Barclay learned the bats' secret by spying on three colonies living in the charmingly named city of Medicine Hat, Alberta. The bats roost in the attics of elementary-school buildings. Over the course of 15 years, Barclay snagged the bats in nets at night or plucked them from their roosts among the attic beams to examine them.

Since females return to their birth colony every year to breed, while males disperse, these colonies mainly held mothers and babies. Barclay was able to track which females were pregnant and what kinds of babies they had--and when.

"When" turned out to be the important question. Overall, the Eptesicus fuscus bats gave birth to equal numbers of male and female babies. But certain springs turned out a glut of girl bats, nearly twice as many as boys. By later in the summer, the ratio evened out again.

What was special about these girl-heavy springs, Barclay found, was that the whole colony gave birth earlier than usual. "The entire birth period shifts from year to year, depending on the weather," he wrote in an email. "When it is cold and damp in the spring and there are not many insects for the bats to feed on, the pregnant mother bats drop their body temperature to save energy and wait out the bad weather." This waiting period is called torpor, "a sort of shorter version of hibernation," Barclay says. In addition to lowering the mother's body temperature, it slows the growth of the embryo inside her. It was in the warmest springs, when mothers could end their torpor early, that they favored girls.

Biology says that mothers should skew the sex ratio of their offspring when it will let them pass on their own genes most effectively. A male baby bat won't give his mother any grandchildren until his second year of life, regardless of when he's born. However, "if a mother gives birth to a female baby early enough in the summer for it to be able to grow and put on enough fat for the winter," Barclay says, "that baby will be able to produce her own baby the next summer, as a 1-year-old." Having an extra year's worth of grandchildren is a major evolutionary benefit for a mother bat.

What gives girls a head start on reproduction is the bats' weird way of breeding. Mating happens in the fall and winter, while the bats born that spring and summer are still juveniles--and the young males haven't yet started making sperm. But female bats don't ovulate until the spring. At that point, the male contribution she's stored all winter finally fertilizes her eggs. This means female bats, if they're born early enough, can ovulate and give birth within their first year of life.

Big brown bats have just one baby at a time. But several eggs are fertilized and implant in the mother at once. At some unknown point during gestation, she reabsorbs all but one of those developing embryos into her body. However it happens, evolution has given mother bats the power to choose a female embryo over the others when spring arrives early.

Bats are far from the only species capable of skewing their babies' sex ratios. Other mammal and bird species have been observed giving birth to extra male or female offspring at certain times, depending on their own set of influencing factors. Even humans, it's been suggested, can bias their birth ratios based on life expectancy or parents' wealth or the weather. The mechanisms are mysterious, but evolution will always favor moms whose children produce more grandchildren.

Whatever secrets they're still keeping, the attic bats have taught their young downstairs neighbors a few things about biology. "When we worked in the schools we would give talks to the students about bats, the importance they have in the environment, and how cool it was that they had bats right in their own school," Barclay says. "We frequently had kids come in the evening to watch the bats as they exited to go and feed." One of the hundred-year-old schools is named Elm Street, as in Nightmare on. "A great place to study bats on a dark, moonless night!" Barclay adds.

Even spookier than attic bat colonies is the reminder that our species' whole evolutionary history had a hand in determining whether we were born. We, and the bat babies, should probably thank our moms.

Barclay, R. (2012). Variable Variation: Annual and Seasonal Changes in Offspring Sex Ratio in a Bat PLoS ONE, 7 (5) DOI: 10.1371/journal.pone.0036344

Images: Big brown bat by cotinis/Flickr; school building by Robert Barclay.

Blogday Octopus

2012-05-09T17:36:00.000-05:00

Thank goodness my office octopus was watching the calendar, or else I would have missed my second blogday entirely.

It's been quite a couple of years. I've stayed up late writing about missing snow and synesthesia; I've gotten up early to search for images of drunken flies, problem-solving crows, and mustached monkeys. I yawned roughly nine thousand times while working on a story about yawning triggers, and ruined two meals working on a piece about placenta eating. I may have covered every breaking news story in the field of poop.

And every day I've been surprised and happy to see you--yes, you--reading, sharing, commenting, liking, tweeting, Stumbling and Digging (the last two are especially appropriate, given my propensity for poop stories). Thank you.

If you want to celebrate with Octopus and me, why not comment on a post sometime? We'd love to hear your voice. Or send a story to a friend! The more the merrier, as I'm pretty sure they say under the ocean. Unless you're a top predator species or something that lives alone under a rock.

Why a Sperm Cell Is Like a Roomba

2012-05-08T09:05:00.002-05:00

A sperm cell, much like an expensive robotic vacuum cleaner, is a minimally intelligent body on a mission. Both the Roomba and the male gamete have to navigate a walled space without much idea where they're going or why. And although it won't clean your floors on the way, the sperm cell uses some of the same strategy as the robot vacuum.

To discover the set of rules that sperm cells steer by, researchers used--what else?--sperm mazes. Led by fluid dynamics researcher Petr Denissenko at the University of Warwick, a group of scientists in the United Kingdom built hair-thin tunnels in various shapes. Then they sent human sperm into the curving or zigzagging tunnels. A camera watched through a glass wall on each channel to see what paths the tiny explorers took.

In a narrow tunnel, frantically swimming sperm soon come up against a wall. Then, the camera showed, they follow that wall, seeming to keep their heads against it as they swim. (This same trick will get you out of a corn maze if you're lost, though you might want to keep a hand on the wall instead of your head.)

Wall-following is also one of the rules used by a Roomba. In the case of the robot, it ensures that the edges of the room and the base of the sofa get clean. In the case of sperm, wall-following keeps them moving in one direction as they trace the twists and folds of a fallopian tube.

But sperm aren't experts. When the wall takes a sharp turn away from them, sperm often don't notice; they simply shoot off in the direction they were already swimming. Luckily, they'll find another wall soon. "There are no large open spaces in the reproductive tract," Denissenko says.

Not all sperm are equally spacey about following walls. When the path bends, some follow it better than others. If future research finds a connection between wall-following skill and sperm success--are better navigators also better fertilizers?--then fertility doctors might be able to sort out the best sperm using mazes.

Knowing the rules that sperm swim by also means doctors can coax all of them to travel in the same direction. Denissenko and his coauthors built another maze, shaped like a wreath of grapes, that herds sperm into U-turns until they're all swimming one way.

Roombas use other rules that sperm don't. For example, a Roomba knows to avoid cliffs, a hazard human sperm are unlikely to encounter since there are no staircases inside a human.

Sperm have their own rule too: When they collide with each other, they swim off in different directions. Is this a trick for getting out of traffic? And how do sperm cells know they've hit a fellow swimmer, rather than a wall? Scientists aren't sure yet. "Understanding the role of collisions is really on my to-do list now," Denissenko says.

Like cat-harassing robots, humans' own little automatons rely on a few simple algorithms to do their job. It's nice to see that these seemingly clueless cells know a thing or two. Now if only they'd take on some household chores.

Denissenko, P., Kantsler, V., Smith, D., & Kirkman-Brown, J. (2012). Human spermatozoa migration in microchannels reveals boundary-following navigation Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1202934109

Image: IBRoomba/Flickr

Hearing: Your Other Sense of Touch

2012-05-03T10:05:00.001-05:00

Those of us without prehensile ears tend to think of our senses of hearing and touch as separate. But our sensory abilities overlap with each other more often than our kindergarten teachers let on. Our sense of smell gets help from our vision centers. Tasting food is mostly done with our noses. And a new study says hearing is just another sense of touch. The same genes can make you good--or deficient--at both.

Hearing a bird chirp and picking up a pencil from your desk, though they seem like wildly different tasks, are really the same trick performed by your body twice. Cells that receive physical input from the outside world (the edge of the pencil against your fingertips, or the vibration of sound waves rattling your inner ear) have to turn that information into an electrical signal and send it back to your brain.

So researchers in Germany guessed that the same genes affect both senses, in people as well as in other vertebrates. They used human subjects to ask the question in several different ways.

First, the team studied a group of more than 500 hearing subjects. In a battery of tests, people listened to tones and clicks, responded to tiny vibrations on their fingertips (measuring their touch sensitivity), and felt surfaces with narrow ridges (touch acuity).

There was plenty of variability in subjects' hearing and touch abilities. Both senses clearly grew worse with age. And in many of the tests, women outperformed men. These data let researchers chart how a healthy person's senses should act throughout their lives.

Then 100 pairs of twins came in for testing. Geneticists love twins: Identical sets have all the same genes, so any differences between them must come from somewhere outside their DNA. Fraternal sets share about half their genes, but are the same age and grew up (usually) in the same environment, so they can be easily compared to identical twins.

Subjecting the twin sets to the same tests, the researchers saw that touch sensitivity and touch acuity both have major genetic components, just like hearing does. And they saw that the two senses correspond to each other: People with good hearing are more likely to have good sense of touch too.

What about people with bad hearing? The researchers recruited another set of 39 teenagers and young adults from a school for the hearing impaired. About a fifth of the deaf subjects had "very poor touch performance."

There are plenty of genetic and non-genetic reasons people are born deaf, and the researchers don't know which of these factors were present in their subjects. But it seems that for some hearing-impaired people, whatever damaged their hearing did the same to their sense of touch. The simple explanation is that the same genetic mutation affects both senses.

Finally, the researchers examined a group of subjects with an illness called Usher syndrome that causes deafness and blindness. Scientists know of several genes that are involved--a mutation in any one of then can cause Usher syndrome. The German team found that patients with a certain Usher gene mutation also had significantly worse touch acuity than normal.

The twins and the deaf young adults showed that hearing and touch go along with each other, seeming to rely on shared genes. The Usher syndrome patients let researchers go a step further and identify one specific gene that affects both senses. "Both senses require cells that convert tiny changes in mechanical force into an electrical signal," said senior author Gary Lewin. "Genes may code for proteins that play a similar role in this process in the two types of cells." In other words, if our cells use the same genes for hearing and touch, they may also share a set of molecular tools.

I asked Lewin whether science is on the path to trimming down our number of senses. If we begin to understand hearing and touch as one mechanism, and if taste barely exists without smell, do we really have three senses? "No, I think we will stick with five and even more senses," Lewin said. "The cellular mechanisms and the way these different sensory cells are connected are highly unique."

Even so, our sensory skills continue to surprise us. Our kindergarten teachers may not have been wrong, but our understanding of human senses is growing up.

Frenzel, H., Bohlender, J., Pinsker, K., Wohlleben, B., Tank, J., Lechner, S., Schiska, D., Jaijo, T., Rüschendorf, F., Saar, K., Jordan, J., Millán, J., Gross, M., & Lewin, G. (2012). A Genetic Basis for Mechanosensory Traits in Humans PLoS Biology, 10 (5) DOI: 10.1371/journal.pbio.1001318

Image: AiyaHMPH/Flickr

Math Shows Today's Writers Are Less Influenced by the Past

2012-04-30T14:01:00.000-05:00

When Charles Dickens wrote It was the of, it was the of, the immortal first words in A Tale of Two Cities, he can't have imagined that 21st-century computer scientists would parse his prepositions and pronouns as part of vast literary data sets. But today's researchers are studying the unimportant words in books to find important literary trends. With the meaty words taken out, language becomes a numbers game.

To see how literary styles evolve over time--a science dubbed "stylometry"--researchers led by James Hughes at Dartmouth College turned to Project Gutenberg. The site contains the full text of more than 38,000 out-of-copyright books. Researchers began their mining expedition by digging out every author who wrote after 1550, had a known date of birth and (when relevant) death, and had at least 5 English-language books digitized.

These criteria gave the researchers a set of 537 authors with 7,733 published works. But they weren't interested in every word of those books. Nouns and adjectives were out: No Kareninas or Lolitas, nothing nice or bad or beautiful, no roads or homes or people. Most verbs were out, except for forms of the utilitarian to be. No one could speak or walk or Fly, good Fleance!

It may seem that the researchers were stripping all the information-containing words out of the sentences, and in fact that was their goal: "Content-free" words were all they wanted. The 307-word vocabulary that remained from the books was mostly prepositions, conjunctions, and articles.

This linguistic filler, the little stitches that hold together the good stuff, is known to contain a kind of authorial fingerprint. We may not think much about these words when we're writing or speaking, but scientists can use them to define our style.

Hughes and his team used computer analysis to score each author's similarity to every other author. They found that before the late 18th century, authors's stylistic similarity didn't depend on how close to each other they lived. (Each author was represented by a single year, the midpoint between his or her birth and death.) During this time period, authors who lived in the same generation didn't influence each other's styles much more than authors who lived hundreds of years away.

But from the late 18th century to today, it was a different story. Stylistically, authors were more similar to their contemporaries than to other writers. By the late 19th century, writers closely matched the style of other writers who lived at the same time (at least according to the computers tallying up their non-content words). This influence dropped off outside of 30 years. In other words, authors who lived more than three decades away each other may as well have lived centuries away, for all the similarity between their writing.

Looking at more recent books, that window of influence seems to become even tighter. Among authors from the first half of the 20th century, the similarity of style drops off beyond just 23 years.

Over time, authors have become more and more influenced by the other authors writing at the same time. The researchers say this may simply be due to the number of books published. In the early part of their dataset, there were few enough books around that a studious person could read, well, most of them. But as more and more books were published, contemporary books made up a larger share of what was available to read. Authors have filled more and more shelves in their libraries with books by their peers--and this has made them more likely to echo each other's styles.

Because Project Gutenberg relies on public-domain material, there weren't very many authors after the mid-20th century included in this study. Looking forward, "You would expect a continued diminishing of influence," says Daniel Rockmore, the paper's senior author. Contemporary books take up an ever greater portion of what's available to read. In addition to the huge number of books published each year (more than 288,000 in the United States in 2009), there are now e-books and e-readers and Japanese Twitter novels.

A century from now, we may be able to look back and see that today's authors had an ever-condensing frame of influence. Of course, by then literary styles might only last a week. Most books will be forgotten, but every author will be a revolutionary.

James M. Hughes, Nicholas J. Foti, David C. Krakauer, & Daniel N. Rockmore (2012). Quantitative patterns of stylistic influence in the evolution of literature PNAS : 10.1073/pnas.1115407109

Image: Library of Congress from ep_jhu/Flickr

Baby Corn Plants Recruit Helpful Bacteria Posse

2012-04-27T10:30:00.001-05:00

When you're a newly sprouted corn seedling, all alone in the dirt, you need any advantage you can get. After all, you can't pick up your roots and travel to find resources or avoid pests. That's why corn plants emit toxic chemicals that keep away hungry insects aboveground and harmful microbes below. But to at least one kind of bacteria, this poison is more of a beacon. They follow the toxic trail back to the corn plant, set up camp in its roots, and help the vulnerable seedling grow.

A plant's roots are the center of a miniature ecosystem called the rhizosphere. Local bacteria feed on sugars and proteins that trickle out of the roots, like antelopes at a watering hole. Symbiotic fungi enmesh themselves in the plant's roots. Helpless as it may appear, the plant can even release chemicals that encourage certain microbes to live there and discourage others, or prevent competing plant species from growing nearby.

Researchers in the United Kingdom studied one of the toxic chemicals released by the roots of corn plants. The compound is a benzoxazinoid, mercifully abbreviated as BX. Seedlings of corn and other grasses secrete BX molecules to protect themselves from pests and harmful microbes.

But the team, led by Andrew Neal at Rothamsted Research, suspected that certain bacteria weren't bothered by the toxin at all. Neal says this was a bit of a "leap of faith." Many bacteria that are used to clean pollutants from soil are closely related to bacteria that colonize plant roots. And some of the toxins that plant roots produce are similar to these pollutants. So the team asked whether Pseudomonas putida--"one of the best root colonizers we know of," Neal says--might be resistant to plant toxins.

The researchers first took both the plants and bacteria out of the soil to see what was going on. They found that corn seedlings produce the most poison at one week old, protecting themselves at their most vulnerable stage of growth. Over the next couple of weeks, production drops off.

Testing P. putida bacteria, they saw that the concentration of BX molecules around a seedling's roots didn't hurt the bacteria at all. But another common soil bacterium had serious trouble growing, even at a much lower concentration of the toxin. The chemical also broke down more quickly in the presence of P. putida, suggesting that the bacteria might not only tolerate the poison, but eat it.

Next Neal and his coauthors turned to the genes of P. putida to see which ones are most active when the toxic chemical is around. A few dozen genes popped up. Some of these had to do with "chemotaxis," a trick in which bacteria use their wiggly arms to travel toward a high concentration of a chemical they like. Were P. putida bacteria actively seeking out the toxin and the corn roots that released it?

Further experiments showed that the bacteria do, in fact, travel toward areas with more BX molecules. And in the soil, corn seedlings making the toxin attract more P. putida to their roots. (Genetic mutants that can't make BX molecules attract fewer bacteria.) The effect fades by the time the plant is three weeks old.

This is the first time scientists have seen an otherwise toxic root chemical attracting helpful bacteria. A corn plant that has successfully recruited P. putida has a leg up--or a root up--in its development. These bacteria and other friendly microbes keep harmful bacteria away by crowding them out and producing antibiotics against them. They also help the plant reach nutrients such as iron and phosphorous in the soil. The bacteria, too, have an advantage over other microorganisms in the area because they can tolerate the plant's toxin and may even eat it.

Neal says that through breeding, some crops have lost their ability to generate this chemical. "Modern varieties of cereals such as corn, wheat, barley, etc., now produce widely varying amounts of the benzoxazinones we studied," he writes. "Some produce quite a lot, others produce none." Neal hopes this research has shown why BX production is a helpful trait for plants to have.

Today's breeders, better informed about what goes on beneath the soil than their predecessors, may want to create new crop varieties that can once again make their own toxins. Plants that generate BX molecules can inhibit pests and diseases--and call friendly bacteria to their aid. We might be able to use fewer pesticides and fertilizers if we let our crops' bacterial helpers help us, too.

Neal, A., Ahmad, S., Gordon-Weeks, R., & Ton, J. (2012). Benzoxazinoids in Root Exudates of Maize Attract Pseudomonas putida to the Rhizosphere PLoS ONE, 7 (4) DOI: 10.1371/journal.pone.0035498

Image: Noël Zia Lee/Flickr

Life Advice: Think More about Death

2012-04-24T11:35:00.000-05:00

The other kids on the school bus used to shriek when we stopped at my house. Or hold their breath. I lived directly across the street from a cemetery, and until I started riding the bus I had no idea this was supposed to be scary.

My parents claim that the realtor who sold them the house, perhaps out of desperation, told them people were "dying to move in!" I was aware of our deceased neighbors but unbothered by them. My dad explained how visitors to the Jewish graveyard put stones on top of the grave markers to show respect, so I pocketed small rocks on our walks there and left them on lonely-looking headstones. Friends came over for the best sledding in the neighborhood. (My baby sister, though, didn't immediately grasp the concept. One day while a funeral went on outside, my parents asked her what she was watching out the window. She answered, "All those people are lined up waiting for their turn to die!")

Psychologists have put a great deal of study into how reminders of mortality affect people. They call it "terror management," assuming that most people view death like those kids on the bus viewed my street: It's gross and we want to be far away from it. So we build up psychological protections for ourselves, which of course are not any more useful than holding our breath but make us feel better.

A new paper published in Personality and Social Psychology Review looks over the accumulated evidence and concludes that thinking about death can make your life better. Previous terror management research has focused on the dark side of our psychological protections: Psychologists say that reminders of death can make us more hostile toward people we see as outside our own group. But researchers led by Kenneth E. Vail III at the University of Missouri, Columbia, say the perks of morbid thinking are too great to ignore.

Conscious reminders of death can encourage people to stay healthy and pursue their goals. In various studies, subjects smoked less, planned to exercise more, and were more conscientious about sunscreen after being made to think about death.

When people were asked to list their goals immediately after answering questions about death, they placed more importance on what psychologists call "intrinsic" goals--those related to relationships and personal growth, for example, rather than wealth or attractiveness. But after a delay, they went back to those "extrinsic" (shallower) goals. People who were asked to do daily contemplations of mortality for a week also put greater importance on intrinsic goals.

Other studies have looked at what happens when people are primed subtly to think about death. In an experiment with an elaborate setup designed to seem accidental, subjects walked through a cemetery (or not) and overheard a person talking on a cell phone about "the value of helping." A little while later, subjects saw a second person drop a notebook. Those people walking through the cemetery seemed to be more receptive to the helpfulness hint, and were much more likely to stop and help the struggling passerby. Similar experiments got subjects to feed the homeless, donate to sick children, or help disabled people by reminding them of death.

Thoughts about dying may strengthen our bonds to others, too. Studies have found that after reminders of mortality, people feel more committed to their romantic relationships and strive more for intimacy. They're also more inclined to have children.

Tapping into the benefits of our fear of death, the authors say, could make people "more inclusive, cooperative, and peaceful." The downside of our psychological response to death is hostility toward outsiders. But as long as people view themselves as part of a larger community, thinking about our mortality can encourage us to clean up our acts. We may be more helpful to others, more committed to our relationships, more focused on healthy habits, and more thoughtful about our long-term goals.

The healthy side effects of dwelling on death inspired game designer Jane McGonigal to create a game called Tombstone Hold 'Em.* She's organized large-scale events in cemeteries around the world. During a game, competitors pair off and race around a graveyard to find the best "hand" made out of two tombstones. The game is built to tap into the psychological plus-sides of working with a group, running around outside, and--yes--thinking about dead people.

Not everyone believes turning a graveyard into a giant poker game is a good idea. Tombstone Hold 'Em stirs some controversy among people who think frolicking among one's deceased neighbors is disrespectful. But McGonigal thinks respect for the dead can come from positive experiences we have while we're around them.

Consciously or not, we took the same tactic in my neighborhood, where families used to gather on top of the cemetery hill to watch Fourth-of-July fireworks. Parents stood between the tombstones while kids sat on top of them for a better view. The youngest ones got hoisted up to stand on tall stones, their parents' hands beneath their armpits for balance, so they could see the distant bursts. No one had to hold their breath.

Vail, K., Juhl, J., Arndt, J., Vess, M., Routledge, C., & Rutjens, B. (2012). When Death is Good for Life: Considering the Positive Trajectories of Terror Management Personality and Social Psychology Review DOI: 10.1177/1088868312440046

*I read about Tombstone Hold 'Em in Jane McGonigal's very interesting book about gaming, Reality Is Broken.

Image: Necropolis in Glasgow, Scotland, by me.

Dueling Birds Evolve New Egg Colors in Decades

2012-04-20T09:50:00.000-05:00

"Arms race" might seem like too dire a phrase for what's essentially an egg-dying contest. But for the two bird species hurrying to outwit each other, it really is a matter of survival. The stakes in this colorful competition are so high, in fact, that they drive evolution at a pace that's rarely seen.

The two birds in question reside in Zambia. One is the tawny-flanked prinia, a petite warbler. The other is the cuckoo finch, a species that's not a cuckoo at all but shares a habit with that family of birds. Some cuckoos are known for sneaking their own eggs into other birds' nests for their unwitting adoption, a tactic called brood parasitism. The cuckoo finch is a brood parasite too. Its target: the prinia.

How difficult it is for an interloping bird to drop off its egg for permanent babysitting depends on its host. Some brood parasites leave giant, obviously mismatched eggs in other birds' nests. Their only precaution is to toss one of the host bird's eggs away in exchange. The hosts, perhaps not bright enough to notice the difference, tend the egg and eventually feed the oversized baby bird alongside (or instead of) their own.

The cuckoo finch faces a bit more of a challenge, though. Prinias are adept at spotting mismatched eggs and booting them out of the nest. Their species has evolved to lay eggs with a wide range of colors and markings, but each individual female lays just one kind of egg. This makes it hard for a brood parasite to match her distinctive eggshell style, and easy for her to notice any mismatched eggs in the nest. Raising a cuckoo finch would be a costly mistake, taking resources away from her own young. (And the adopted bird might evict its siblings from the nest altogether.)

Cuckoo finches, in turn, lay eggs in a variety of colors and patterns similar to the prinia's. They have to spread these eggs around and rely on the odds that at least some of them will match their borrowed nests. This is the only way for their offspring to survive.

Claire N. Spottiswoode and Martin Stevens at the University of Cambridge asked whether competition between the tawny-flanked prinia and its parasite has created an evolutionary arms race. In each generation, prinias with unusual-looking eggs should be better able to avoid brood parasitism. And only cuckoo finches that can make new eggs to match will reproduce.

The researchers gathered eggs from both species in the wild. They also studied preserved eggs from a museum, which had been collected 20 to 30 years earlier. Using spectrophotometry and computer modeling, they analyzed how egg colors and patterns had changed over the decades--not just to human eyes, but as a bird would see them.

Even in the span of those few decades, both birds' eggs had changed color. For example, Spottiswoode said, most of the cuckoo finch eggs from 30 years ago are reddish (at least to our eyes), but are bluish today. The prinia today more often lays olive-green eggs, apparently staying one step ahead of its parasite. (At the top of this page, you can see the range of prinia egg colors in the outside circle and the range of cuckoo finch eggs inside.)

Cuckoo finch eggs from the past are a better color match to prinia eggs from the past, and cuckoo finch eggs from the present day match modern prinia eggs. This tells us the color shift over the past few decades was almost certainly not random. Instead, the two species are evolving in response to each other at an amazingly brisk pace.

The color shift hasn't just been in one direction, though. Both host and parasite eggs have become significantly more varied over the past 30 or so years, as if each species expanded the Crayola box it was working with.

But there's no way the birds could have kept up this expansion over thousands or millions of years of evolutionary history. They would quickly run out of colors. The authors speculate that instead, the two species are locked in an unending cycle.

First the color palette expands, as is happening today. Host birds with bigger Crayola boxes have an advantage at escaping parasites, and parasites develop more egg colors to keep up. But once colors get sufficiently wild, host birds that lay average-colored eggs have more of an advantage. When all the parasitic birds are laying eggs at the edges of the color spectrum, they can't match host eggs that are in the center of that spectrum. As the cuckoo finch catches up and starts laying boring-colored eggs of its own, extreme colors once again become beneficial for the prinia, and the cycle starts over.

In another few decades, maybe the prinia and cuckoo finch will be narrowing their palettes again. Forget fossil records: A cold war between host and parasite can drive evolution that's fast enough for us to watch in real time.

Spottiswoode, C., & Stevens, M. (2012). Host-Parasite Arms Races and Rapid Changes in Bird Egg Appearance The American Naturalist, 179 (5), 633-648 DOI: 10.1086/665031

Images: Egg rainbow, Spottiswoode and Stevens. Brood parasitism by a cuckoo, Per Harald Olsen/Wikimedia Commons.

Human Dung Wins Interspecies Taste Test

2012-04-17T13:42:00.000-05:00

A panel of experts in Nebraska has declared human dung more appealing than that of several other species. These experts didn't so much announce their decision as fall headfirst into baited poop traps while looking for a meal. Still, you won't find a more discerning group of judges than nine thousand dung beetles.

The various species of dung beetle that live together in the Great Plains region have evolved to consume, and share peacefully, its turd piles.* Some species are specialists, preferring one animal's feces to any others. Others will eat anything that falls their way. Two entomologists--Sean Whipple at the University of Nebraska, Lincoln, and W. Wyatt Hoback at the University of Nebraska, Kearney--set out to mess with the balance between these dung beetle species.

The researchers set traps all over a large organic cattle ranch. Each trap consisted of a large bucket sunken into the ground with a pile of dung at the bottom. The bait came from 11 different species that included carnivores, herbivores, and omnivores. Some of these dung flavors were ones the beetles might encounter regularly: bison, moose, cougar. Others were "exotic," from animals that don't normally leave their excrement around Nebraska: zebra, lion, human.

(The animal feces came fresh from a local zoo. As for the human specimens? "I will say this much," Sean Whipple said when I asked. "It is difficult to find volunteers for a study such as this.")

Human and chimpanzee feces were the clear winners of the popularity contest. Almost 9,100 dung beetles stumbled into the authors' traps, belonging to 15 different species. The beetles in the human and chimp dung buckets far outnumbered any of the rest.

Different beetle species preferred different types of dung, which explains how they can all share resources normally. But overall, omnivores were a favorite. Pig dung, while not as wildly popular as human or chimpanzee, still attracted a lot of beetles.

Whipple says the scent of omnivore dung is especially alluring. "Previous research has shown that the dung of omnivores is generally more attractive than that of herbivores, likely as a result of odor," he wrote in an email.

Incidentally, if the dung beetles had gotten a chance to eat all that sweet-smelling human dung, it would have been a good choice nutritionally. Chemical analysis showed that the human dung had the highest nitrogen content, a measure of "dung quality," Whipple says.

Herbivore dung wasn't only less popular than omnivore dung. It was also beaten out by carnivore dung. And the most widely ignored droppings came from bison--a species that local dung beetles evolved alongside, and that would have provided much of their diet just a century and a half ago.

Like five-year-olds who are bored with their green beans and would like some dessert already, please, most dung beetle species in this study were eager to switch from their usual plant-based poops to something new and exciting. They're not likely to start encountering a lot of human or chimpanzee feces on their Nebraska ranch. But a non-native animal that's introduced to an area where dung beetles live (and they live all over the world) could upset the balance between its native inhabitants. Beetles might start competing for the exotic food source, for example, or ignoring piles of poop they would ordinarily clean up.

If you're wondering what makes our own species' dung so appealing, the authors say diet doesn't seem to be a factor. Among the zoo animals whose dung they used, all the carnivores were fed the same diet, and so were the herbivores. But the dung beetles preferred some carnivore or herbivore dung to others, suggesting there's more to poop flavor than the food it started out as.

Though the human subjects may have eaten different diets, their specimens were "thoroughly mixed to ensure homogeneity," Whipple says. Now that's appetizing.

Whipple, S., & Hoback, W. (2012). A Comparison of Dung Beetle (Coleoptera: Scarabaeidae) Attraction to Native and Exotic Mammal Dung Environmental Entomology, 41 (2), 238-244 DOI: 10.1603/EN11285

Image: icadrews/Flickr

*Yes, I realize that three out of the last four posts here have involved poop (hyena, penguin, and that eaten by dung beetles). Apparently I'm in a dung rut. At least it's not a dung bucket.

Space Census Finds Extra Penguins, Poop

2012-04-13T13:19:00.000-05:00

Playing what might have been the world's most tedious game of Where's Waldo?, scientists used photos taken from space to count all the emperor penguins in Antarctica. They found more than a hundred thousand birds that hadn't been spotted before. The news may affect the penguins' fate in a warming world. Besides, what's a better surprise than extra penguins?

Researchers from several institutions, including the British Antarctic Survey in Cambridge, undertook the emperor penguin space census. They thought previous penguin counts might not be accurate. For one thing, the last estimate of the Antarctic penguin population is almost 20 years old. For another, humans can't easily travel very far from their Antarctic research bases to seek out half-frozen bird huddles. So penguin colonies that are farther out in no man's land might have never been spotted by people.

Thanks to emperor penguins' habit of clumping together in giant colonies during breeding season--and their convenient lack of camouflage against the snow--the researchers knew high-resolution satellite photos should reveal the penguins. They used images from all around Antarctica's coastline, where penguin colonies camp out. Forty-six colonies appeared, including several that hadn't been counted before.

A penguin colony on the Antarctic coastline, spotted from above.

After zooming in on each colony and sharpening the images, the researchers used computers to count the penguins one by one. The challenge was for the computer to decide which dark pixels represent penguins, rather than shadows on the snow--or penguin poop. Author Peter Fretwell explains that in this method, "you 'train' the computer to recognize the pixels that are penguin, guano, snow or shadow by giving it sample pixels. The computer then goes away and splits the whole image into each pixel type."

Zooming in on a penguin colony and sharpening the image. I think I found the guano.

As long as the images have a high enough quality, Fretwell says, this technique is "usually quite accurate." Where the satellite pictures were more shadowy, penguin counts would be a little less certain. For some of the colonies, though, researchers were able to check their numbers against estimates others had made from the ground or from aerial photography.

And then there were the missing penguins. All the satellite images were taken during the breeding season, when emperor penguins congregate to create adorable new baby penguins. The new parents take turns babysitting: While one penguin takes care of the chick, the other goes out to sea and swallows lots of fish to regurgitate later. While the chicks are small, they spend most of their time balancing on top of their parents' feet to keep warm. Once the chicks are old enough to walk around on their own, both parents may leave to forage.

So for every individual counted in a satellite photo, the authors assumed there was a hidden chick and a second adult at sea hunting for food. (They were only interested in counting breeding adults, not the chicks, most of which will die.) Later in the season, some of the penguin pixels may have been kids instead of adults. But since a young penguin standing on the ice probably has two parents away foraging, the researchers figured that pixel still stood for two adult penguins.

The final count was about 595,000 adult emperor penguins in all of Antarctica. That's roughly the (human) population of Milwaukee. It's also substantially higher than the last estimate, which put the population between 270,000 and 350,000 adult birds.

The census could easily have overestimated or underestimated the true number of penguins. But, Peter Fretwell says, "The main thing is that this gives us an initial benchmark from which we can monitor emperor penguin numbers in the long term."

As climate change tightens its grip on every part of the globe--all the way to the poles--penguins will certainly see some changes around them. The sea ice along the coastlines they inhabit will disappear; shifting food webs may make their prey scarcer; and severe storms might become more frequent. Knowing how many emperor penguins are there now, and where to find their colonies, will help scientists monitor how the species is coping with the changes. We might even be able to keep them from becoming harder to find than Waldo.

Fretwell, P., LaRue, M., Morin, P., Kooyman, G., Wienecke, B., Ratcliffe, N., Fox, A., Fleming, A., Porter, C., & Trathan, P. (2012). An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space PLoS ONE, 7 (4) DOI: 10.1371/journal.pone.0033751

Image: Close-up penguins from Hannes Grobe/AWI/Wikimedia Commons; satellite images from Fretwell et al.

Note for British readers: You may know Waldo as Wally.

Google Searches Give Away a Country's GDP

2012-04-10T09:59:00.001-05:00

Anytime we travel through the Internet we leave piles of data behind us, like Pigpen shedding his cloud of filth. It's too bad if you're concerned about privacy. But if you're a mathematician, that heap of dirt is more like a goldmine, and digging into it can turn up unexpected nuggets. A study of worldwide Google searches, for one thing, reveals that people in wealthier nations think less about the past.

Google collects data on what search terms people around the world are using. Researchers who want to use this data to compare search terms across different countries are usually restricted to places that share a language. But the authors of a new paper in Scientific Reports got around that problem by looking only at numerical search terms.

"We realized...that years represented in Arabic numerals are an almost universal written representation," author Helen Susannah Moat wrote in an email. By looking only at search terms such as 2011 or 2010, she and her coauthors could compare search data from nearly the whole globe.

"It seemed a logical first step to consider to what extent Internet users were searching for dates in the future compared to dates in the past," Moat says. For example, looking at data from 2010, the researchers compared searches including 2011 to those including 2009. The ratio of forward-looking to backward-looking searches in each country became its "future orientation" score.

The authors culled data from 45 countries with substantial Internet-using populations. Then they sorted those 45 countries by GDP ("also the most obvious variable," Moat says). A clear pattern popped out of the numbers: Countries with lower GDPs had lower future orientation scores, and vice versa. People in poorer countries did more searches concerning the previous year; those in wealthier nations searched more for the next year. The trend was strong, and it held up in data from 2009 and 2008 as well.

Countries with the lowest future orientation scores included Pakistan and Vietnam, where previous-year searches outnumbered next-year searches by a factor of three or four to one. In the United States and Canada, countries toward the higher end in future orientation, searches for the last year and the next year were roughly equal. Switzerland, Australia, and the United Kingdom were among the most forward-looking countries of all.

"One of the possible interpretations of our results," Moat writes, "is that a focus on the future supports economic success." In other words, populations that are more forward-thinking become wealthier. This up-by-the-bootstraps explanation doesn't seem like the simplest one, though.

Another possibility is that populations with more money and leisure time can afford to spend it thinking about the future. A person in a wealthier nation might search online for next year's concert tickets, dates of work holidays, or when the new iPad is coming out. Someone without disposable income, though, might not have many such events to look forward to.

Here's some good news for people in all nations: Google Trends is available online for aspiring data analysts to play with. Panning for gold in its graphs won't cost anything except your free time.

Preis, T., Moat, H.S., Stanley, H.E., & Bishop, S.R. (2012). Quantifying the Advantage of Looking Forward. Scientific Reports, 2, 350. DOI: 10.1038/srep00350

Hyenas Fast During Lent Too

2012-04-06T10:41:00.000-05:00

Carnivores that shape their lives around humans may find themselves following human calendars. And that includes our religious observances. In Ethiopia, spotted hyenas eat meat scraps left by humans for most of the year. But when those humans go vegan for Lent, the hyenas become hunters.

You might not expect dietary discretion from spotted hyenas, as they're possibly the world's least picky eaters. They're just as happy to scavenge on found carcasses as to kill their own meat. They've been observed devouring all kinds of mammals, birds, fish, and reptiles--not to mention garbage, dung, and carcasses infected with anthrax spores. The hyena's digestive system even handles bones without a problem. Hair and hooves are the only remains left after a thorough hyena meal.

But in northern Ethiopia, where populations of their natural prey are severely depleted, spotted hyenas rely on humans for food. Not that they eat humans, that is. Hyenas scavenge animal remains that Ethiopians dump outside their compounds, and since they stay away from the people supplying those carcasses, human and hyena tolerate each other's company. (At a veterinary school, humans even count on hyenas to keep the campus clean.)

There's just one hitch for the hyenas. The population in this part of the country is primarily Orthodox Christian. The Ethiopian Orthodox Tewahedo Church dictates fast periods throughout the year, the most prolonged of which is the eight-week Lent. During this period, Christians give up all meat, dairy and eggs to follow a vegan diet.

Researchers led by Gidey Yirga at Ethiopia's Mekelle University set out to see how the Lenten fast affected local hyenas. At sites around Mekelle, they collected hyena scat on the first day of Lent (representing what hyenas ate beforehand); the last day of Lent (for what they ate during the fast); and 55 days later (after a return to their normal diet). By digging animal hairs out of the hyenas' feces, researchers could identify the species that had made up their meals.

A wide variety of animals were represented in the hyenas' dung, including livestock such as sheep, goats, donkeys, cattle, and horses. (In the study areas, livestock outnumber humans.) And the hyenas' diet had significantly changed during Lent. With their usual supply of leftovers lacking, hyenas' scat showed that they had feasted on donkey meat.

The authors explain that live donkeys are an easy target for hungry hyenas because, unlike other livestock, their owners leave them outside the compound at night. Additionally, "weak donkeys are abandoned altogether, which makes them a relatively easy food source."

With plenty of hapless donkeys around, the hyenas weren't exactly facing hardship during Lent. But they adjusted their behavior with impressive ease. During Lent, the hyenas became active hunters, taking down live animals to feed on. After Lent, they returned to scavenging trash.

The flexibility of predators such as hyenas means that removing a food source might be a good way for humans to change animals' behaviors. The hyenas in this study don't harass people too much. But when the predators hanging around your city (or your livestock) are lions, it can help to know how to get them on a different diet.

Hyenas' adaptability also means humans aren't the only ones that can follow a different diet from one calendar period to the next. But outside of the fasting seasons, hyenas are probably relieved to get back to the comfort of a pre-killed meal. And when Easter arrives, the donkeys might be the happiest of all.

Yirga, G., De Iongh, H., Leirs, H., Gebrihiwot, K., Deckers, J., & Bauer, H. (2012). Adaptability of large carnivores to changing anthropogenic food sources: diet change of spotted hyena (Crocuta crocuta) during Christian fasting period in northern Ethiopia Journal of Animal Ecology DOI: 10.1111/j.1365-2656.2012.01977.x

Image: Rob Willock/Flickr

Dinosaur Age Not Dramatic Enough? Add Fire

2012-04-03T10:23:00.001-05:00

As if a world dominated by hungry, house-sized lizards weren't sufficiently exciting, scientists have added another set piece to our image of the Cretaceous: raging wildfires.

The Cretaceous period, which ended about 65 million years ago with the extinction of the dinosaurs, was hot. That's thanks to volcanos that pumped carbon dioxide into the atmosphere and created a greenhouse effect. Researchers from London and Chicago now say it was also a "high-fire" world. Frequent blazes may have kept animals on the run, created some of the fossil beds we study today, and helped determine which plant species survived into the next era.

Led by graduate student Sarah Brown from the Royal Holloway University of London, the researchers tracked the appearance of charcoal in ancient sediments. Like a set of sooty footprints right through the fossil record, the charcoal evidence showed when and where fires had occurred.

The team saw that wildfires had increased during the Cretaceous period. These fires were probably sparked by lightning, and their flames were fanned by the high concentration of oxygen in the ancient atmosphere. Today, oxygen makes up about 21% of our air. But during the Cretaceous, it may have risen as high as 25% or more.

This high oxygen content, the authors say, would have allowed plants to burn without being bone dry. A spark in a green forest, instead of dying out as it would today, might become a full-blown fire.

Brown and her coauthors did not find any evidence that these fires contributed to killing off the dinosaurs. But they note that after a fire burns through a piece land, erosion is likely. There may be rapid flooding or mudslides. In the Cretaceous, these events might have trapped and killed dinosaurs and other animal life--and helped preserve their bones.

The authors point to certain fossil beds that lie in floodplains and contain charcoal, as well as plant and animal remains. These could be sites where wildfires triggered flooding, conveniently sweeping lots of informative fossils into one place for future scientists to find.

Charred plant remains in these fossil beds provide another clue about the effect of fire. As the Cretaceous went on, the types of plants being fossilized gradually changed. Flowering plants, called angiosperms, became more and more common. Gymnosperms--the more ancient, flowerless species such as cone-bearing trees, cycads, and ginkgos--faded into the background.

A charred flower fossil from the Late Cretaceous.

Frequent fires may have given an added edge to the angiosperms. The new types of plumbing these plants had invented let them grow faster and more efficiently. Rather than trees, the flowering plants growing during the Cretaceous seem to have been weedy and shrubby types. After a fire, they could regrow faster than the gymnosperms. And their new growth provided fresh fuel for wildfires, creating a cycle that encouraged the growth of flowering plants and left older models in the dust.

Though fire didn't do in the dinosaurs, then, it may have helped set the stage for the dominant plants of the modern age. (As if we needed any more drama.)

Brown, S., Scott, A., Glasspool, I., & Collinson, M. (2012). Cretaceous wildfires and their impact on the Earth system Cretaceous Research DOI: 10.1016/j.cretres.2012.02.008

Images: Gorgosaurus from Nobu Tamura/Wikimedia Commons; flower fossil from Brown et al.

The Plus Side of Eating Placenta

2012-03-30T12:54:00.000-05:00

He's not suggesting new parents pause in the delivery room to whip up a placenta sandwich. But neuroscientist Mark Kristal says human mothers might be missing out on the benefits other mammals receive from gobbling up their afterbirth. With luck, there might be a way for us to take advantage of placenta power that's not totally disgusting.

Mark Kristal is a professor at the University of Buffalo who's been studying the practice of placenta eating--or placentophagia, if you want to bring it up in polite company--for more than 40 years. His interest in the subject sprang from his study of maternal behaviors in mammals giving birth. "I had the field to myself," he said in an email.

And he knows it's gross. "Unfortunately, people often ask me what my research is on during dinner," he says. "It always gets a laugh (and a gag)."

Humans, with the exception of some naturopaths and celebrities, don't eat placentas. But that makes us nearly alone among mammals. From rodents to cattle to apes, new moms turn to the business of eating or licking up the afterbirth, including the liver-like placenta, as soon as the baby is out.

In a new review paper (soon to be available here), Kristal and his coauthors discuss the potential benefits of placentophagia for mammals that practice it, as well as for mammals that don't (us). There are several practical reasons why animals might ingest their placentas. Maybe they want to hide the odor of blood from predators, for example, or to keep their nests clean. Maybe mothers are famished after the ordeal of giving birth, or perhaps the placenta replaces nutrients that were depleted during pregnancy.

Though some of these explanations fit subgroups of mammals, none of them works universally. So Kristal thinks there must be a more basic evolutionary explanation for placentophagia. If almost every mammal does it, the simplest explanation is that they do it for the same reasons.

One intriguing possibility, and the strongest lead researchers have so far, has to do with pain. In the 1980s, researchers discovered that female mammals' bodies produce pain-relieving endorphins during labor and delivery. Studying rats, Kristal found that eating the placenta increased the effect of these endorphins. The placenta didn't dampen pain on its own. But rats that ingested placentas felt less pain, because they responded more strongly to their bodies' own pain relievers.

The effect also works with morphine, a similar pain suppressant. Rats that ate placenta, or amniotic fluid, experienced greater pain relief from morphine. Kristal found that the pain-relief-enhancing effect of afterbirth works in male rats, too, and in animals of other species. It also worked when researchers fed rats with human placentas.

This suggests human placentas have the same health benefits as other mammals'. So why do humans, alone among land mammals, deny ourselves the pleasures of eating placenta? It's possible, Kristal says, that evolution destroyed our appetite for afterbirth for a good reason. Maybe it has to do with toxins caught in the placenta as the organ filters them out of the fetus's environment. Or maybe extra-painful childbirth was helpful in human evolution because it encouraged women to help each other through delivery.

Kristal thinks that with further research, scientists can identify the ingredient in placenta that enhances pain relief from morphine or endorphins. Then the compound can be made in the lab and used as a drug--for all kinds of pain in males and females, not just childbirth.

These days, a few women who have gotten wind of the potential advantages of placentophagia are experimenting with it themselves. But they're interested in more than just pain relief. There are claims that eating one's placenta cures conditions ranging from postpartum depression to nursing difficulties.

Though such claims aren't backed up by any research, Kristal is interested in these same postpartum problems--which, he says, are uniquely human. Sure, other mammals sometimes go so far as to kill and eat their newborns. Rodents, for example, are tempted to ingest everything that comes out of them during delivery, baby included. But a healthy newborn will get its mother's attention by moving around and making noise. Other mammals only eat their young after an extremely stressful pregnancy.

Kristal says none of these behaviors, though, are parallel to the human problems of postpartum depression or an inability to bond with one's baby. If scientists could pinpoint the mechanisms that cause these issues, they could then start asking whether any element in the placenta might help treat them.

While science lags behind, eager placenta-eaters are going ahead with their own methods. Actress January Jones recently outed herself as a fan of placenta pills. After delivering her son, she had her placenta dried and made into capsules. Pill poppers are also featured in this gruesomely detailed 2011 New York Magazine article about placentophagia. (Focused on trend-conscious Brooklynites, the story contains the horrifying sentence, "I threw a chunk of placenta in the Vitamix with coconut water and a banana.")

Mark Kristal gets emails "all the time" from women who have tried placentophagia, he says. Without exception, they all insist it helped them.

But the claims of placentophagia fans are the same regardless of how much placenta they ingested, when they took it, or how they prepared the organ (cooked? raw? encapsulated? smoothied?). And it's unlikely that any real medicinal effect of the placenta could be so universal. For example, experiments have shown that placenta loses its pain-suppressing power when it's heated.

It's more likely that the benefit human women report from eating their afterbirths is the benefit of placebo. The ability to make women feel that they're tapping into a primal force to keep themselves healthy may be the real power of placenta.

Mark B. Kristal, Jean M. DiPirro, & Alexis C. Thompson (2012). Placentophagia in Humans and Nonhuman Mammals: Causes and Consequences Ecology of Food and Nutrition

Image: avlxyz/Flickr (Note: This is a picture of someone's French toast remains. Not placenta.)

Adorable Lemur's Sordid Nightlife Revealed by Lice

2012-03-27T10:24:00.000-05:00

How do you study the social habits of an animal that's shy, comes out only at night to scurry through tree branches in dense jungles, and is the size of an M&M packet? You could try talking to its body lice.

The brown mouse lemur (Microcebus rufus) is an almost supernaturally adorable primate that lives in Madagascar. Thanks to its tininess and hard-to-access habitat, scientists don't know much about its behavior. So to get the scoop on the lemur's social life, a group of researchers turned to the lemur's less adorable companion: the louse Lemurpediculus verruculosus.

This louse is much like the ones you're familiar with. It clings to a host's hairs while sucking its blood, and is happy to switch hosts if another animal comes in close physical contact. The brown mouse lemur's louse lives mainly on the primate's ears, where fur is sparser and skin is easy to reach. It also hangs out on lemurs' eyelids and testes.

(I declined the authors' advice to "See Figure S1a for an image of the lice observed on the testes.")

Led by Sarah Zohdy from the University of Finland, researchers trekked into the jungle and placed traps for mouse lemurs, baiting them with fresh banana. During their study period, they managed to catch 32 of the elusive primates. On each lemur, the researchers did a thorough lice check with a comb, like a kindergarten teacher would. (They note that it's easy to spot the lice since their size is so great compared to the size of the lemur.) Then, without removing any lice, they marked the bugs on each lemur's ears with a lemur-specific code--a set of colored nail-polish dots applied to every louse's back with a toothpick--and after a few seconds for drying, set the lemurs free again.

Whenever the team recaptured a lemur they'd already seen, they checked the animal's lice to see whether it was still carrying only its own bugs, or had shared with a friend. Their observations coincided with the lemurs' brief breeding season, during which they expected to see a sharp increase in sharing.

Sure enough, almost all the louse swaps that Zohdy and her team observed happened during the breeding season. They also happened exclusively between males, who were the main carriers of lice. Among the 9 female lemurs they captured, the researchers found just 1 with lice. But 14 out of 23 males were infested at some point during the experiment.

Though male lemurs are known to share nests, Zohdy speculates that the spike in louse sharing during breeding season comes from males grappling with each other to compete for females. It's possible that some lice were transferred during mating, spending time on female lemurs in between male hosts. But for the most part, the lice seem to prefer male company.

And we're not just talking about their choice of host. Though the researchers only marked lice that were living on lemurs' ears, they usually found these same lice later living on a host's testes. The lice may prefer this piece of real estate because of its thin fur and rich blood supply--especially during the breeding period when these appendages are, in the authors' words, "dramatically distended." ("See Figure S6 for an example.")

The lice seemed to say, then, that male mouse lemurs have the closest contact with each other when they're fighting over females during mating season. They also revealed that brown mouse lemurs range farther than previously thought. Based on previous trapping studies, the researchers expected that lemurs would stay within a small range, and that louse sharing would decrease as they got farther from their home base. But lemurs surprised researchers by spreading their lice far afield.

So brown mouse lemurs aren't homebodies, after all. And though they're shy, they may bump elbows with plenty of their peers during mating season. This information isn't just useful for understanding the lives of lemurs: Since lice and other parasites can carry diseases, knowing how they travel can help scientists predict the spread of infections.

The technique of using parasites as surveillance bugs could help scientists spy on other hard-to-find animals and learn more about their lives--sordid details included.

Zohdy, S., Kemp, A., Durden, L., Wright, P., & Jernvall, J. (2012). Mapping the Social Network: Tracking lice in a wild primate (Microcebus rufus) population to infer social contacts and vector potential BMC Ecology, 12 (1) DOI: 10.1186/1472-6785-12-4

Images: Iraiidh/Wikimedia Commons; Sarah Zohdy.

How Stress Makes Oranges Better for You

2012-03-23T10:21:00.001-05:00

Though Sicily may seem like a relaxing oasis, it's really a stressful climate where rogue elements can turn you bloody--whether you have a run-in with the mafia, or you're an orange. New research shows why the Italian blood orange prefers this hostile environment to your backyard. With a little coercion, though, we might someday convince this extra-healthy fruit to move abroad.

A variety of the sweet orange Citrus sinensis, the blood orange has eerie red flesh and is grown most successfully around Sicily. To develop their trademark color, the oranges need to ripen in a climate where the nights are much colder than the days. They're cultivated in a few other places outside of Italy, and their color can be enhanced by storing them in the cold after picking them. But in general, the blood orange is an inflexible character.

The blood orange's pickiness makes it hard to mass produce and get onto grocery store shelves. A team of researchers from the United Kingdom, Italy, and China (where another variety of blood orange grows) set out to find what makes the orange so finicky.

Pigments called anthocyanins give the fruit its gory look. These same pigments are responsible for the deep purplish hues of blueberries, eggplant peels, and Japanese maples. Combing through the blood orange's DNA, the researchers found a gene they named Ruby that turns on the fruit's anthocyanin machinery.

When Ruby is activated, the plant makes anthocyanin and the orange turns red. To demonstrate this, the researchers snuck the Ruby gene into a tobacco plant. Tobacco leaves normally make anthocyanin only in small amounts. But with Ruby added to their genes, tobacco plants cranked up the pigment's production and sprouted reddish leaves.

If Ruby is the foreman who hits the ON button at the anthocyanin factory, he apparently needs a cold snap to get him out of bed--because without cold nighttime temperatures, blood oranges don't turn bloody. The researchers discovered that the element waking Ruby up is a kind of rogue gene called a transposon.

Also called "jumping genes," transposons are chunks of DNA that can hop around a genome and insert themselves wherever they like. At some point in the blood orange's evolution, a tranposon stuck itself right in front of Ruby and became the on-switch for the on-switch.

Ordinarily, the plant suppresses the transposon. It's not a good idea, after all, to let wandering genes start bossing around the rest of your DNA. But transposons often get turned on when plants are stressed. Scientists think this may be a desperate trick plants evolved to use when times are tough: The normal order of business isn't working, so plants set their rogue genes free to see if they have any useful innovations. When blood orange trees are stressed by cold temperatures, they release their hold on the transposon in front of Ruby. The transposon wakes up the factory foreman, and you know the rest.

Now that we've found the secret to making blood oranges bloody, senior author Cathie Martin says genetic engineers could create a new variety that doesn't need the cold at all. Scientists could tweak the orange's genome so that Ruby is active all the time, keeping the pigment factory going in any temperature.

Imagining a job for a task force of tree psychologists, I asked Martin if we could grow unmodified blood orange trees in warm climates and just stress them out some other way. But she said that probably wouldn't work. You also can't create a blood orange by chilling regular "blonde" oranges or orange trees--this particular team of rogue gene and factory foreman is specific to this variety of Citrus sinensis.

Of course, you could always just stick to the fruits that grow easily in your climate. But Martin says blood oranges are even better for us than regular oranges. "There are many examples of...dietary anthocyanins having a beneficial effect on health," she says, "especially for cardiovascular disease and obesity." In mice, blood orange juice (but not regular orange juice) limits weight gain and prevents obesity.

If these pigments are as healthful as they seem--and especially if climate change is going to make the tree's home turf less comfortable--maybe it's worth pursuing a way to get the blood orange out of Sicily.

Butelli, E., Licciardello, C., Zhang, Y., Liu, J., Mackay, S., Bailey, P., Reforgiato-Recupero, G., & Martin, C. (2012). Retrotransposons Control Fruit-Specific, Cold-Dependent Accumulation of Anthocyanins in Blood Oranges THE PLANT CELL ONLINE DOI: 10.1105/tpc.111.095232

Image: ccharmon/Flickr

When Keen Minds Are Quick to Wander

2012-03-20T10:24:00.000-05:00

We're all afflicted with wandering minds. Those that are especially prone to gallop away during an easy task may just have more horsepower to begin with.

Working memory is the place where your mind holds and manipulates the things you're currently thinking about. If you can fit more items in there at once, you have a better working memory capacity--and odds are you score better on IQ and other tests. Previous studies have shown that when our working memory is busier, our minds wander less. Does this mean wandering uses resources from working memory, taking valuable brainpower away from other tasks?

Daniel Levinson, a graduate student at the University of Wisconsin, Madison, led a study of working memory and mind wandering. Scientists call wandering "task-unrelated thought" or TUT, as in the chastising sound you might imagine when you catch yourself drifting away from your work.

Levinson used two experiments to study whether people with better working memories are more likely to let their attention drift during a simple assignment. In the first experiment, 74 subjects performed an easy visual task on a screen, pressing keys in response to the letters they saw. In the second, 42 subjects did an even duller task, pressing a key in time with their own breathing. Both experiments were periodically interrupted by a message on the computer screen asking whether subjects had just been thinking about something besides the job at hand.

All subjects also completed a standard test of their working memories. In both experiments, people with higher working memory scores reported more episodes of mind wandering (or TUT).

Levinson thinks that since the tasks used here were simple, using only a minimum of working memory resources, subjects' minds were free to wander. Those who had greater resources to begin with had more left over after clicking the keyboard, and tended to spend it elsewhere--say, planning a grocery list. In previous studies, more challenging tasks had eaten up working memory resources and left little behind for daydreaming.

Of course, a correlation between working memory and mind wandering doesn't prove that one causes the other, as Levinson readily agrees. To show that, he says, you'd have to increase individuals' working memory and see that their ability to mind wander also increased. Alternatively, maybe people with better working memories just find these computer-screen tasks easier to begin with, and that sends some other part of their minds meandering.

But Levinson says the subjects in his study with higher working memory, for the most part, didn't outperform others (as you might expect if they found those tasks easier). When researchers removed the one measure by which those subjects did do better from their analysis, the result stayed the same: Minds with greater working memory resources wandered more.

If mind wandering really does depend on working memory, Levinson says there are various theories about how that relationship might work. One idea is that a fragmentary thought can pop into your consciousness spontaneously, or because your stomach rumbles and reminds you of lunch. Your working memory may grasp that fragment and spin it into a longer yarn of thought: Where should I get lunch today? After lunch do I have time to go to the library? Now you're gathering and elaborating on bits of information that aren't in your immediate environment--a job that requires your working memory.

Levinson thinks this kind of research could lead to training methods that help people keep their minds on task. Until then, maybe we can hack the system on our own.

To keep my own mind on task while I'm writing, I like to be in a mildly distracting environment. A subdued Starbucks works, as does playing classical music at my desk. (TV, music with lyrics, or that horrible guy on his cell phone next to me at Starbucks do not work.) Paradoxically, giving myself a small distraction to handle seems to help me focus. Judging by the scarcity of open outlets at most coffee shops, I'm not the only person who does this.

I asked Levinson whether committing part of my working memory to tuning out a distraction should help tone down my mental chatter. "Yes!" he said. "People with more working memory are better at blocking out visual distractors on a screen. So people think that working memory is used to filter out distractions." Spending some resources on this task should leave me with less free rein to wander. Though, he points out, I'd also have fewer remaining resources for the task at hand.

Levinson suggests a different trick. Working memory is known for helping you keep track of your priorities and override your habits, he says. If you set a goal to rein in your mind when you notice it wandering, the simple act of remembering that goal may claim some of your working memory resources and make you less likely to drift.

Though this tactic may sound like a recipe for frustration (Wandering again? Tut tut!), Levinson considers it empowering. "It's a choice that I'm actually making when I elaborate on my mind wandering, and I'm using my resources when I do it," he says. "I also have a choice to invest those resources somewhere else."

There's also the zen approach. "It's impossible not to mind wander," Levinson says. "On average, people will mind wander for half of their daily lives." We can't help it. But maybe we can take a moment along the way to appreciate what a mobile mind says about our brainpower.

No, really, just a moment. You can go now.

Levinson, D., Smallwood, J., & Davidson, R. (2012). The Persistence of Thought: Evidence for a Role of Working Memory in the Maintenance of Task-Unrelated Thinking Psychological Science DOI: 10.1177/0956797611431465

Image: VickyvS/Flickr

How to Slim Down, Manage Your Man, and Stay Tight with Your Girlfriends!

2012-03-16T10:24:00.000-05:00

Who ever said science wasn't for us ladies? This week's research is full of tips on looking good, eating right, and taking care of your man! Plus: Don't miss a shocking true story about a girls' get-together turned deadly.

DIET
The calorie-free way to de-bland your diet

You try to eat right. But sometimes that low-sodium poached chicken breast on lettuce doesn't thrill your taste buds. What if merely looking at pictures of steak, pizza or pastries made your healthy meal taste heartier? New research from Switzerland says that just might work.

A group of Swiss scientists studied 14 healthy adults. The subjects held an electrode on their tongues while researchers flashed pictures of foods in front of them. The electrode gave off little buzzes of "electric taste," triggering subjects' taste buds with a neutral, slightly metallic taste.

People experienced a more pleasant flavor in their mouths when the electric taste was paired with a high-calorie food picture than a low-calorie one. The scientists say these images of forbidden foods light up the parts of our brains that go "Mmm!"

Could you try this trick in your own home? The researchers didn't study what happened when people ate actual food while looking at pictures. But if your gluten-free, high-fiber bread is blander than a piece of metal, staring at a picture of chocolate cake might make it seem tastier.

FITNESS
This surprising workout trick will have you handing back unwanted pounds!

If you're overweight, you might find exercise frustrating. Just a few minutes of exertion can leave you feeling overheated and sweaty. But research presented at an American Heart Association meeting may provide a solution to your problem: colder hands.

Researchers at Stanford University conducted a small study on obese women between the ages of 30 and 45. All the women participated in a 12-week exercise program that included push-ups, lunges, and using a treadmill. Half the women held their hands in cylinders of cold water while they were on the treadmill, while the other half kept their hands in body-temperature water.

Because the women who exercised with their hands in cold water stayed cool, they were less likely to get frustrated and drop out of the exercise program. (They even stuck it out through those dreaded push-ups!) These women lost more weight and got in better shape than the other group of women.

You probably don't have one of these cold-water exercise devices in your local gym. But you can still apply the findings to your own exercise routine. In the summer, why not freeze water bottles and hold them in your hands while you work out? And in colder months, get outside and ditch those gloves! After all, everyone can agree that a beach-ready body is worth a little numbness in the extremities.

MAN MANUAL
Are cheeseburgers turning your guy's swimmers into toast?

Bad news, drive-through lovers! Fertility specialist Jill Attaman says a diet high in saturated fat is bad for sperm counts.

Attaman studied the swimmers of 99 men who came to a fertility clinic. She also gathered data about the men's diets and divided them into three groups based on their fat intake. The men in the highest fat-consuming group had sperm counts 43 percent lower than men who consumed the least fat. That's news that will chill some men's hearts colder than a Shamrock Shake.

But it's not all bad news for fats. While saturated fats were tied to low sperm counts, healthy fats called omega-3's seem to be good for sperm. Men who were in the highest third for consumption of this kind of fat had healthier, better-formed swimmers. So next time you cook your burger king a thoughtful dinner, think of his own little sesame seeds and try salmon instead of steak.

TRUE LIFE READ
"I was part of a hot defensive bee ball"

Bertha,* a Japanese honeybee, was hard at work in her hive one day when she became aware of an intruder. A giant hornet, Vespa mandarinia japonica, was inside the entrance of the hive. Suddenly Bertha found herself swept up in a buzzing mass of bodies.

"I'd heard rumors about the hot defensive bee ball before," Bertha says, "but I'd never been a part of one myself." The sister honeybees clumped together in a tight swarm around the massive body of the hornet. (They don't call them giants for nothing. Check out some mug shots of these unpopular predators here.)

Vibrating their muscles to generate heat, the bees cranked the temperature in the swarm up to 46 degrees Celsius, or 115 degrees Fahrenheit. That's even hotter than your Bikram class! It was uncomfortable for Bertha--but for the hornet, it was worse.

Within an hour, the hornet was dead. The bees dispersed. And that's when they found themselves, instead of at the hive's entrance, inside a glass beaker. The attack had all been a ruse perpetrated by scientists. The hornet hadn't even been coming after the bees in earnest; researchers had shoved it inside the hive on a wire.

"I felt sort of used," Bertha says. "I was just swept up in the moment, and now I know I was manipulated into joining the bee ball. But at least it was for science." (Bertha was luckier than some of her sisters, who were forced to donate their heads to science as well.)

The researchers wanted to find out what genes were activated in bees' brains while they formed the hot defensive bee ball. They found one gene of note. But the same gene was active when bees were heated up outside of the bee ball. So it seems to be a response to the furnace-like environment the bees create, not a cause of the mysterious ball-forming impulse.

To find out what drives bees to form hot, deadly mobs in the first place, scientists--and Bertha--will have to wait.

*Some names have been changed.

Ohla, K., Toepel, U., le Coutre, J., & Hudry, J. (2012). Visual-Gustatory Interaction: Orbitofrontal and Insular Cortices Mediate the Effect of High-Calorie Visual Food Cues on Taste Pleasantness PLoS ONE, 7 (3) DOI: 10.1371/journal.pone.0032434

Attaman, J., Toth, T., Furtado, J., Campos, H., Hauser, R., & Chavarro, J. (2012). Dietary fat and semen quality among men attending a fertility clinic Human Reproduction DOI: 10.1093/humrep/des065

Ugajin, A., Kiya, T., Kunieda, T., Ono, M., Yoshida, T., & Kubo, T. (2012). Detection of Neural Activity in the Brains of Japanese Honeybee Workers during the Formation of a “Hot Defensive Bee Ball” PLoS ONE, 7 (3) DOI: 10.1371/journal.pone.0032902

Images: plates of food Ohla et al.; glove peanutian/Flickr; burger guy Mr. T. in DC/Flickr; bee klugi/Flickr

Accounting for Taste: Why a Bear, but Not a Seal, Will Steal Your Cupcake

2012-03-13T10:13:00.001-05:00

Humans aren't the only mammals with a sweet tooth. Omnivores from beagles to grizzlies can detect a wide range of flavors and enjoy the taste of sugar. But other mammals with narrow carnivorous diets have been subjected to evolution's "use it or lose it" decree. These meat-eaters are genetic mutants without working taste receptors for sweets. Not only do they not want your cupcake, but they can't even taste it.

Researchers led by Peihua Jiang at Monell Chemical Senses Center in Philadelphia wanted to know how often evolution has removed tastes from animals' repertoires. Omnivores such as humans can detect five basic tastes: sweet, sour, bitter, salty, and umami (a meaty flavor). Previous studies had shown that cats, though, are indifferent to sweetness. Cats were also known to have a mutation in the gene for the sweet taste receptor, rendering it nonfunctional. Had other carnivores' sweet receptors met the same fate?

For 12 carnivore species, the authors sequenced the genome section containing the sweet taste receptor. In just 5 of these species, the gene was intact. These included the aardwolf, Canadian otter, spectacled bear, raccoon, and red wolf.

It was presumably not practical to round up all these animals and give them tests to confirm that they like sugar. But the authors were able to test four spectacled bears, a charismatic South American species. When given a choice between a bowl of plain water and a bowl of sugar water, the bears strongly preferred the sugar water. They even enjoyed some artificial sweeteners (Splenda, for instance, but not NutraSweet).

Spectacled bear: Yes cupcakes.

The other 7 carnivore species in the study had mutations in their sweet taste receptors. These animals came from widely separated branches of the mammal family tree: sea lion and seals; Asian small-clawed otter; hyena; fossa (a cat-like creature from Madagascar); and banded linsang (a secretive jungle creature from Southeast Asia).

Though, again, the authors didn't recruit any hyenas or jungle cats for their study, they did bring in two Asian small-clawed otters for testing. The otters were given the same bowls of sweetened and unsweetened water that the bears tasted. But the otters were totally indifferent to sugar water.

Asian small-clawed otter: No cupcakes.

An aardwolf, since you asked: Yes cupcakes, yes termites.

Finally, the researchers looked at the dolphin genome, which had been previously published. Not only was the dolphin's sweet taste receptor mutated, but so was the receptor for umami flavor. There seemed to be no intact gene for a bitterness receptor, either.

It seems incredible that an animal could be so deficient in tasting. But previous studies have suggested that dolphins can't taste sugar and have a reduced ability to taste bitterness. A close look at their tongues reveals only a few taste bud-like structures. The same is true of the sea lion: It has barely any taste buds, and has a mutated gene for the umami receptor as well as sweet.

They wouldn't have much chance to taste their food even if they did have taste buds, though, because neither sea lions nor dolphins chew their prey. They both gulp down fish whole.

Dolphin: No cupcakes, no chewing.

Despite these similarities, sea lions and dolphins lost their taste separately. Their lineages took to the sea separately and 15 million years apart. Their genetic mutations, too, are different.

In fact, out of all the genetic anomalies the researchers found in carnivores' sweet taste receptors, no two mutations were the same. This means that again and again, evolution has removed the ability to taste sugar from carnivores. There must be some cost, then, to keeping unnecessary taste receptors. When animals evolve to consume an all-meat diet, it's better for them to prune their unnecessary tastes. And when they evolve to swallow their food whole, it seems there's not much need to taste anything.

Even within close families of mammals, evolution has tweaked individual species' taste receptors as they evolved different diets. Black bears love raisins but also enjoy insects and fish; panda bears, which only eat bamboo, can't taste umami. Though many bats feed on fruit, the vampire bat only eats blood and can't taste sugar.

Taste receptors aren't purely for enjoyment, though. A bitter or sour taste can be our clue that a food is spoiled or toxic. So it's surprising that even the bitter taste receptor, which evolved for our protection, can apparently be thrown away.

Maybe when animals have a strictly specialized diet (of fish, or bamboo, or blood) they can rely on their eyes and other senses to ensure they're eating the right thing. But we omnivores have to decide on our diets by taste. It means we must think harder about what we're eating--but it also means we can enjoy every flavor of cupcake.

Jiang, P., Josue, J., Li, X., Glaser, D., Li, W., Brand, J., Margolskee, R., Reed, D., & Beauchamp, G. (2012). Major taste loss in carnivorous mammals Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1118360109

Images: bear Cburnett/Wikimedia Commons; otter Patrick Gijsbers/Wikimedia Commons; aardwolf Dominik Käuferle/Wikimedia Commons; dolphin Just Taken Pics/Flickr.

Note: This post was originally titled "Accounting for Taste: Why a Bear, but Not an Otter, Will Steal Your Cupcake." But my attentive husband pointed out that there was a type of otter in the sugar-tasting group, as well as the sugar-ignoring one. I should admit now that I actually don't know whether any of these animals steals pastries.