This chimp may look innocent, but he may harbor any of dozens of diseases that infect humans. Photo by AfrikaForce

Anyone who has read a Richard Preston book, such as The Hot Zone or Panic in Level 4, knows the danger of tampering with wildlife. The story usually goes something like this: Intrepid explorers venture into a dark, bat infested cave in the heart of East Africa, only to encounter something unseen and living, which takes up residence in their bodies. Unknowingly infected, the happy travelers jump on a plane back to Europe or the States, spreading their deadly pathogen willy-nilly to every human they encounter upon the way. Those people, in turn, bring the novel virus or bacterium back home to strangers and loved ones alike. Before the world knows it, a pandemic has arrived.

This scenario may sound like fiction, but it’s exactly what infectious disease experts fear most. Most emerging infectious diseases in humans have indeed arisen from animals–think swine and bird flu (poultry and wild birds), SARS (unknown animals in Chinese markets), Ebola (probably bats) and HIV (non-human primates). Therefore, experts prioritize the task of figuring out which animals in which regions of the world are most prone to delivering the latest novel pathogen to hapless humanity.

With this in mind, researchers at Harvard University, the University of Granada and the University of Valencia set out to develop a new strategy for predicting the risk and rise of new diseases transmitted from animals before they happen, describing their efforts in the journal Proceedings of the National Academy of Sciences.

To narrow the hypothetical disease search down, the team chose to focus on non-human primates. Because monkeys and great apes are so closely related to us, their potential for developing and transmitting a pathogen suited to the human body is greater than the equivalent risk from animals such as birds or pigs. As a general rule, the more related species are, the greater the chances they can share a disease. The researchers gathered data from 140 species of primates. They overlaid that information with more than 6,000 infection records from those various primate species, representing 300 different pathogens, including viruses, bacteria, parasitic worms, protozoa, insects and fungus. This way, they could visualize which pathogens infect which species and where.

Like mapping links between who-knows-who in a social network, primates that shared pathogens were connected. This meant that the more pathogens an animal shared with other species, the more centrally located it was on the tangled web of the disease diagram.    

A diagram depicting shared parasites among primate species. Each bubble represents one species, with lines connecting species by shared pathogens. The larger the bubble, the more emerging infectious diseases that species harbors. The dark blue bubbles represent the top 10 primates that share the most emerging infectious diseases with humans. Photo by Gomez et al., via PNAS

From studying these charts, a few commonalities emerged. Animals at the center of the diagram tended to be those that lived in dense social groups and also covered a wide geographic range (yes, similar to humans). These species also tended to harbor parasites that are known to infect humans, including more pathogens identified as emerging infectious diseases. In other words, those species that occurred in the center of the diagram are the best positioned to kick off the next pandemic or horrific infectious disease, and thus should be the ones that experts should keep the closest watch on.

Such animals could qualify as “superspreaders,” or those that receive and transmit pathogens very often to other species.”The identification of species that behave as superspreaders is crucial for developing surveillance protocols and interventions aimed at preventing future disease emergence in human populations,” the authors write.

Apes appeared in the heart of the disease diagram and are among the species we should be most worried about, which is not surprising considering that diseases such as malaria and HIV first emerged from these animals. On the other hand, some non-ape primates, including baboons and vervet monkeys, also popped up in the center of the diagram and turn out to harbor many human emerging disease parasites. 

Currently, our ability to predict where, when and how new emerging infectious diseases might arise is “remarkably weak,” they continue, but if we can identify those sources before they become a problem we could prevent a potential health disaster on a regional or even global scale. This new approach for identifying animal risks, the authors write, could also be applied to other wildlife groups, such as rodents, bats, livestock and carnivores. “Our findings suggest that centrality may help to detect risks that might otherwise go unnoticed, and thus to predict disease emergence in advance of outbreaks—an important goal for stemming future zoonotic disease risks,” they conclude. 

Image via NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Last year, to celebrate the 42nd Earth Day, we took a look at 10 of the most surprising, disheartening, and exciting things we’d learned about our home planet in the previous year—a list that included discoveries about the role pesticides play in bee colony collapses, the various environmental stresses faced by the world’s oceans and the millions of unknown species are still out in the environment, waiting to be found.

This year, in time for Earth Day on Monday, we’ve done it again, putting together another list of 10 notable discoveries made by scientists since Earth Day 2012—a list that ranges from specific topics (a species of plant, a group of catfish) to broad (the core of planet Earth), and from the alarming (the consequences of climate change) to the awe-inspiring (Earth’s place in the universe).

Even the supposedly pristine Antarctic landscape is marred by trash heaps. Image via Germany Federal Environment Agency Report (PDF)

1. Trash is accumulating everywhere, even in Antarctica. As we’ve explored the most remote stretches of the planet, we’ve consistently left behind a trail of one supply in particular: garbage. Even in Antarctica, a February study found (PDF), abandoned field huts and piles of trash are mounting. Meanwhile, in the fall, a new research expedition went to study the Great Pacific Garbage Patch, counting nearly 70,000 pieces of garbage over the course of a month at sea.

2. Climate change could erode the ozone layer. Until recently, atmospheric scientists viewed climate change and the disintegration of the ozone layer as entirely distinct problems. Then, in July, Harvard researcher Jim Anderson (who won a Smithsonian Ingenuity Award for his work) led a team that published the troubling finding that the two might be linked. Some warm summer storms, they discovered, can pull moisture up into the stratosphere, an atmospheric layer 6 miles up. Through a chain of chemical reactions, this moisture can lead to the disintegration of ozone, which is crucial for protecting us from ultraviolet (UV) radiation. Climate change, unfortunately,  is projected to cause more of these sorts of storms.

3. This flower lives on exactly two cliffs in Spain. In September, Spanish scientists told us about one of the most astounding survival stories in the plant kingdom: Borderea chouardii, an extremely rare flowering plant that is found on only two adjacent cliffs in the Pyrenees. The species is believed to be a relic of the Tertiary Period, which ended more than 2 million years ago, and relies on several different local ant species to spread pollen between its two local populations.

4. Some catfish have learned to kill pigeons. In December, a group of French scientists revealed a phenomenon they’d carefully been observing over the previous year: a group of catfish in Southwestern France had learned how to leap onto shore, briefly strand themselves, and swim back into the water to consume their prey. With more than 2,000,000 Youtube views so far, this is clearly one of the year’s most widely enjoyed scientific discoveries.

5. Fracking for natural gas can trigger moderate earthquakes. Scientists have known for a while that whenever oil and gas are extracted from the ground at a large scale, seismic activity can be induced. Over the past few years, evidence has mounted that injecting water, sand and chemicals into bedrock to cause gas and oil to flow upward—a practice commonly known as fracking—can cause earthquakes by lubricating pre-existing faults in the ground. Initially, scientists found correlations between fracking sites and the number of small earthquakes in particular areas. Then, in March, other researchers found evidence that a medium-sized 2011 earthquake in Oklahoma(which registered a 5.7 on the moment magnitude scale) was likely caused by injecting wastewater into wells to extract oil.

6. Our planet’s inner core is more complicated than we thought. Despite decades of research, new data on the iron and nickel ball 3,100 miles beneath our feet continue to upset our assumptions about just how the earth’s core operates. A paper published last May showed that iron in the outer parts of the inner core is losing heat much more quickly than previously estimated, suggesting that it might hold more radioactive energy than we’d assumed, or that novel and unknown chemical interactions are occurring. Ideas for directly probing the core are widely regarded as pipe dreams, so our only options remains studying it from afar, largely by monitoring seismic waves.

The berries of Pollia condensata were found to produce the most intense color in the natural world. Image via PNAS

7. The world’s most intense natural color comes from an African fruit. When a team of researchers looked closely at the blue berries of Pollia condensata, a wild plant that grows in East Africa, they found something unexpected: it uses an uncommon structural coloration method to produce the most intense natural color ever measured. Instead of pigments, the fruit’s brilliant blue results from nanoscale-size cellulose strands layered in twisting shapes, which which interact with each other to scatter light in all directions.

8. Climate change will let ships cruise across the North Pole. Climate change is sure to create countless problems for many people around the world, but one specific group is likely to see a significant benefit from it: international shipping companies. A study published last month found that rising temperatures make it probable that during summertime, reinforced ice-breaking ships will be able to sail directly across the North Pole—an area currently covered by up to 65 feet of ice—by the year 2040. This dramatic shift will shorten shipping routes from North America and Europe to Asia.

9. One bacteria species conducts electricity. In October, a group of Danish researchers revealed that the seafloor mud of Aarhus’ harbor was coursing with electricity due to an unlikely source: mutlicellular bacteria that behave like tiny electrical cables. The organisms, the team found, built structures that traveled several centimeters down into the sediment and conduct measurable levels of electricity. The researchers speculate that this seemingly strange behavior is a byproduct of the way of the bacteria harvests energy from the nutrients buried in the soil.

Kepler 62f, discovered yesterday, is the most promising exoplanet candidate yet in terms of its potential to harbor life. Image via NASA/Ames/JPL-Caltech

10. Our Earth isn’t alone. Okay, this one might not technically be a discovery about Earth, but over the past year we have learned a tremendous amount about what our Earth isn’t: the only habitable planet in the visible universe. The pace of exoplanet detection has accelerated rapidly, with a total of 866 planets in other solar systems discovered so far. As our methods have become more refined, we’ve been able to detect smaller and smaller planets, and just yesterday, scientists finally discovered a pair of distant planets in the habitable zone of their stars that are relatively close in size to Earth, making it more likely than ever that we might have spied an alien planet that actually supports life.

Lashed to a spear made in the Gilbert Islands, researchers found a tooth from a dusky shark, a species previously unknown in the area. Image via PLOS ONE/Drew et. al.

For decades, a total of 124 swords, tridents and spears taken from the Pacific Ocean’s Gilbert Islands in the mid-1800s sat untouched in vaults in Chicago’s Field Museum. The weapons—each made up of dozens of individual shark teeth that islanders lashed to a wooden core with coconut fibers—were primarily considered artifacts of anthropological value.

Then, Joshua Drew, a marine conservation biologist at the museum, had an unusual idea: that the shark teeth lining the serrated blades could also serve as an ecological snapshot of the reefs that lined the islands more than a century ago. Sharks can be clearly identified solely by their teeth, so the teeth that islanders had harvested and used for their weapons might reflect historical biodiversity in the reefs that’s since been lost due to environmental degradation.

When Drew and others closely examined the hundreds of teeth on the weapons, they found that they came from eight different shark species, six of which were known to commonly swim in the Gilbert Islands’ waters. Two species, though—the dusky shark (Carcharhinus obscurus) and the spottail shark (Carcharhinus sorrah)—were something of a surprise. When the researchers looked at the scientific literature and various museum holdings of fish collected in the area, they found that these two species had never been documented within thousands of miles of the islands.

A trident lined with shark teeth, used in the study. Image via PLOS ONE/Drew et. al.

Drew calls this “shadow biodiversity”—a reflection of the life that lived in an ecosystem before we even started studying what was there. “[These are] hints and whispers of what these reefs used to be like,” he said in a press statement accompanying the paper documenting his team’s find, published today in PLOS ONE. “It’s our hope that by understanding how reefs used to look we’ll be able to come up with conservation strategies to return them to their former vivid splendor.”

Working with Mark Westneat, the museum’s curator of fishes, and Christopher Philipp, who manages the anthropology collections, Drew classified each tooth on every weapon by shark species, primarily using field guides and photos. In cases where the tooth’s identity was ambiguous, he made use of the Museum’s own ichthyological holdings, comparing it to preserved specimens from each shark species.

Because dusky and spottail shark teeth were found on the weapons—crafted sometime between the 1840s and 1860s, shortly before they were collected—the researchers believe these two species were once part of the ecosystem and have since been eradicated. There is the possibility that the teeth were harvested elsewhere and came to the Gilbert Islands via trade, but the team says it’s unlikely.

For one, sharks figure largely in the islanders’ traditional culture, and it’s well-known that they had effective shark-fishing techniques, making it unlikely that they’d go to the trouble of exporting teeth from afar. The two species’ teeth were among the most common found on the weapons, so it also stands to reason that they were fairly abundant nearby. Secondly, there is no historical or archaeological evidence that trade occurred between the extremely remote Gilbert Islands and either the Solomon Islands (the closest known location of spottail sharks) or Fiji (for dusky sharks).

It’s impossible to know for sure, but given the environmental degradation that’s occurred over the past century in the Pacific’s coral reefs, the researchers suspect that humans played a role in these sharks’ local eradication. Because sharks mature slowly and have a small number of offspring per individual, they can be wiped out quickly by moderate levels of fishing, and the commercial shark fishing industry started up in the area as early as 1910.

Rigorous fish surveys of the Pacific didn’t begin for a few more decades, so these weapons—and perhaps other human artifacts that incorporate biological specimens—serve as a valuable time capsule of the ecosystems that predated scientific study. Drew thinks that the “shadow diversity” we’ve since lost should inspire people in the marine conservation field to recreate the biodiversity that predates the Industrial Age.

“When we set up modern conservation plans, we shouldn’t sell ourselves short,” he told Nature last year, when he revealed his preliminary results at a conference. “We might not recapture the vivid splendor of those super-rich levels, but this information argues for setting up management plans to protect what sharks are there.”

Roosters have an internal circadian rhythm, which keeps them crowing on schedule even when the lights are turned off. Image via Wikimedia Commons/Muhammad Mahdi Karim

Some scientists investigate the universe’s biggest mysteries, like the Higgs boson, the mysterious particle that endows all other subatomic particles with mass.

Other researchers look into questions that are, well, a bit humbler—like the age-old puzzle of whether roosters simply crow when they see light of any kind, or if they truly know to crow when the morning sun arrives.

Lofty or not, it’s the goal of science to answer all questions that arise from the natural world, from roosters to bosons and everything in between. And a new study by Japanese researchers published today in Current Biology resolves the rooster question once and for all: The birds truly do have an inner circadian rhythm that tells when to crow.

The research team, from Nagoya University, investigated via a fairly straightforward route: They put several groups of four roosters in a room for weeks at a time, turned the lights off, and let a video camera running. Although roosters can occasionally crow at any time of day, the majority of their crowing was like clockwork, peaking in frequency at time intervals roughly 24 hours apart—the time their bodies knew to be morning based on the sunlight they’d last seen before entering the experiment.

This consistency continued for about 2 weeks, then gradually began to die out. The roosters were left in the room for 4 weeks in total, and during the second half of the experiment, their crowing began occurring less regularly, at any time of day, suggesting that they do need to see the sun on a regular basis for their circadian rhythms to function properly.

In the experiment’s second part, the researchers also subjected the roosters to alternating periods of 12 hours of light and 12 hours of darkness, while using bright flashes of light and the recorded crowing of roosters (since crowing is known to be contagious) to induce crowing at different times of day. When they activated these stimuli near at or near the dawn of the roosters’ 12-hour day, crowing rates increased significantly. At other times of day, though, exposing them to sudden flashes of light or playing the sound of crowing had virtually no effect, showing that the underlying circadian cycle played a role in the birds’ response to the stimuli.

Of course, many people who live in close proximity to roosters note that they often crow in response to a random light source turning on, like a car’s headlights, no matter what time of day it is. While this may be true, the experiment shows that the odds of a rooster responding to a car’s headlights depend on how close the current time is to dawn—at some level, the rooster’s body knows whether it should be crowing or not, and responding to artificial stimuli based on this rhythm.

For the research team, all this is merely a prelude to their bigger, more complex questions: Why do roosters have a biological clock that controls crowing in the first place, and how does it work? They see the simple crowing patterns of the rooster as an entry point into better understanding the vocalizations of a range of animals. “We still do not know why a dog says ‘bow-wow’ and a cat says ‘meow,’” Takashi Yoshimura, one of the co-authors, said in a press statement. “We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model.”

At the bottom of the Mariana Trench, nearly eight miles below the ocean’s surface, abundant communities of bacteria thrive. Image via PNAS/Yayanos et. al.

The Challenger Deep, the deepest point on the entire seafloor, lies in the Mariana Trench off the coast of the Pacific Ocean’s Mariana Islands. It is nearly 36,000 feet—6.8 miles—below the ocean’s surface. If you were to stand at this remarkable depth, the column of water above your head would exert 1000 times the amount of pressure you normally experience at the surface, crushing you instantly.

Even in this extreme environment, though, organisms can survive. One type, it turns out, can even prosper: bacteria. A new study, published today in Nature Geoscience, finds that unexpectedly abundant bacteria communities grow in the depths of the Mariana Trench, with organisms living at densities ten times greater than in the much shallower ocean floor at the trench’s rim.

To probe the ultra-deep ecosystem, the international research team, led by Ronnie Glud of the University of Southern Denmark, sent a specially-designed, 1300-pound robot down to the bottom of the trench in 2010. The robot was equipped with thin sensors that can slice into the seafloor sediments to help measure the organic consumption of oxygen. Because living things consume oxygen as they respire, tallies on how much ambient oxygen is missing from the sediments can be used as a proxy for the amount of microorganisms living in that area.

The research team’s specialized robot, designed to take samples under extremely high pressure. Photo by Anni Glud

When the team used the device to sample the sediments at a pair of sites with depths of 35,476 and 35,488 feet, they found surprisingly high amounts of oxygen consumption—levels that indicated there were ten times more bacteria present at the ultra-deep site than at another, shallower site they sampled for reference about 37 miles away, at a depth of just 19,626 feet.

The robot also collected a total of 21 sediment cores from the two sites, and these cores were hauled up and analyzed in the lab. Although many of the microorganisms died when they were brought up to the surface—after all, the creatures are adapted for the high pressure and low temperature of the ocean floor—the finding was confirmed: Cores from the Mariana Trench had much higher densities of bacterial cells than those from the reference site.

The team also remotely recorded video of the ocean floor, using lights to illuminate the pitch-black environment, and found a few life forms much larger than bacteria scurrying around on top of the sediment. When they used baited traps to recover a few of the specimens and bring them to the surface, they determined they were Hirondellea gigas, a species of amphipods—small crustaceans typically less than an inch in length.

A video still from the seafloor reveals an amphipod (left) scurrying across the bacteria-filled sediment. Image via Nature Geoscience/Glud et. al.

The discovery of such abundant bacterial life is particularly surprising because conventional wisdom would suggest that not enough nutrients are present at such depths to support much growth. Photosynthetic plankton serve as the nutrient base for nearly any ocean food chain, but they’re unable to survive on the lightless seafloor. The waste products (such as dead animals and microorganisms) of ecosystems higher up in the shallow light-filled waters do filter down and feed deeper food webs, but typically, less and less organic matter makes it down as depths increase.

In this case, though, the scientists seem to have found an exception to the rule, since the ultra-deep trench was home to so much more bacterial activity than the nearby shallower reference site. Their explanation is that the trench acts as a natural sediment trap, gradually collecting nutrients that filter down and land at shallower locations on the ocean floor nearby, then are dislodged by earthquakes or other perturbations.

In the years since the 2010 exploration, the research team has sent the same robot down to sample the Japan Trench (roughly 29,500 feet deep) and plans to sample the Kermadec-Tonga Trench (35,430 feet deep) later this year. “The deep sea trenches are some of the last remaining ‘white spots’ on the world map,” Glud, the lead author, said in a press statement. “We know very little about what is going on down there.”

Scientists discovered that the penguins plumage is even colder than the surrounding air, potentially allowing them to absorb heat through convection. Image © Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France

Antarctica, as you might expect, gets pretty darn cold: Temperatures as low as -40 degrees Fahrenheit are often recorded during the winter. For the creatures who live there, this extreme cold demands innovative survival strategies that enable the loss of as little heat as possible.

Scientists recently discovered that Emperor Penguins—one of Antarctica’s most celebrated species—employ a particularly unusual technique for surviving the daily chill. As detailed in an article published today in the journal Biology Letters, the birds minimize heat loss by keeping the outer surface of their plumage below the temperature of the surrounding air.

At the same time, the penguins’ thick plumage insulates their body and keeps it toasty. A team of scientists from Scotland and France recently came to the finding by analyzing thermal images (below) of penguins taken at a coastal Emperor breeding colony in Adélie Land, an area of Antarctica claimed by France.

The research drew upon theromgraphic images of the penguins collected in the wild. Image © Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France

The researchers analyzed thermographic images like this one taken over roughly a month during June 2008. During that period, the average air temperature was 0.32 degrees Fahreinheit. At the same time, the majority of the plumage covering the penguins’ bodies was even colder: the surface of their warmest body part, their feet, was an average 1.76 degrees Fahrenheit, but the plumage on their heads, chests and backs were -1.84, -7.24 and -9.76 degrees Fahrenheit respectively. Overall, nearly the entire outer surface of the penguins’ bodies was below freezing at all times, except for their eyes and beaks.

The scientists also used a computer simulation to determine how much heat was lost or gained from each part of the body—and discovered that by keeping their outer surface below air temperature, the birds might paradoxically be able to draw very slight amounts of heat from the air around them. The key to their trick is the difference between two different types of heat transfer: radiation and convection.

The penguins do lose internal body heat to the surrounding air through thermal radiation, just as our bodies do on a cold day. Because their bodies (but not surface plumage) are warmer than the surrounding air, heat gradually radiates outward over time, moving from a warmer material to a colder one. To maintain body temperature while losing heat, penguins, like all warm-blooded animals, rely on the metabolism of food.

The penguins, though, have an additional strategy. Since their outer plumage is even colder than the air, the simulation showed that they might gain back a little of this heat through thermal convection—the transfer of heat via the movement of a fluid (in this case, the air). As the cold Antarctic air cycles around their bodies, slightly warmer air comes into contact with the plumage and donates minute amounts of heat back to the penguins, then cycles away at a slightly colder temperature.

Most of this heat, the researchers note, probably doesn’t make it all the way through the plumage and back to the penguins’ bodies, but it could make a slight difference. At the very least, the method by which a penguin’s plumage wicks heat from the bitterly cold air that surrounds it helps to cancel out some of the heat that’s radiating from its interior.

And given the Emperors’ unusually demanding breeding cycle (celebrated in the documentary March of the Penguins), every bit of warmth counts. Each winter, they trek from inland coastal locations to the coast inland—walking as far as 75 miles—where they breed and incubate their eggs. After the females lay eggs, the males incubate them by balancing them on top of their feet in a pouch for roughly 64 days. Since they don’t eat anything during this entire period, conserving calories by giving up as little heat as possible is absolutely crucial.

A study shows that wild perch are less fearful, eat faster and are more anti-social when exposed to a common pharmaceutical pollutant. Image via Bent Christensen

It’s obvious that anti-anxiety medicines and other types of mood-modifying drugs alter the behavior of humans—it’s what they’re designed to do. But their effects, it turns out, aren’t limited to our species.

Over the past decade, researchers have repeatedly discovered high levels of many drug molecules in lakes and streams near wastewater treatment plants, and found evidence that rainbow trout and other fish subjected to these levels could absorb dangerous amounts of the medications over time. Now, a study published today in Science finds a link between behavior-modifying drugs and the actual behavior of fish for the first time. A group of researchers from Umeå University in Sweden found that levels of the anti-anxiety drug oxazepam commonly found in Swedish streams cause wild perch to act differently, becoming more anti-social, eating faster and showing less fear of unknown parts of their environment.

The research group, led by ecologist Tomas Brodin, put wild perch in water with 1.8 micrograms of oxazepam diluted per liter—a level consistent with samples taken from surface waters near human development around Sweden. After 7 days swimming in the contaminated water, the perch had levels of the drug in their tissues that were similar to those of wild perch samples, indicating that the pharmaceutical was being absorbed into their bodies at rates similar to what’s happening in rivers and streams.

When they closely observed the behavior of these contaminated fish, the results were unmistakable. Those dosed with the anti-anxiety drug were more active, more willing to explore novel parts of their environment and more likely to swim away from the rest of their group as compared to fish that were kept in pristine waters. They also ate faster, finishing a set amount of plankton in a shorter time.

The researchers also included a third group of fish, exposed to levels of the drug way higher than those present in the environment. All of the changes shown in the fish exposed to the mild level of the drug were greatly exaggerated in this group, indicating that the drug was indeed responsible for the behavioral changes observed.

The idea of drug-addled fish might be funny, but the researchers say it could be a troubling sign of the way mounting levels of water-borne pharmaceuticals are affecting natural ecosystems. Because perch and other predator fish play a key role in food webs, altered foraging behavior—say, eating more prey—could lead to proliferation of the algae that their prey typically eat, upsetting an ecosystem’s balance as a whole. Or, if wild perch are engaging in more risky behavior (exploring parts of their environment they usually shy away from) it could lower the species’ survival rate.

Additionally, the research group worries that the drug could affect a broad spectrum of wildlife, because the particular receptor it binds to in the brain is widely distributed among aquatic species. And Oxazepam is far from the only drug that’s been found to pollute aquatic ecosystems—in the U.S., traces of over-the-counter painkillers, birth control hormones and illegal drugs have all been detected. “That environmentally relevant concentrations of a single benzodiazepine [oxazepam] affect fish behavior and feeding rate is alarming, considering the cocktail of different pharmaceutical products that are found in waters worldwide,” the researchers note in the paper.

These drug molecules can enter the environment in a few different ways. The practice of flushing old pills down the toilet is the first that probably comes to mind—and the easiest to prevent—but many pharmaceutical pollutants result from drug molecules that are ingested properly, go through the human body, pass out in urine and make it through wastewater treatment plants and into the environment. ”The solution to this problem isn’t to stop medicating people who are ill but to try to develop sewage treatment plants that can capture environmentally hazardous drugs,” Jerker Fick, one of the paper’s co-authors, said in a statement.

Chromodoris reticulata, native to the Pacific, engages in mating behavior unknown in the rest of the animal kingdom. Image via Stephen Childs

Even in the utterly dry language of science, there is no way to describe the mating behavior of the sea slug Chromodoris reticulata as anything other than bizarre. The creature, native to the Pacific Ocean, engages in simultaneous hermaphroditic mating—that is, each slug has both a penis and a vagina, and when mating, both members of a couple inserts their penises into the other’s vagina at the same time—but that’s not nearly the strangest aspect of their reproduction efforts.

As discovered by a group of Japanese scientists and revealed today in the journal Biology Letters, it’s what C. reticulata does after sex that is particularly unexpected—and previously unknown in the animal kingdom. After copulating for about 10 minutes, each slug discards its penis and immediately begins growing a new one, which is ready for use within 24 hours.

Two slugs engaged in simultaneous hermaphroditic mating, each inserting a penis into the other’s vagina (center). Image via Biology Letters, Sekizawa et. al.

The slug’s discarded penis, free-floating after copulation. Image via Biology Letters, Sekizawa et. al.

The research team, led by Ayami Sekizawa of Osaka City University, gathered a number of specimens from coral reefs off of Okinawa and observed their mating behavior in lab tanks. They found that the slugs typically mated for roughly 10 minutes—with each member of a couple assuming both the female and male roles simultaneously—then disengaged, wherein their penises fell off and floated free in the water.

Within roughly 24 hours, the slugs’ penises grew back and they were able to mate once again. If they put a slug in a tank with another before that period had elapsed, it either served just a female role during copulation or avoided mating entirely.

With a full day for regeneration, though, their mating behavior was entirely regular. One particularly vigorous specimen was even able to grow its penis back twice in a row, mating 3 times consecutively with 24 hours between each instance.

The physiology that allows the slug to achieve this feat is fascinating in itself. The researchers observed that the animal’s vas deferens—the coiled internal duct that transports sperm outward—serves as a sort of “next penis” (their phrasing), extending out of the body to replace the old discarded penis.

Why would an organism go to the trouble of regenerating a new penis each time it mates? The scientists speculate that the strange behavior could be an evolutionary response to competition among mates.

The tips of the slugs’ penises, it turns out, are covered with microscopic barbs that were observed to be coated with sperm after mating. This might not be the particular slug’s sperm, the researchers theorize, but a competitor’s—and the barbs might exist to remove sperm deposited by previous slugs in their mates’ vaginas, thereby increasing the chance that it’s their sperm that leads to reproduction. Afterwards, instead of retaining a penis covered in a competitor’s sperm, it’s simpler to discard it and grow a new one.

So no matter how difficult your romantic trials and tribulations, it’s worth remembering: We still have it quite a bit easier than C. reticulata.

The utterly strange-looking star-nosed mole sees the world with one of the most sensitive touch organs in the animal kingdom. Photo by Kenneth Catania

That’s an actual, earthly animal you’re looking at in the photo above—not, as you might have assumed, a creature out of Star Wars. The star-nosed mole, which resides in the bogs and wetlands of the eastern U.S. and Canada, is roughly the size of a rat when fully-grown. It’s functionally blind and eats insects, worms and small fish.

But the most noticeable aspect of the animal is its utterly strange appearance, dominated by its 22-tentacled ultra-sensitive snout, called a star (those aren’t its eyes and face at the center of the pink fleshy area, but rather its nostrils). This snout, used to hunt and grab prey, features more than 100,000 nerve endings packed into an area barely more than 1 cm in diameter, making it one of the most sensitive touch organs in the whole animal kingdom.

A star-nosed mole searches for prey with its star. Photo by Kristin Gerhold and Diana Bautista

In a paper published today in the journal PLOS ONE, a team of biologists and neuroscientists from UC Berkeley and Vanderbilt University have examined the activity of the mole’s star on a molecular level to figure out just how it conveys information to the animal’s brain. One of the team’s most interesting findings is that the star is relatively poor in neurons sensitive to pain, but extremely rich in neurons specifically adapted to be touch-sensitive.

Each of the star’s 22 tentacles (called “rays”) is covered by small domed structures known as Eimer’s organs—the average snout has some 30,000 in total. By way of contrast, an entire human hand contains roughly 17,000 touch fibers (which are analogous to Eimer’s organs), but the mole’s star is smaller than a single human fingertip.

One of the study’s authors, Vanderbilt neuroscientist Kenneth Catania, has studied the strange animal for more than two decades and has previously suggested that, for the mole, the sensory information it receives from its star most closely resembles the visual information we get from our eyes. That is, just as our world is largely defined by visual stimuli, the star-nosed mole’s is most directly defined by touch.

For evidence, he points to the fact that the moles’ brains are spatially organized around tactile signals coming from their stars in much the same way our brains are arranged the visual information generated by their eyes. Their neocortex—the outer layers of each of the brain’s hemispheres—features a map of nerves that spatially corresponds with the data coming from each of the star’s rays. That is, the brain region that matches up with one particular ray is adjacent to the region that matches with the next ray over. Our visual cortex is arranged in much the same manner.

The moles’ use of their stars also resembles the way we (and many other mammals) use our eyes to understand our environment. When Catania and other researchers filmed the moles’ behavior, they discovered that upon coming into contact with an object of interest, the moles immediately began rapidly probing it with their smallest rays (the two hanging at the bottom-center of the star).

This is similar to the way primates use vision, relying on short, rapid eye movements so that the fovea centralis—the central, highest-resolution part of the eye—to can discern visual details. What’s most fascinating is that both the moles’ smallest rays and our fovea centralis are over-represented in terms of area in the neocortex. Thus, instead of seeing the world with eyes, the functionally blind star-nosed mole apparently ‘sees’ its underground environment with its snout.

Some reindeer really do have red noses, a result of densely packed blood vessels near the skin’s surface. Image courtesy of Kia Krarup Hansen

In 1939, illustrator and children’s book author Robert May created Rudolph the Red-Nosed Reindeer. The character was an instant hit—2.5 million copies of May’s booklet were circulated within a year—and in the coming decades, Rudolph’s song and stop-motion TV special cemented him in the canon of cherished Christmas lore.

Of course, the story was rooted in myth. But there’s actually more truth to it than most of us realize. A fraction of reindeer—the species of deer scientifically known as Rangifer tarandus, native to Arctic regions in Alaska, Canada, Greenland, Russia and Scandinavia—actually do have noses colored with a distinctive red hue.

Now, just in time for Christmas, a group of researchers from the Netherlands and Norway have systematically looked into the reason for this unusual coloration for the first time. Their study, published yesterday in the online medical journal BMJ, indicates that the color is due to an extremely dense array of blood vessels, packed into the nose in order to supply blood and regulate body temperature in extreme environments.

“These results highlight the intrinsic physiological properties of Rudolph’s legendary luminous red nose,” write the study’s authors. “[They] help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer’s brain, factors essential for flying reindeer pulling Santa Claus’s sleigh under extreme temperatures.”

Obviously, the researchers know reindeer don’t actually pull Santa Claus to deliver gifts around the world—but they do encounter a wide variation of weather conditions on an annual basis, accounting for why they might need such dense beds of capillary vessels to deliver high amounts of blood.

To come to the findings, the scientists examined the noses of two reindeer and five human volunteers with a hand-held video microscope that allowed them to see individual blood vessels and the flow of blood in real time. They discovered that the reindeer had a 25% higher concentration of blood vessels in their noses, on average.

They also put the reindeer on a treadmill and used infrared imaging to measure what parts of their bodies shed the most heat after exercise. The nose, along with the hind legs, reached temperatures as high as 75°F—relatively hot for a reindeer—indicating that one of the main functions of all this blood flow is to help regulate temperature, bringing large volumes of blood close to the surface when the animals are overheated, so its heat can radiate out into the air.

In an infrared image, a reindeer’s nose (indicated by arrow) is shown to be especially red, a reflection of its temperature-regulating function. Image via Ince et. al.

Read more articles about the holidays in our Smithsonian Holiday Guide here

A new study shows that microscopic barbs allow porcupine quills to slice into flesh easily and stay there stubbornly. Image via Jeffrey Karp

If you’ve ever had a violent encounter with a porcupine, it probably didn’t end well. The large rodents are most well-known for the coat of some 30,000 barbed quills that cover their backs, an evolutionary adaptation to protect against predators. Although they appear thin—even flimsy—once quills lodge in your flesh, they’re remarkably difficult and painful to get out.

Recently, a group of scientists led by Jeffrey Karp of Harvard decided to closely investigate just what makes these quills so effective. As they report in an article published today in the Proceedings of the National Academy of Sciences, their analysis revealed a specialized microscopic barbed structure that enables the quills to slide into tissue extremely easily but cling to it stubbornly once it’s in place.

A microscopic image of a porcupine quill’s barbs. Image via Jeffrey Karp

Each cylindrical quill, it turns out, is coated with backwards-facing barbs interspersed with smooth, scale-like structures. When a porcupine brushes up against an adversary (or against anything else), it sheds its quills; the barbs around the circumference of the quill act like the teeth on a slicing serrated knife, providing a cleaner cut into tissue and making penetration easier. Once the quill has dug into the other animal, these same barbs have the opposite effect, lifting up and preventing the needle from sliding out easily.

The researchers took a rather interesting approach to arrive at these findings: They measured how much force it took to push in and pull out porcupine quills into pig skin and raw chicken meat. They then performed the same experiment with other quills, which they’d rendered smooth by carefully sanding off all the barbs.

All this research had a greater purpose than merely satisfying the authors’ curiosity about porcupines. Like velcro (inspired by plants’ burrs that get stuck on your clothing) and tape-based adhesives (inspired by the sticky coating on geckos’ hands and feet), the scientists studied the characteristics that made the barbs so effective in hopes of developing next-generation hypodermic needles.

If one could be designed that would require less force to penetrate human tissue, it might mean less pain with your next flu shot. The quills’ staying power could be useful for needles that need to stay in place for a longer period of time, like an I.V. drip.

As a proof-of-principle, the team made replica porcupine quills made out of plastic and put them through the same battery of tests on tissue and skin. The plastic quills worked like a charm. The researchers speculate that such technology could someday be incorporated into a range of medical applications beyond hypodermic needles, such as staples that hold wounds together during healing and adhesives used to hold drug delivery systems in place.

Prehistoric humans correctly depicted the gait of four-legged animals, such as this bull in the famous cave paintings of Lascaux, France, more frequently than modern artists. Image via Horvath et. al., PLOS ONE

The iconic caveman in popular culture is Fred Flintstone: slow-witted and unskilled. In general, we think of the cave art produced by prehistoric people as crude and imprecise too—a mere glimmer of the artistic mastery that would blossom millenia later, during the Renaissance and beyond.

If this is your impression of prehistoric humans, a new study published today in PLOS ONE by researchers from Eotvos University in Budapest, Hungary, might surprise you. In analyzing dozens of examples of cave art from places such as Lascaux, the group, led by Gabor Horvath, determined that prehistoric artists were actually better at accurately depicting the way four-legged animals walk than artists from the 19th and 20th centuries.

The researchers evaluated the prehistoric artists on the basis of the landmark 1880s finding by British photographer Eadweard Muybridge that horses (and, it was later discovered, most four-legged animals) move their legs in a particular sequence as they walk. The “foot-fall formula,” as it’s called, goes LH-LF-RH-RF, where H means ‘hind,’ F means ‘fore,’ and L and R mean ‘left’ and ‘right,’ respectively. At the time of Muybridge, this was thought to be an entirely novel discovery.

Except, as it turns out, prehistoric people apparently knew it too—and got it right in their drawings the majority of the time. Of the 39 ancient cave paintings depicting the motion of four-legged animals that were considered in the study, 21 nailed the sequence correctly, a success rate of 53.8%. Due to the number of combinations of how a four-legged animal’s gait can be depicted, the researchers state that mere chance would lead to a 26.7% rate of getting it right. Cavemen artists knew what they were doing.

This labelled contour drawing of the Lascaux painting shows that the hoofs are placed on the ground in a realistic manner according to the foot-fall formula. Image via Horvath et. al., PLOS ONE

When the researchers looked at 272 paintings and statues of four-legged animals made during modern times but before Muybridge’s findings in the 1880s, such as a famous horse sketch by Leonardo da Vinci, it turned out that these more recent artists were much worse: They only got the sequence right 16.5% of the time. Remarkably, even the 686 paintings and statues studied that were made more recently than 1887, after scientists knew for sure how four-legged animals walked, still got it right just 42.1% of the time.

In this drawing, even Leonardo da Vinci draws the sequence of a horse’s gait in an unrealistic manner. Image via Horvath et. al., PLOS ONE

Even apart from artists, a sizable number of depictions of four-legged animals made during the 20th century specifically for the sake of accuracy got the sequence wrong too, according to references used in the study. Out of 307 renditions analyzed, just 58.9% of depictions in natural history museums were correct, along with 56.9% of those in taxidermy catalogues, 50% of animal toy models and 36.4% of illustrations in animal anatomy textbooks.

Although the amount of art studied in each group varies greatly, the accuracy rate for animal depictions in prehistoric times is noteworthy. How could prehistoric humans possibly be this skilled at depicting animals such as bulls, antelopes and wild horses? For a potential answer, consider the way these ancient artists probably thought about the animals: as prey.

For prehistoric humans, “the observation of animals was not merely a pastime, but a matter of survival,” the study’s authors write. “Compared to artists of latter eras, when people were not as directly connected to nature, the creators of such cave paintings and carvings observed their subjects better and thus they depicted the walk of the animals in a more life-like manner.”

Illacme plenipes, the record-breaking millipede, only lives in a few woodlands in Northern California. Image via Marek et. al.

Yesterday, the first full description of the species was published in the joural ZooKeys. The study was led by Paul Marek of the University of Arizona. The millipede is known only from 17 live specimens Marek’s team found in a home range that is remarkably specific: three small wooded areas strewn with Arkose sandstone boulders in the foothills of San Benito County, California, near San Francisco.

The rareness of the millipede meant that from 1928 until 2005—when Marek, then a Ph.D. student, found a few specimens in the woods near San Juan Bautista—most scientists had simply assumed the species had gone extinct. Over the past seven years, Marek and his colleagues have taken several trips to the area, typically searching for hours before finding a single specimen clinging to the side of a boulder or tunneling four to six inches down into the ground.

In studying these specimens under a microscope, Marek has discovered a number of surprising characteristics that go beyond its legs. ”It basically looks like a thread,” Marek told LiveScience. “It has an uninteresting outward appearance, but when we looked at it with SEM [scanning electron microscopes] and compound microscopes, we found a huge, amazingly complex anatomy.”

The new analysis revealed that the millipede has no eyes, disproportionately long antennae and a rudimentary fused mouth adapted for sucking and piercing plant structures. It also has specialized body hairs on its back that produce silk, which may be used as a defense mechanism to clear bacteria off the millipedes’ bodies.

A microscope image of the species’ specialized body hairs that produce a silk secretion. Image via Marek et. al.

Of course, the legs are the most striking part of the species’ anatomy. Despite the name millipede, no species are known to have 1,000 legs, but Illacme plenipes comes closest (its Latin name actually means “in highest fulfillment of feet”). The male specimens examined had at most 562 legs, but the females had more, with the winner at 750.

Most millipedes have somewhere between 80 and 100 legs. Marek and his colleagues speculate that this species’ extreme legginess could be a beneficial adaptation for subterranean tunneling or even for clinging to the boulders widely found in the species’ habitat.

Most millipedes have 80 to 100 legs, but this species has up to 750. Image via Marek et. al.

DNA analysis has revealed that its closest cousin, Nematozonium filum, lives in Africa, with the two species’ ancestors apparently splitting apart sometime soon after the breakup of Pangea, more than 200 million years ago.

The team has tried to grow the millipedes in a lab but has so far been unable to. They caution that the species could be extremely endangered—in 2007, they stopped searching for wild specimens out of fears that they were depleting the population—and advocate for a formal protection listing, so scientists will have the time to learn more about them before the millipedes go extinct.

Scientists discovered a pair of spade-toothed carcasses in New Zealand. Previously, the species was only known from specimens such as this skull found in the 1950s, currently held at the University of Auckland. Image via Current Biology

In December 2010, visitors to Opape Beach, on New Zealand’s North Island, came across a pair of whales—a mother and her calf—that had washed ashore and died. The Department of Conservation was called in; they took photos, collected tissue samples and then buried the corpses at a site nearby. At first, it was assumed that the whales had been relatively common Gray’s beaked whales, widely distributed in the Southern Hemisphere. (You can see the graphic images here, should you wish.)

Months later, when researchers analyzed the tissue DNA, they were shocked. These were spade-toothed whales, members of the world’s rarest whale species, previously known only from a handful of damaged skulls and jawbones that had washed ashore over the years. Until this find, no one had ever seen a complete spade-toothed whale body. The researchers scrambled to exhume the corpses and brought them to the Museum of New Zealand Te Papa Tongarewa for further analysis.

“This is the first time this species—a whale over five meters in length—has ever been seen as a complete specimen, and we were lucky enough to find two of them,” said biologist Rochelle Constantine of the University of Auckland, one of the authors of a paper revealing the discovery that was published today in Current Biology. “Up until now, all we have known about the spade-toothed beaked whale was from three partial skulls collected from New Zealand and Chile over a 140-year period. It is remarkable that we know almost nothing about such a large mammal.”

The species belongs to the beaked whale family, which is relatively mysterious as a whole, mostly because these whales can dive to extreme depths and for very long periods—as deep as 1,899 meters and for as long as 30 minutes or more. Additionally, the majority of beaked whale populations are thinly distributed in very small numbers, so of the 21 species in the family, there are thorough descriptions of only three.

Of these species, the spade-toothed whale may have been the most mysterious. Scientifically known as Mesoplodon traversii, it was named after Henry H. Travers, a New Zealand naturalist who collected a partial jawbone that was found on Pitt Island in 1872. Since then, a damaged skull found on White Island in the 1950s and another found on Robinson Crusoe Island off the Coast of Chile in 1986 are the only evidence of the species.

Because the whales were never seen alive, scientists knew nothing of their behavior. In the paper, they are described as “the least known species of whale and one of the world’s rarest living mammals.”

“When these specimens came to our lab, we extracted the DNA as we usually do for samples like these, and we were very surprised to find that they were spade-toothed beaked whales,” Constantine said. To determine that, the researchers compared mitochondrial DNA from both of the stranded whales’ tissue samples and found that they matched that from the skulls and jawbones collected decades ago. “We ran the samples a few times to make sure before we told everyone,” Constantine said.

The researchers note that New Zealand’s national policy of collecting and sequencing DNA from all cetaceans washed ashore has proven especially valuable in cases like these—if this policy weren’t in place, no one might ever have known that the body of a spade-toothed whale had been seen for the first time.

This delayed discovery of a species that has been swimming the oceans all along hints at how much we still don’t know about the natural world—especially the oceans—even in this well-informed age. “It may be that they are simply an offshore species that lives and dies in the deep ocean waters and only rarely wash ashore,” Constantine said, explaining how it could take so long to find the species for the first time. “New Zealand is surrounded by massive oceans. There is a lot of marine life that remains unknown to us.”

Last week, we reported on a beluga whale discovered off the coast of California that had learned to make noises that sound just like human speech. Well, an Asian elephant named Koshik that lives at the Everland Zoo in South Korea has done one better. Even if you don’t speak Korean, you’ll be impressed by the video above: He’s learned to convincingly mimic five different words of the notoriously difficult language while stuffing his trunk in his mouth.

As described in paper published today in Current Biology, zoo staff say that Koshik is capable of uncannily emulating five commonly used Korean words: annyong (hello), anja (sit down), aniya (no), nuo (lie down) and choah (good). They first discovered that the now 22-year-old elephant could do this in 2006—and the cognitive researchers from the University of Vienna and elsewhere who wrote the study on Koshik’s speech say that the the circumstances of his adolescence might account for this unusual ability.

Koshik was the only elephant in the zoo for the first five years of his life, a period crucial for elephant bonding and socialization. “We suggest that Koshik started to adapt his vocalizations to his human companions to strengthen social affiliation, something that is also seen in other vocal-learning species—and in very special cases, also across species,” Angela Stoeger of the University of Vienna, the lead author of the paper, said in a statement. During this formative stage, Koshik was so desperate to connect with others that he learned to mimic the words most commonly said to him by trainers and zoo visitors, in order to generate a response from them.

Whatever his motivation, Koshik’s way of accurately replicating these five words is especially unusual. The elephant vocal tract is radically larger than a human’s, so to match the pitch and timbre of human speech, Koshik stuffs his trunk in his mouth, altering the shape of the vocal tract as he makes the words.

Koshik mimics human words by stuffing his trunk in his mouth, making it more closely resemble the human vocal tract. Image via Current Biology

Several bird species, including parrots and mynah birds, have been known to mimic human speech. There are anecdotal accounts of domesticated elephants doing so as well—Batyr, a longtime resident of a Kazakhstan zoo, was said to have a vocabulary of more than 20 Russian and Kazakh phrases—but his abilities were never scientifically tested. Critics said that his supposed abilities merely reflected the fact that observers expected to hear the words after being told that he was capable of making them.

In this case, the researchers performed a number of tests in order to definitively determine whether Koshik actually mimics human words. To start, they played audio recordings of Koshik’s words to native Korean speakers and asked them to write down what they heard. “We found a high agreement concerning the overall meaning, and even the Korean spelling of Koshik’s imitations,” Stoeger said. They also acoustically evaluated his speech and found that, in terms of frequency, it differed from typical wild elephant calls and much more closely matched those of Koshik’s human trainer, Kim-Jong Kap.

Of course, there’s no evidence Koshik actually understands the meaning of his words, just that saying them can elicit the attention of people. Nevertheless, the fact that such a highly intelligent species has been found to be physically capable, at least, of making human-like noises, should be encouraging. After years of efforts to train apes to say words, scientists have come to the conclusion that although they may be smart enough to learn meaning (as demonstrated with sign language), they lack the fine motor control of the vocal tract necessary for speech. If elephants are physically capable of mimicking words, it leaves open the possibility that we could someday teach them to speak, too.