Robots are great at what they do — if the job is dull and predictable. Throw in the unexpected, and robots can do the unpredictable.

The task of programming a robot’s brain for the real world can be gnarly, says Josh Bongard, an assistant professor in the University of Vermont College of Engineering and Mathematical Sciences. “It turns out that building a robot, and programming it to do something interesting is a very non-intuitive process, and it’s a difficult one for humans to do well.”

The real world, he says, “is quite messy.”

Robots, in the jargon, need “adaptive behavior” to accommodate changing circumstances, says Bongard. When programming a free-roaming robot, “We are not likely to factor in a lighting change or people moving in and out of the field of view.”

It’s not clear how animals or people make adaptations, Bongard says, “and so it’s difficult to program a robot to do them.”

Robots: Are they alive?

Bongard, like a number of roboticists, is turning to biology for answers. But he does not want to emulate living structures. Instead, he wants to use evolution to craft robot control.

The process is akin to the “artificial selection” that helped lay the foundation for the science of evolution. Darwin, after all, wrote about how animal breeders had changed their livestock by repeatedly breeding the best animals and eating the rest.

In January, 2011, Bongard reported that he had taught four-legged, digital robots to stand and run toward a light source, by grading their control software on its ability to meet those goals.

Adaptive behavior was necessary, he says, because the light source could appear anywhere, or even take evasive action, “so the robot can’t just move its legs blindly every time.”

The robots had five seconds to do or die, and their first movements were grotesque because the control software initially moved their body parts at random. After every attempt, the control programs were graded by their ability to walk, stay upright and approach the light.

It’s brutal. More than 100 million failed programs went to the virtual graveyard in the name of science, Bongard says. The programs that showed some promise were retained, randomly varied and re-tested.

The same process is found in nature, where successful genes that face random mutation are re-tested by tomorrow’s environment.

Like the average biological mutation, the mutated robot software usually failed. But over a year of supercomputer time — equivalent to 1,000 years on a desktop computer — the winning programs evolved the ability to walk toward the light.

Weird winners

Considering the amount of trial and error, that was a satisfying but not necessarily surprising result. But here’s something to chew on. Bongard found that robots “born” with four legs had a handicap. During repeated simulations, the robots that started as snakes and developed legs during the five-second experiment were much quicker to learn the task.

You might guess — we would have — that the quick learning would have occurred in robots with full-time four-leg drive, given their longer experience with legged locomotion, but Bongard says the leg-free starters benefited by chunking the challenge: a) learn to approach the light, and b) learn to walk.

These robots “could evolve the ability to go from point A to point B while they still look like a snake, they don’t have to worry about balance, because they are already on the ground,” Bongard says. “Once evolution has figured out how to move toward the light, the ability to move on four legs could evolve.”

Meanwhile, the four-legged counterparts may still be flipping, flopping and floundering (Note to self: sell soul as political hit-man if science-writing gig crash-burns?) “The robots that had to stand upright would fall over, and it took evolution a long time to master balance,” Bongard says.

The approach — take the winners and vary them for a retest — resembles directed chemical evolution, which aims to create a better antibiotic by modifying and retesting molecules that show some ability to kill bacteria. “It’s basically the same idea,” says Bongard, “but instead of a candidate drug, we have virtual robots, and instead of selecting for … resistance to disease, they are selected for the ability to get to the light.”

Robots resemble rodents?

As a final exam for the digital robots, Bongard tested their balance with a blast of air. Although the leg-less robots “had evolved into legged robots that looked exactly like the other species, they were better able to run around under simulated windy conditions,” Bongard reports.

Bongard is first to acknowledge that he is “stealing from biology to help us build better robots,” but says, “the more interesting question is what this tells us about biological evolution. This recent work suggests that robots that change their bodies gain an adaptive advantage … and you see the same radical changes in body plan in nature: in insects, reptiles and in humans as they develop from infant to adult.”

Astronomers have just discovered two Earth-size, rocky planets around a nearby star. Though the planets are way too broilsome for life, they suggest that steady improvements in telescope technology has made the discovery of habitable planets just a matter of time.

But as astrobiologists continue to search for life in space, geo-biologists (ok, we coined that) continue to find bizarre life in strange places on Earth: in the dark ocean depths, between grains of sand, and at roasty-toasty temperatures once considered deadly.

Hot, humid, and totally alive!

Fifty years ago, nobody believed organisms could survive near the boiling point of water. When Thomas Brock started probing the hot springs in Yellowstone in the 1960s, he was not looking to overthrow a ground rule of biology. Instead, the University of Wisconsin-Madison professor, then at Indiana University, sought to study bacteria in a simplified, real-world environment.

At the time, and even today, precious little was known about how bacteria live their lives — unless they cause disease.

As Brock sampled his way up a hot stream, he approached its source in a hot spring, and the water temperature rose steadily.

At the time, biologists thought life would not tolerate temperatures near 80° C. But Brock kept finding bacteria, so he kept looking. Eventually, he found some that could live and reproduce near the temperature of boiling water — 100° C.

The prize of his collection was a bacterium he named Thermus aquaticus (for its hot-water habitat) and placed in a public repository for study by other scientists.

Over the years, T. aquaticus proved interesting indeed. For one thing, it was the first of more than 50 species of thermophilic bacteria known to tolerate or require temperatures near water’s boiling point.

For another, it was the first of the Archaea (ancient ones), primitive microorganisms that scientists now regard as a separate and highly primitive kingdom of life.

Deep roots indeed

Because thermophiles are Archaeans, and prefer the steamy conditions typical of early Earth, many scientists think they may tell us about the origin of life itself.

To any basic scientist, those contributions would be enough. But because their enzymes work in high temperatures, where chemical reactions are faster, the thermophiles have proven to be extraordinarily useful.

Today, enzymes derived from thermophiles are used to convert millions of pounds of corn (maize) into sugar to sweeten soft drinks.

But more important, at least to scientists who don’t guzzle fizzy pop at the lab bench, T. aquaticus supplied TAQ polymerase, the essential enzyme for polymerase chain reaction, AKA PCR.

PCR is an artificial technique that does what living critters do every day — replicate DNA. But PCR is the rocket ship of replication, since it allows you to multiply a piece of DNA a billion times in a few hours. That produces enough DNA to analyze to your heart’s content — for genetic engineering, biotechnology and forensic purposes.

PCR depends on TAQ polymerase.

Aware that PCR and soda pop are both billion-dollar industries, corporations and scientists around the world have frantically searched for other thermophiles that may have equally useful enzymes. They’re looking in odd places — not just hot springs and volcanoes, but also deep-sea vents, hot petroleum-bearing rock, the outflow of geothermal power plants, and smoldering piles of garbage.

Prowling for glow-in-the-dark squid

Call me Bob.

Short for bobtail squid. (Did I mention that I’m a 3-4 centimeter cephalopod, formally Euprymna Scolopes?)

Anyway, I hang out in shallow waters around Hawaii. Save your crocodile tears — somebody’s got to live in the sunny, tropical ocean. Anyway, here’s my problem: Even though I have 10 tentacles, I don’t have spines, poisons, or any other decent defense.

So I spend my days burrowed in sand at the ocean bottom, trying to keep out of mischief. Still, a fellow’s got to eat, don’tcha know, so I cruise at night, looking to grab a bite.

Here’s the snag: All sorts of nocturnal predators seem to have this thing about calamari sushi.

Light before flashlights

A long time ago, my ancestors evolved a nifty defense against their big teeth: stealth. Even their tiny squid brains figured out that predators could see them from below, as tasty dark blobs against the bright ocean surface.

Since this was before flashlights, my relatives had to improvise. So they press-ganged billions of luminescent bacteria into making light for them. The idea was to make us just as bright as the ocean surface — and hence invisible.

At least, this is how my great-aunt Tentacla tells it. To tell the truth, I think it had more to do with the evolutionary advantage of being hard to see.

Anyway, my ancestors fed the bacteria, and gave them a home in two specialized light-emitting organs. These “photophores” have a reflective membrane to shine all their light down, toward the hungry predators. They use a diaphragm to control brightness, and even have a lens to spread the light.

The photophore reminds me of a backwards eye — one that makes light rather than detects it.

My folks even figured out how to switch the bacteria “on” when needed.

In return, the bacteria got room and board, in the biological deal they call “symbiosis” or “mutualism.” Sometimes I think people could learn from this cooperative spirit….

But that’s enough thinking for today. My squid brain is squashed.

As I burrow into the sand for another daytime nap, permit me to introduce somebody who considers me almost as fascinating as I do.

Seriously speaking…

Margaret McFall-Ngai, a biologist at University of Wisconsin-Madison, says the bobtail squid may pretend it’s cooperating in a symbiosis with those light-making bacteria, but the reality is more ominous.

She says there’s evidence that this may be slavery, not symbiosis, since the squid, “inhibits the growth of the bacteria to enhance their luminescence.” The bacteria, Vibrio fischeri, could make a better living drifting in the ocean, or in the gut of another marine animal, McFall-Ngai observes.

The concept of bacterial enslavement broadens our perspective on the many possible relationships in the living world.

Most people, if they think about bacteria at all, conjure up disease and decay, but people would be dead without bacteria, since the little critters play essential roles in producing vitamins and preventing disease.

Since the bacteria in our guts vastly outnumber the cells in our bodies, it helps that they’re helpful!

Nevertheless, and for understandable reasons, bacteriologists have traditionally focused on disease-causing organisms, and, for simplicity, on one species at a time. But that skews our view of how bacteria actually live, says McFall-Ngai.

Three cheers for complexity!

Complexity and subtlety may be the hallmarks of these interactions, and the complexity begins by recognizing that V. fischeri is closely related to V. cholerae, which causes the human intestinal disease, cholera.

Cholera is caused by a V. cholera toxin similar to a toxin produced by the light-emitting bacterium. But far from harming the poor little bobtail, that toxin signals it to secrete food for V. fischeri, so the toxin is really a chemical “dinner bell.”

And this raises the intriguing notion that a cholera bug secretes toxins not to kill its host but to discuss its menu. If so, our whole notion of pathogenesis may need rewriting, McFall-Ngai suggests. “Maybe when we’ve been studying cholera pathogenesis we’ve been studying an aspect of a normal conversation that’s gone wrong.”

Indeed, the traditional bacteriological view of bacteria as pathogens to be studied in pure culture may be “like trying to understand the complexity of all the cultures that lived in Paris by studying the activity of the Nazi occupiers,” McFall-Ngai suggests. “You are studying groups that don’t belong there, and have disrupted the normal activities.”

Want more on how the flashlight squid bullies its bacterial brethren?

Between the grains

(1996 story, only photos have been updated)

To zoologist Robert Higgins, small is beautiful. His infatuation with small creatures — “meiofauna” — dates to a student job in a biology lab that paid 35 cents an hour. Instead of quitting for more lucrative work, Higgins was intrigued.

He’d heard about tiny, amazingly diverse creatures, and put grains of sand and muck through a fine mesh, and used a microscope to find hundreds of organisms.

Forty-four years later, Higgins has retired from the Smithsonian Institution, but he’s still goggling at meiofauna — a complex group of animals found in most Earthly environments.

Indeed, a handful of wet sand could contain more biological diversity than a whole rain forest, Higgins says.

In the course of peering through countless microscopes, Higgins has discovered hundreds of species. With Danish biologist Reinhardt Kristensen, he found an entire phylum, called Loricifera.

Phyla are the broadest categories of organisms, based on structure, and according to the International Association of Meiobenthologists, “The majority of recognized phyla have meiofaunal representatives. Currently, 20 phyla considered to be meiofaunal from the 34 recognized phyla of the Kingdom Animalia. Out of these 20 phyla, five are exclusively meiofaunal in size.”

Photo: Giulio Melone, department of biology, Milan University.

A bdelloid (a type of meiofauna) shrinks when it undergoes anhydrobiosis. The dormant, dehydrated bdelloid has greater resistance to environmental stress but is ready to spring back to the active form in conducive conditions.

Meiofauna living between grains of sand have made some fancy adaptations to their harsh environment. Some have hooks on their feet, used to grab the sand. Others have hooked mouthparts, also useful for locomotion.

Beyond freeze-dried

To survive a difficult environment, meiofauna called tartigrades have evolved an amazing adaptation called “anhydrobiosis.” In this form of suspended animation, the animals replace water in their cell membranes with sugar, protecting the membrane from destruction through radiation and freezing. Microorganisms die when their cell membrane ruptures.

During anhydrobiosis, organisms are rather like plant seeds or bacterial spores, Higgins explains. “They can dry up for 100 years, and be rewetted, and come right back to active metabolism.”

Fun is fun. But what is the practical importance of studying stuff that can hardly be seen, doesn’t seem to cause disease, and is — at least to some — utterly ugly?

In other word, who cares about microscopic beach crud?

Meet the beach-cleaning crew

Anybody who likes to hang on the sand should be interested, Higgins says. “This is the system that helps keep our beaches clean.” Plankton, bacteria, all sorts of dead material is continually washing ashore, and a lot of people love to sit on beaches.

There’s a public-health angle here. Hookworms occur on beaches where dogs defecate, but meiofauna may consume hookworms, along with other nematodes. “So if we upset that, we could upset beach cleanliness,” Higgins says.

Higgins notes that meiofauna comprise a basic part of the food web, and disturbing them could have unforeseen consequences for the entire system.

Still, it’s hard to escape the notion that most of the motivation here is the pure scientific urge to discover, to classify, to understand. Meiofauna, Higgins notes, were seen under the microscope Anton van Leeuwenhoek invented in 1683.

The key to finding these things, Higgins indicates, in patience, technology, curiosity — and institutional support. “If you stare through a microscope for hour after hour, you have a chance of finding these things, but if you need to get out a certain number of papers each year, you have to take shortcuts and you won’t find as much.”

Fantastic freak show

If you’ve hung around a big-city park, you may think that pigeons are countless — or uncountable. But according to scientists from New Zealand, pigeons now join the short list of animals that can count — or at least, can places images containing two countable items in numerical order.

It’s blue news for those who think only humans deserve human capacities. From empathy and altruism to murder and war, animals seem to have caught on to some of our best — and worst — tricks.

Now Damian Scarf, a post-doctoral researcher at the University of Otago, with his colleagues, has taught three pigeons to order pairs of numbers in the range from one through nine.

This is not exactly counting, but it certainly is a sign of numerical awareness in birds.

More important, the researchers have taught these retired racing pigeons the concept of smaller-to-larger, Scarf says. “Previously, this number abstraction was only known in primates, and now we have shown that it is not unique to primates.”

Serious screen-time serves science

The experiment began with a year-long training period, during which the birds were shown pairs of images, each containing one, two or three countable items. If the birds pecked at both images, smaller number first, they were rewarded with some wheat. (Although the images never contained a numeral, we refer to the “number” they contain for brevity.)

To prevent the birds from focusing on color, shape or other non-numerical details, the images showed a range of items, so that the only correct answer would reflect their number rather than other distinctions.

“The training time reflects how difficult it is for them to abstract,” Scarf says. “It’s such a foreign situation, number is not the first port of call when presented with a stimulus to discriminate. That’s why we had so many shapes, colors, surface areas.”

Even if the birds originally made their judgments based on color, “we pushed them to use a different strategy, to break away from that. Number is not the default discrimination mechanism” for pigeons, says Scarf, who worked under advisor Michael Colombo of Otago.

A genius for abstraction?

This does not mean that the birds are counting, says Scarf. “It’s more a fuzzy representation in the brain of what ‘three’ is. We can apply this verbal label to three, but they cannot. Pigeons, and animals in general, don’t have a definite idea of a number, that’s why they don’t perform perfectly, and why we see the distance effect.”

When the numbers on the test pair are further apart, Scarf found, “the fuzziness overlaps a little less.”

A greater distance between the numbers produced a quicker response and greater accuracy. For adjacent numbers, like four and five, the birds scored about 66 percent accuracy, compared to more than 95 percent for numbers separated by at least six. Once the difference rose to at least three, the pigeons did as well as monkeys in a path-breaking 1998 study that opened the field of numerical “thinking” in animals.

Scarf stresses that the birds were not just regurgitating what they had learned, but were learning numerical rules. “The goal was to find out whether they could acquire an abstract rule. We were just training for one through three, but they learned some flexibility, an abstract, ascending rule for ordering numbers” that would apply to other numbers on the screen.

Rooted in evolution, but where?

Being able to recognize that one thing is more numerous than another could help an animal survive, Scarf says. “When food is available in multiple places, an animal has to develop an optimal strategy for figuring out where the most food is, and I think we have subverted that capacity for this task.”

Where this capacity arose is anybody’s guess at this point. The evolutionary lineage of mammals and birds divided about 300 million year ago, Scarf says. “If this derived from a common ancestor, it’s very old. It’s also possible that primates and birds have evolved this independently.”

“I do think it’s important, just as our study of mirror self-recognition in monkeys, from the fundamental standpoint of how these abilities come about,” says Luis Populin, a professor of anatomy at the University of Wisconsin-Madison, who has found that, under certain conditions, monkeys can recognize themselves in a mirror. “It’s very nice and is yet another step toward understanding how our cognitive functions develop.”

You have to hand it to these birds, which have set a new standard for avian aptitude. “The new part is the idea that this abstraction of numbers is not tied to training,” says Scarf. “Most numerical tests with animals involve training and testing with the same numbers, but we were training with a limited set of numbers and testing them with numbers outside the range. They learned an abstract rule, and that’s what makes this study unique.”

If you drop a worker ant from an Amazonian treetop, what happens? In the species Cephalotes atratus, 87 percent of the time, that ant will wind up back where it started — a few meters lower down the same tree. Drop things that drift down at random, and only 5 percent of them will hit the tree.

In other words, these ants are controlling their flight — even though they don’t have wings.

That finding, which Stephen Yanoviak, Robert Dudley and Michael Kaspari¹ reported in 2005, provides a great starting point for untangling one of the mysteries of biology:

When and how did so animals take to the air?

Fly high

Flight is pretty common — among critters with wings, or something that resembles them, like a stretched membrane of skin. Birds, bats, moths and butterflies can fly. Even some lizards, snakes, fish and squirrels can glide under control toward the ground, which is not the same thing as falling.

Studies of ants in South America provide good data on “controlled aerial descent,” says Dudley, a professor of integrative biology at the University of California at Berkeley. In the course of some rather entertaining research, he and his colleagues have found that Cephalotes atratus ants:

During the controlled descent, at speeds above 4 meters per second, the ants perform “rapid postural adjustments,” Dudley says. “The limbs are moving, it’s not like a paper airplane.”

Dudley, an expert in the biomechanics of flight, says hundreds of species of tree-living ants in tropical Amazonian forests have evolved controlled gliding. Dropping to the forest floor can make them a meal for a mean and hungry ground-dwelling ant.

Looking at evolution

Perhaps the coolest part of the story is its evolutionary angle. Previously, scientists intrigued by the origin of flight have looked for evidence of wings and feathers, which appear more than 100 million years back in the fossil record.

But if flight really originated in arthropods that could not survive a fall from a tree or a cliff, that could wind the evolutionary clock back a good deal further. (Arthropods are animals with external skeletons and jointed legs, including spiders, insects and crustaceans like the horseshoe crab.)

Gliding under control is neither rare nor constrained to ants, Dudley says. “There are wingless aphids and flat spiders that live under the bark that can glide at a 45° angle. Controlled aerial descent has hundreds or thousands of independent origins in terrestrial arthropods.”

As old as the hills?

Over all, Dudley says, directed descent probably originated about 280 million years. If jumping like a flea or grasshopper is also deemed a form of flight, the origin could date back more than 400 million years.

The gliding hypothesis would not only help explain the origin of a common and cool behavior, but could take wind out of the sails for a favorite anti-evolutionary argument. Creationists, Dudley notes, have long demanded to know how wings evolved by asking, “What good is half a wing?” But according to the gliding hypothesis, wings unable to hold an animal airborne could still have evolved to help control a descending behavior that had long been in existence.

Flight of the control freaks?

Controlled gliding, Dudley says, “preceded the origin of wings, and so the evolution of flight is more about control than about the formation of wings.”

The new analysis “addresses qualms about the [supposed] lack of intermediate forms in the fossil record,” Dudley says. “Here is a viable intermediate form. There are lots of behavioral and ecological contexts where stubby, partial airfoils are useful.”

– David J. Tenenbaum

She asks if she’s overweight, and you wait half-a-second before responding, “Of course not, dear! I’ve just been noticing how slim you look these days.”

Any well-schooled husband knows the pitfalls of faltering in this “marital duet.”

Photo courtesy Eric Fortune and Melissa Coleman.
Video courtesy Science/AAAS

This image is an adult male plain-tailed wren.
Watch the video explaining how the bird-songs
study worked — with ultra-cool bird songs.

And now, we find a similar phenomenon among a singing duet by plain-tailed wrens, natives of the cloud forest in Ecuador.

Pairs of these wrens engage in a high-speed duet that relies on perfect timing: She utters a call, and if he chimes in on cue, she sings her part, and the duet continues.

If he’s late or silent, she is slow to resume the song.

This is cooperative behavior, but close examination also reveals a new mental phenomenon, says Eric Fortune, an associate professor of psychological and brain sciences at Johns Hopkins University. Fortune, first author of a study of the wrens that appears today, says his research “indicates that the full mental representation of the song exists in both birds, even though each one contributes only half of the song.”

The study looked at the interaction between the hearing and motor circuits in the brain via a concept called “mirror neurons.” Discovered in 1983 by Dan Margoliash of the University of Chicago, mirror neurons were “a key discovery that has profoundly shaped our thinking,” Fortune says. “He showed that an area of the brain used to control song responded only when the bird heard a playback of its own song, but not of any other bird’s song.”

Zina Deretsky,
National Science Foundation

Takes two to tango: The song of the plain-tailed
wren is a his-and-hers production.

These nerve cells, since seen in people, other primates and birds, are now called mirror neurons. In simple terms, mirror neurons allow a bird that hears its own song to “imagine” singing that song.

Brainiest birds?

In the new study, however, the mirror response occurs when an individual in a pair hears both birds singing — a sound that each bird cannot produce by itself.

In 2006, scientists identified the plain-tailed wren’s song as a two-part composition that required cues from both partners. “When we heard about these wrens, where one-half of the song is produced by the female, and the other half by the male, we thought, ‘This is amazing. Here’s a song this bird has learned completely in the sensory part of the brain, but it has only half of the motor program.’”

How could this work?

To unravel the sensory-motor linkage, Fortune, with Gregory Ball of Johns Hopkins and Melissa Coleman of Claremont McKenna College, recorded pairs of plain-tailed wrens, manipulated the songs in various ways, and then played them back.

They found that the birds not only sang in pairs, but sometimes also sang solo, making the same calls it would otherwise contribute to the duet, but with altered timing. They found that when a male flubbed his lines, the female might continue to sing, but with a measurable delay. “She’s waiting for him, then gives up and sings anyway,” Fortune says.

The birds were basing their behavior on what they heard — not very surprising. But the fascinating part emerged from the fact that they were engaged in a truly cooperative, back-and-forth behavior that was deeply embedded in the mirror neurons.

Both images courtesy Eric Fortune and Melissa Coleman

Like many field worker, Fortune had to make do with local material, as
shown in this laboratory. Rollover for a look at their solar and
hydro-powered neurophysiological rig, featuring a home-made version
of a $7,000 vibration damper.

Such cooperation, also evinced by dancers and musical ensembles, requires each party to know its own part, but the brain studies showed that they knew much more than that, says Fortune, who is also a visiting professor at Catholic University in Quito, Ecuador. “Both birds had very similar patterns of activity. The neurons responded most strongly to the combined song, not to their own part. The brain knows that they were trying to do this together.”

Got my eye (and ear) on you, mister!

Although Fortune says the songs are probably used to defend territory, he suspects she is also checking him out, gauging his evolutionary fitness, much as female birds rate a fellow’s feathers. “The female is testing the male’s ability to cooperate,” Fortune says. “She produces a long song, and the male has to work hard to insert his syllables at exactly the right time.”

Louis Vest

People also learn cooperatively. Do these
tango dancers hold a representation of the
complete dance in their heads, or is this just
another example of sexual selection at work?

These wrens, he says, “are wired to cooperate. There is a set of rules and the male’s job is to respond rapidly and accurately to the female’s challenge.”

It’s not just feathery guys that fail to respond on cue, and the evolutionary significance could extend far beyond birds. “This happens a lot in people,” Fortune speculates. “Why do women get annoyed when you forget their birthday? They are challenging your neural circuitry. It’s not like flexing your muscles; they are probing your brain. That’s a stronger cue for sexual selection.”

Bringing it back to birds, Fortune says, “It’s most surprising that these animals have a memory of their cooperative behavior in the brain, which includes the performance of another animal; this had not been shown before on a neurological basis. You can take their own half of the song, and play it back, and the motor neurons fire,” but the response is much more powerful when the bird hears the full, two-part song.

— David J. Tenenbaum

Poke deep inside an insect cell, and you may be in for a shock. At least we were startled to learn that bacteria live inside many insects, including the fruit fly, one of the workhorses of biology.

Photo: Biodiversity Institute of Ontario

The star of the study, Drosophila mauritiana.

Today, we hear how bacteria of the genus Wolbachia boost egg production in certain fruit flies. The mechanism, says Horacio Frydman, an assistant professor of biology at Boston University, involves a two-step: first the fly makes more egg cells, and then it blocks a process that would normally prune away extra eggs.

Insects, like other animals, are frequently “married” to bacteria in a relationship that benefits one or both parties. This is common: Bacteria in the cow’s rumen break down cellulose eaten by the cow. Bacteria in the human gut form vitamin K, necessary for blood clotting.

And bacteria in aphids synthesize essential amino acids that the aphids cannot make by themselves.
Wolbachia are not essential to the fruit flies, but their presence can quadruple egg production.

Speeding breeding

Producing four times as many offspring “is a powerful driver of infection,” Frydman says. “Wolbachia manipulate their host reproduction to favor their own spread in nature,” noting that in less than 20 years after Wolbachia was detected in fruit flies in southern California, the infection had spread as far as Canada. “It’s considered one of the largest pandemics in the recent evolution of life. Because Wolbachia influence their host reproduction, they also impact the evolutionary history of innumerable hosts.”

Wolbachia have been linked with a wide variety of effects in the insect realm. Wolbachia “lives in at least 20 percent of the world’s arthropods, including insects, spiders, mites, and crustaceans,” according to the Wolbachia project, making them an active area of investigation.

How could this symbiosis work to increase the number of offspring?

Using sophisticated microscopy, Frydman, Ph.D. student Eva Fast and colleagues tracked the location of Wolbachia in fruit flies. In D. mauritiana, a species native to the Mauritius Islands in the Indian Ocean, the bacteria congregate in the germline stem cell niche — a structure that supports stem cells that develop into eggs. In D. melanogaster, the bacteria accumulate in the niche that harbors a different type of stem cell, which produces the eggshell.

In the germline stem cell niche, the bacteria actually outnumber mitochondria, organelles involved in making energy for the fly.

Having the bacteria in the germline stem cell niche doubled the rate of division among those stem cells. Further investigation showed that the bacteria later also halved the rate of programmed cell death.
So the bottom line was a four-fold increase in egg production.

The virtue of pruning

“It’s remarkable that there are two mechanisms being manipulated by the bacteria, the rate of egg production and the rate of programmed cell death,” says Frydman.

Hitting both systems makes sense, Frydman adds, although the mechanisms remain unclear. “It is not surprising that Wolbachia would evolve to manipulate those two process, because they are key in controlling the rate of egg production, and therefore it has a profound impact in the reproductive success of the infected host and in spreading of bacteria in nature.”

Anything that increases the number of eggs and offspring is likely to be favored by natural selection, Frydman adds.

Photo: CDC, #373

Parasitic worms cause elephantiasis, which afflicts this man from the Philippines. Could killing Wolbachia prevent this disfiguring disease?

A healthy thing?

Beyond an insight into the fascinating biology of symbiosis, the finding could also have health implications. Parasitic worms that cause diseases like elephantiasis seem to benefit from Wolbachia infection.

And Wolbachia can affect insect immunity: Tests have shown that infected fruit flies are more resistant to some viruses, for example. And a recent paper in Nature found that mosquitoes in Australia could not transmit dengue fever if they carried a Wolbachia strain derived from Drosophila.

Mosquitoes also transmit malaria. Conceivably, better knowledge of the interaction between Wolbachia and insects might convert mosquitoes from a carrier of this ancient scourge into a defense against it.

– David J. Tenenbaum

If you think slavery has been abolished, consider the case of the gypsy moth and the virus. For more than 100 years, people have noticed that some gypsy moth caterpillars climb to the top of trees before they die and decompose, or “melt.”

Melting releases more virus particles and is the normal fate of these caterpillars, but why did only some caterpillars perform this ascending death march?

Gypsy moths are voracious insects that have been spreading across the United States for a more than a century, so nobody is feeling too sorry for them, especially people who have seen them strip forests bare.

Still, it’s nice to read a good explanation for this peculiar “climb, croak, melt” behavior.

All the better to infect you with, my dear!

A study published today identifies a viral gene that blocks one stage of maturation in gypsy moth caterpillars, which normally hide during the day. But when Kelli Hoover, a professor of entomology at Penn State, and her colleagues infected bottled caterpillars with the virus of doom, the caterpillars showed the same climbing ‘n’ dying behavior that appears in the field.

In nature, those caterpillars would melt and then rain virus down to infect other gypsy moths.

The moth misbegotten

Gypsy moths were introduced to Massachusetts in the late 1800s by a bumbler who wanted to raise silk by crossbreeding them with silkworms — a different species, says Hoover. “It was crazy; this guy did not know anything about species, apparently.”

Still, the gypsy moths did bring fecundity and a ferocious appetite to the table — or forest. “They eat so many different kinds of trees and plants … in a bad outbreak, the insect frass dropping down sounds like rain, so you need a hat,” Hoover says.

We had to look it up to be sure, but frass is basically insect poop.

Gypsy moths are such effective defoliators that authorities try to control them with Bt, a bacterial spray that unfortunately kills beneficial insects, not just harmful ones.

Hoover’s study focused on a viral gene called egt, which inactivates a hormone that starts molting – a process that ends each stage, or “instar,” of the caterpillar’s development. “When they stop molting, they keep feeding, and that’s why we looked at egt,” Hoover says.

Photo: USDA APHIS Pest Survey Detection and Exclusion Laboratory

The battle against gypsy moths was joined before 1900, when an unknown chemical was sprayed against the invader.

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A dangerous meal

In every case, Hoover says, “if the gene was active, the moth died at the top of the bottle. If the gene was inactivated, it died at the bottom.”

It’s not clear, Hoover says, exactly why the gene changes behavior, but this is the first time it was traced to a single gene.

Because LdMNPV (the Lymantria dispar nucleopolyhedrovirus) infects only gypsy moths, and kill them at a young age, it might work as a biocontrol agent against a disastrous insect invasion. However, Hoover says, “the experiment’s goal was more basic – to understand how the virus enslaves its host.”

Certainly there is evolutionary logic behind changing your host’s behavior for your own benefit, assuming you are a pathogen or parasite, and “body-snatching” is well-known. For example, a fungus forces ants to climb, zombie-like, and die where they can easily spread fungal spores.

And it’s not just insects. The rabies virus, Hoover adds, “causes dogs, raccoons and bats to become more aggressive, to be out during the day, where they approach people and try to bite them,” which spreads the virus even though it endangers the animal.

And toxoplasmosis, a parasite, can make mice less fearful of cats, Hoover says, “so they are more likely to get eaten and infect the cat.”

There is even speculation that toxoplasmosis may cause men to behave with greater jealousy, Hoover says, “but the only thing that’s really been looked at is that mice with toxoplasmosis have a higher level of dopamine,” a feel-good neurotransmitter.

Is slavery therefore not all drudgery?

— David J. Tenenbaum

Since they were discovered 200 years ago, the plesiosaurs have posed a riddle. Long, brawny, toothy, their skeletal architecture was unsuited to laying eggs and sitting on a nest — and yet, there was no evidence that these reptiles gave birth to live young.

Until now.

In the journal Science tomorrow, a pair of paleontologists will describe a stunning fossil that shows a maturing plesiosaur inside its mother’s abdomen.

The fossil, dating to 78 million years ago, had lain in a museum basement for many years, says first author F. Robin O’Keefe, professor of biological science at Marshall University in Huntington, West Virginia. “Finding a pregnant animal fossil is always really rare, for any group of aquatic reptiles, and finding an undisturbed specimen is very unusual.”

O’Keefe collaborated with Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles, in studying the fossil, which is part of a new dinosaur-era exhibit at the museum.

Common, but curious

The plesiosaurs were monsters of the deep, says O’Keefe, having lived from roughly 200 million years ago until they went extinct along with the dinosaurs 65 million years ago. “These were apex predators, killer-whale size, and there is a very long, diverse fossil record.”

The specimen in question was complete, except for the head and some neck vertebrae, and was about 4.65 meters long.

Although the fetus was no midget – at 1.5 meters long — it was not ready to be born, O’Keefe says. “It’s really a guesstimate, but we think it is maybe two-thirds developed, definitely not ready for prime time. We have a bit of the back of its skull, and it’s poorly ossified [hardened]. If it was born like that, it would be like having your head made of Play Doh. It had no teeth, tiny flippers, and could not move around.”

The Cretaceous ocean, with its range of giant predators, was “not a place to be that helpless.”

Pride of the plains?

The pregnant plesiosaur was excavated in 1987 by Kansas landowner Charles Bonner. “He knew at the time that this was something interesting, but when it comes out of the ground, it’s inside a plaster jacket,” O’Keefe says. Removing a 15-foot specimen embedded in rock “is a time-intensive and expensive operation.”

But when the natural history museum decided to mount a new paleontology exhibit, the plesiosaur seemed a logical display, and director Luis Chiappe contacted O’Keefe. “He knew it was something interesting, thought it’s maybe a baby,” says O’Keefe. “Would I be interested in working on the specimen?”

A question answers itself

Would any paleontologist not be? And so O’Keefe found himself handling ancient evidence of reptilian motherhood. “My first thought was not some great scientific thought: ‘It’s really cool, you don’t often see fossils that neat.’”

When the rocks spoke, they revealed that this well-known reptile was, finally, in a maternal mood. “So here we have a pregnant plesiosaur, after 200 years of mystery, we have the smoking gun, we now know they gave live birth.”

To prove that, however, the scientists had to discount alternative explanations for finding an embryo inside an adult of the same species:

Does momma care?

We tend to think of reptiles as egg layers, but various flavors of birthing live young have evolved at least 80 times among marine reptiles. “The mother could retain the egg and have it develop inside her, or it could go all the way to a full-blown mammalian pattern, using a placenta to connect to the uterine wall,” O’Keefe says. “Given how big this fetus was, there probably had to be some pretty significant communication between mother and young.”

Paleontology shows structure, not behavior. O’Keefe says the new find suggests that mother plesiosaurs probably cared for their young, a rarity among modern reptiles. If one offspring “has absorbed all your reproductive energy, it makes a lot of sense to take care of it,” he points out.
In raising this possibility, he says, “We climbed out as far out on a limb as we thought we could get.”

And although there is no suggestion that the plesiosaurs nursed their young, live birth would distinguish them from many reptilian relatives and move them closer to modern, maternal marine mammals like whales and dolphins.

– David J. Tenenbaum

Wondrous weevils sport super screw!

In animal appendages, some joints resemble hinges. Others, like your hip, are unmistakably akin to the ball-and-socket joint, another mechanical mainstay.

Now, scientists have found a biological screw in a type of beetle called a weevil. Obliquely described as having “rotational movement combined with a single-axis translation,” the new screw-and-nut assembly was first seen in a weevil from New Guinea, says entomologist Alexander Riedel.

The discovery of the first biological screw-and-nut assembly emerged from an exploration of the weevil’s characteristic defense mechanism, says Riedel, an entomologist and curator who specializes in weevil classification at the State Museum of Natural History in Karlsruhe, Germany.

Two things weevils have in common are small size – the Trigonopterus oblongus under study was about 4 millimeters long – and legs that fold under the body. “We wanted to look at their particular defense mechanism,” says Riedel, “to know how it works.”

Using a microscopic counterpart to CT scanning, German researchers snapped electron micrographs of the weevil’s trochanter (“screw”) and (ROLLOVER) coxa (“nut”).”

Image © Science/AAAS

It’s all in the scan, man!

Given the small size, the scientists relied on a kind of micro CT scan driven by X-rays from a synchrotron, “We realized there is a very nice screw joint,” Riedel says, “We’ve had this information for some time, but while talking with a herpetologist colleague, we realized there is no other case in the whole animal kingdom, in all of biology, with a similar screw joint.”

The nut-and-screw are located at one of three major joints in the beetle’s leg; when the leg is retracted, the screw tightens in the nut, which remains stationary, Riedel says. Overall, the screw and nut would be able to turn 345 ° although the leg itself does not move that much.

A (good) turn of the screw!

“The weevils, or snout beetles, have been known from ancient times,” says Riedel. “There are grain weevils and lots of other species, including the boll weevil [a cotton pest]. Many other species are not pests … and so are of no particular interest to humans, which is why nobody knows much about them.”

Why does every weevil species that that Riedel examined have such a mechanism? Weevils, which spend a lot of time climbing on vegetation, apparently evolved from beetles that usually walk on a flat surface or underneath bark, Riedel says. “If a weevil is sitting on the edge of a leaf and wants to walk on a small twig, it’s essential that it can grip under its body, and this motion goes very nicely with this screw joint. A ground [walking] beetle would have great difficulty walking in similar conditions.”

The screw joint now joins the hinge, ball-and-socket and saddle joint as fundamental technologies invented by evolution, Riedel says. Historians of technology have long wondered about the origin of the incredibly useful screw, and it turns out that screws and nuts were in their flour bins all along – but only visible to those who happened to have a handy synchrotron!

– David J. Tenenbaum

For controlling agricultural insects, bats are worth at least $3 billion a year to U.S. agriculture, according to a 2011 study from Boston University. “People often ask why we should care about bats,” said study co-author Paul Cryan, a research scientist with the U.S. Geological Survey in Fort Collins, Colo. “This analysis suggests that bats are saving us big bucks by gobbling up insects that eat or damage our crops. It is obviously beneficial that insectivorous bats are patrolling the skies at night above our fields and forests—these bats deserve help.”

As conservation officials scramble to respond to white nose, they are enacting quarantines to prevent people – cavers, bat-lovers and scientists alike – from transporting the fungus between caves. Last year, for example, the National Wildlife Refuge System halted public access to all caves and mines on its refuges, and set protocols to prevent scientists from spreading the infection.

In May, 2011, the Fish and Wildlife Service rolled out a national plan for confronting and controlling white nose syndrome.

But bats can do plenty of transportation on their own. Even non-migratory bats may fly 200 miles between their hibernation site and their summer range, says David Blehert, a microbiologist at the U.S. Geological Survey National Wildlife Health Center in Madison, Wis., and a leader of white nose studies. “They can move large distances, across state lines, so there is potential for significant disease spread based on bat-to-bat interactions.”

What is the white nose syndrome situation now? Why is it so deadly? What bright ideas are afoot to preserve insect-eating bats, and what is the likely end game?

Why deadly?

In the short time since white nose syndrome appeared in 2006, scientists have pinpointed a fungus called G. destructans as the killer. But how does G. destructans do its work? One clue comes from the fact that it only kills during hibernation, when bats live in mines and caves at a rather chilly 7°C. “The fungus only grows in the cold, and when insectivorous bats hibernate in a temperate region, they drop their core body temperature to the ambient level,” says Blehert.

(The fungus is not likely to attack fruit-eating bats, says Blehert, because they do not have long periods of “torpor,” the slow-metabolism hibernation state that is conducive to the white-nose fungus.)

A low body temperature allows the bats to survive winter without eating, but it could also curtail the immune system, Blehert says. “Studies of bat immunology are in their infancy, but based on what is known about the physiology of other hibernating mammals, especially the 13-lined ground squirrel it’s likely that the immune system becomes suppressed, and that leaves them particularly vulnerable” to the fungus.

How does the fungus kill? It apparently does not enter systemic circulation, as internal organs are not damaged. All mammals awaken from hibernation occasionally, but Craig Willis of the University of Manitoba has speculated that infected bats have more waking hours, causing them to run out of energy during a period when they neither eat nor drink.

Blehert and his colleagues favor a second explanation: dehydration. Despite the “white nose” name, Blehert says, the most significant infection occurs on the wings. “The wings of a bat have eight times as much skin as the trunk; it’s a massive, very delicate and exposed membrane” with a single layer of epidermis surrounding a thin layer of connective tissue and some muscles and glands. “The fungus selectively invades the wing skin, and destroys everything in its path,” Blehert says.

Beyond their role in flight, bat wings are also needed to regulate temperature, fluids and electrolytes. “The wings may be the Achilles heel that exposes them to such significant infection,” Blehert says.

Indeed, an emerging disease that is devastating amphibians, the chytrid fungus, also affects the skin, and is thought to kill by causing an electrolyte imbalance. “The amphibian’s skin is very important for the balance of water and electrolytes, which has been the basis for our hypothesis about why white nose syndrome is so deadly. There was a paper¹ in 2009 that demonstrated that a superficial chytrid infection causes an ion imbalance in frogs, causing a disruption of the potassium gradient that causes the heart to stop. A superficial fungal infection causes a cardiac arrest! This is a very different concept than getting athlete’s foot and having an itchy foot.”

Stopping the wave of death

As dead bats pile up in caves, what can be done to stop the spread of G. destructans? The first step, trying to slow dispersal, is already under way in affected states, with restrictions on cave entry, and new protocols for disinfecting equipment and people who have a legitimate reason to visit hibernation spots.

The fungus does respond to common anti-fungal agents, according to a 2011 study, which found, unexpectedly, that the meds worked at the low cave temperatures that the fungus prefers. “The challenge is, how could you use pharmaceuticals to manage a disease in free-ranging wildlife?” says Blehert. “They don’t go to the doctor, and they inhabit environments that are likely contaminated with fungus. Say you could treat bats and cure them of the infection. If you can’t remediate their hibernation sites, they will become reinfected when they re-enter the cave.”

The authors of the anti-fungal study did raise the possibility of using meds to decontaminate caves, but this process is not being done, Blehert says. “Going into a cave with a general fungicide would be like dropping a nuclear bomb on a city. Caves are full of bacteria, fungi, invertebrates and vertebrates that may only exist in that unique ecosystem, and getting rid of such an important group of organisms [fungi] could risk significant unintended consequences.”

Willis has proposed using little heaters, since bats seem to fare better in warmer regions of caves, perhaps because that sustains immune function. Small heaters are being tested as bat refuges in some New York State caves, says Lisa Warnecke, a post-doctoral fellow at Manitoba.

Lessons from Europe

G. destructans is an “emerging exotic disease,” and to investigate such diseases, scientists always want to know how the pathogen interacts with hosts in its land of origin, which seems to be Europe:

In 2009, the fungus was found in a greater mouse-eared bat in France²;

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Photo: Gabrielle Graeter, NCWRC

Is this bat unhappy about the tufts of fungus on its muzzle — or the researcher’s big hands?

During the winter of 2009-2010, infected bats were found in 76 of 98 sites in the Czech Republic; and

A 2010 study³ in Europe found a white nose pathogen in 21 of 23 suspected bats that was “100% identical” to the U.S. pathogen.

Although the fungus been found in at least five bat species in Europe, die-offs have not been seen there, suggesting that something is different about how the pathogen, host and environment interact. Pathogens and hosts co-evolve through time in a complex dance:

The pathogen may become milder, improving its own survival (and that of its host);

hosts may evolve immune resistance; and

hosts can change their behavior to reduce exposure to the disease.

In the lab in Manitoba, Willis and Warnecke are studying how long little brown bats are awake during hibernation, whether the fungus is a necessary and sufficient cause of death, and if the North American or European strains of fungus have different effects on the bats. “If both isolates show the same severity for North American bats, that may mean that bats in Europe have co-evolved with the fungus and are resistant to it,” says Warnecke. “On the other hand, if the European isolate does not cause trouble for North American bats, then the fungus in North America is a mutant that has gotten really aggressive.”

Other factors could explain the lack of disease in Europe, says Blehert. “European bats are larger, which may provide them with more of a buffer against a physical insult like a fungal infection.” The little brown bat, the preeminent victim of white nose, weighs about 6 grams – about the weight of two pennies, Blehert says.

European bats also tend to hibernate in small groups. “They don’t have those 100,000-plus hibernacula like we see in the United States. With fewer animals, the disease transmission dynamic is likely to be reduced, with less amplification of the fungus, and lower rates of bat-to-bat transmission.”

In the long run, Blehert says, American bats may evolve some resistance. “In general, the population decline in caves and mines comes to about 78 percent, but the bats have not disappeared. We would expect something that gets into population to cause high mortality and a steep drop-off in population. Then, with fewer animals around, disease transmission could moderate.”

Although the regional extinction of the brown bat has been predicted to occur 16 years from now, “our bats may ultimately develop population dynamics more like Europe, with fewer animals and moderated disease transmission and progression,” Blehert says.

Evolution, in other words, could select for animals that, for behavioral or immune reasons, are less susceptible to white-nose.

But letting the situation play out without trying to help the bats, Blehert says, amounts to a high-stakes gamble with one of the wonders of the night sky.