by David Braun
The ants formed a ball after being swirled in a beaker. (Photo Credit 4.4)
When the researchers put ants in a dry beaker and gave the container a swirl, the ants rolled into a ball—much like a rolling snowball, Mlot said. It was easy to grasp the ball with a pair of tweezers and submerge the ants, he added. A shimmering layer within the underwater ball shows the edges of an air bubble trapped by the “ant sphere.” If the ball had been placed on top of the water, the ants would have instead formed a raft.
Robo-Ant
Research on fire ants could influence robotics. Nathan Mlot, an engineering student at Georgia Tech, explains: “With the ants, we have a group of unintelligent units acting on a few behaviors that allow them to build complex structures … In autonomous robotics, that’s what is desired—to have robots follow a few simple rules for an end result.”
Just One Ant
Even a single ant is buoyant in clean water, thanks to rough, waxy hairs that trap air around the insect’s body. Soap and other surfactants can reduce the surface tension of water, which in turn reduces an ant’s buoyancy.
Despite being denser than water, a single ant can walk on water, thanks to surface tension and hydrophobic (water-repelling) feet. To study how the ant’s exoskeleton traps air, the team needed to weigh the ant down. “The only way we could keep an ant underwater was by tying an elastic band around its body and attaching a weight to it,” Mlot said.
But surface tension is too weak to support larger objects, which is why it’s been a mystery how ant rafts could stay afloat. The answer lies in numbers: When linked together in a raft, the ants’ collective water repellency was actually 30 percent higher than that of an individual ant, the researchers found.
Acting Fluid
The Georgia Tech team found that fire ant clusters act like fluids with predictable physical properties: A cluster is a fifth as dense as water but has ten times the surface tension and is ten million times more viscous. Modeling a group of fire ants as a fluid, with each ant representing a molecule, makes describing an ant raft much like describing a drop of oil spreading on the surface of water, the study authors say. Of course, ant “droplets” do not follow totally predictable rules, with individual ants moving randomly within the raft, unlike individual oil molecules.
But when the ant clusters are handled, they don’t feel or behave the way water does. In fact, ant clusters feel more like putty when handled, Mlot said. “You could pick up that ball and it would have the same texture as soft putty. You could give it a squeeze. You could toss it in the air and the ants would stay together.”
When the ants are linked together, they behave like a liquid, researchers found. (Photo Credit 4.5)
FANTASTIC VOYAGE!
Snails Survive Being Eaten
by Birds
In the wild kingdom, it’s expected that when one animal swallows another one, the digested party dies. But not so with these surprising snails who are able to take a trip through a bird’s gullet and come out alive.
Tiny snails can survive being eaten by birds—and the gastropods come out the other end perfectly healthy, a recent study says.
They Will Survive!
Researchers studying feces of wild Japanese white-eye birds had noticed a surprising number of intact snail shells, especially of Tornatellides boeningi. This 0.1-inch (0.25-centimeter) snail is common to Hahajima Island about 620 miles (a thousand kilometers) south of Tokyo.
So Shinichiro Wada, a graduate student at Tohoku University in Japan, and colleagues fed more than a hundred snails to captive white-eyes and 55 to captive brown-eared bulbuls, another bird known to eat T. boeningi. The team found that roughly 15 percent of the snails passed through both bird species’ guts alive. One snail even gave birth shortly after emerging—apparently unfazed by its incredible journey.
TRUTH:
A SNAIL CAN CRAWL ALONG THE EDGE OF A RAZOR WITHOUT CUTTING ITSELF.
Branching Out
While the snails are passing through the birds’ guts—a process that takes between 30 minutes and two hours—the snails may be inadvertently hitching a ride to new digs. For example, the team found that T. boeningi snails in the wild were part of one large genetic group. T. boeningi snails whose shells weren’t initially found in the white-eye birds’ poop, or were found broken, were much more genetically isolated—in other words, they did not tend to move to new locations.
However, there are limits to this mode of travel, the scientists say. Since the birds’ digestion is not exactly leisurely, “we are thinking it might be difficult for the snail to migrate over an archipelago,” Wada said via email.
Snail Survival a Mystery
The remaining mystery is how the snails manage to survive being eaten. Their small size may prevent their shells from cracking, but the digestive process shouldn’t be a comfy ride for any living creature.
Wada said these snails, like many land snails, have the ability to seal their shells’ opening with a mucus film called the epiphragm. “This may be a big factor, because their tiny shell aperture and epiphragm would prevent inflow of digestive fluids,” he said.
WEIRD BUG TRICKS
Five Weirdest Bugs
If the natural world were to hold a talent contest, we’re confident that these five creatures would be in the running for the weirdest bug trick.
A favorite children’s book, The Very Hungry Caterpillar, tells the story of how a caterpillar gorges himself before he becomes a butterfly. His huge appetite sets him apart from the rest, and these bugs, worms, slugs, and leeches have their own very special talents as well.
BUG 1
The Very Toothy Leech
When this leech feeds, large teeth emerge from its anterior sucker. (Photo Credit 4.6)
A new leech king of the jungle, Tyrannobdella rex—or “tyrant leech king”—was discovered in the remote Peruvian Amazon in 2010. The up to 3-inch-long (about 7-centimeter-long) leech has large teeth, like its dinosaur namesake Tyrannosaurus rex. The T. rex leech uses its teeth to saw into the tissues of mammals’ orifices, including eyes, urethras, rectums, and noses—the first recognized specimen was plucked from the nose of a girl in Peru’s central Chanchamayo Province. What’s more, the newfound critter’s “naughty bits are rather small,” noted study co-author Mark Siddall, curator of invertebrate zoology at the American Museum of Natural History in New York City. “We didn’t say the large teeth were compensating for that, but it did come to mind,” he quipped.
Can you hear me now? Gryllotalpa vinae is the loudest of the insects. (Photo Credit 4.7)
BUG 2
The Very Loud Cricket
The mole cricket species Gryllotalpa vinae is the loudest of the insects. The critter uses its specialized front legs to dig a megaphoneshaped burrow. Standing inside that dugout, a cricket can chirp loudly enough that humans can hear it nearly 2,000 feet (600 meters) away. Microphones placed 3 feet (a meter) from a cricket’s burrow entrance have recorded peak sound levels of 92 decibels, or about the volume of a lawn mower. In fact, using the burrow, G. vinae is able to turn an astonishing 30 percent of its energy into sound.
The colorful Borneo ninja slug is green and yellow. (Photo Credit 4.8)
BUG 3
The Very “Ninja” Slug
Boasting a tail three times the length of its head, the newly described long-tailed slug is found only in the high mountains of the Malaysian part of Borneo. The new species shoots its mate with “love darts” made of calcium carbonate and spiked with hormones—hence its nickname: ninja slug. Scientists believe this Cupid-like behavior may increase reproduction success.
BUG 4
The Very Musical Water Bug
The water boatman’s song comes from a very private place. (Photo Credit 4.9)
The 0.07-inch (2-millimeter) water boatman species Micronecta scholtzi has an unusual talent: musical genitalia. Engineers and evolutionary biologists in Scotland and France recorded the boatman—which is roughly the size of a grain of r
ice—“singing” in a tank; the song is loud enough that humans can hear the sounds while standing at the edge of a boatman’s pond, but nearly all the sound is lost when the noises cross from water to air. The boatman creates his songs by rubbing his penis against his belly in a process similar to how crickets chirp. Sound-producing genitalia are relatively rare within the animal kingdom, but animals have evolved hundreds of other ways to boost their hoots, howls, and snaps.
Other cockroach species can swim or hiss, but this is the only one that can jump. (Photo Credit 4.10)
BUG 5
The Very Bouncy Cockroach
Prior to the discovery of Saltoblattella montistabularis in South Africa’s Table Mountain National Park, jumping cockroaches were known from only the late Jurassic period. The newfound species has legs specially built for jumping. “You don’t think of cockroaches and cute going in the same sentence, but these guys are really pretty neat,” said Quentin Wheeler, the director of Arizona State University’s International Institute for Species Exploration. “I like it because it helps clean up the tarnished image of cockroaches”—only a small fraction of the thousands of cockroach species are true pests, he said. “Everyone paints them all with the same nasty brush—this is an example of a cute little animal doing its thing.”
RECALLED TO LIFE
Spider “Resurrections”
Take Scientists by Surprise
A group of drowned spiders may have been down, but they weren’t out. A few hours later, they baffled scientists by “coming back to life.”
Like zombies, spiders in a lab twitched back to life hours after “drowning”—and the scientists were as surprised as anyone. The spiders, it seems, enter comas to survive for hours underwater, according to a study.
The unexpected discovery was made during experiments intended to find out exactly how long spiders can survive underwater—a number of spiders and insects have long been known to be resistant to drowning.
TRUTH:
MALE WOLF SPIDERS DON’T LIVE FOR MORE THAN A YEAR, BUT THE FEMALES OF SOME SPECIES CAN LIVE FOR SEVERAL YEARS.
Sleeping Spiders
In particular, researchers wanted to determine whether spiders in flood-prone marshes had evolved to survive longer underwater than forest-dwelling spiders can.
Scientists at the University of Rennes in France collected three species of wolf spider—two from salt marshes, one from a forest. The team immersed 120 females of each species in seawater, jostling the spiders with brushes every two hours to see if they responded.
As expected, all the forest wolf spiders (Pardosa lugubris) apparently died after 24 hours. The two salt marsh-dwelling species took longer—28 hours for Pardosa purbeckensis and 36 hours for Arctosa fulvolineata. After the “drownings,” the researchers, hoping to weigh the spiders later, left them out to dry. That’s when things began to get weird.
Good as New
Hours later, the spiders began twitching and were soon back on their eight feet. “This is the first time we know of arthropods returning to life from comas after submersion,” said lead researcher Julien Pétillon, an arachnologist now at Ghent University in Belgium.
Marsh-dwelling A. fulvolineata, which took the longest to “die,” typically requires about two hours to recover, the researchers discovered. In the wild, the species doesn’t avoid water during flooding, while the other salt marsh species generally climbs onto vegetation to avoid advancing water.
The spiders’ survival trick depends on a switch to metabolic processes—the processes that provide energy for vital functions in the body—that do not require air, the researchers speculate. Whatever trick these spiders have mastered, Pétillon said, they may not be alone. “There could be many other species that could do this that we do not know of yet.”
CLONED FATHERS MATE WITH INSECT DAUGHTERS
All in the Family
Are males necessary? Maybe not for long, at least in an insect species whose females have begun to develop sperm-producing clones of their fathers inside their bodies.
In the cottony cushion scale—a common agricultural pest that grows to about a fifth of an inch (half a centimeter) long—a new phenomenon has arisen: When some females develop in fertilized eggs, excess sperm grows into tissue within the daughters.
This parasitic tissue, genetically identical to the female’s father, lives inside the female and fertilizes her eggs internally—rendering the female a hermaphrodite and making her father both the grandfather and father of her offspring, genetically speaking.
TRUTH:
AUSTRALIAN LADYBIRD BEETLES ARE USED TO CONTROL COTTONY CUSHION SCALES, WHICH ARE A THREAT TO CITRUS ORCHARDS.
Loving Yourself
Though this new form of reproduction hasn’t replaced cottony cushion scale sex, “this parasitic male has taken off like an epidemic in population,” said study leader Andy Gardner, an evolutionary theorist at the University of Oxford.
“Once [this trend] gets started, it’s going to sweep through the population so all the females carry it. So there’s no point for regular males to exist,” Gardner added. If the females begin passing on the parasitic male to their offspring, there may eventually be no more need for “baby boy” cushion scales that grow up and produce sperm and fertilize females, Gardner said.
Gardner and the University of Massachusetts’s Laura Ross created a population model that predicted how females would respond to this infectious tissue living within their bodies. The results, published in American Naturalist, suggest that the females would benefit from the infection, negating the need for males.
“[T]his parasitic male has taken off like an epidemic in population … Once [this trend] gets started, it’s going to sweep through the population so all the females carry it. So there’s no point for regular males to exist.”
Andy Gardner
zoologist, Oxford University
Asexuality Still a Mystery
Though the exact timeline of male decline for the species is unknown, Gardner said, in the “long run, I’d expect the [insect species] to suffer because of asexuality.”
For instance, though 30 percent of animal species are asexual, in the “vast majority of cases, when we look at species that are asexual, they’re relatively recent [evolutionary] events … [and they] seem to go extinct quite rapidly. If you mate with yourself, that doesn’t generate the sort of adaptive variation that regular sex does.”
There are “obvious benefits” of straight-up sex, he said—the offspring get new combinations of genes that can make the species more robust in general.
Overall, it’s a mystery why there are so few insect hermaphrodites—only three species are known, all cushion scales. In general, insects are very sexually variable, reproducing in almost every way known to nature—including, in some species, males that can develop from unfertilized eggs.
Confusing matters, cushion scales are “not really hermaphroditic in the usual sense—it’s actually two ‘individuals’ in one body, [which] makes it more intriguing,” he said. “We’re sort of groping around in the dark just now.”
CAN BUG BRAINS BUST BACTERIA?
Cockroach Brains
May Hold New Antibiotics?
Cockroaches may make your skin crawl, but the insects—or, to be exact, their brains—could one day save your life.
Put away that roach spray! Cockroaches may come bearing unexpected gifts: The central nervous systems of American cockroaches produce natural antibiotics that can kill off bacteria often deadly to humans, such as methicillin-resistant Staphylococcus aureus (MRSA) and toxic strains of Escherichia coli, scientists said. Two species of locust tested so far also have the same bacteria-killing molecules in their tiny heads.
Insects Against Infection
The findings suggest that the insect world—which makes up 80 percent of all animals on Earth—may be teeming with new antibiotics, said study co-author Simon Lee of the University of Nottingham in the United Kingdom. Such a discovery is crucial be
cause scientists are scrambling to combat strains of several infectious diseases, including MRSA and E. coli, that are resistant to traditional antibiotics.
“It’s a promising new lead. We are looking in an unusual place, and to my knowledge no one else is looking there,” Lee said. “That’s what we need in terms of [finding new] antibiotics, because all the usual places”—such as soil microbes, fungi, and purely synthetic molecules—“have been exhausted.”
A Clever Defense
Lee and colleagues dissected the tissues and brains of cockroaches—which “smell as bad as they look,” Lee said—and locusts in the lab. The team tested nine separate types of antibacterial molecules found in the insects’ brains and discovered that each molecule is specialized to kill a different type of bacteria. This “very clever defense mechanism” allows the bugs to survive in the most dirty of domains, Lee said.
The scientists found the bugs had antibiotics only in their brain tissue, the most essential part of the body, he added. A bug might live with an infected leg, for instance, but a brain infection would almost certainly be fatal.