PLOS ONE’s Spookiest Images of 2014


As we take a look back at research articles published so far in PLOS ONE in 2014, we realize we have no shortage of images to terrify our readers, or at least sufficiently creep them out long enough to last through … Continue reading »

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Yersinia pestis, Ghost of Plagues Past

Skeleton Blog2

Who’s afraid of the big bad plague? Bet you the owners of the bones above were. This Halloween, we’re highlighting the work of researchers who tested (extremely carefully) for the presence of the pathogen Yersinia (Y.) pestis (a.k.a., the “Bubonic Plague”) in human skeletal remains from three sites in Germany and Switzerland.  Thought to be victims of the Black Death, these individuals died alongside an estimated 75-200 million other Europeans affected by this outbreak of the plague, which diminished Europe’s population during the 14th century by one third.

The specialized protocol the researchers used in this study was carefully created to be in line with modern plague diagnostic procedures and to address the unique challenge of working with ancient DNA (aDNA), which varies in quality from sample to sample and is easily contaminated with modern DNA. Contamination is common and can be hard to identify, often resulting from poor handling practices at excavation or during preparatory procedures. The researchers  did their best to avoid the possibility by thoroughly cleaning the surfaces of the bones and teeth that samples were drawn from, and using multiple controls to highlight any points of contamination from the laboratory that occurred during the experiments. At a time when the results from testing of aDNA samples can be highly contested, a validated  DNA replication process was used to ensure authenticity of the tests and to prevent misinterpretation of the results by the scientific community.

Bones and teeth from 29 individuals, ranging from 300-600 years old, were collected from sites in Manching-Pichl and Brandenburg in Germany and Basel, Switzerland and housed at the State Collection for Anthropology and Palaeoanatomy  in Munich. Selected samples were then moved to newly constructed labs at the ArcheoBio Center of the Ludwig Maximilian University  Munich for preparation and aDNA extraction. Researchers followed a strict protocol to prevent any sample contamination at this stage. The new facility contains three air-locked and pressurized rooms, each meant to provide a contamination-free workplace for processing aDNA samples for replication. Before admittance to the three-room complex, staff were required to shower, wash their hair, and enter a gowning room to replace their freshly laundered clothes with two pairs of gloves, a hairnet, hooded overalls, and a screened facemask. A second gowning room required the addition of another set of hooded overalls. Scientists then moved through the rooms sequentially, preparing the aDNA samples and negative controls (meant to test for contamination in the replication process) for analysis.

Once preparatory procedures were complete, sealed tubes containing the negative controls and aDNA were transferred to the Bundeswehr Institute of Microbiology for the addition of positive controls (tubes containing DNA from Y. pestis), DNA replication and analysis. Of the 29 samples tested, seven contained fragments of a Y. pestis gene after an initial round of replication, and four additional samples tested positive for Y. pestis after further rounds of testing.

Although the skeletons above are not, Y. pestis is still alive and well in parts of the world. Now called the “Modern Plague” to differentiate it from previous plagues caused by the same pathogen, such as Justinian’s plague and the Black Death, the disease affects 1,000-3,000 people per year. Modern treatments have thankfully limited the number of deaths that result from these cases, leaving us less likely to end up in the ground after getting sick, like these poor individuals. Nevertheless, research on the presence of the pathogen in ancient samples remains crucial for our continued understanding of how this disease affected our population in the past.

So, in case you need a scary costume idea for tonight’s festivities, why not draw some inspiration from our friends above? A skeletal Black Death victim and a masked, double-overalled plague researcher sound like great costume ideas to us.

Happy Halloween from PLOS ONE!

Citation: Seifert L, Harbeck M, Thomas A, Hoke N, Zöller L, et al. (2013) Strategy for Sensitive and Specific Detection of Yersinia pestis in Skeletons of the Black Death Pandemic. PLoS ONE 8(9): e75742. doi:10.1371/journal.pone.0075742

Image Credit: Courtesy of the authors and the Bavarian State Department of Historical Monuments

Halloween Highlights: Crushing Jaws!

Happy Halloween to those goblins and ghouls amongst you! Before you go trick-or-treating tonight, let’s wrap up our month-long series on creepy critters and things that go bump in the night with one final critter and its modern-day cousin.

The unassuming reptile pictured above is the tuatara. The tuatara are found only in New Zealand, and are often called “living fossils” because of their physiological similarities to their ancient ancestors.

In research published today in PLOS ONE, researchers led by Dr. Oliver Rauhut discovered the fossil remains of an ancient relative of the tuatara, Oenosaurus muelheimensis. The species is named in honor of the Franconian Alb, the wine-growing region in Germany where the fossil was discovered, and the German village of Mühlheim.

Pictured to above is the Oenosaurus’ lower jaw, which in life featured a set of ever-growing tooth plates and multitudinous “pencil-like” teeth. Researchers posit that the arrangement and morphology of the lower jaw suggests that it moved in a crushing motion.

We recently invited Dr. Oliver Rauhut, the corresponding author of the paper, to share the group’s thoughts on their new findings. He writes:

The incentive for our research was the find of a new specimen of a rhynchocephalian from the Late Jurassic of Germany, which we name Oenosaurus muelheimensis. Rhynchocephalians are an ancient group of reptiles, today only represented by the Tuatara that lives on small islands off the coast of New Zealand and is regarded as a classic example of a living fossil. The new fossil has an extremely unusual dentition, and at first we were all at a loss as to what kind of animal this was, with ideas ranging from a chimeran fish to a rhynchosaur -[a] pig-like reptile that lived in the Triassic (which, incidently, is also reflected in the name…). After identifying the animal as a rhynchocephalian, we had a closer look at the dentition, which is unique amongst tetrapods in presenting large, continuously growing tooth plates. Such an extreme adaptation in a Jurassic rhynchocephalien contradicts the traditional idea that these animals were conservative and evolutionary inferior to lizards. Thus, we challenge the current opinion that the decline of rhynchocephalians during the later Mesozoic was mainly caused by selection pressure by radiating lizards and early mammals; instead climate change in the wake of continental break-up at that time might have been responsible.

This concludes our month-long celebration of some the spooktacular science you can find on PLOS ONE. If you are interested in learning about other creepy critters that we have covered in past years, please visit these links.

Have a safe and happy Halloween!



Rauhut OWM, Heyng AM, López-Arbarello A, Hecker A (2012) A New Rhynchocephalian from the Late Jurassic of Germany with a Dentition That Is Unique amongst Tetrapods. PLoS ONE 7(10): e46839. doi:10.1371/journal.pone.0046839

The first image is provided courtesy of Helmut Tischlinger and can be found accompanying the institution’s press release.

The second image is Figure 2F in the manusript.

Halloween Highlights: Carnivorous Plants

Plants may not generally be associated with the spooky sentiments of Halloween, but put the right Hitchcock soundtrack with the video below and it could have come straight out of a Hollywood horror film.

Carnivorous plants have inspired many creative minds over time, perhaps most memorably in the cult classic, Little Shop of Horrors which featured a fictitious new hybrid that thrived only on human blood. The real plants may not be so scary to us but for insects, they’re certainly something to be wary of.

The video above  shows the particularly dramatic “active” trapping mechanism employed by one carnivorous species the Drosera glanduligera, a sundew that feeds on insects. Even the abstract of the study Catapulting Tentacles in a Sticky Carnivorous Plant conjures cryptic images:

Prey animals walking near the edge of the sundew trigger a touch-sensitive snap-tentacle, which swiftly catapults them onto adjacent sticky glue-tentacles; the insects are then slowly drawn within the concave trap leaf by sticky tentacles.

“Passive” trapping mechanisms used by other carnivorous plants can be equally creepy when documented close up (and paired with the right soundtrack). Take a look at Video S1 and S3, below, of a paper published in 2007 investigating the digestive fluid of the Nepenthes rafflesian, a pitcher plant that relies on its unique shape and a pool of  highly viscoelastic fluid to trap insects for digestion. The first video shows how easily a fly can escape a pool of water, while the second video shows the distinct advantage the digestive fluid gives the plant. Both demonstrate the classic horror film qualities science can evoke!



Citation: Poppinga S, Hartmeyer SRH, Seidel R, Masselter T, Hartmeyer I, et al. (2012) Catapulting Tentacles in a Sticky Carnivorous Plant. PLoS ONE 7(9): e45735. doi:10.1371/journal.pone.0045735

Citation: Gaume L, Forterre Y (2007) A Viscoelastic Deadly Fluid in Carnivorous Pitcher Plants. PLoS ONE 2(11): e1185. doi:10.1371/journal.pone.0001185

Factoring in fear: what scares us most?

Maybe you’ve seen a ghost, or been told the house in this picture is haunted, or watched enough scary movies to associate houses like this with spooks.

But which of these three is the most likely to scare you away? A study published early this week in PLOS ONE suggests any of the three could keep you from stepping in.

Fear is a conditioned response, meaning that we learn to be afraid through a variety of mechanisms, including past experiences, direct instruction, and learned associations. There’s little evidence, though, to show whether one kind of conditioning is stronger than the other.

The authors of this study addressed this question by investigating whether people avoided threats differently depending on how they had learned about them: by direct exposure to the threat, verbal instruction about the threat, or a ‘derived generalization’ that they learned to associate with the threat.

In the first case, participants were trained to associate circles of specific colors with mild electric shocks, a direct exposure to the “threat”. A second group of participants was told verbally that when circles of specific colors appeared on a screen, they would receive a mild shock. A third group of participants were first trained to associate nonsense words with circles of specific colors, and then tested for how strongly they associated the words with the possibility of a shock. Participants were then informed that if they pressed a certain button in response to seeing a color associated with shock, they could avert the unpleasant experience. The study found that, regardless of how the participants had learned to associate the colors or words with the shock, all three groups avoided the unpleasant experience to the same extent.

However, the researchers found differences in the avoidance behavior of groups during the learning period. For example, they found that people who received a verbal warning that certain colors would cause shocks rated the probability of a shock higher in the last phase than the group that had made ‘derived associations’ between words, circles and the possibility of a shock. Why these differences occurred wasn’t clear from this study, the researchers say, but their observations do imply that verbal warning can have a powerful effect on behavior.  Their results may also point to ways that unpleasantness and fear can be associated with certain activities more strongly (or weakly).

Fear conditioning is useful when making decisions about, say, whether to enter a spooky building, but extreme forms of avoidance can lead to severe clinical conditions like anxiety disorders that can hinder day-to-day activities. Previous research shows that anxiety disorders tend to be associated with stronger fear conditioning, and direct contact with an unpleasant event isn’t necessarily required for this conditioning to grow stronger. For example, people with social anxiety disorder tend to avoid large gatherings even though their experience of these may be fairly limited. Studies such as this one could help understand how we learn to avoid stimuli that are perceived as unpleasant even in the absence of repeated exposure, and perhaps eventually point to ways that we could overcome some fears.

Citation: Dymond S, Schlund MW, Roche B, De Houwer J, Freegard GP (2012) Safe From Harm: Learned, Instructed, and Symbolic Generalization Pathways of Human Threat-Avoidance. PLoS ONE 7(10): e47539. doi:10.1371/journal.pone.0047539 

Image Credit: wilsx4 on Flickr CC-by license

Halloween Highlights: Spooktacular Science in PLOS ONE

October is here, which means the holiday season is almost upon us – starting, of course, with Halloween. PLOS ONE doesn’t publish much in the way of goblins, ghouls, or ghosts, but we realized that we do have quite a few spook-inducing papers, so to get you in the holiday spirit, we are bringing you some of our creepiest papers over the course of the month. Today we start with a Halloween icon: bats.

Bats may not be vampires in disguise, but even so, their bite can be dangerous. Bats host and transmit a number of diseases that affect humans, and these pathogens seem to be infecting bats in expanding habitats, specifically Europe. In June, a team of researchers identified the first cases of European bats carrying a virus from a large family called paramyxovirus, members of which are responsible for a number of human and animal diseases, including mumps and measles. Bats carrying this family of viruses had previously only been found in Africa, Australia, South America, and Asia.

A second study from some of the same authors, published in August, reported three novel viruses called orthoreoviruses isolated from European bats. These viruses have not been shown to cause disease in humans, but the authors suggest that their zoonotic potential should be investigated further. A final similar example, also published in August, describes the isolation of a previously unknown bat papillomavirus in Hong Kong.

Despite these potential dangers, it’s also important to note that bats do much good for the ecosystem, including eating lots of pesky bugs, pollinating plants, distributing fruit seeds, and providing valuable guano fertilizer. They’re not so creepy either, really. And sadly, they are currently struggling against a mysterious affliction called White-nose syndrome, which appears to disrupt their hibernation and has been  charged with the deaths of millions of bats in the US and Canada.

Regardless of whether you think bats are creepy or cute, dangerous or misunderstood, it’s unlikely that they’ll kick their eerie associations anytime soon, so here’s to kicking off a month of spooktacular science.


Kurth A, Kohl C, Brinkmann A, Ebinger A, Harper JA, et al. (2012) Novel Paramyxoviruses in Free-Ranging European Bats. PLoS ONE 7(6): e38688. doi:10.1371/journal.pone.0038688

Kohl C, Lesnik R, Brinkmann A, Ebinger A, Radoni? A, et al. (2012) Isolation and Characterization of Three Mammalian Orthoreoviruses from European Bats. PLoS ONE 7(8): e43106. doi:10.1371/journal.pone.0043106

Tse H, Tsang AKL, Tsoi H-W, Leung ASP, Ho C-C, et al. (2012) Identification of a Novel Bat Papillomavirus by Metagenomics. PLoS ONE 7(8): e43986. doi:10.1371/journal.pone.0043986

Reeder DM, Frank CL, Turner GG, Meteyer CU, Kurta A, et al. (2012) Frequent Arousal from Hibernation Linked to Severity of Infection and Mortality in Bats with White-Nose Syndrome. PLoS ONE 7(6): e38920. doi:10.1371/journal.pone.0038920

Image credit: Taylor PJ, Stoffberg S, Monadjem A, Schoeman MC, Bayliss J, et al. (2012) Four New Bat Species (Rhinolophus hildebrandtii Complex) Reflect Plio-Pleistocene Divergence of Dwarfs and Giants across an Afromontane Archipelago. PLoS ONE 7(9): e41744. doi:10.1371/journal.pone.0041744