April 9, 2013
For thousands of years, humans have shared their beds with blood-sucking parasites. The ancient Greeks complained of bedbugs, as did the Romans. When the lights go off for those suffering from this parasitic infestation today, from under the mattress or behind the bedboard creeps up to 150,000 of the rice grain-sized insects (though average infestations are around 100 insects). While bedbugs are one of the few parasites that live closely with humans yet do not transmit a serious disease, they do cause nasty red rashes in some of their victims, not to mention the psychological terror of knowing that your body becomes a buffet for crawling bloodsuckers after dark.
By the 1940s this age-old parasite was mostly eradicated from homes and hotels in the developing world. But around 1995, the bedbug tides again turned. Infestations began flaring up with a vengeance. Pest managers and scientists aren’t sure what happened, exactly, but it may have been a combination of people traveling more and thus increasing their chances of encountering bedbugs in run down motels or infested apartments; of bedbugs bolstering their resistance to common pesticides; and of people simply letting their guard down against the now unfamiliar parasites.
Large cities such as New York have particularly suffered from this resurgence. Since 2000, the New York Times has run dozens of articles documenting the ongoing plague of bedbugs, with headlines such as Even Health Dept. Isn’t Safe from Bedbugs and Bringing Your Own Plastic Seat Cover to the Movies.
As many hapless New Yorkers have found, detecting stealthy bedbugs is only the first step of what usually turns into a long, desperate eradication battle. Most people have to combine both pesticides and non-chemical methods for purging their apartments. In addition to dousing the apartment and its contents in pesticides, this includes throwing away all furniture the bugs are living on (streetside mattresses in NYC with a “BEDBUGS!” warning scrawled across them are not an out-of-the-ordinary sight), physically removing the bodies of poisoned bugs, subjecting the home to extreme heat or cold, or even hiring a bedbug sniffing dog. Sometimes, after so many sleepless nights and days spent meticulously combing the cracks between the mattress and sheets or searching behind couch cushions, residents simply throw up their hands, move out and start their lives over.
Recognizing this ongoing problem, researchers are constantly trying to come up with new methods for quickly and efficiently killing the pests. The latest technique, described today in the Journal of the Royal Society Interface, takes a hint from mother nature and history. For years, people in Eastern Europe’s Balkan region have known that kidney bean leaves trap bedbugs, sort of like a natural fly paper. In the past, those suffering from infestations would scatter the leaves on the floor surrounding their bed, then collect the bedbug-laden greenery in the morning and destroy it. In 1943, a group of researchers studied this phenomenon and attributed it to microscopic plant hairs called trichomes that grow on the leaves’ surface to entangling bed bug legs. They wrote up their findings in “The action of bean leaves against the bedbug,” but World War II distracted from the paper and they wound up receiving little attention for their work.
Rediscovering this forgotten research gem, scientists from the University of California, Irvine, and the University of Kentucky set out to more precisely document how the beans create this natural bedbug trap and, potentially, how it could be used to improve bedbug purging efforts. “We were motivated to identify the essential features of the capture mechanics of bean leaves to guide the design and fabrication of biomimetic surfaces [or synthetic materials that mimic ones found in nature] for bed bug trapping,” they write in their paper.
They used a scanning electron microscope and video to visualize how the trichomes on the leaves stop the bedbugs in their ravenous tracks. Rather than a Velcro-like entanglement as the 1943 authors had suggested, it seems that the leaves stick into the insects’ feet like giant thorns, physically impaling the pests.
Knowing this, the researchers wondered if they could improve upon the method as a way to treat bedbug infestations, because leaves themselves dry out and can’t be scaled up to larger sizes. “This physical entrapment is a source of inspiration in the development of new and sustainable [or scalable and chemical-free] methods to control the burgeoning numbers of bed bugs,” they write.
They used fresh bean leaves as a template for micro-fabricating produced surfaces that precisely mimicked the leaves. To do this, they created a negative molding of the leaves, then poured in polymers sharing a similar material composition of the living plant’s cell walls.
The team then allowed bedbugs to walk across their synthetic leaves to test their effectiveness compared to the real deal. The fabricated leaves did snag the bugs, but they didn’t hinder the insects’ movements quite as effectively as the living plants. But the researchers are not deterred by these initial results. They plan to continue working on the problem and improving their product by more precisely incorporating the mechanical properties of the living trichomes. The optimistically conclude:
With bed bug populations skyrocketing throughout the world, and resistance to pesticides widespread, bioinspired microfabrication techniques have the potential to harness the bed bug-entrapping power of natural leaf surfaces using purely physical means.
March 31, 2013
You probably think of the Arctic as a cold, frozen tundra—home to lichen, polar bears and scattered herds of reindeer. In many places, this view would be accurate, but in a few relatively southern areas in Canada, Alaska and Russia, warming temperatures over the past few decades have allowed new types of plants, such as shrubs, to take root.
And by 2050—if current warming trends continue—we’ll see a dramatically different ecosystem across the Arctic, starting with something that’s largely unknown in the area currently: trees. According to research published today in Nature Climate Change, tree cover in the Arctic could increase by more than 50 percent over the next few decades.
The research team, which included scientists from a number of universities and was led by Richard Pearson of the American Museum of Natural History, made the calculation based off of current projections of how the Arctic’s climate will change by 2050. So far, temperatures in the region have risen about twice as fast as those for the planet as a whole.
They created a model that predicts which class of plants (various grasses, mosses, shrubs or trees) will grow given a particular temperature and precipitation range expected for the future; for each spot on a map of the Arctic, they fed in the 2050 projections. Doing this kind of vegetative modeling for the Arctic, they say, is relatively straightforward compared to doing it for somewhere like the tropics, because there are hard limits on the temperature and growing season length that given plant types can tolerate.
They found that tree cover will expand drastically, covering up to 52 percent more land area than currently, rising far north of the current tree line in Alaska and Canada. This new tree cover will mostly come at the expense of areas currently covered by shrubs, but shrubs will take over places now dominated by tundra plants (lichens and mosses), and some areas presently under ice will convert into tundra.
In effect, the area’s warming climate and lengthening growing season will shift all current vegetation zones to more northerly and colder regions. Already, these vegetation zones have shifted an average of five degrees of latitude over the past 30 years–in other words,
the vegetation in one spot resembles how a location five degrees south looked 30 years ago .
But by 2050, this shift will be even more dramatic—perhaps equaling 20 degrees of latitude—and a projected 48 to 69 percent of the Arctic’s vegetated areas will switch to a different class of plants. Some rare plant species could be at risk of extinction if they’re not able to migrate as quickly as the vegetation zones move.
Because plants are the base of any food chain, this conversion will have wide-ranging effects, both locally and elsewhere. “These impacts would extend far beyond the Arctic region,” Pearson said in a press statement. “For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting.” Their migrations patterns would presumably be altered by the growth of forests on what had been open tundra.
Most troubling, the conversion of white, snow-covered land to dark vegetation will further
affect the warming of the planet. Because darker colors absorb more radiation than the white of ice and snow, shifting large masses of land to a darker color is projected to further accelerate warming, creating a positive feedback loop: more warming leads to a greener Arctic, which leads to more warming.
Given all the other problems that the area is rapidly encountering as the climate changes—melting glaciers, increasing oil exploration and hybridizing bear species—it’s clear that the Arctic will be one of the most environmentally fragile regions of the planet over the coming century.
March 27, 2013
In recent years, research has upended one of the most intuitive ideas of modern science: that bacteria simply make us sick. Scientists have discovered that many types of bacteria living in and on the human body play a crucial role in its healthy functioning—and that these colonies are remarkably populous, with an estimated ten times as many bacterial cells as human ones in the average person.
Similarly, most research into the microorganisms living on fresh produce has focused on a few species of bacteria that cause disease, such as poisonous strains of E. coli, instead of the billions of harmless or even beneficial bacteria cells that live on fruits and vegetables.
Finally, though, the field is catching up: For the first time, researchers have sampled and sequenced the DNA of the hundreds of varieties of bacteria that harmlessly live on the produce you buy at the grocery store. Their study, published today in PLOS ONE, revealed 17 to 161 families of bacteria on each of the fruits and vegetables they tested, with grapes, peaches and sprouts hosting the largest diversity of bacteria.
The researchers—Jonathan Leff and Noah Fierer of the University of Colorado, Boulder—studied 11 types of produce in total: apples, grapes, lettuce, mushrooms, peaches, bell peppers, spinach, strawberries, tomatoes, alfalfa sprouts and mung bean sprouts. For each fruit or vegetable, they swabbed the surface, isolated the DNA from the swab, sequenced the DNA and analyzed which bacterial family it fell into.
All species host billions of individual bacterial cells, but the research showed that some tend to host a more limited diversity of bacteria. Most of the colonies living on spinach, tomatoes and strawberries, for example, all belonged to one particular family. Others, such as apples and peaches, not only carried a greater total number of bacterial families, but had bacterial colonies more evenly divided amongst each of the families.
The team also looked at the raw quantity of bacteria belonging to the Enterobacteriaceae family in particular, a broad group that encompasses both harmful and beneficial species. For many of the fruits and vegetables, they also compared conventionally grown samples to organic. As a whole, organic produce had lower amounts of bacteria in this family, but some organic vegetables (such as lettuce) actually had higher levels than conventional counterparts.
Research into breadth of bacteria on produce is still in fledgling stages, so it’s difficult to say what this all means. Scientists still aren’t sure what agricultural factors can affect the levels of bacteria on produce, or even which types of the bacteria identified are harmful, harmless, or beneficial.
There’s also the matter of how these types of bacteria interact with the colonies that already live inside our digestive tracts. In terms of nutrition, this dynamic could be crucial: Some of the bacteria living in us help us digest carbohydrates, while closely related strains can cause us to absorb excess levels of fat during digestion.
What this work does reveal is that when you bite into a juicy peach or tart grape, you’re simultaneously eating billions of bacterial colonies. Do they give a peach the ripe taste of summer or the grape its piquancy? Do these bacteria supplement the nutrition of our produce? Further research, the authors note, will hopefully reveal more.
March 25, 2013
As Easter draws near, we begin to notice signs of nature’s very own annual resurrection event. Warming weather begins “breeding lilacs out of the dead land,” as T.S. Elliot noted, and “stirring dull roots with spring rain.” Where a black and white wintery landscape just stood, now technicolor crocus buds peak through the earth and green shoots brighten up the azalea bushes.
Aside from this grand show of rebirth, however, nature offers several cases of even more overtly stunning resurrections. From frozen animals jumping back into action during spring thaws to life blooming from seemingly desolate desert sands, these creatures put a new spin on nature’s capacity for revival.
As its name suggests, during a drought the resurrection fern shrivels up and appears dead, but with a little water the plant will burst back into vibrant life. It can morph from a crackled, desiccated brown into a lush, vibrant green in just 24 hours.
The fern doesn’t actually die, but it can lose up to 97 percent of its water content during an extreme dry spell. In comparison, other plants will usually crumble into dust if they lose more than 10 percent of their water content. Resurrection ferns achieve this feat by synthesizing proteins called dehydrins, which allow their cell walls to fold and reverse back to juicy fullness later.
Resurrection ferns are found as far north as New York and as far west as Texas. The ferns needs another plant to cling to in order to grow, and in the south it’s often found dramatically blanketing oak trees. A fallen oak branch covered in resurrection ferns are common features in southern gardens, though the ferns have also turned up in more uncanny locales: in 1997, astronauts took resurrection fern specimens onto the Space Shuttle Discovery to study how the plant resurrects in zero gravity. As investigators write (PDF), the fern “proved to be a hardy space traveler and exhibited regeneration patterns unaltered by its orbital adventure.” This earned it the title of “first fern in space.”
Brine shrimp, clam shrimp and tadpole shrimp
In the deserts of the western U.S., from seemingly life-barren rocks and sands, life blooms by just adding a little rain water. So-called ephemeral pools or “potholes” form tiny ecosystems ranging from just a few millimeters across to several meters deep. The ponds can reach up to 140 degrees Fahrenheit in the summer sun or drop below freezing during winter nights. They can evaporate nearly as quickly as they appeared, or linger on for days or weeks. As such, the animals that live there all have special adaptations for allowing them to thrive in these extreme conditions.
Some of the potholes’ most captivating critters include brine shrimp (of sea monkey fame!), clam shrimp and tadpole shrimp. These crustaceans practice a peculiar form of drought tolerance: In a process known as cryptobiosis, they can lose up to 92 percent of their body water, then pop back into fully-functional action within an hour of a new rain’s arrival. To do this, the tiny animals keep their neural command center hydrated but use sugar molecules instead of water to keep the rest of their cells intact throughout the drought. Like resurrection ferns, brine shrimp, too, have been taken into space–they were successfully hatched even after being carried outside of the spacecraft.
Most of these animals only live for about ten days, allowing them to complete their entire life cycle (hopefully) before their pool dries up. Their dried eggs are triggered to hatch not only when they’re hydrated again but also when oxygen content, temperature, salinity and other factors are just right. Some researchers, such as this zoologist quoted in a 1955 newspaper article, think that the eggs can remain dormant for several centuries and still hatch when conditions are right.
Some amphibians undergo their own sort of extreme hibernation in order to survive freezing winter temperatures. This suspended animation-like state allows them to slow down or stop their life processes–including breathing and heartbeat–just to the brink of death, but not quite. Wood frogs, for example, may encounter freezing conditions on the forest floor in winter. Their bodies may contain 50 to 60 percent ice, their breathing completely stops and their heartbeat is undetectable. They may stay like this for days, or even weeks.
They achieve this through a specially evolved biological trick. When the frogs encounter the first signs of freezing, their bodies pull moisture away from its central organs, padding them in a layer of water which then turns into ice. Before it freezes, the frog also floods its circulatory system with sugar molecules, which act as an antifreeze. When conditions warm up again, they can make a complete recovery within a day, which researchers call “spontaneous resumption of function.” Here, Robert Krulwich explains the process:
As seen through these examples, some creatures really do come back from the brink of death to thrive!
March 7, 2013
A new study published today in Science found that the drug isn’t just popular among humans. A group of scientists from Newcastle University in the UK and elsewhere found that low doses of caffeine are present in the nectar of coffee flowers and many types of citrus plants—and that when the honeybees imbibe the drug while foraging, they demonstrate measurably improved memory for a particular floral scent afterward.
The research team, led by Geraldine Wright, measured the levels of caffeine present in the nectar of three types of coffee plants (robusta, arabica and liberica) along with four different kinds of citrus (grapefruit, lemons, pomelo and oranges). All nectars studied contained slight amounts of the drug—with the coffee nectars containing more than the citruses—and all nectars are commonly consumed by honeybees in the wild.
To see exactly what effect this caffeine has on honeybees, the scientists investigated what the drug did to bees in a lab setting. First, they trained the insects to associate a particular floral scent with a sugar and water solution: They gave the honeybees a drink of the sugar mixture if they extended their proboscis immediately after smelling the aroma; after a number of trials, all the bees were conditioned to perform the action upon being exposed to the scent. For some bees, though, the researchers had introduced varying levels of caffeine into their sugar solution.
When the bees’ memory was tested 24 hours later—by checking if they still responded to the scent by immediately extending their proboscis—those that had caffeine in their solution demonstrated notably better memory for the scent. They were three times more likely to perform the action, and even after a full 72 hours, they were still twice as likely to remember the aroma.
The findings shed light on what had long been a caffeine mystery. The drug, which is bitter when tasted in isolation, has conventionally been thought of as a defense mechanism for plants, reducing the chance that they’ll be eaten by herbivores.
In this context, botanists had long wondered why bitter caffeine is present in low doses in nectar. The sweet liquid is produced to attract bees, insects and other animals that serve as pollinators, spreading pollen between individual plants of the same species to aid in reproduction—so why would a bitter defense mechanism be included?
The levels of caffeine in the nectar of all the plants studied, it turns out, are too low to taste bitter to the bees, but just high enough to provide the memory boost. This happy medium could provide a benefit for both the bees and the plants.
“Remembering floral traits is difficult for bees to perform at a fast pace as they fly from flower to flower,” Wright, the lead author, said in a press statement. “We have found that caffeine helps the bee remember where the flowers are.” As a result, the drug gives bees the ability to more quickly find flowers that provide valuable nectar—and plants are provided with more frequent pollination from the insects.
The researchers hope that their findings will do more than let coffee drinkers know they share something in common with honeybees. In an era when crashing populations of honeybees and other pollinators are getting scientists concerned about the yields of dozens of pollinated crops and wild plant biodiversity, a better understanding of the bee foraging and pollination process could be crucial for finding a solution.