March 5, 2013
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 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.
February 14, 2013
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.
February 13, 2013
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.
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.
January 30, 2013
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.
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.
December 18, 2012
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.