Of all the environmental resources we take for granted, large, older trees might be near the top of the list. Not only do we rely on trees for oxygen and wood products, but about 180 different animal species rely on the hollow-bearing features of these trees for shelter, roosting, and nesting. Unfortunately, rapid urbanization poses an enormous threat to the existence of these trees.
Large old trees take centuries to mature, and scientists are paying particular attention to the changes in wooded areas as urbanization spreads. The authors of a recent study published in PLOS ONE utilized a simulation model to determine the future of older trees in and around Canberra, Australia. In this urban area of Australia where the population is projected to double from 375,000 people by 2056, the authors found that dramatic changes to the terrestrial environment could occur.
The simulation model developed by the authors calculated the average number of trees in a given area using pre-defined rates of tree mortality and existing data for trees they had catalogued and measured. The data collection included the total number of trees, how fast new ones were growing, and how quickly existing ones were dying or being removed. By extrapolating from this data, they were able to assess tree population changes in the coming years.
Unfortunately, building for a growing human population means clearing out these older trees that may pose a safety threat or may simply be in the way. By projecting the current rate of decline for existing trees in the next 300 years, the researchers found that these trees die or are removed at a rate so rapid that it could lead to their eventual disappearance. To put that threat into numbers, it seems that the population of these hollow-bearing trees will decline by nearly 87% over the next 300 years. In a worst case scenario, we could lose all old, hollow-bearing trees within 115 years. That’s a terrifying thought.
According to the authors’ review of tree population changes, several policies may need to change to reverse the decline of these trees. Only with a combined management strategy, including planting more trees and forming more hollow-bearing habitats, would the population of the trees increase over 250 years after a short period of decline. A decline in older, hollow-bearing trees, including some endangered Eucalyptus varieties, means a decline in shelter for the birds, bats, squirrels, and invertebrates that inhabit them.
Luckily, urbanization brings new innovation, and innovation inspires new solutions to important problems. Environmental consciousness in the public requires a discussion about improving tree management, community engagement, conservation strategies, and biodiversity offsets. For example, we now have the technology to give hollow-bearing features to trees in urban areas by using other hollow-structures or artificial nest boxes.
If large older trees are facing almost certain decline due to urbanization, we need to put forth significant efforts to develop conservation and management strategies to change that. With the research available today, we can develop strategies to protect the large trees in existence, improve regeneration for ones we lose, and develop plans to build structures for animals who are displaced. We are not the only living beings on Earth, and we need to take into consideration how we effect change in our environments.
Citation: Le Roux DS, Ikin K, Lindenmayer DB, Manning AD, Gibbons P (2014) The Future of Large Old Trees in Urban Landscapes. PLoS ONE 9(6): e99403. doi:10.1371/journal.pone.0099403
“I never quit until I get what I’m after. Negative results are just what I’m after. They are just as valuable to me as positive results.” – Thomas A. Edison
The publication of negative results is vitally important for many reasons, not least that it helps prevent duplication of research effort and potentially expedites the process of finding positive results. However, the struggle to find a home to publish the work, and the effort necessary to submit and publish what can feel like negligible scientific contributions, has led to concerns that negative findings are becoming the missing pieces in the scientific literature.
Today PLOS ONE launches a new collection to highlight studies that present inconclusive, null findings or demonstrate failed replications of other published work. The collection has been titled ‘Missing Pieces’ in reference to the many null results filed away indefinitely and ultimately excluded from the scientific record.
Selected examples focus on the lack of a significant effect of postpartum psychological distress on mothers in rural Bangladesh, despite differing positive findings in India.
Frequency discrimination training (FDT) using integrated training with computer-gameplay has previously been reported to show limited improvement in treating the symptoms of tinnitus, however, recent results from a randomised controlled trial did not translate to therapeutic benefit.
The failure to replicate previously published work is prominently highlighted in the popular PLOS ONE psychology paper, Failing the Future. Three attempted replications on the existence of precognition failed to support the previously significant results supporting retroactive facilitation of recall.
The publication of negative results, such as the works featured in the collection, is essential to research progress. Many journals, however, reject studies reporting negative or inconclusive results because the work is not considered impactful enough. In contrast, PLOS ONE does publish such studies; our publication criteria state that we will consider all work that makes a contribution to the field independent of impact.
Through this collection we hope to demonstrate that negative results are valuable to the community in cases where the result is illuminating in the context of previous work.
This collection serves to highlight negative result studies and to encourage the submission of negative results to PLOS ONE. If you would like your work to be considered for the Missing Pieces Collection, please contact firstname.lastname@example.org
As winter grips the Northern Hemisphere tightly, many of us are happy to retreat to the comfort of our warm homes. But for some animals, this season plays a vital role in the formation of something necessary for their survival, ice. There is one thing that we are becoming increasingly sure about: not all winters are created equal. In some years, ice and snow blanket the ground until mid-spring, and in others, light dustings of snow only last for a couple days. For animals that depend on ice for survival, varying winter conditions year to year may provide challenges to finding food, breeding, and making it from one day to the next.
PLOS ONE has recently published several studies that take a closer look at three different animals’ relationship with ice: penguins, polar bears, and ivory gulls.
Searching for Emperor Penguin Breeding Grounds
Emperor penguins rely on Antarctic sea ice for breeding and foraging, but a recent study published in PLOS ONE may have uncovered a new breeding behavior, where the penguins utilize a different type of ice.
Using satellite and aerial surveys to observe four emperor penguin breeding colonies, the authors of this study discovered something unusual. Two of the penguin colonies always appeared on the ice shelf rather than where we expected them to be—on sea ice—but the other two colonies were on both ice shelves and on sea ice in different breeding seasons. Researchers used synthetic aperture radar to assess how the largest of the four colonies may sometimes breed on the shelf and other times on the sea ice.
The authors found that in years where sea ice forms late in the season, the colony relocates onto the ice shelf. Three of the four breeding colonies were in the warmest northern conditions in Antarctica, where sea ice formation is less reliable. What may be a new breeding behavior at these warmer sites could provide clues for understanding how this near threatened penguin species may cope with future sea ice loss.
Polar Bears on the Move
On the other side of the globe, Arctic polar bears also rely heavily on ice for hunting and breeding, but sea ice has declined by over 9% in the Arctic over the past 20 years. The authors of a recent PLOS ONEstudy investigated how these changes may impact polar bear movement around the Arctic. The authors of this study analyzed genes from over 2,700 polar bears to evaluate whether polar bear genetic diversity and structure have changed in the past two decades. They then compared current polar bear genetic patterns with past patterns during ancient climate fluctuations.
Scientists identified four geographic polar bear populations: Eastern Polar Basin, Western Polar Basin, Canadian Archipelago, and Southern Canada (pictured above). They found evidence of gene flow within the past three generations, from Southern Canada and the Eastern Polar Basin toward the Canadian Archipelago, an area thought by scientists to be a possible future refuge for polar bears as climate-induced habitat decline continues.
They also found that the current population shift may differ from previous periods with respect to sea ice variation during the Holocene, where polar bears may have used both the Canadian Archipelago cluster and part of the Eastern Polar Basin cluster as an interglacial refuge. The scientists suggest more genetic samples are needed, but documenting population changes in the past and present may aid in conservation efforts as sea ice continues to decline.
Ivory Gulls on the Icy Edge
Living their entire lives in the Arctic, the near-threatenedivory gulls have scheduled their activities around ice. Foraging, migrating, and breeding are all dependent on ice, but little data exists on their year-round location and timing of these activities. In a recent PLOS ONEstudy, scientists interested in following the ivory gulls’ movement around their Arctic habitat attached satellite transmitters to 12 ivory gulls on Seymour Island, Canada in 2010, and tracked their migration over four breeding seasons.
Scientists have long thought the ivory gulls migrate along the Greenland coast, but the tracking data shows that individual birds varied the timing and their routes greatly. Ivory gulls avoid flying over open water, and scientists suggest birds may vary their migration route with the variations in sea ice formations. Further analysis of their movement revealed that the ivory gulls overwintered near the ice edge in Davis Strait and the Labrador Sea, which likely provided them with a consistent source of food, like fish, or scavenging opportunities, like polar bear remains.
Further research is needed to better understand these patterns, but may aid in predicting their ability to adapt to future sea ice changes.
While scientists are finding evidence that sea ice formation may be changing, they are also working to gain insight into animal behavior and develop conservation measures that might be designed around their current activities. While we humans in the Northern Hemisphere may be ready for winter to be over, animals at the Antarctic and Arctic poles may be hoping that more ice is on the way.
Citations: Fretwell PT, Trathan PN, Wienecke B, Kooyman GL (2014) Emperor Penguins Breeding on Iceshelves. PLoS ONE 9(1): e85285. doi:10.1371/journal.pone.0085285
Peacock E, Sonsthagen SA, Obbard ME, Boltunov A, Regehr EV, et al. (2015) Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic. PLoS ONE 10(1): e112021. doi:10.1371/journal.pone.0112021
Spencer NC, Gilchrist HG, Mallory ML (2014) Annual Movement Patterns of Endangered Ivory Gulls: The Importance of Sea Ice. PLoS ONE 9(12): e115231. doi:10.1371/journal.pone.0115231
While humans may be the only ones with a day dedicated to celebrating romantic love, rest assured that the semblance of ‘love’ is alive and well in the animal kingdom too. While ‘love’ in this context may not hold the same meaning we normally think of, animals on land, air, and sea are diligently working to keep their species alive. In honor of them, the PLOS ONE staff has gathered a few of our favorite ‘animal love’-themed research articles to share with you this Valentine’s Day.
Letting people know you’re taken can be important, and no one knows this better than the male stony creek frog. The males of this species change color from boring brown to a ‘look at me!’ yellow in a matter of a few minutes during mating (pictured above). The authors of “The Neuro-Hormonal Control of Rapid Dynamic Skin Colour Change in an Amphibian during Amplexus” aimed to determine the hormones behind this color change. Previous studies, showing that stress in this species may trigger the color change during mating, helped the authors narrow down their focus to look specifically at stress hormones. By exposing captured, wild male frogs to epinephrine (also known as adrenaline), testosterone, and a control substance, they were able to determine that epinephrine likely plays a key role in turning the frogs yellow. Based on their observations, the authors hypothesize that the bright yellow color is a signal to other males that they have secured a female, and a way to possibly prevent other males from getting in the way of an all-important mating session.
Fighting among males for mates is fairly common in the animal kingdom, but a group of researchers investigated whether there were any evolutionary patterns in snakes exhibiting this behavior. The authors of “Phylogeny of Courtship and Male-Male Combat Behavior in Snakes” looked at 33 male snake courtship behaviors across 76 species, retrieving these details from pre-existing literature. Some of these behaviors included ‘biting,’ ‘tail whipping,’ and ‘spur poking.’ They also note that since snake behavior often goes unrecorded, future data collection is needed. They mapped these behaviors on a phylogeny, an evolutionary map that included 30 species of snakes belonging to the superfamily Colubroidea. After analyzing this comparison, they were able to discern a pattern (see image above) and gain idea of the time period that certain behaviors were introduced to a species. Based on this evaluation, a “head raise with simultaneous downward push” and “spur poking” were some of the earliest attack methods deployed in combat between these male snakes, all in the name of ‘love,’ of course!
While there are many species of birds that are ‘monogamous,’ many also mate outside social pairs. The authors of “Steller Sex: Infidelity and Sexual Selection in a Social Corvid (Cyanocitta stelleri)” aimed to determine what role male ornamental plumage plays in Steller jay chick paternity. The authors worked with a population of Steller jays in which 25 social pairs (life partners) were known and collected blood samples from the birds and their chicks. They were then able to determine the number of chicks that hatched after extra-pair mating. After analysis, the authors found that 15% of chicks in this Steller jay population were the product of extra-pair mating. Additionally, they found that jays whose male mates had lower quality plumage had more extra-pair chicks, while those whose mates had higher quality plumage had fewer extra-pair chicks. However, a nest full of extra-pair chicks does not go unpunished. Other studies have shown that bird nests with a higher percentage of extra-pair chicks result in less effort toward parental care on the part of the male.
My Sweet Little Dumpling [Squids]: Getting Frisky in Front of Flatheads
Being a “third wheel” can be an uncomfortable situation, but Nature takes that to another level when a predator “third wheel” approaches two mating creatures. You would think that the presence of predators would put animals on high alert and deter them from mating, but that may not always be the case. Many animals face a trade-off between survival and reproduction, and sometimes reproduction is their most viable option. Female dumpling squid (one pictured above) produce ink to mask their coupling from hungry sand flathead predators, but male dumpling squid do not bother to produce any defense mechanisms when they are mating.
To observe this mating behavior, the authors of “Does Predation Risk Affect Mating Behavior? An Experimental Test in Dumpling Squid (Euprymna tasmanica)” matched fifteen pairs of dumpling squid, and then subjected each pair to three separate predation simulations. The dumpling squid couple and the sand flathead were separated by a clear acrylic sheet with holes in the top, so that they could see and hear one another. The predator was introduced before, during, and after the squid couples’ mating, to observe whether its introduction would interrupt or stop the squids from getting busy. They found that females inked significantly more when a predator was introduced before mating, but the males did not ink. Males would not cease mating to protect themselves because an interruption would mean fewer sperm would be transferred, and he would be less likely to impregnate the female. In addition, predation risk did not influence the squids’ likelihood or duration of their mating. The image above depicts a pair of mating dumpling squid, and you can watch a video of their inking, jetting, and copulation behaviors here:
Reindeer (Rangifer tarandus) may look cute and innocent, but they can be aggressive when it comes to mating. During the rutting season, female reindeer move in large groups either to sample mates, or to avoid harassment from the males—not exactly the most romantic of situations. Often the dominant males will herd the females in a group, rather than follow an individual female, both to act as their protector and to increase their chances of successful reproduction. The authors of “Highly Competitive Reindeer Males Control Female Behavior during the Rut” investigated these behaviors by observing 11 male and 34 female semi-domestic reindeer during the breeding season, tracking and recording their GPS position every 15 minutes, for a total of 3800 recordings. They measured the average number in a group and how long the group remained together, and compared those measurements with the length of the mating season and the social rank of the dominant male, which is established based on several variables, such as a large body mass and antler size. Through this model, the researchers demonstrated that the dominant reindeer males, through herding and other mating-related activities, strongly influence the females’ movement patterns. In other words, the reindeer males were a bit machismo when it came to ‘love.’ The females, however, may not have as much choice in their mating partner—quite a double-standard, and not a very modern romance relationship for this animal pairing!
In contrast to the female reindeers’ relative lack of choice in a mate, female moths (Spodoptera litura) may be a bit pickier when choosing a mate. The authors of “Female and Male Moths Display Different Reproductive Behavior when Facing New versus Previous Mates” found that female moths can tell if they’ve mated with a male moth before, and they prefer to mate with new partners. Male moths, on the other hand, will generally mate with whichever female is present—in other words, he won’t mind if she’s an old flame. In the study, the researchers played a little moth matchmaker, pairing moths up in boxes in the lab to see if they’d mate with one another. They recorded the mating behaviors of the females when they were exposed to new mates, taking note of their expansion of the pheromone gland to attract a male mate (known as calling), the male’s courtship of the female by fanning his wings around her, and the mating of the two moths. They found that females called earlier and more often when paired with a new male partner, but males courted new and previous female mates the same way. This isn’t to say the males’ wooing techniques were boring by any means—in fact, male moths can create some lovely melodies to serenade their lovers.
We hope you enjoyed exploring the mating behaviors of some of our favorite animals— who knows, maybe you were even able to relate to some of them. Such behaviors show that many animals seem to subscribe to the “all’s fair in love and war” mantra—or at least the males do! Whether you’re “assertive” or not when it comes to love, rest assured there’s probably a member or two of the animal kingdom that has recently behaved the same way. Happy Valentine’s Day from PLOS ONE!
Written by PLOS staff members Tessa Gregory and Kaitlyn Keller
Kindermann C, Narayan EJ, Hero J-M (2014) The Neuro-Hormonal Control of Rapid Dynamic Skin Colour Change in an Amphibian during Amplexus. PLoS ONE 9(12): e114120. doi:10.1371/journal.pone.0114120
Senter P, Harris SM, Kent DL (2014) Phylogeny of Courtship and Male-Male Combat Behavior in Snakes. PLoS ONE 9(9): e107528. doi:10.1371/journal.pone.0107528
Overeem KR, Gabriel PO, Zirpoli JA, Black JM (2014) Steller Sex: Infidelity and Sexual Selection in a Social Corvid (Cyanocitta stelleri). PLoS ONE 9(8): e105257. doi:10.1371/journal.pone.0105257
Franklin AM, Squires ZE, Stuart-Fox D (2014) Does Predation Risk Affect Mating Behavior? An Experimental Test in Dumpling Squid (Euprymna tasmanica). PLoS ONE 9(12): e115027. doi:10.1371/journal.pone.0115027
Body G, Weladji RB, Holand Ø, Nieminen M (2014) Highly Competitive Reindeer Males Control Female Behavior during the Rut. PLoS ONE 9(4): e95618. doi:10.1371/journal.pone.0095618
Li Y-Y, Yu J-F, Lu Q, Xu J, Ye H (2014) Female and Male Moths Display Different Reproductive Behavior when Facing New versus Previous Mates. PLoS ONE 9(10): e109564. doi:10.1371/journal.pone.0109564
PLOS ONE and PLOS Biology are excited to return to the Biophysical Society’s Annual Meeting. The event will be held at the Baltimore Convention Center located in downtown Baltimore, Maryland. All are encouraged to stop by booth #636 to speak with PLOS staff and learn more about our journals. We look forward to meeting current and prospective authors, Academic Editors, reviewers, and anyone else interested in PLOS!
Be sure to grab a copy of the PLOS Editors’ Picks for Biophysical Sciences Articles postcard. PLOS editors’ picks include:
Whether tromping alone or running in a pack, all prehistoric creatures got around somehow. Paleontologists can use fossilized bones to learn more about what dinosaurs ate, what they looked like, and even how they might have moved, but bones are only part of the “rocky” story. We can study fossils of all shapes, sizes, and sources to piece together missing information about how these creatures moved, interacted, and lived. Trace fossils, which include fossilized impressions like footprints and belly drag marks left in the ground, can tell us a surprising amount about how animals of the past lived and moved. They are more common than you might think, but typically aren’t studied as often as fossilized bones. PLOS ONE recently published two separate studies where authors used trace fossils to provide insight on tyrannosaurs social life and the slow and slithering movements of an ancient temnospondyl, bringing two prehistoric creatures to ‘life.’
Many tyrannosaur bones have been collected and documented, but few scientists have studied their footprints. In a new PLOS ONEstudy, researchers found three 75 million-year-old three-toed tyrannosaurid footprint with claw marks tracks heading southeast within an 8.5 meter-wide corridor in British Columbia, Canada (shown in the image above). Scientists took molds and measurements of the prints (shown in the image below) to understand the track-makers’ behavior. Scientists aren’t sure exactly which species of tyrannosaur made the prints, but similarities in depth and preservation of the tracks indicate that these three trackways were made by dinosaurs walking alongside each other in the same direction at a normal pace, around 8.50 kilometers per hour.
These trackways add to previous research about tyrannasaurid social behavior and locomotion, but the authors acknowledge that there is the possibility, although unlikely, that three dinosaurs could have passed through the same spot separately within a short period of time. Either way, the tracks make up the first record of the walking gait of tyrannosaurids and provide insight about how they moved across Western Canada.
A 200 million-year-old mysterious trackway, called Episcopopus ventrosus, in southern Africa may have been made by a dinosaur, or maybe by an early ancestor of the crocodile. Researchers that mapped, cast, and laser-scanned the best-preserved part of the Episcopopus ventrosus trackway found that the track belongs to a primitive amphibian-like animal from one of the earliest groups of limbed vertebrates, temnospondyls. The author’s estimate the track-maker was 3.5 meters long and dragged the hind portion of its body along a wet sand bar on the bank of a river bend, using only the claw-less tips of its digits (pictured above).
The movements were likely made by a large-headed, slithering, and slow-moving amphibian-like animal. Researchers usually use hind-limb-driven salamanders as a model for temnospondyl locomotion, but this discovery is causing researchers to re-examine their use of salamander models for this front-limb-driven temnospondyl.
Socializing and Slithering
From signs of dinosaurs moving in packs to amphibian-like animals slithering across river banks, trace fossils can support what we already know about prehistoric creatures, but they can also shake up the assumptions we’ve made, and in the case of the tetrapod, potentially change the way we study them. Fossilized bones may still be the better known field of study, but footprints and other trace fossils may help shape our understanding of patterns, reconstructing of past lives, and bringing of prehistoric animals back to “life.”
Citation: McCrea RT, Buckley LG, Farlow JO, Lockley MG, Currie PJ, et al. (2014) A ‘Terror of Tyrannosaurs’: The First Trackways of Tyrannosaurids and Evidence of Gregariousness and Pathology in Tyrannosauridae. PLoS ONE 9(7): e103613. doi:10.1371/journal.pone.0103613
Marsicano CA, Wilson JA, Smith RMH (2014) A Temnospondyl Trackway from the Early Mesozoic of Western Gondwana and Its Implications for Basal Tetrapod Locomotion. PLoS ONE 9(8): e103255. doi:10.1371/journal.pone.0103255
For most animals, the sex of their offspring is determined by genetics. However, for tuatara, a lizard-like reptile that inhabits select New Zealand islands, the number of males versus females is related to the temperature during a specific period of the egg’s development.
The name for the scientific concept of temperature influencing the sex of your offspring is environmental sex determination (ESD) and is a trait found in many reptiles. For tuatara, the warmer it is, the more likely an egg is to develop into a male, and an incubation temperature of 69.8˚F gives about an equal chance of either gender developing.
What’s so special about these creatures? Tuatara are native to New Zealand, the only place in the world that they can be found. They are special for another reason, too: they are the only living members of the order Rhynchocephalia, which has earned them the nickname “living fossils.”
Tuatara stand out reproductively as well. It can take them up to 20 years to reach the age of reproduction, and once they do, the females only lay eggs every 2 to 5 years. They can also live to be more than 100 years old.
In a recent PLOS ONEstudy, the authors looked at a population of Tuatara living on North Brother Island in New Zealand to investigate the current male-to-female ratios and predict what these numbers may look like if temperatures increase based on current climate models.
For this study, the authors first looked at surveys conducted between 1988 and 2001 and found that approximately 60% of the population was male. They then looked at more recent surveys conducted between 2005 and 2011 to compare temperatures and sex ratios, the results of which revealed a 70% male population.
The authors then used a model to predict the ratio of males to females that might be born in future years, based on the soil temperature in various nesting sites. From this, they estimated that an increase of less than 1 degree Celsius would over time shift the population to 57% male, and an increase by 3-4 degrees Celsius could eventually shift the entire population to be male. Unfortunately, a large sex bias, especially toward males, has the potential to put tuatara at risk for extinction.
Though this population of tuatara has not yet been classified as endangered, the authors suggest that the potentially large effect a small temperature change could have on the population means that further population monitoring will be important. Increases in the temperature of their environment, combined with their slow reproductive cycle, means that it could be difficult for them to “bounce back” from population shifts toward fewer females. The authors note that in such a case, human interventions, such as artificially incubating eggs or modifying habitat, may be necessary to save the species.
The loss of tuatara would not only result in an extinct species, but the entire order Rhynchocephalia would be lost. However, since this species has not yet reached an endangered status, we are provided with an opportunity to take action. Future studies and monitoring of tuatara may allow us to prevent the grim fate that all other species of this order have reached.
Even though our favorite pet dogs are now well-domesticated, we can still catch glimpses of their primal past when we watch them devour a bone or hunt those pesky squirrels. Sadly, new research shows that the status of dogs in the human family may have had a rocky start, often leaving them to dodge physical harm and rely on scavenging.
Unfortunately, there is little research available on archaeological dog remains, making it difficult to compare patterns of skeletal damage. Researchers also lack sufficient records of human life and culture in the presence of canines; it seems that early tribes weren’t regularly recording details of dog domestication.
Researchers at the University of Alberta have begun to shed light on these practices by analyzing ancient dog teeth. In their recent PLOS ONEstudy, they describe canine dental specimens with extensive damage to teeth and bone, including tooth loss, trauma, and defects. The authors analyzed and compared these remains with wild canids, such as foxes, jackals, and wolves, to better understand early dog behavior and help interpret signs of trauma.
These weren’t just any dogs, though. The authors studied four main types of dental and skeletal damage from museum collections in Northern Canada and Russia (see the map above). Using remains from these northern locations allowed the researchers to investigate the unique challenges dogs face when living in cold climates, where hunting and sled driving were common. The authors focused on tooth loss and fractures, as well as traumatic lesions on the cranium or jaw bone.
Determining the cause of tooth damage can be tricky, but overall, they found that tooth loss occurred in a higher percentage of the dogs rather than wolves. More than that, the overall percentage of teeth lost (per dog) was also higher in the dog population. This indicates that human owners may have played a part in removing some teeth, perhaps to stop dogs from chewing their possessions or the ropes tethering them to their sleds.
Furthermore, dogs on the whole showed higher rates of tooth loss, fracture, and traumatic lesions compared to wolves from the same region (click to enlarge image above). Notably, tooth fracture was present in similar teeth within the mouths of different dogs. The higher prevalence of this trauma among the dogs could be explained by aspects of feeding, such as how their food was obtained, or the qualities (density, texture) of what they were chewing.
As an example, dogs likely received leftovers from human food and had to work their mouths harder to chew and extract nutrients from what was left. Given the geographic location, they may also have been fed whale blubber, or chunks of frozen meat with bones in them. These unlikely additions to their diet may have caused the higher frequency of tooth fracture or damage that was seen in the dog population compared to the wolves.
The rate of traumatic lesions on the jaw and skull of the dogs was also higher than those of free-roaming wolves. There is always the possibility that fighting between animals caused these lesions, especially on the skull and snout. However, the rates of scarring and the involvement of humans in the lives of these dogs suggests another explanation for this physical damage: a result of humans physically controlling the dogs.
If there’s one thing that’s evident from these results, it is that the life of a domesticated dog in our society was not always easy. Access to human-provided food gave the dogs some freedom from food stress but exposed them to other hazards posed by humans, such as weapons and controlling behavior. Although it was clearly a complicated and difficult transition for these animals to make, it is a glimpse into the history of the new human-dog bond we have today.
Dogs from these cold, hunting-driven climates were valued by us for their strength, hunting assistance, and ability to fend for themselves. We owe them for their commitment to us, and for sticking with us through better or potentially worse. Tonight, give Fido an extra soft treat and a hug.
Citation: Losey RJ, Jessup E, Nomokonova T, Sablin M (2014) Craniomandibular Trauma and Tooth Loss in Northern Dogs and Wolves: Implications for the Archaeological Study of Dog Husbandry and Domestication. PLoS ONE 9(6): e99746. doi:10.1371/journal.pone.0099746
An apple a day might keep the doctor away, but honey may fight some infections.
Bacterial cell walls are not only responsible for sustaining the cell’s shape but are also necessary for the bacteria’s growth, survival, and reproduction. A class of antibiotics called beta-lactams, which includes the familiar antibiotics penicillin and ampicillin, attack the cell wall’s proteins, causing the cell wall to fall apart and die. While this is effective for treating many common bacterial infections in people, microbes have long been developing resistance to antibiotic drugs, referred to as antibiotic resistance. In the race to protect ourselves from these bugs, scientists are looking for promising alternatives that may combat microbes with the same effectiveness as antibiotics.
Previousstudies have investigated honey’s ability to kill and halt growth of certain strains of bacteria. Taking this into account, researchers compared the efficacy of Canadian honey on killing E. coli, strains of bacteria commonly associated with feces and contaminated food, as well as a vital part of all human bodies. The authors of the study, published in PLOS ONE, investigated honey’s antibacterial activity and its potential ability to inhibit growth of antibiotic-resistant strains of E. coli.
The authors conducted a series of experiments by applying various concentrations of honey or antibiotics to bacterial cell cultures and then visualizing changes in the cell structure to determine the necessary concentrations of each to inhibit growth and kill cells. Using scanning electron microscopy (SEM), as seen in the image above, the authors observed the transformation in cell structure over time as they increased the amount of added honey or ampicillin. Flourishing E. coli are typically rod- shaped with filaments, but within 18 hours of application of honey or ampicillin, the shape appeared to transform into “spheroblasts,” as seen in the image below. Spheroblasts are what remains after the cell wall has been broken by an antibiotic drug, as well as the debris of the dead cell. According to the authors, the results may indicate that like ampicillin, honey can interfere with E. coli’sability to survive and reproduce.
Many strains of E. coli are resistant to beta-lactams like ampicillin, and to test honey’s effect on these strains, the researchers repeated their experiments with honey on ampicillin-resistant strains of E. coli and again visualized cell shape changes and inhibition of bacterial growth. The honey appeared to halt the growth of the ampicillin-resistant bacteria with the same efficiency as it halted non-resistant strains.
The image above illustrates the destruction of the cell wall and the death of the ampicillin-resistant cell after exposure to honey (panel A before treatment, and panel B after honey application). Recent studies have suggested that honey’s antibacterial mechanisms may be attributed to the concentration difference between honey and water molecules, referred to as high osmolarity, and honey’s ability to inhibit bacterial communication. Honey is a natural mixture of many compounds, and while scientists have yet to confirm the exact compounds responsible, the results of the above study support the idea that honey and ampicillin may have similar antibacterial efficacies, with possibly different mechanisms of attack.
As microbes become increasingly resistant to our standard treatments, it’s important to investigate alternative mechanisms of antibacterial defense. Although more work remains to be done here, the authors’ evidence of honey-induced cell death with apparently similar efficacy to ampicillin may pioneer future studies in the field. In other words, honey could be just what the doctor ordered.
Citation: Brudzynski K, Sjaarda C (2014) Antibacterial Compounds of Canadian Honeys Target Bacterial Cell Wall Inducing Phenotype Changes, Growth Inhibition and Cell Lysis That Resemble Action of β-Lactam Antibiotics. PLoS ONE 9(9): e106967. doi:10.1371/journal.pone.0106967
2014 has been an exciting year for PLOS ONE. We saw the journal reach a milestone, publishing its 100,000th article. PLOS ONE also published thousands of new research articles this year, including some ground-breaking discoveries, as well as some unexpected and controversial findings.
All year long, the staff editors at PLOS ONE carefully scan newly submitted manuscripts before they’re sent to our Editorial Board for assessment and scientific peer review. Among the thousands of titles that each PLOS ONE staff editor has seen over the past year, there were bound to be some year-end favorites! We polled the PLOS ONE staff editors and asked them to send along their picks, presented in no particular order.
As we increasingly rely on multimedia devices in our personal and professional lives, we may wonder what impact our habits have on our brains. Studies have indicated that media multi-tasking—that is, the concurrent use of multiple media devices—may have a negative impact on a number of cognitive functions, but the neural changes responsible for these declines remain largely unexplored.
Using MRI to explore structural associations with our use of media, the authors of “Higher Media Multi-Tasking Activity Is Associated with Smaller Gray-Matter Density in the Anterior Cingulate Cortex” show that users who frequently engage in media multi-tasking may have a lower density of gray-matter in the anterior cingulate cortex, a region in the brain crucial for a number of higher cognitive processes. While the authors cannot yet state that media multi-tasking causes decreased gray matter, it does make us wonder whether our devices are, quite literally, becoming a substitute for our brains.
2. Improving Zebrafish Care and Welfare in the Lab
The use of zebrafish in developmental and biomedical research has increased substantially in recent years. The popularity of this relatively new model species has sparked an interest in assessing—and potentially improving—their welfare in the lab environment. Evaluating the “humaneness” of euthanasia is a critical research aim, since nearly all zebrafish are sacrificed at the end of an experiment.
In “Conditioned Place Avoidance of Zebrafish (Danio rerio) to Three Chemicals Used for Euthanasia and Anaesthesia,” the authors report the results of a behavioral test designed to evaluate and compare the animals’ aversion to three commonly used euthanasia agents: tricaine methanesulfonate (referred to as TMS or “MS-222”), clove oil, and metomidate hydrochloride. The researchers found that zebrafish exposed to TMS spent less time in the side of the experimental tank that they had previously preferred, indicating aversion. Exposure to the other two chemicals did not elicit such a response, leading the authors to conclude that clove oil and metomidate hydrochloride are less aversive to zebrafish and could be pursued as “humane alternatives” to TMS for euthanasia. This finding may play an important role in the updating of guidelines for the care and use of zebrafish in the research setting.
This paper was picked by two PLOS ONE Editors! Do our genes determine whether we could live to be 110? To answer this question, the authors of “Whole-Genome Sequencing of the World’s Oldest People” sequenced the genomes of 17 supercentenarians and compared their DNA to that of the general population. Despite trying several ways of searching, the researchers did not find any specific genetic variations associated with supercentenarians, but they did generate a unique, publicly available dataset and a useful resource that may help us someday uncover the genetic code for a long life (or else determine that one may not exist)!
This was another paper that got more than one vote from the PLOS ONE Editors. The Stanford University authors of “Foldscope: Origami-Based Paper Microscope” bring microscopy to the masses with their invention. Fabricated from paper and assembled in 10 minutes using origami folding techniques, the Foldscope comes in at a per unit cost of less than $1 and represents an exciting opportunity to inexpensively fabricate microscopes in bulk. It uses an LED light that provides up to 50 hours of light on a single button battery, making it usable for field applications. The Foldscope may find its way into the hands of students, educators, and scientists worldwide for a wide-range of purposes, including future disease-specific designs for rapid diagnoses in the field.
This study from MIT, published way back in January, held strong as one of our favorites throughout this year. With the problem of waterborne diseases causing up to ~1.8 million deaths annually, “Water Filtration Using Plant Xylem” describes the use of plain old sapwood from coniferous trees as a way to remove bacteria and pressure-filter up to several liters of clean drinking water per person per day. Like the Foldscope mentioned above, this method may be useful for the public, readily available, inexpensive, and to top it off, completely biodegradable and disposable. If implemented, this method may be able to help address the need for clean water in developing countries and areas where resources are otherwise limited.
Schizophrenia and biopolar disorder are highly heritable, but the genetic contributions to these disorders are not well understood. In “Pathway Analyses Implicate Glial Cells in Schizophrenia,” the authors used publicly available data from the Psychiatric Genomics Consortium and sought associations between these illnesses and biological pathways (groups of genes), rather than studying single gene associations. Results showed that a glia-oligodendrocyte pathway was associated with both disorders, supporting a model in which genetic factors contribute to white matter abnormalities observed in brains of patients with schizophrenia. This methodological advance may be instrumental in increasing our understanding of multi-genic diseases and disorders that have eluded geneticists for decades.
8. SAFE 2013: Exploring Sexual Harassment in Science
In “Survey of Academic Field Experiences (SAFE): Trainees Report Harassment and Assault,” authors detail a self-selected survey of 666 field researchers, where nearly two in three surveyed reported experiencing sexual harassment, and over one in five reported suffering sexual assault. According to the study, women were more likely than men to be subject to harassment or assaults, and unlike men, the women reported receiving abuse more from superiors than from peers. Unfortunately, victims felt they had limited awareness of policies and reporting mechanisms. Published in July, this study has helped open up a conversation about sexual harassment and assault in anthropology and scientific research more broadly, including extensive discussion in media and blogs lasting much long than the usual media cycle for a publication. The study was also quoted by a member of the US Congress. It was one of our most-viewed PLOS ONE articles in 2014, and in the top ten by social shares—the most tweeted PLOS ONE article this year—and has 79 media links so far.
As legend has it, penicillin was discovered when an unwelcome fungus floated through an open window, landed in a petri dish, and blocked the growth of bacteria. If this serendipitous event could transform modern medicine, what is the potential of the over 5 million fungal species that have yet to be characterized? In “Sloth Hair as a Novel Source of Fungi with Potent Anti-Parasitic, Anti-Cancer and Anti-Bacterial Bioactivity,” the authors visited the microbe-rich tropics of Central America and offered nine wily three-fingered sloths a free haircut. The hair samples yielded dozens of novel fungal strains, many of which displayed activity against bacteria, parasites, and cancer cells. These findings may provide leads for drug development and underscore the untapped potential hiding in microbial biological diversity.
Although birds are direct descendants of theropod dinosaurs, they cannot be used confidently to gain insights into certain aspects of dinosaur biology because their bodies have changed so much over the course of evolution. In an effort to explore chickens as a model for dinosaur locomotion, the authors of “Walking Like Dinosaurs: Chickens with Artificial Tails Provide Clues about Non-Avian Theropod Locomotion” attached an artificial tail to two-day-old chicks to substitute for the bony tail of dinosaurs that was lost to evolution. As adults, the chickens exhibited a displaced center of mass, and changes in limb posture and range of motion, creating a potential model for investigating dinosaur locomotion mechanics and energetics.
12. Working Together, Not Against: The Tale of H4K16ac and ISWI
Histone proteins, assembled into a nucleosome structure, are essential for compacting DNA into tiny nuclei inside eukaryotic (membrane-bound) cells. However, access to specific regions of DNA is necessary during a cell’s lifetime, and chromatin remodelers such as ISWI, alongside chemical modifications to the histones, such as acetylation of Lysine 16 on Histone (H4K16ac), can help unravel the DNA. Somewhat paradoxically, evidence seems to suggest that H4K16ac actually works against ISWI and inhibits it. As all evidence indicating that H4K16ac inhibits ISWI was performed using peptides or arrays containing just one nucleosome, the authors of “ISWI Remodelling of Physiological Chromatin Fibres Acetylated at Lysine 16 of Histone H4” decided to approach the puzzling question using nucleosomes arrays made of 25 nucleosomes to more closely mimic the chromosome. Using this system, researchers showed that H4K16ac did not in fact stop ISWI in its remodeling capabilities as previously thought, putting the conundrum to rest.
13. How Available are the Results of Clinical Trials?
Studies were less likely to publicly disclose the results if i) they were a phase 2 versus a phase 3/4 clinical trial, ii) if the sample size was small, or iii) if the study design involved randomization. These findings broadly support previous studies of clinical trial reporting, including a PLOS ONEstudy in 2013 by Huser et al.
There you have it! A diverse selection of papers that we hope gives you a taste of the scope and breadth of research published in PLOS ONE. Here’s to another huge round of exciting research in 2015!
Happy New Year!
The PLOS ONE Staff Editors
Damian Pattinson, Iratxe Puebla, Catriona MacCallum, Meghan Byrne, Michelle Dohm, Matt Hodgkinson, Eric Martens, Adrian Aldcroft, Gina Alvino, Sarah Bangs, Christna Chap, Eileen Clancy, Alejandra Clark, Renee Hoch, Jessica Rozek, Nicola Stead, and Edward Sucksmith