Author: Kayla Graham

3000 Years Ago, We Were What We Ate

Efate, VanuatuFor many of us, moving to a new house means recruiting a couple good friends to help pack and haul boxes. After a day or two of work, everyone shares a pizza while resting tired muscles at the new home. But 3000 years ago, enjoying a post-move meal may have required a little more planning. Early settlers of remote tropical islands in the Pacific had to bring along all resources needed for survival, including food, from their original homes overseas.

The Lapita people were early settlers of islands in the Pacific, called Remote Oceania (pictured below). When these people, whose culture and biology links to Southeast Asian islands, first decided to sail to the island Vanuatu, they brought domestic plants and animals—or what you might call a ‘transported landscape’—that allowed them to settle this previously uninhabited, less biodiverse (and less resource-available) area. However, the extent to which these settlers and their domestic animals relied on the transported Remote Oceanialandscape at Vanuatu during the initial settlement period, as opposed to relying on the native flora and fauna, remains uncertain.

To better understand the diet and lives of the Lapita people on Vanuatu, archaeologist authors of a study in PLOS ONE analyzed the stable carbon, nitrogen, and sulfur isotopes from the bones of ~ 50 adults excavated from the Lapita cemetery on Efate Island, Vanuatu.

Why look at isotopes in human remains? Depending on what we eat, we consume varying amounts of different elements, and these are ultimately deposited in our bones in ratios that can provide a sort of “dietary signature”; in this way, the authors can investigate the types of plants, animals, and fish that these early people ate.

For instance, plants incorporate nitrogen into their tissue as part of their life cycle, and as animals eat plants and other animals, nitrogen isotopes accumulate. The presence of these different ratios of elements may indicate whether a human or animal ate plants, animals, or both. Carbon ratios for instance differ between land and water organisms, and sulfur ratios also vary depending on whether they derive from water or land, where water organisms generally have higher sulfur values in comparison to land organisms.

Scientists used the information gained about the isotopes and compared it to a comprehensive analysis of stable isotopes from the settlers’ potential food sources, including modern and ancient plants and animals. They found that early Lapita inhabitants of Vanuatu may have foraged for food rather than relying on horticulture during the early stages of colonization. They likely grew and consumed food from the ‘transported landscape’ in the new soil, but appear to have relied more heavily on a mixture of reef fish, marine turtles, fruit bats, and domestic land animals.

The authors indicate that the dietary analysis may also provide insight into the culture of these settlers. For one, males displayed significantly higher nitrogen levels compared to females, which indicates greater access to meat. This difference in food distribution may support the premise that Lapita societies were ranked in some way, or may suggest dietary differences associated with labor specialization.  Additionally, the scientists analyzed the isotopes in ancient pig and chicken bones and found that carbon levels in the settlers’ domestic animals imply a diet of primarily plants; however, their nitrogen levels indicate that they may have roamed outside of kept pastures, eating foods such as insects or human fecal matter. This may have allowed the Lapita to allocate limited food resources to humans, rather than domestic animals.

Thousands of years later, the adage, “you are what you eat” or rather, “you were what you ate” still applies. As the Lapita people have shown us, whether we forage for food, grow all our vegetables, or order takeout more than we would like to admit, our bones may reveal clues about our individual lives and collective societies long after we are gone.

Citation: Kinaston R, Buckley H, Valentin F, Bedford S, Spriggs M, et al. (2014) Lapita Diet in Remote Oceania: New Stable Isotope Evidence from the 3000-Year-Old Teouma Site, Efate Island, Vanuatu. PLoS ONE 9(3): e90376. doi:10.1371/journal.pone.0090376

Image 1: Efate, Vanuatu by Phillip Capper

Image 2: Figure 1

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Ask EveryONE: Corrections

My paper was recently published in PLOS ONE, but I’ve noticed an error. Can it be corrected?

PLOS ONE corrects major errors found in published articles via the addition of a Formal Correction to the paper. Formal Corrections are reserved for errors that significantly affect the understanding or utility of the paper.  In addition to being published on the PLOS ONE website, corrections are also indexed in PubMed Central and PubMed.

When a paper has been corrected, a correction notice will appear in a gray box at the top of the article page.  A CrossMark logo now appears on every PLOS article page and in the downloadable PDF; clicking the logo on a corrected article’s page will bring up a status box showing that the paper has been corrected.

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Example of a Formal Correction notice (click to enlarge)

If you notice an error in your published paper, you should contact our corrections team at corrections@plos.org.  Please include the title and DOI of your paper; a description of the problem; and any corrected figures, tables, or supporting information files. PLOS staff will decide whether a Formal Correction is appropriate and will work with you to publish a correction as quickly as possible.

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corrections image2Example of a Formal Correction (click to enlarge)

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Ask EveryONE: Why does my corrected article show up twice in PubMed?

After my paper was published, I discovered an error and contacted PLOS ONE to have it fixed. Now my paper shows up twice in PubMed. Is this a mistake?

If your paper had a formal correction, this is not a mistake; your paper will be listed in PubMed twice.

If a published paper contains a significant error, we publish a Formal Correction to fix that error; the Formal Correction is its own publication and therefore has its own DOI.  The Formal Correction then receives its own, separate entry in PubMed in order to link to the original correction on the PLOS ONE website. The correction’s title will include the word “Correction” followed by the original paper’s title. PubMed mandates that the original and the correction both be entered in its database, as you can see here.

Please note that your corrected paper will show up only once in PMC (PubMed Central), because the correction will be embedded in the PMC entry for the original paper itself.

 

 

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Two Shark Studies Reveal the Old and Slow

Sharks live in the vast, deep, and dark ocean, and studying these large fish in this environment can be difficult. We may have sharks ‘tweeting’ their location, but we still know relatively little about them. Sharks have been on the planet for over 400 million years and today, there are over 400 species of sharks, but how long do they live, and how do they move? Two recent studies published in in PLOS ONE have addressed some of these basic questions for two very different species of sharks:  great whites and megamouths.

The authors of the first study looked at the lifespan of the great white shark. Normally, a shark’s age is estimated by counting growth bands in their vertebrae (image 1), not unlike counting rings inside a tree trunk. But unfortunately, these bands can be difficult to Great white vertdifferentiate in great whites, so the researchers dated the radiocarbon that they found in them. You might wonder where this carbon-14 (14C) came from, but believe it or not, radiocarbon was deposited in their vertebrae when thermonuclear bombs were detonated in the northwestern Atlantic Ocean during the ‘50s and ’60s. These bands therefore provide age information. Based on the ages of the sharks in the study, the researchers suggest that great whites may live much longer than previously thought. Some male great whites may even live to be over 70 years old, and this may qualify them as one of the longest-living shark species. While these new estimates are impressive, they may also help scientists understand how threats to these long-living sharks may impact the shark population.

A second shark study analyzed the structure of a megamouth shark’s pectoral fin (image 2) to understand and predict their motion through the water. Discovered megamouth finin 1976, the megamouth is one of the rarest sharks in the world, and little is known about how they move through the water. We do know that the megamouth lives deep in the ocean and is a filter feeder, moving at very slow speeds to filter out a meal with its large mouth. But swimming slowly in the water is difficult in a similar way flying slowly in an airplane is difficult. Sharks need speed to control lift and movement.

To better understand the megamouth’s slow movement, the researchers measured the cartilage, skin histology, and skeletal structure of the pectoral fins of one female and one male megamouth shark, caught accidentally and preserved for research. The researchers found that the megamouth’s skin was highly elastic, and its cartilage was made of more ‘segments’ than any other known shark, which may provide added flexibility compared to other species. megamouth jointThe authors also suggest that the joint structure (image 3) of the pectoral fin may allow forward and backward rotation, motions that are largely restricted in most sharks.  The authors suggest that this flexibility and mobility of the pectoral fin may be specialized for controlling body posture and depth at slow swimming speeds. This is in contrast to the fins of fast-swimming sharks that are generally stiff and immobile.

In addition to the difficulties in exploring deep, dark seas, small sample sizes present challenges for many shark studies, including those described here. But whether studying the infamous great white shark or one of the rare megamouths, both contribute to a growing body of knowledge of these elusive fish.

Citations: Hamady LL, Natanson LJ, Skomal GB, Thorrold SR (2014) Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks. PLoS ONE 9(1): e84006. doi:10.1371/journal.pone.0084006

Tomita T, Tanaka S, Sato K, Nakaya K (2014) Pectoral Fin of the Megamouth Shark: Skeletal and Muscular Systems, Skin Histology, and Functional Morphology. PLoS ONE 9(1): e86205. doi:10.1371/journal.pone.0086205

Images1: doi:10.1371/journal.pone.0084006.g001

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Image 3: doi:10.1371/journal.pone.0086205.g004

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Rainforest Fungi Find Home in Sloth Hair

Bradypus_variegatusMost of us have seen a cute sloth video or two on the Internet. Their squished faces, long claws, and scruffy fur make these slow-moving mammals irresistible, but our furry friends aren’t just amusing Internet sensations. Like most inhabitants of the rainforest, little is known about the role sloths play in the rainforest ecosystem.

Three-toed sloths live most of their lives in the trees of Central and South American rainforests. Rainforests are some of the most biodiverse ecosystems in the world and home to a wide variety of organisms, some of which can be found in rather unusual places.

Due to their vast biodiversity, rainforests have been the source for a wide variety of new medicines, and researchers of this PLOS ONE study sought to uncover whether sloth hair may also contain potential new sources of drugs that could one day treat vector-borne diseases, cancer, or bacterial infections. Why look in sloth fur? It turns out that sloths carry a wide variety of micro- and macro-organisms in their fur, which consists of two layers: an inner layer of fine, soft hair close to the skin, and a long outer layer of coarse hair with “cracks” across it where microbes make their homes. The most well-known inhabitant of sloth fur is green algae. In some cases, the green algae makes the sloth actually appear green, providing a rainforest camouflage.

In the study, seventy-four separate fungi were obtained from the surface of coarse outer hair that were clipped from the lower back of nine living three-toed sloths in Soberanía National Park, Panama, and were cultivated and tested for bioactivity in the lab.

Researchers found a broad range of in vitro activities of the fungi against bugs that cause malaria and Chagas disease, as well as against a specific type of human breast cancer cells. In addition, 20 fungal extracts were active in vitro against at least one bacterial strain. The results may provide for the first time an indication of the biodiversity and bioactivity of microorganisms in sloth hair.

Since sloths are moving around in one of the most diverse ecosystems in the world, it’s possible that they may pick up “hitchhikers,” so the researchers can’t be sure how these fungi came to live on the sloth fur. They may even have a symbiotic relationship with the green algae. However the fungi ended up in the fur, the authors suggest their presence in the ecosystem provides support for the role biodiversity plays both in the rainforest and potentially our daily lives.

Citation: Higginbotham S, Wong WR, Linington RG, Spadafora C, Iturrado L, et al. (2014) Sloth Hair as a Novel Source of Fungi with Potent Anti-Parasitic, Anti-Cancer and Anti-Bacterial Bioactivity. PLoS ONE 9(1): e84549. doi:10.1371/journal.pone.0084549

Image: Bradypus variegates by Christian Mehlführer

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Thanking Our Peer Reviewers

In 2013 PLOS ONE published 31,500 articles, nearly 8,000 more than in 2012. In reaching this milestone, we would like to take a moment to recognize the hard work and dedication of our peer reviewers. Without their critical insight, support, and hard work, we couldn’t do what we do.

Last year we had over 78,000 unique reviewers from 172 countries. The top 20 institutions that contributed nearly 4,000 reviews are represented below (find the interactive version here).Reviewer word cloud

We would like to send a sincere thank you to all of our amazing peer reviewers. We are enormously grateful for your contributions and look forward to working with you in the New Year!

In addition to PLOS ONE’s record-breaking year, PLOS has just announced the publication of its 100,000th article, so we also  extend our thanks for the hard work of the peer reviewers contributing to all of the PLOS journals.

Best wishes in the New Year!

PLOS ONE Team

Image: http://tagul.com

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Snail Mucus May Alter Plant Defenses

Michael_Gwyther-Jones_-_Garden_Snail_smallPredator-prey relationships make up a large part of the food chain, and both predators and prey have developed visual, auditory, physical, and even chemical abilities to better their respective chances for surviving, whether that means catching a meal or avoiding turning into one. Ants may mimic spiders to avoid predators and a grizzly bear’s size and strength allow them to feast on pretty much anything. But what about the interactions between a slow-moving predator, like the garden snail pictured above, and completely stationary “prey,” like a plant?

Garden snails are found throughout the world and feast on many species of plants, including those in our gardens. One of those species is the black mustard plant. Originally from the Mediterranean, black mustard is now common throughout the world. Scientists are working to understand if a common plant, like black mustard, may be able to pick up chemical signals from snail mucus called kairomones and preemptively change their biochemistry to become less appealing to snails. Snails produce mucus during motion, and its presence is often a good indicator to plants that a snail is nearby.

In a recent article published in PLOS ONE, a researcher from the Department of Zoology at the University of Wisconsin-Madison studied whether “unwounded” black mustard plants exposed to snail mucus before being exposed to actual snails experienced lower rates of snail predation.

The researcher exposed black mustard plants at different ages to snail mucus, collected on paper, when the plant was a seed, a seedling, or when it was a seed and again when it was a seedling. The control plant group was not exposed to mucus at any point. After plants were exposed to one of these treatments, a single adult garden snail was then placed with one of the plants to measure if the snail would munch on each plant equally.

Plants that received early exposure or a repeated exposure to mucus during the seedling stage showed a reduced susceptibility to snail feeding or “attack,” but plants in the control group experienced no significant reduction in feeding. The author suggests that plants may pick up on chemicals associated with plant eaters—in this case snail mucus—that may prompt them to become less appealing before an initial attack even occurs.

Although the chemical mechanism that the plants used to make themselves less appealing isn’t clear, in this predator-prey-like interaction, the predators may actually be inadvertently making their dinner less appealing. Turns out gardeners aren’t the only ones that don’t like slimy snail trails.

Citation: Orrock JL (2013) Exposure of Unwounded Plants to Chemical Cues Associated with Herbivores Leads to Exposure-Dependent Changes in Subsequent Herbivore Attack. PLoS ONE 8(11): e79900. doi:10.1371/journal.pone.0079900

Image: Garden Snail by Michael Gwyther-Jones

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A Rat’s Journey Through Virtual Reality

Virtual EnvironmentFew ideas excite the imagination more than virtual reality. We humans use virtual reality for training, entertaining, and even education, but we can also use it to study human and animal behavior. Adaptive behavior, or the ability to adjust to new situations, is influenced by what we see, hear, and experience in our environment; unfortunately, for this reason, it is difficult to isolate the possible stimuli that affect it. The authors of this recently published PLOS ONE paper developed a virtual reality environment to try to isolate and measure the impact of visual and sound cues on rats navigating through a virtual space.

The virtual reality navigation test is based on an experiment called the Morris Water Maze, a standard lab test where a rat swims through water using visual cues on the walls to Virtual Reality Rat Harnessnavigate. The virtual version uses a 14 square-foot room with visual cues projected on each wall and sounds from 4 sides (pictured above). The rat is at the center of the room, wearing a harness (pictured on the right) on a spherical treadmill placed on a three-foot circular table.

Before beginning the navigation tasks, researchers trained nine male rats to move in virtual reality. The rat started from one of 4 random start locations, facing the wall (see video below). The northeast quadrant of the space was designated as the ‘reward zone,’ indicated by a white dot. Upon entry to this zone, the rat was rewarded with sugar water (if only all video games worked this way).

After training, the researchers tested each rat’s ability to navigate to the reward zone using one of three cues: audiovisual, visual, or auditory. Once the rat found the reward zone, a 2-second blackout period was initiated, and then the rat was ‘moved’ back to one of the 4 random start locations. The video below shows the visual cue test.

Scientists found that rats can learn to navigate to an unmarked location based on visual cues—with a moderate amount of training. However, the rats were unable to use the auditory cues to navigate to the reward zone, and instead moved in circles to try to locate it.

Although the rat’s harness may look a little funny, it is a relatively noninvasive test, and since the animal is not in water, like in the Morris Water Maze test, it is easier to combine this test with tools to measure neural and physical variables in the task. Additionally, the virtual maze may contribute to new methodology evaluating the underlying factors in adaptive behavior, specifically because no other cues besides the audiovisual, visual, and auditory defined the spatial location of reward, something that is difficult to achieve in the real world. Despite humans not yet understanding what virtual reality means to us, we can already use it to better understand animal learning and behavior.

Citation: Cushman JD, Aharoni DB, Willers B, Ravassard P, Kees A, et al. (2013) Multisensory Control of Multimodal Behavior: Do the Legs Know What the Tongue Is Doing? PLoS ONE 8(11): e80465. doi:10.1371/journal.pone.0080465

Image 1: doi:10.1371/journal.pone.0080465

Image 2: doi:10.1371/journal.pone.0080465

Video 1: doi:10.1371/journal.pone.0080465

Video 2: doi:10.1371/journal.pone.0080465

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Moonlit Rendezvous: The Box Jellyfish’s Monthly Meet-up in Waikiki

Box Jellyfish

When you think about tropical paradise, Hawaii is often at the top of the list. Waikiki is one of the most iconic Hawaiian beaches on Oahu and is a popular swimming and surfing spot. However, it is also a popular stop for the box jellyfish, one of the most venomous animals in the world. Once a month, about 8 to 12 days after the full moon, the shallow waters of Waikiki beach are temporarily flooded with box jellyfish. They are not coming in for a mai tai under the waning moon; rather, scientists believe that jellyfish reproduce in these waters. This monthly influx creates a hazard to swimmers due to the jellyfish’s painful—and even lethal—stings.

The environmental factors that affect these influxes are not well understood, and learning more about them may help us predict and mitigate the risk that box jellyfish pose to swimmers. Several scientists from Hawaiian institutions published the first long-term (14-year) assessment of the environmental conditions that potentially correlate with box jellyfish population changes in the North Pacific Sub-tropical Gyre.

The researchers surveyed a 400-m section of Waikiki beach during the days jellyfish were present. They counted more than 66,000 jellyfish over 14 years and compared the data to 3 measures of how the climate changes over time, called climate indices; 13 physical and biological variables, such as sea surface temperature and plankton; and seven weather measurements, including wind speed, air temperature, and rainfall.

They confirmed that box jellyfish arrive at Waikiki monthly after each full moon and stay for 2- 4 days. They counted on average 400 jellyfish each month, but the range was quite wide at 5-2,365 individuals. Rather than seeing a net population change over 14 years, researchers observed approximately 4-year periods of increased population count followed by 4-year periods of decreased population count, which coincided with fluctuations in three main environmental factors: oceanic changes in salinity and nutrient availability, called the North Pacific Gyre Oscillation, small organisms’ ability to access nutrients, called primary production, and abundance of small zooplankton.

The researchers suggest that the relationship between environmental fluctuations and jellyfish population changes at Waikiki may result from changes in the availability of food for jellyfish in the ocean around Hawaii, brought about by the North Pacific Gyre Oscillation. During an increase in nutrient availability, phytoplankton populations also increase, meaning more food for jellyfish, allowing them to grow faster and increase their rate of reproduction.

Previous studies have shown that jellyfish populations change due to human-caused disturbances, but this is one of the first long-term studies showing that large-scale climate patterns may also impact box jellyfish populations. Understanding long-term climate and oceanic trends and their effects on jellyfish populations may provide information to develop strategies for avoiding mass stinging events and beach closures at Waikiki and other popular recreation sites in the Pacific.

 

Citation: Chiaverano LM, Holland BS, Crow GL, Blair L, Yanagihara AA (2013) Long-Term Fluctuations in Circalunar Beach Aggregations of the Box Jellyfish Alatina moseri in Hawaii, with Links to Environmental Variability. PLoS ONE 8(10): e77039. doi:10.1371/journal.pone.0077039

Image Credit: Jellyfish by James Brennan Molokai Hawaii

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Watch Out, Here Comes the Round Goby: How One Fish Changed the Danube River

Round Goby (Neogobius_melanostomus)

As big as a pickle and about as intimidating as one, too, the round goby pictured above doesn’t look like an aggressive invader. But this little fish is naturally invasive and uses more than its meager looks to work its way up waterways, conquering native species, settling new habitat, and creating a completely new ecosystem along the way.

Understanding the invasion process of this fish may help scientists better estimate the ecological impacts that invasive species have on their new environments. The round goby is actively invading the German stretch of the Danube River and the authors of this PLOS ONE study used this opportunity to monitor the characteristics of the invasion to better understand the the process. Specifically, they measured the round goby’s population composition, physical characteristics, and feeding and sexual behavior at ten sites as it invaded a 200 kilometer stretch of the upper Danube River from 2009 to 2011. The sites were divided into ten stages of invasion, ranging from already established populations in the lower portion of the river to the ‘invasion front,’ or where they anticipated the goby would invade next.

Scientists found that the invading goby populations differed from their established counterparts when they compared sex ratio, age, size, feeding, and sexual behavior. Contrary to the researcher’s predictions, invaders were more likely to be female, even though male gobies are more exploratory. The authors suggest that a female-dominated invasion front may allow the established, primarily male population to better handle their roles in parental care and territorial defense.

What’s more, the invaders were physically larger than the established populations and appeared to use their size to establish populations in the ‘invasion front,’ rather than depending on rapid reproduction, or a “frequency in numbers” approach. The ‘invasion front’ contained a wider range of food sources, and the invading gobies’ ability to shift their diet from insects and crustaceans to mollusks may have contributed to their increased size. Overall, these results suggest that the round goby’s ability to physically and behaviorally adapt to changing habitats may play a role in invasion success.

All in all, it took the round goby two years to invade and establish populations in the Danube River study area—a rapid change, ecologically speaking. Fierce territorial defenders, 73% of the fish population is now goby in the settled study sites, leaving behind only fish and invertebrate populations able to compete with the goby for food and territory.

The impacts of these changes remain relatively unknown, but studying them may help researchers estimate impacts on ecosystems during future invasions. The Danube River is not the only habitat facing invasion, as this native of both the Black and Caspian Seas has also hitched a ride to the Great Lakes.

Citation: Brandner J, Cerwenka AF, Schliewen UK, Geist J (2013) Bigger Is Better: Characteristics of Round Gobies Forming an Invasion Front in the Danube River. PLoS ONE 8(9): e73036. doi:10.1371/journal.pone.0073036

Photo: Round goby fish by Eric Engbretson

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