Science-- there's something for everyone

Wednesday, July 31, 2013

Just for fun: The clearest lake in the world

Blue Lake in New Zealand's South Island has amazingly clear water. To give you an idea of just how clear it is, here's a comparison. If you filled a lake with distilled water, you'd be able to see down about 80 meters. If you stare into the depths of Blue Lake, you can see for up to 76 meters. 

That means you can get pictures like these.

Blue Lake: on New Zealand’s South Island

Hat tip: Not Exactly Rocket Science.

Tuesday, July 30, 2013

T. rex wasn't just a scavenger

There’s a debate among paleontologists as to whether Tyrannosaurus rex was predominantly a predator or a scavenger. Did it chase down or ambush living prey like large cats, or did it seek out already dead carcasses like vultures? Researchers led by Robert DePalma II of the Palm Beach Museum of Natural History believe they have the paleontological equivalent of a smoking gun: a T. rex tooth embedded in a healed over wound in the tail bone of a hadrosaur.

To be clear, predators also scavenge. Almost any meat-eater will gladly forego the bother and risk of killing its own prey when there’s a perfectly good carcass just lying around. In contrast, true scavengers almost never set their table with a living victim. So the question is not whether T. rex ever scavenged but rather whether it also killed its own prey.

T. rex definitely had a bite that was powerful enough to subdue and kill its victims. It was also probably fast enough to run them down. However, neither of these attributes necessarily mean that it was a hunter. Physical prowess is also useful for driving other predators away from carcasses, not to mention for attracting mates.

So why is this tail wound so instructive? First, let’s state the obvious: dead animals don’t heal. If the T. rex had broken off a tooth while attempting to consume an already dead hadrosaur, the tail bone wouldn’t have healed. Because the tail had healed over, we know that the plant-eater had escaped the T. rex attack and lived long enough afterwards for the bone to heal. Second, the position of the bite, at the rear end of the victim, strongly suggests that the hadrosaur was fleeing at the time of the attack.

We still can’t say how often T. rex killed for itself. It might have mostly relied on finding the remains of other predators’ kills. Thanks to this find, we do know that it wasn’t exclusively a scavenger, which is a good thing because nobody wanted to think of T. rex that way anyway.

Photo by Daniel Schwen, 11/5/2010.

Robert A. DePalma, David A. Burnham, Larry D. Martin, Bruce M. Rothschild, & Peter L. Larson (2013). Physical evidence of predatory behavior in Tyrannosaurus rex Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.1216534110.

Monday, July 29, 2013

Don’t bother to sterilize space craft

One of the reasons people are so interested in Mars is that it might once have harbored life. It’s even possible that life exists there today, somewhere under the surface. If we do ever find signs of life on Mars, we’ll want to know whether it originated on that planet, rather than being the result of contamination from Earth. To make that distinction, astrobiologists on Earth have been trying their best to sterilize everything we send into space. However, Alberto Fairén of Cornell University and Dirk Schulze-Makuch of Washington State University think we shouldn’t bother. In all likelihood, Mars has already been contaminated with Earth species.

We know that Earthly bacteria could survive the journey through space and land intact on Mars. This makes it seem to be critical to sanitize everything we send out that way, until you consider two things. First, it would be impractical, not to say impossible, to ensure that no Earth microbes found their way en route to Mars. Second, even if we did make that extra effort going forward, earlier Mars missions have already landed an assortment of completely unsterilized objects on the surface of Mars. And that doesn’t even count the nearly 4 billion year history of possible meteorite transfer of life forms from Earth to Mars. 

In short, if Earthly life can thrive on Mars, it’s there already.

The authors argue that either present day Earth species cannot survive on Mars, in which case there is no need for pre-flight sterilization, or Earth species can survive on Mars, in which case they’re already there so there’s still no need for sterilization. In the first scenario, decontamination is unnecessary and in the second it’s too late to do any good. 

Even if there is indigenous life on Mars that isn’t related at all to Earth species, these two scenarios still hold. Martian species won’t be affected by Earth species that die upon arrival, and Martian species must have already adapted to Earth species that can thrive on Mars.

According to Fairén and Schulze-Makuch, if there is a reason to sterilize outgoing space craft, it’s to make the job of distinguishing Earth from Martian species easier, a task we may never be faced with. They contend that, given the limited budget for Mars missions, the money be reallocated to more important tasks. 

Alberto Fairén, & Dirk Schulze-Makuch (2013). The overprotection of Mars Nature Geoscience DOI: 10.1038/ngeo1866.

Friday, July 26, 2013

Closing in on the bee killers

By now you’ve no doubt heard that honey bees (Apis mellifera) are dying off in great numbers all over the world. This isn’t just tragic for bees and apiculturists. Bees are responsible for pollinating $15 billion worth of crops in the U.S. alone. We’re not just talking about honey. Without bees, we wouldn’t have more than 90 of our favorite fruits and vegetables. About a quarter of the human diet is utterly dependent on honeybees. 

As you can see from this video, there have been many culprits named in the demise of the honey bee. Pesticides, fungicides, parasites, toxins and habitat destruction have all been blamed. Thanks to new research from the University of Maryland, the Bee Research Laboratory and USDA-APHIS, we may finally be able to say what's causing the die off. Unfortunately, it's all of the above.

How might these different factors interact? Although not in themselves lethal to bees, insecticides and fungicides can alter bees’ enzyme activity, which in turn can effect development, behavior and immune function. Combinations of these chemicals might affect bees' life cycles and make them more susceptible to diseases like those caused by the parasite Nosema.

Until recently, these interactions were missed simply because scientists had been testing single chemicals on bees. Instead of repeating that practice, researchers led by Dennis vanEngelsdorp of the University of Maryland collected pollen directly from foraging bees. They then identified and quantified the number and type of insecticides, herbicides, fungicides and other chemicals associated with those pollen grains. In that way, they figured out what combinations of chemicals bees actually encounter while going about their business. 

All the pollen samples contained various insecticides and fungicides, and a quarter contained herbicides as well. This might be a good place to point out that bees feed pollen to their young.

Pollen from these same fields were fed to bees that had been inoculated with Nosema. When introduced in the combinations found in actual fields, the various pesticides did not have the same effect as when they’d been tested individually. In particular, pesticides commonly used by beekeepers themselves to control hive mites made the bees twice as susceptible to Nosema infection.

This is all, of course, very bad news for people who were hoping for a quick fix to this problem. As vanEngelsdorp explains:
The pesticide issue in itself is much more complex than we have led to be believe. It’s a lot more complicated than just one product, which means of course the solution does not lie in just banning one class of product.
This year, the European Union has decided to ban the use of insecticides known as neonicotinoids in an effort to save their bees. However, in this study, neonicotinoids were only present in apple pollen and were associated with decreased risk of Nosema infection. Clearly, banning a single chemical is not going to save our bees.

To make matters worse, regardless of hive placement, bees often returned with wild pollen. Because so much of the collected pollen did not come from the intended crop but from nearby wild flowers and weeds, the authors suggest that beekeepers investigate spray programs in nearby fields as well as the ones in which they’re placing their hives. This will make controlling for chemical contamination all the harder.
Hat tip: Cathy Earle.

Jeffery S. Pettis, Elinor M. Lichtenberg, Michael Andree, Jennie Stitzinger, Robyn Rose, & Dennis vanEngelsdorp (2013). Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae PloS ONE DOI: 10.1371/journal.pone.0070182.

Thursday, July 25, 2013

Life in Lake Vostok

Lake Vostok is the 7th largest and 4th deepest lake on Earth. If you're wondering why you've never seen it on a map, it's because Lake Vostok is located in Antarctica under nearly 4000 meters of ice. And that's not even the most interesting thing about it. Despite this less than ideal location, Lake Vostok does contain life. 

Lake Vostok is the largest and probably the deepest of Antarctica’s subglacial lakes. In order to find out what types of life might be lurking in those pitch black, high pressure waters, researchers from Bowling Green State University examined frozen ice cores samples (see my previous post about Antarctic subglacial lakes). Sections of the ice cores that were close to the liquid surface of the lake (shown by the arrows in the picture below) were carefully brought to the lab, melted and analyzed for nucleic acids.

Schematic cross-section of Lake Vostok (above), drawn to scale. 
Credit: Yury M. Shtarkman et al. Subglacial Lake Vostok (Antarctica) Accretion Ice Contains a Diverse Set of Sequences from Aquatic, Marine and Sediment-Inhabiting Bacteria and Eukarya. 
PLoS ONE, 2013; 8 (7): e67221 DOI: 10.1371/journal.pone.0067221.

Most of the life forms were bacteria. The 4% that were eukaryotes were mostly fungi. I found it interesting that the authors made a point to say that the newly discovered creatures 
were similar to organisms specific to lakes, brackish water, marine environments, soil, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants.
Well, that seems to cover pretty much everything. They were similar to other life on Earth then, I guess. So, little chance that life hiding under two miles of ice was of extraterrestrial origin. Good to know.

Yury M. Shtarkman, Zeynep A. Koçer, Robyn Edgar, Ram S. Veerapaneni, Tom D’Elia, Paul F. Morris, & Scott O. Rogers (2013). Subglacial Lake Vostok (Antarctica) Accretion Ice Contains a Diverse Set of Sequences from Aquatic, Marine and Sediment-Inhabiting Bacteria and Eukarya PLoS ONE DOI: 10.1371/journal.pone.0067221.

Wednesday, July 24, 2013

Just for fun: Batman song

Now this is something I could listen to over and over again. It's the theme of Batman sung by actual bats. 

Okay, the bats weren't actually organized into a choir. The bats' sounds were recorded, digitally reduced to frequencies that humans can hear, and mixed by Ulrich Seidel of Erfurt, Germany. The video clip was compiled by Sándor Seuntjens of Brussels, Belgium.

Tuesday, July 23, 2013

Can we change our DNA methylation patterns?

It’s becoming increasingly evident that the pattern of DNA methylation in genes matters just as much as the actual DNA sequence. After all, methylation affects gene expression (whether genes are used to make protein products and how much product they make), which is really the point of having genes in the first place. Methylation patterns are not set for life, they can change over time. However, we're just beginning to understand what sorts of circumstances will alter methylation patterns. According to Tina Rönn and her colleagues from Lund University, exercise is one of them.

The scientists compared genome-wide DNA methylation in the adipose tissue (fat cells) of 23 ordinarily sedentary men before and after a six month exercise regimen. The exercise consisted of about 2 sessions/week of either an hour of spinning or an hour aerobics. The researchers found changes at nearly 20,000 nucleotides. When they checked to see which of these changes actually affected gene expression, they found differences in 197 different genes. Most of these genes showed an increase in DNA methylation, which corresponded to a decrease in gene expression. That is, most of the genes were making less protein products after exercise. Even more interesting, 53 of the affected genes are known to be implicated in obesity. 

I’ve written recently about differences in the methylation patterns of genes involved in metabolism in kids born after their mothers had gastric bypass surgeries. Those changes occurred in utero before the kids were born. This new data suggests that the methylation patterns can be purposefully altered by a person’s own activities. If this proves true, it may open up whole new ways of looking at and treating metabolic disorders.

Rönn T, Volkov P, Davegårdh C, Dayeh T, Hall E, Olsson AH, Nilsson E, Tornberg A, Dekker Nitert M, Eriksson KF, Jones HA, Groop L, & Ling C (2013). A Six Months Exercise Intervention Influences the Genome-wide DNA Methylation Pattern in Human Adipose Tissue. PLoS genetics, 9 (6) PMID: 23825961.

Monday, July 22, 2013

Congratulations, Pluto, your moons have names

Pluto may not be a planet anymore, but it has more moons than the Earth does. Pluto’s 4th and 5th moons were discovered in 2011 and 2012. At that time, only three of Pluto’s moons had been named. Recently, the International Astronomical Union (IAU) chose two proper names for the previously dubbed P4 and P5. Those moons will henceforth be known as Kerberos and Styx, respectively.

This discovery image, taken by the NASA/ESA Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The darker stripe in the centre of the image is because the picture is constructed from a long exposure designed to capture the comparatively faint satellites of Nix, Hydra, Kerberos and Styx, and a shorter exposure to capture Pluto and Charon, which are much brighter. Kerberos has an estimated diameter of 13 to 34 kilometres, and Styx is thought to be irregular in shape and 10 to 25 kilometres across. 
Credit: NASA, ESA and M. Showalter (SETI Institute)

The IAU gave the public a chance to weigh in on the name choices. All the selections had to fit with Pluto’s ‘theme’, which is Greek/Roman mythology related to the underworld. Pluto’s three other moons are Charon, Nix and Hydra, so Kerberos and Styx will fit in nicely with them.

In case you’re interested, Styx was a goddess who ruled the underworld river by the same name, and Kerberus is an alternative spelling for ‘Cerberus’, the three-headed dog that guards the underworld. Nix (or Nyx) is the goddess of the night. Charon is the ferryman who transports souls across the river Styx. Finally, Hydra was a many-headed beast that was eventually killed by Hercules.

All four of the newer moons (Hydra, Nix, Kerberos and Styx) were discovered in images from the Hubble Space Telescope. They’re also all tiny. Charon, discovered in 1978, is the only one of Pluto’s moons that a person couldn’t easily circumnavigate on foot.

Here's an older pre-name change family picture:

Hubble image of Pluto and its moons

This image, taken by NASA's Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5, as photographed by Hubble's Wide Field Camera 3 on July 7.
Credit: NASA; ESA; M. Showalter, SETI Institute

Friday, July 19, 2013

For chasing strategies, ears can be as good as eyes

I have a confession to make. The only reason I picked this story is because I find the idea of making college students run around a football field while blindfolded to be delightful. Aah, science! So, besides spending an amusing afternoon, what exactly did Dennis Shaffer and his colleagues from The Ohio State University find? Blind people chase moving targets the same way that sighted people do.

There are two basic ways to intercept a moving target. You can charge right at your target, following him move for move. This works well if you’re much faster than your prey, but if you’re both about the same speed, you’ll never catch up. In that case, it’s best to aim for where you expect your target to be at some time in the future, based on his speed and direction. This is called a ‘constant-angle’ strategy, and it’s one that most people instinctively employ.

Sure enough, when researchers told students to chase down someone carrying a football across a field, the students used the constant-angle pursuit strategy rather than running directly toward the ball carrier. No surprise there. However, when blindfolded students were asked to tag runners carrying beeping footballs, they also used the constant-angle strategy.

I should say that this was a very small study with only a handful of participants. Still, it’s amazing to think that people can estimate angles and direction as well with their ears as they can with their eyes. That’s something I wouldn’t have predicted.

Dennis M. Shaffer, Igor Dolgov, Eric Mcmanama, Charles Swank, Andrew B. Maynor, Kahlin Kelly, & John G. Neuhoff (2013). Blind(fold)ed by science: A constant target-heading angle is used in visual and nonvisual pursuit Pyscon Bull Rev DOI: 10.3758/s13423-013-0412-5.

Thursday, July 18, 2013

Sterilizing without electricity

A key feature in medical care that does more good than harm is the ability to properly sterilize instruments. This is tricky enough in modern hospitals, which are constantly battling outbreaks of MRSA and biofilms. Imagine how difficult it is in regions of the world without access to electricity. Rice University researchers are working to remedy that problem by adding nanoparticles to autoclaves.

Autoclaves are devices that sterilize equipment by exposing them to high pressure steam. If used properly, an autoclave will denature proteins, effectively destroying not only microbes but viruses and spores as well. Unfortunately, most autoclaves rely on electricity to create the super hot steam they require. Enter light-absorbing nanoparticles.

When suspended in liquid, these tiny particles act as nucleation points that convert solar energy to steam at 80% efficiency. The small bubbles of vapor around each nanoparticle grow and spread throughout the liquid, even though the temperature of that liquid has not reached boiling. With enough exposure to sunlight, the liquid does eventually boil, leading to steam that is much hotter than what could be achieved without the presence of the nanoparticles. The nanoparticles are not damaged or degraded by this process and can be reused indefinitely.

The researchers found that their solar nanoparticle autoclaves were capable of maintaining a temperature of 115°C for over 30 minutes, more than sufficient to achieve complete sterilization. Remember, this was done without electricity.

To be fair, the authors did make use of parabolic solar collectors to funnel the sun’s energy into their autoclaves more efficiently. I don’t mean to give the impression that you could just sit a can of nanoparticle-containing water in a field somewhere and turn it into an autoclave. Still, once you buy or construct your equipment, you have no more material or energy costs. That should be an enormous help in many poor communities.

Oara Neumanna, Curtis Feronti, Albert D. Neumann, Anjie Dong, Kevin Schell, Benjamin Lu, Eric Kim, Mary Quinn, Shea Thompson, Nathaniel Grady, Peter Nordlander, Maria Oden, & Naomi J. Halas (2013). Compact solar autoclave based on steam generation using broadband light-harvesting nanoparticles Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.1310131110.

Wednesday, July 17, 2013

Just for fun: Brain Scoop

Do you love natural history museums? How about quirky facts about biology as discussed by the charmingly enthusiastic Emilie Graslie? Then you're going to love The Brain Scoop YouTube channel. 

A couple of examples:

Emilie explains the difference between horns and antlers:

She also takes us on a multipart journey behind the scenes at Chicago's Field Museum. I guarantee you've never seen anyone so excited about platypuses.

Hat tip: Not Exactly Rocket Science.

Tuesday, July 16, 2013

Good news about the flu vaccine

Each year, the World Health Organization (WHO) makes an educated guess about which strains of influenza virus will be most prevalent in the upcoming flu season. Based on their recommendations, vaccine manufacturers mass produce that year’s flu vaccine. Sometime, the predictions are spot-on, but other times, there’s considerable mismatch between the vaccine and the circulating viruses. The good news is that it may not matter.

Researchers from universities and hospitals in Ontario, Canada scoured clinical trials to find people who had come down with the flu after being vaccinated for influenza. After narrowing down their search criteria to exclude studies without laboratory-confirmed influenza, proper placebo controls or full vaccination, the scientists ended up with 34 trials, covering 47 influenza seasons and involving nearly 95,000 participants.

Even when the vaccines did not match that year’s flu strains, the vaccines were considerably better than placebo at preventing influenza infection. A mismatched live-attenuated vaccine (nasal spray) reduced infection rates by 60% and an inactivated vaccine (shot, or jab) did so by 56%. In comparison, properly matched vaccines reduce the risk of contracting the flu by 77% and 65%, respectively.

This means that individuals should not shirk from getting vaccinated even if they hear that the current vaccine doesn’t match that season’s flu virus. It also means that communities will benefit from herd immunity when their members get vaccinated regardless of whether the WHO was correct in their predictions.

Tricco AC, Chit A, Soobiah C, Hallett D, Meier G, Chen MH, Tashkandi M, Bauch CT, & Loeb M (2013). Comparing influenza vaccine efficacy against mismatched and matched strains: a systematic review and meta-analysis. BMC medicine, 11 (1) PMID: 23800265.

Monday, July 15, 2013

Hubble finds a blue exoplanet

Astrophysicists have confirmed that at least one other exoplanet in the Milky Way galaxy is blue. You can see a somewhat melodramatic artist’s impression below.

Even through the Hubble telescope, exoplanets are usually too close to their stars to directly observe, and HD 189733b is no exception. Light reflected from the planet blends with light coming from its star. However, Tom Evans at the University of Oxford and his colleagues used an ingenious method to separate out the contribution of light from the planet. They compared spectrographic data of the star plus planet to data from just the star when the planet was eclipsed behind it. When the planet was behind the star, there was less blue light, indicating that the planet was the source of that blue light.

Although this is exciting news, we shouldn’t plan waterskiing trips to HD 189733b. There’s every indication that the planet is a gas giant, similar to Jupiter. It most likely does not contain liquid water or even a water vapor atmosphere. Researchers speculate that the blue color could be due to a low lying clouds of silica (glass).

The folks at have created the following helpful infographic:

Infographic: Facts about the hot blue gas giant planet HD 189733b.

Thomas M. Evans, Frédéric Pont, David K. Sing, Suzanne Aigrain, Joanna K. Barstow, Jean-Michel Désert, Neale Gibson, Kevin Heng, Heather A. Knutson, & Alain Lecavelier des Etangs (2013). The Deep Blue Color of HD 189733b: Albedo Measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at Visible Wavelengths The Astrophysical Journal Letters, 772 (2) : doi:10.1088/2041-8205/772/2/L16.

Friday, July 12, 2013

Taste receptors in the testes

A few years ago, researchers were surprised to find taste buds in lungs. Apparently, that’s not the only unusual place to find taste receptors. They’re also present in testes and sperm. Bedrich Mosinger and his colleagues from the Monell Chemical Senses Center bred some special mice to investigate why that’s so.

TAS1R receptors are responsible for detecting sugar (sweet) and umami (amino acids, or protein). That’s a useful function when the receptors are in the mouth or even in the gastrointestinal tract. After all, nutrition and taste are closely connected. An operating sense of taste dictates not only what animals choose to eat but also how much they eat. But what would taste receptors be doing in testes or sperm?

Well, we still don’t know. We do know that they play some critical role in reproduction because male mice that lack these testes taste receptors are sterile. Admittedly, there weren't a lot of data points for this because the scientists were only able to breed two male mice that were completely lacking the taste receptors, despite many tries. Both of those mice seemed to be perfectly healthy and ordinary, apart from being sterile. 

However, when the researchers bred mice to have a human version of TAS1R, they could reversibly sterilize the mice by feeding the mice compounds that block those receptors. Thus, not only did the taste receptors have to be present, but they also had to be functional in order for the male mice to reproduce.

This is significant because compounds that are chemically similar to the ones the researchers used to block the taste receptors are currently used in anti-lipid medications for humans and in herbicides. The authors speculate that these compounds may be affecting human male fertility.

Mosinger B, Redding KM, Parker MR, Yevshayeva V, Yee KK, Dyomina K, Li Y, & Margolskee RF (2013). Genetic loss or pharmacological blockade of testes-expressed taste genes causes male sterility. Proceedings of the National Academy of Sciences of the United States of America PMID: 23818598.

Thursday, July 11, 2013

Don't walk and text

We all know that using a cell phone while driving is a bad idea. Apparently, it’s not much better to use a cell phone while walking. Jack Nasar of Ohio State University and Derek Troyer of the Ohio Department of Transportation confirmed this unsurprising result.

Pedestrians who are talking on phones tend to have inattentional blindness. That is, they don’t notice what’s going on around them. This can be problematic when people are trying to do things like navigate city streets. 

Using data from the National Electronic Injury Surveillance System (NEISS), which collects information directly from hospital emergency rooms, the authors found that 3.7% of pedestrian injuries are caused by talking on phones while walking. In comparison, only 2.3% of driver injuries are caused by mobile phone usage (that's a lot of injuries, so don't take this as permission to use your phone while driving. Plus, of course, injuries received while driving can be much more horrific). You can also see that the injury rate for pedestrians has been climbing, though that might be due to increased mobile phone usage. 

Full-size image (30 K)

Consumer Product Safety Commission national estimate of injuries related to cell phone use among pedestrians and drivers.
Accident Analysis & Prevention, 57, 91-95 DOI: 10.1016/j.aap.2013.03.021.

The best part of this story were the examples of pedestrian injuries:
23 year old male walking on the middle line of the road talking on a cell phone and was struck by a car, contusion hip 
14 year old male walking down road talking on cell phone, fell 6–8 ft off bridge into ditch.
And my favorite:
28 year old male walked into pole talking on phone and lacerated brow.

Nasar, J., & Troyer, D. (2013). Pedestrian injuries due to mobile phone use in public places Accident Analysis & Prevention, 57, 91-95 DOI: 10.1016/j.aap.2013.03.021.