Field of Science


Long-Suffering Snail Dads Carry Illegitimate Babies

If you can't find the snail in the photo above, it's because he's loaded down with thousands of cannibalistic babies—and most of them aren't even his. Dads in this marine species do all the egg-sitting, while moms scoot off to mate with other males. The males' willingness to care for the eggs of their rivals isn't just unusual: it's opposite to the standard rules of evolution.

Rather than laying their eggs on, say, a rock, female Solenosteira macrospira snails glue egg-stuffed capsules to their male partners after mating. The male waits patiently for what may be several hours while the female produces and attaches the packets, which each hold about 250 eggs. By the end of the mating season, each male will have partnered with a handful of females (both literally and figuratively) and will be totally covered in eggs.

It takes about a month for each "clutch," or batch of eggs, to turn into baby snails and crawl away. While he's waiting, the father protects the eggs and keeps them from being buried in sand or drying out during low tide. Meanwhile, females carry on mating with other males, never returning to the mollusk Baby Bjorns they've left all over the neighborhood.

An evolutionary rule of thumb is that the more energy a male puts into caring for his young, the more certain he should be that he's the father. Care by dads is rare in the animal kingdom. It usually makes more sense for males to spend their energy mating with as many females as possible and hope some of their young survive. In other species where fathers care for the young (such as various fish, sea spiders, and giant water bugs), males guard females after mating or take other measures to ensure their partners aren't cheating on them.

But since Solenosteira macrospira females can store sperm from many males at once inside their bodies, the dads getting eggs glued to them have no such assurance. And they don't seem to object. To find out just how bad the male snails have it, UC Davis researcher Stephanie Kamel led a daytime-TV-worthy investigation into snail paternity.

Kamel collected 15 egg-covered males from the waters off the coast of Sonora, Mexico. "It's very obvious once you see the snails to tell the clutches apart," she says, because the batches of egg capsules left by different females have distinct shapes and colors. By examining the genes of about 90 embryos from the back of each snail, the researchers could guess what percentage of his eggs each babysitting dad had actually fathered.

The answer was bad news for the dads. On average, males had fathered only 24% of the eggs they were carrying. A given male could be carrying babies from 20 or more other fathers.

Researchers also looked at the genes within several entire egg clutches to find out how many different males each mom had mated with. They found that mothers were highly promiscuous: in a single clutch, they laid eggs from 10 to 15 fathers.

This system might make sense if males truly weren't bothered by carrying around a backful of eggs for a few months. To find out, the researchers gathered many egg-carrying males and unstuck the capsules from their backs. Then they glued eggs back onto half of them and released them into the water, tethered to a 2-meter length of fishing line.* After just two weeks, snails covered in eggs had lost about 8 percent of their body weight. But unburdened males were the same weight or had grown.

Males sacrifice their health so they can cart around babies that are mostly unrelated to them. "This system is really cool," Kamel says. Which is to say, this system seems like it never should have evolved.

One explanation, Kamel says, might be that female snails have a strong preference for males with eggs already glued to them. Males that try to get mates without carrying eggs "won't get any love, so to speak," she says. Females might even insist on gluing down some of their eggs before mating.

For moms, coupling with a variety of males lets them produce young with many different sets of genes. Before they hatch from their capsules, these snail embryos will aggressively cannibalize each other. (She doesn't do much else for her young, but the mother does leave them with a large supply of snacks—in the form of their brothers and sisters.) Out of her genetically diverse babies, only the very fittest will survive long enough to hatch.

Since at least a few of their own offspring are in the mix, babysitting dads would probably prefer it if their charges didn't eat each other. But if they want to have any young at all, the dads have to follow the rules. "At this point it really does appear that males can't do anything to improve their situation," Kamel says. "Females in this system seem to have won the battle in the conflict over parental care."

Stephanie J. Kamel, & Richard K. Grosberg (2012). Exclusive male care despite extreme female promiscuity and low paternity in a marine snail. Ecology Letters DOI: 10.1111/j.1461-0248.2012.01841.x

Photos by Richard Grosberg. Top: a male covered in eggs. Bottom: a male next to a female. 

*The paper indicated that only 70 percent of snails were recovered at the end of the two-week period. "I'm wondering how one loses a leashed snail," I wrote to Kamel. She sent back the grim answer: "They get eaten by birds."

Blood Test Reveals the Time Inside You

Like flowers opening and closing with the sun, our bodies have a rhythm that follows the daily turning of the earth. Processes speed up and slow down; hormones rise and fall; we feel wakeful or tired. But our internal clocks aren't always in sync with the day. By finding out what time our bodies think it is, doctors can time their treatments to work better. And now, there might be a simple way to check the time on our inner clocks.

The idea of coordinating medical treatments with the ticking of patients' internal watch hands is called "chronotherapy." Hiroki Ueda, a researcher at the RIKEN Center for Developmental Biology in Kobe, Japan, says that some doctors are already using chronotherapy in treatments such as chemo for colon cancer. Checking a patient's internal schedule before delivering medicine can make a treatment both more effective and less toxic.

But doctors don't have an easy way to check the body clock. "It was labor-intensive and time-consuming for clinical researchers to measure body time using classical methods," Ueda says. One method involves keeping subjects under controlled conditions for more than a day while constantly sampling their blood to check levels of cortisol or melatonin (two hormones with a strong daily cycle). Methods like this aren't exactly practical, which has been an obstacle to chronotherapy. So Ueda and his colleagues have been working on a better technique.

The researchers took inspiration from a hypothetical garden described by 18th-century Swedish botanist Carolus Linnaeus. The Horologium Florae (Latin for "clock of flowers"), as Linnaeus imagined it, would hold a few dozen varieties of flowers that he'd chosen for the precise timing with which they opened and closed each day. By simply looking around the garden, a knowledgeable gardener could tell the time of day.

Instead of flowers, the Japanese researchers used molecules circulating in the bloodstream that wax and wane over the course of the day. They'd previously built this kind of molecular flower clock for mice; now they tried it with humans.

They recruited six healthy volunteers who were willing to pretty seriously jet-lag themselves inside a lab. First, subjects stayed awake and sitting in a chair for a day and a half while researchers fed them and took their blood every two hours.

In these blood samples, the researchers found 58 molecules that cycled over the course of the day. (Since subjects weren't sleeping, moving around, or eating normal meals, they knew these molecular rhythms were intrinsic to their bodies and not a reaction to their environment.) They created a timetable  that would predict the time of day based on the levels of all these molecules in the blood.

Next came the jet-lagging. For a week, subjects were put on a 28-hour cycle of sleeping and waking instead of the usual 24. This was to knock their internal rhythms out of alignment with the true time of day. Then subjects sat through the same day and a half of blood sampling as before.

The frequent blood samples let researchers find their subjects' internal body time the old-fashioned way, by closely plotting the rise and fall of one hormone (cortisol). This gave them a cheat sheet against which they could check the answers from their molecular flower clock.

Using the timetable they'd created in the first part of the experiment, Ueda and his team found that any pair of blood samples taken 12 hours apart could accurately tell their subjects' body time to within 2 or 3 hours. If a person's body thought it was 4:00 PM when it was really noon outside, the molecular timetable could detect the difference.

Ueda's subjects for this study were all young adult males. But he says the cycling molecules in the timetable—including steroid hormones, amino acids, and lipids—should apply to females and other age groups as well. One of the researchers' next steps will be to start testing their molecular clock in these other populations. They'd also like to hone the technique so it works with a single blood sample, rather than two.

Even when we're not trapped inside a sleep lab with manipulative researchers, our circadian rhythms can get misaligned. Jet lag or night shifts at work can push people's bodies out of sync with the sun. Genetic mutations can create whole families of extra-early risers who wake up before dawn.

If a simple blood test allows doctors to peek at patients' internal clocks, they could more easily diagnose these disorders. They could also better tailor chemotherapy and other treatments to patients' bodies. And recent research in mice suggested that high-fat foods consumed during the usual sleeping hours contribute more to obesity than the same foods eaten during waking hours. Understanding our individual clocks might keep us not just sleeping and waking well, but blooming with health.

Takeya Kasukawa, Masahiro Sugimoto, Akiko Hida, Yoichi Minami, Masayo Mori, Sato Honma, Ken-ichi Honma, Kazuo Mishima, Tomoyoshi Soga, & Hiroki R. Ueda (2012). Human blood metabolite timetable indicates internal body time. PNAS : 10.1073/pnas.1207768109

Image: Josh Greenberg/Flickr

The Shambulance: Zero-Calorie Noodles?

(The Shambulance is an occasional series in which I try to find the truth about overhyped health products. My Shambulance co-captains this week are Steven Swoap and Daniel Lynch, both of Williams College.)

It could almost be a Zen question: What do you call a food with no food in it? In Japan they're called shirataki noodles, and are made from the root of the konjac plant. In the United States they're called "Miracle Noodles" or a "healthier alternative to pasta" and promise "NO calories...NO net carbs...NO GUILT!!!"

The konjac root's contribution to the noodle is straight dietary fiber, in a form called glucomannan. Since the noodles are made of nothing but fiber and water, the idea goes, they'll hurry right through you without leaving any calories behind. This is attractive to American dieters who would like to be able to eat a whole plate of food without actually eating any food. A dinner of pasta topped with marinara sauce becomes a dinner of marinara sauce topped with time on the toilet.

The Chicago-based brand "NoOodles" displays a set of nutrition facts with zeros nearly all the way down, like a perfect report card. However, "Don't be mistaken," says Williams College physiologist Steven Swoap. "These noodles have calories!"

Insoluble fiber, Swoap explains, does pass through our bodies untouched and make up the bulk of our feces. But glucomannan is a soluble fiber. This means it's dissolvable in water; it's also digestible by the bacteria living in our guts. The bacteria break down soluble fiber into products that we absorb as calories. (They also make methane, which, as Swoap points out, "we don't absorb but rather share with our surroundings.")

The key to the zero-calorie claim made by NoOodles might lie in that 1.6-ounce serving size at the top of the label. The FDA permits calories under 5 to be rounded to 0. If each of those dainty servings really has 4 calories, a whole package—which would fill a plate—has about 20. It's hardly a calorie count that will ruin anyone's diet. But zero, in this case, doesn't really mean zero.

Shirataki noodles have a distinctly non-zero amount of offensive odor, as I discovered when I tried some NoOodles for myself. (They're in the refrigerator aisle, which I only mention in case you want to buy your own and also want to avoid having this conversation with two different grocery store clerks: "I'm looking for a product called noodles?")

The product's website describes the smell, caused by the calcium hydroxide, as "a little odd." I would have used different words, like maybe "neglected fish." But the odor rinses away with water. The rectangular shape of the package is harder to dispel.

I followed directions and heated my NoOodles in a dry nonstick pan until all the water had evaporated, though they looked otherwise the same. At this point it's recommended that you cook the NoOodles with some sort of sauce (or eggs or ice cream), but I wanted to try them in their unadulterated form. As promised, they tasted like nothing at all. They had a texture, though, that I was deeply not okay with, like biting through rubber bands. I managed one mouthful followed by a lot of water.

The water is recommended too, because soluble fiber sucks up water in your body. In 2010, Health Canada issued an advisory about the importance of drinking a full glass of water when taking pills or powders containing glucomannan. It also urged consumers not to use glucomannan supplements right before bed, because the stuff can swell up and cause choking or blockages in the intestine while you sleep. The health advisory didn't address shirataki noodles.

The water that NoOodles absorb makes the material passing through your gut especially slippery, so your small intestine can't absorb nutrients (which is to say, calories) as easily. Their website claims this makes the rest of your meal less caloric too, as everything slides through you along with the NoOodles. But Swoap says that experiments have shown this simply isn't true. "The small intestine is still long enough to get all of the calories from your food."

Among several other promises, NoOodles makers also say their product makes you feel fuller, so that "one tends to eat less when NoOodle is part of the meal." It's certainly possible, though it's also possible that one tends to make up those calories at one's next meal, when one is starving because one only ate marinara sauce for dinner. "The key word that gets them off the hook is 'tends,'" Swoap says. "Otherwise the FDA would have a major problem with this."

Not all the claims made about glucomannan noodles are spurious. The product does let dieters eat more food for fewer calories. And some studies have found that glucomannan can lower cholesterol, both in healthy and diabetic subjects.

So is an all-fiber noodle really a "healthier alternative?"

"The 'benefits' are in comparison to refined wheat flour that is used to make breads, pastas, etc. Most everyone acknowledges that is not good in excess," says Daniel Lynch, a biochemist who's also at Williams College. "But moderation is the key." He adds, "You might as well just have a glass of Metamucil or Citracel as a pre-dinner cocktail and then enjoy real food in smaller portions!"

Swoap says, "I don’t think this is necessarily bad for you. I would just prefer to get my fiber with vegetables that also bring along a lot of micronutrients." In other words, if you want to bulk up your meal with a low-calorie fiber source, there are less rubbery and more vitamin-filled ways to do it.

If you're still tempted to try a food-free plate of pasta, go for it. Just remember to drink water.

Arvill A, & Bodin L (1995). Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men. The American journal of clinical nutrition, 61 (3), 585-9 PMID: 7872224

Chen HL, Sheu WH, Tai TS, Liaw YP, & Chen YC (2003). Konjac supplement alleviated hypercholesterolemia and hyperglycemia in type 2 diabetic subjects--a randomized double-blind trial. Journal of the American College of Nutrition, 22 (1), 36-42 PMID: 12569112

Thanks to Chris F. for the tip! If you want to summon the Shambulance to the site of an emergency, leave a comment or send me an email at the address above.

Wasps Follow Order of Succession When Queen Dies

The office of postmaster general to the United States used to come with a perk totally unrelated to mail. In the unlikely event that an accident wiped out the president, vice president, and every member of their cabinet, the postmaster general would become the leader of the country.

In reality, the line of succession has never gotten beyond the vice president. But there are 16 people lined up behind the VP to take over (a list that no longer includes the postmaster general and now culminates, less quaintly, with the secretary of homeland security). In the United Kingdom, the order of succession to the throne winds bafflingly through a giant family tree of princes, dukes, viscounts, and so on.

Wasps of the species Ropalidia marginata never have to argue about titles or families: when the queen dies or disappears, the other wasps in the colony unanimously agree on who her successor is. And if that queen disappears too, they know who comes after her. Though the ordering system is invisible to human eyes, the wasps adhere strictly to their line of succession and follow it all the way down (if necessary) to their equivalent of the postmaster general.

Alok Bang and Raghavendra Gadagkar, researchers at the Indian Institute of Science in Bangalore, have been determinedly assassinating wasp queens to try to figure out how the R. marginata system works. Until the researchers get to her, each nest's queen lives a peaceful life. She doesn't bother anyone, and no one bothers her as she pumps out new generations of fertilized eggs.

The queen's quiet lifestyle, like that of most royalty, is in stark contrast to the lifestyle of her subjects. All around their docile ruler, worker wasps live in continuous violence. Gadagkar says the wasps chase, bite, and "nibble" one another, pin each other in place by holding body parts in their mouths, and crash down on each other from above. These displays of aggression don't usually injure the wasps, but maintain a hierarchy of dominance among them.

When the peaceful queen dies, or is plucked from the nest by interfering scientists, things get shaken up. One worker wasp—and only one—suddenly becomes hyperaggressive. Within minutes of the queen disappearing, this worker begins attacking the wasps around her at 10 or even 100 times her usual frequency, Gadagkar says. She distributes her attacks evenly among anyone nearby, and no one fights back. It's all a show to announce that this wasp is the heir to the throne.

Over the following week or so, the heir's aggression dies down and her ovaries develop. She becomes another peace-loving, egg-laying machine.

The researchers believe that this successor is chosen somehow before the original queen disappears. Even though she's outwardly identical to the other wasps in the nest, she's predestined to be second in line to the throne. "The fact that there is invariably one and only one individual who becomes hyperaggressive" is one clue, Gadagkar says. That no one challenges this hyperaggressive individual is an even stronger clue. And in previous studies, the researchers have shown that the heir isn't simply the first wasp to get the news of the queen's death. The successor seems to know who she is ahead of time, and the other wasps know and respect it too.

If that weren't impressive enough, Bang and Gadagkar have now found that when they remove the first heir, a second one steps up just as quickly. In a new paper in PNAS, the authors say they've discovered a succession of at least five potential queens.

Each of these new queens jumps into action as soon as a the previous queen disappears, attacking any workers around her. Again, only one wasp steps forward, and no one challenges her. Within several days, this new queen starts laying her own eggs and maintaining the colony. In an entire nest of 20 or 30 individuals, the researchers say, there's no reason to believe the succession doesn't continue—maybe down to the very last wasp.

Having an agreed-upon order of succession makes sense for insects living in small colonies like R. marginata, the authors say. Unlike in a large honeybee colony, where queens are determined from birth and workers know they'll never lay their own eggs, workers in the termite colony actually have a shot at reproducing. Knowing where they are in the queen queue could help them decide whether to stay in their original nest or move out to start a nest of their own.

Even if it makes perfect sense for the wasps to have an orderly system of succession in place, that doesn't explain how on Earth they figure it out.

"That is the million-dollar question we are working on!" Gadagkar says. The researchers found that older wasps were more likely to be the immediate heirs to the throne, but the order doesn't go strictly by age. It also doesn't have anything to do with the dominance hierarchy in the nest.

"Perhaps it is something very subtle, related to the internal physiology of the wasp, that the wasps themselves can detect and which we have not yet discovered," Gadagkar says. Like obscure duchesses and earls, the wasps know their place in line—indecipherable as it may be to the rest of us—and wait for their day to step forward.

Alok Bang, & Raghavendra Gadagkar (2012). Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata PNAS : 10.1073/pnas.1212698109

Image: Abhadra/Wikipedia

Close Look at Bison DNA Reveals Our Dirty Fingerprints

We really owe the American bison an apology. But where do you buy a card that says, "Sorry we wiped out nearly your entire species, then muddied your DNA by forcing you to mate with cows"? Would flowers be better?

In the 19th century Americans slaughtered bison (also referred to as buffaloes) with impunity. We killed them to sell their skins, to get them out of the way of our new trains, and to make life harder for Native Americans. It wasn't a shining moment. By the end of the 1800s the bison were nearly gone, reduced to perhaps as few as 100 animals in several small herds.

Even as Americans worked to restore bison in the early 20th century, we botched their genetics by breeding the animals with domestic cattle. Breeders wanted to make their cattle beefier and hardier. But the crossing wasn't easy, since the two species are separated by 1 to 2 million years of evolution. In addition to the question of genetic incompatibility, there was one of attraction: female bison refused to mate with male cattle.

James Derr, a professor in the veterinary college at Texas A&M University, explains that the hopeful breeders could only get male bison to mate with female cattle. And their offspring were all female; the species' mismatched genes apparently couldn't create a surviving male. These female hybrids were mated with more male bison. The result was a population of cattle-bison hybrids whose mitochondrial DNA—a little loop of genetic material passed solely through mothers—was 100% cattle.

In today's restored population, many bison still carry cattle mitochondrial DNA left over from the two species' historical tryst. To find out whether that genetic souvenir has any effect on today's animals, James Derr led a study of bison living in the wild and on a feedlot.

The herd of wild bison Derr studied live on Santa Catalina Island, off the southern coast of California, where they were introduced in 1924 for the filming of a silent movie. (Oops, better add that to the card.)  Looking at their DNA, Derr found that almost half the bison carried mitochondrial DNA from cattle.

The second bison population in the study was a group living on a feedlot in Montana, preparing to become products such as bison burgers. (On second thought, maybe a card won't cut it.) In these animals, cattle mitochondrial DNA was much rarer, at 6 percent.

By comparing the animals from the two populations, Derr could look for the effects of cattle mitochondrial DNA in both a wild population with limited resources and a well-fed ranch population. The feedlot bison were clearly beefier; at age 2 the feedlot males had reached a size that the island bison wouldn't attain until they were 17 years old.

Despite the two very different body types in the study, cattle genes had a clear effect across populations. Derr reports in Conservation Biology that bison with cattle mitochondrial DNA were slightly but significantly smaller than bison with mitochondrial DNA from their own species.

Bison that are smaller because of their domestic cattle DNA might be at a disadvantage. Derr says it's not clear yet whether this is the case—smaller size might have no effect on the fitness of bison, or it might even help them in places with limited resources like Santa Catalina Island. He plans to answer that question in a separate study.

If it turns out that having mitochondrial DNA from cattle hurts bison, the next question will be whether conservationists should try to weed these genes out of the population. Overall, Derr says, about 6 percent of bison carry cattle mitochondrial DNA, though in individual herds that number can range from 0 to 100 percent. It may be that by restoring the bison's genome to what it once was, we can start to make amends.

Derr JN, Hedrick PW, Halbert ND, Plough L, Dobson LK, King J, Duncan C, Hunter DL, Cohen ND, & Hedgecock D (2012). Phenotypic Effects of Cattle Mitochondrial DNA in American Bison. Conservation biology : the journal of the Society for Conservation Biology PMID: 22862781

Image: Michael Lusk/Flickr

Hyenas Show It's Better to Be Creative than Try, Try Again

It's not a sentiment you'll see on an inspirational poster anytime soon: When facing a problem, sheer persistence is not enough. At least, not if you're a hyena. Presented with a latched box holding a hunk of meat, wild hyenas tried hard to extract the food. Their success depended on their fearlessness and the number of different strategies they tried, but not on hard work.

Spotted hyenas (Crocuta crocuta) are hardy and adaptable animals. They're resourceful hunters, taking down prey alone or in groups, and they navigate complex social situations among their clans. They're the most common large carnivore in sub-Saharan Africa. To study the animals' problem-solving skills, Michigan State University graduate student Sarah Benson-Amram challenged a wild population of spotted hyenas with a meat-filled puzzle.

For a year, Benson-Amram drove through Kenya's Masai Mara National Reserve administering pop quizzes to hyenas. Whenever she spotted a subject, she stopped the car and deposited  a box made of steel bars on the ground. Then she pulled away, parked, and watched what happened. Hyenas that approached the box could see (and smell) a tantalizing, two-kilogram piece of raw meat inside. The box had handles on the sides that let hyenas drag it or flip it over. But the key was to find a bolt that slid sideways, releasing a swinging door and letting the hyena at the prize. 

Sixty-two hyenas participated ("volunteered" would be overstating it) in the study. The individuals could be told apart by their spot patterns and other distinctive features. Some only took the test once, while others that crossed Benson-Amram's path more often ended up becoming repeat subjects.

Hyenas were scored on how long they waited to approach the box, how long they spent trying to open it, and how many different behaviors they tried—including investigating, biting, digging, flipping the box over, and pushing or pulling it. They were also scored, of course, on whether they ever got the darn thing open.

The hyenas didn't fare very well. Only 9 individuals, a little under 15 percent of the total, ever succeeded in getting the meat. (Was the task too difficult? "We have an adult female hyena in our study area that can open refrigerators," Benson-Amram says, so she knew at least some hyenas could manage simple doors and latches. "But it turned out this was not a skill that most of them have.")

The hyenas that aced the test weren't more likely to be young or old, female or male, or of a certain social status. But they did differ from flunking hyenas in factors that might be called personality traits.

According to a paper published last week in Proceedings of the Royal Society B, two traits helped hyenas solve the puzzle. The first was not being afraid of new things. Benson-Amram scored the animals' "neophobia" based on how long they spent near the box before they touched it. Hyenas that were more fearful were less likely to get the box open in the end.

The second factor that helped them open the box was how many different behaviors they tried. Hyenas that had more ideas about approaching the puzzle—biting the latch, turning the box over, pushing it with their paws—were more likely to find the solution.

Persistence didn't hurt. Animals that gave up quickly didn't succeed. But animals that spent more time working on the box didn't do significantly better. Even though hyenas that failed the test spent an average of almost four and a half minutes trying to open the box the first time they saw it, if they didn't have enough ideas about approaching the puzzle, they wouldn't get the meat.

Benson-Amram says that in the field of animal behavior, "personality" describes how an animal behaves across a range of situations. Since she only tested hyenas in one situation, she can't speak to their personalities in general. Still, boldness and creativity clearly helped hyenas open the puzzle box. "On this task, that personality trait was helpful," Benson-Amram says.

Innovative thinking and fearlessness, the keys to solving the puzzle, showed up more often in young hyenas. Juveniles didn't outdo adults in getting the meat out of the box, maybe because the heavy puzzle was harder for them to maneuver. But in different circumstances, younger hyenas might have been the best problem solvers.

"Hyenas constantly have to innovate solutions to new problems in order to deal with the highly varied challenges in their environment," Benson-Amram says. "They take down zebras that could kill them with a strong kick and they compete with lions for resources." Trying a variety of approaches when they face a new challenge might help hyenas survive, just as it helped some of them pass her test.

The same tactic might help humans find solutions too. In studies of human infants, Benson-Amram notes, researchers have found that babies who use a wider range of behaviors when facing a new problem are more likely to solve  it. Creative thinking might be the trait that lets humans adapt to our own landscape and confront the problems that, like the steel box, appear inexplicably in our paths.

Benson-Amram S, & Holekamp KE (2012). Innovative problem solving by wild spotted hyenas. Proceedings. Biological sciences / The Royal Society PMID: 22874748

Image: Still frame from a video of a hyena opening the puzzle box, from Sarah Benson-Amram and Kay E. Holekamp.

How to Unstick a Gecko

During a downpour in the rainforests of Southeast Asia, one sound you will not hear is the patter of geckos hitting the ground. Their sticky feet keep them adhered in habitats all over the world, from jungles to deserts to glass-windowed cities. Yet scientists have found that there is one way to loosen the lizards. Soaking geckos’ feet in water, or submerging the surface they walk on, defeats their sticky superpower—and gives new clues to researchers trying to replicate it for human use.

Gecko feet have inspired much investigation and imitation by human scientists, who have found that the animals take advantage of attractions between molecules called van der Waal’s forces. These attractions are ordinarily very weak. But the soles of geckos’ feet are covered with tiny, branched hairs that end in flattened pads. This increases the surface area of the feet so much that the weak van der Waal’s forces add up to an adhesive power strong enough to hold a gecko upside-down on a ceiling.

The hairs also strongly repel water, a feature called superhydrophobicity—"an exciting word!" says Alyssa Stark, who's a graduate student in the integrated bioscience department at the University of Akron. “It could be a byproduct of having so many hairs, and those hairs having a certain surface chemistry, and that’s it,” Stark says. In other words, water repellence might be a gratuitous feature, the extra cup-holder of the lizard world. “But I was kind of curious to see if there was anything else to that story.”

Stark led a study to find out whether superhydrophobic toes help geckos hold on in the rain. To simulate various weather conditions, researchers had their seven subjects walk on glass that was dry, misted with water, or submerged in a shallow puddle. In some trials, the geckos' feet were left dry; but in others they got a leisurely 90-minute soaking in a tub. (It's tough to get those foot pads wet, Stark says. Normally, water beads and rolls off of them.) 

After placing the geckos onto the glass surface, the researchers coaxed them into taking one step at a time with a harness attached to their pelvis (Stark describes the geckos as "not necessarily cooperative" during this procedure). The harness was connected to a device that gradually tugged backward on the geckos until they lost their footing, measuring how much force it took to unstick them.

The results, published today in the Journal of Experimental Biology, showed that water impairs geckos. When walking on a submerged surface, or with soaked toe pads, the geckos struggled to stay in place. It took much less force than usual to pull them free from the glass. 

When the geckos walked on a surface misted with water droplets—the condition that most resembled something the animals might find in their natural habitats—things got interesting. The geckos slid more than usual, but weren't totally defeated. “Even though they have lost a significant portion of their stickiness, they can still hang onto a misted glass surface,” Stark says.

That water-repelling power on their foot pads, then, seems to come in handy. Getting soaked would unstick their feet, but geckos are able to prevent this in damp conditions by quickly shedding water drops from their soles. Stark now wants to find out how wild geckos behave in wet weather. Do they walk like normal and let their superhydrophobic feet do all the work? Or, to avoid slipping, do they stay away from wet areas altogether?

Stark is not only a biologist; she's also a polymer scientist. So when she asks how gecko feet work and how the animals compensate for their shortcomings, it's because she's interested in ripping off their technology for human use. We're already well on our way.

"Materials scientists have created many 'gecko-tape' synthetics that are reusable and sometimes work even better than the gecko," Stark says—in dry conditions, that is. Scientists at the University of Berkeley have built a gecko-inspired adhesive that lets a car drive up a precipitous incline (though only on a perfectly smooth "road") and, like gecko toe pads, self-cleans by casting off any particles that stick to it. In Germany, researchers at the University of Kiel created a gecko tape that can hold an adult human with just an 8-by-8-inch square.

Other synthetic coatings and surfaces have been designed to repel water. Combining the two technologies to create a stick-anywhere tape that can handle a little water "would be ideal," Stark says. If we can figure out the trick, we can make adhesives that are more powerful and more versatile, she says—"in essence, more like the gecko."

Alyssa Y. Stark, Timothy W. Sullivan, & Peter H. Niewiarowski (2012). The effect of surface water and wetting on gecko adhesion Journal of Experimental Biology DOI: 10.1242/jeb.070912

Image: A gecko with wet feet slipping, from video by Alyssa Y. Stark

Mom's Genes Make Males Die Sooner

Men who make it to adulthood without succumbing to the male habit of dying in accidents shouldn't congratulate themselves too soon: their life expectancy still doesn't match a woman's. In industrialized countries, women at every age out-survive men. And it's not just humans. Males that die before females have been observed throughout the animal kingdom. It's even true of the lowly fruit fly, and it looks like harmful mutations in mothers' genes are to blame.

This idea, which has been put forward before, is called the Mother's Curse. It has to do with a little loop of DNA that's passed down in humans—and in most other animals—exclusively through the mother. This DNA hides inside the mitochondria, which are the cell's batteries, and doesn't get packaged up with the rest of the genetic material when sperm are made. Those tiny sperm will rendezvous (if they're lucky, of course) with an egg that supplies all its own mitochondria, along with their DNA.

The Mother's Curse theory says that since fathers don't get any say in the makeup of mitochondrial DNA, it could carry mutations that harm men without being weeded out by natural selection. These anti-male mutations might be the reason for males' shorter lifespans.

Researchers led by Florencia Camus at Monash University in Australia examined this question in fruit flies, an animal whose genes are well understood and easily fooled with. By crossbreeding different fly types, they created 13 lines of fruit flies that were identical except for their mitochondrial DNA. They watched these flies for differences in male and female lifespan. Then they sequenced the mitochondrial DNA itself to see what was driving those differences.

In a study published in Current Biology, the team found that males died sooner across all the fly types. They also saw wide variation in male longevity, while female lifespans were more consistent. Females in most of the lines lived for around 60 days; males were variable but never lived much longer than 50 days. Since their mitochondrial DNA was the only thing that differed between the flies, something in that DNA must have been responsible.

Looking at the actual letter-by-letter differences in the mitochondrial DNA, the researchers found that fly types that were farther from each other genetically also differed more in longevity. In other words, more mutations in the mitochondrial DNA led to more variability in lifespan. Together, these findings support the idea that mitochondrial mutations cause males to die early—in fruit flies, anyway.

Mutations that somehow harm males, but not females, are free to pile up in the DNA of mitochondria. Since females pass down this DNA on their own, evolution is essentially blind to its effect on males. It remains to be seen whether the same mechanism is at work in animals that aren't fruit flies, including humans. If so, men will be able to blame their mothers for their shorter life expectancies. They might want to find a more positive way, though, to fill their abbreviated time on Earth.

M. Florencia Camus, David J. Clancy, & Damian K. Dowling (2012). Mitochondria, Maternal Inheritance, and Male Aging. Current Biology DOI: 10.1016/j.cub.2012.07.018


New OCD Symptom: Tail Chasing

The comments on online forums are sometimes resigned, sometimes plaintive. One four-year-old "has always has some OCD issues," reports Brookey77, "especially when it comes to tennis balls. When he was a pup, he sucked on them as a baby would suck on a pacifier...Then he started eating them...For the last few months, he has been eating his leg."

An 8-month-old pitt bull is "a shadow chaser," says ultimatek9. "She is fine at night and when it is overcast, but when the sun comes out she goes into a trance. She locks onto the shadows and will start salivating and trembling."

Dogs with compulsion may pace, chase imaginary flies, or lick their flanks until they get sores, despite their owners' best efforts to make them stop. Certain breeds are especially vulnerable. A staple of canine compulsion is tail chasing, which frequently strikes bull terriers and German shepherds. On one forum, user MatrixsDad complains that his German shepherd "is constantly chasing and barking at her tail...She comes up and puts her backside against anyone who's standing around so she can get a better view of her tail before she starts chasing it."

Although they may seem like nothing more than cute YouTube material, dog compulsions can turn unfunny fast. A user called Fodder describes a cocker spaniel that used to chase and bite his tail whenever stressed. "Finally the day came—we pulled into the garage where he had been staying and he was cowering on the I got closer I realized that he was sitting in a puddle of his own blood. He had chewed his tail completely off."

Because of the apparent similarities between human OCD and dog compulsions, researchers led by Katriina Tiira at the University of Helsinki decided to investigate just how close the connection is. They gave detailed questionnaires to the owners of 368 German shepherds, bull terriers (standard and miniature), and Staffordshire bull terriers. Among their subjects, 218 were tail chasers.

The first clear similarity between tail chasing and human OCD is that they have a genetic component. In humans, OCD is estimated to affect 1 to 3 percent of the population in general. But the twin of a lifetime OCD sufferer has at least a 25 percent chance of OCD himself. Likewise, the fact that certain breeds of dogs chase their tails more suggests that somewhere in the breeding process, that tendency was embedded in their DNA.

The questionnaires turned up many similarities between obsessive dogs and humans. One was the early onset of the behavior: Human OCD often shows up in childhood or adolescence; tail chasing began for the greatest number of dogs in the study between 3 and 6 months old. Some dogs only tail chased occasionally, while others couldn't get enough and repeated the behavior several times a day. And some dogs also seemed to freeze or go into a trance, a symptom similar to one in human OCD patients called "obsessional slowness."

Certain factors appear to make dogs more or less likely to be tail chasers. Owners reported that tail-chasing dogs had been separated from their mothers earlier as puppies. Dogs that live with a lot of other dogs, though, don't chase their tails as often.

Dogs given vitamin and mineral supplements by their owners were less likely to tail chase, and so were females that had been neutered. This might mean that the presence of certain vitamins, or absence of certain hormones, makes tail chasing less likely. However, the authors acknowledge, it could also mean that owners who neuter their dogs or give them supplements are treating the dogs in some other way that lowers their risk of obsessive behaviors.

A subset of the dog owners in the study also filled out a questionnaire on the "personality" of their pets. Tail chasers were shyer and likely to have additional compulsions. Senior author Hannes Lohi says this resembles anxieties and behavioral inhibitions in human OCD sufferers.

"Our major aim is to identify new anxiety genes" in dogs, Lohi says. Those genes could teach us about how these conditions develop in dogs as well as in humans, who share the same environment and aren't that far off physiologically. We might even learn about new treatment avenues in humans. An earlier study found a genetic region that's linked to a flank-sucking obsession in Dobermanns—and the same region has been tied to human OCD and autism. But the new study found no connection between that genetic area and tail chasing.

It's likely, the authors write, that obsessive behaviors in dogs have many different origins and manifestations. The same seems to be true of humans. Hunting down the roots of these behaviors in our canine companions, then, might help us cure our own kinds of tail chasing.

Tiira K, Hakosalo O, Kareinen L, Thomas A, Hielm-Björkman A, Escriou C, Arnold P, & Lohi H (2012). Environmental effects on compulsive tail chasing in dogs. PloS one, 7 (7) PMID: 22844513

Image: Tim Mowrer/Flickr