Why’d the zebra evolve its stripes? Perhaps because stripes seem to keep off horseflies, a new study suggests. There’s good evolutionary reason to escape the ravages of horseflies, at least for horses and their relatives; though flies are just annoying pests from the human perspective, horsefly-bitten horses can grow skinny and have trouble producing milk for their young. And as soon as baby-making is affected by something in the environment, adaptation isn’t far behind.
Other research has shown that horseflies prefer to land on black horses instead of white, which got Gabor Horvath, author of the recent study, thinking about how they’d react to black-and-white specimens, such as zebras. Of course, actual zebras can be hard to experiment on, as The Economist notes in an article on the research:
[Real zebras] insist on moving around and swishing their tails. The team therefore conducted their study using inanimate objects. Some were painted uniformly dark or uniformly light, and some had stripes of various widths. Some were plastic trays filled with salad oil (to trap any insect that landed). Some were glue-covered boards. And some were actual models of zebra. They put these objects in a field infested with horseflies and counted the number of insects they trapped.
Om nom nom…oh, you caught me in the middle of dinner!
While conducting a survey of fish in an area of the Great Barrier Reef, scientists stumbled upon this little tableau: a tasselled wobbegong, or “carpet shark,” in the midst of devouring a brown-banded bamboo shark. (Either that, or they’re just sharing a very intense kiss.) The carpet shark, which hides in the sand and springs out at its prey, has never been photographed eating another shark before, though scientists could tell from poking around in their stomach contents that their distant cousins were sometimes on the menu. Carpet sharks seem to be slow eaters, though: the team hung around for a full 30 minutes to see if it would suck in more of the bamboo shark, but to no avail.
Maybe it just has stage fright.
Images courtesy of Tom Mannering and the journal Coral Reefs
The many-times-magnified photos of the Nikon Small World photomicrography contest entrance us year after year, with mesmerizing close-ups of nature’s microscopic marvels. Now, in the first Small World in Motion movie competition, we get to see the world’s wee wonders in action. The three winning films and eleven honorable mentions chronicle circulating blood, budding yeast, gestating eggs, and more.
First Place: This time-lapse video, at 10x magnification, traces the path of ink injected into an artery of a three-day-old chick embryo. As the ink spreads through the chick’s vascular system, the branching blood vessels and beating heart become clearly visible.
Katydids create their song by scraping one wing across the other, running a hard ridge of tiny teeth, like those on a comb, across the ridge on the opposite wing. The research team examined the size and shape of the teeth on the wings of Archaboilus musicus, as the Jurassic specimen is called, to come up with an estimate of the frequency of the sound that such scraping would have produced. They found that the resulting chirping would have fallen at 6.4 kilohertz, within the range of normal human hearing.
So, if you ever get the chance to travel back 165 million years, keep your ears pricked. You might hear something that sounds like this:
The strangest thing about this Chinese boy’s light blue eyes is not their color. It’s the purported fact that he can see in the dark. His eyes are just like cat eyes, glowing blue-green when you shine a light in them, says this clip from China’s state-run English TV channel. The boy can catch crickets in the dark without a flashlight and even completes a writing test in a pitch-black stairwell. True, or too good to be?
Natalie Wolchover at Life’s Little Mysteries has rounded up some experts and their collective reaction seems to be, “Hmm…” (It doesn’t help that this video has been posted on YouTube under the name, “Alien Hybrid or Starchild Discovered in China? 2012.”) One possibility they consider is whether the boy has a mutation that produced something like a tapetum lucidum, an extra layer of tissue that helps cats see in the dark. James Reynolds, a pediatric ophthalmologist at State University of New York in Buffalo, puts a stop to that idea:
What’s the News: The surprising strength of spider silk has fascinated scientists (and everyone else) for years: it’s stronger than steel, yet incredibly flexible. A new paper gives some delicious details that explain how, exactly, spider silk has such superpowers.
Go With the Flow, Then Stay Strong: The strand of silk that a spider hangs from can stretch to double its usual length. But then, after that virtuosic show of elasticity, it turns rigid.
The reason for that, this team found previously, is that on the molecular level, spider silk is made of scrunched-up proteins that are pulled straight as the silk stretches. But once they’ve been fully unfurled, the proteins lock into a new, stiff pattern called a beta-sheet nanocrystal. For a spider, having the molecules snap to stiffness after stretching is probably analogous to a rock climber arresting a rappel by clipping the end of her rope in place.
Creatures as large as elephants are unusual; it takes a long time to evolve such size.
How long does it take for a mammal as small as a mouse to evolve into something as large as an elephant? A really, really long time, a recent study has found: about 24 million generations, at minimum.
To get that number, researchers looked at the evolution of body mass over the last 70 million years, after the dinosaurs went extinct and surviving animals expanded into the ecological niches they left behind. That estimate is far longer than earlier estimates, which, extrapolating from bursts of super-fast evolution in mice, range from just 200,000 to 2 million generations. Such speedy evolution, in actuality, is probably not sustainable over the long term—hence the lengthy new estimate.
The researchers chose to examine the sperm of crickets, because, as with humans, you can get samples of it without having the male come into contact with a female first.
What’s the News: You might already know that sperm, which can survive for only a few hours when exposed to the outside world, can live for several days in women after ejaculation. But did you know that an ant queen can fertilize her eggs with sperm she’s stored for up to 30 years? And that organisms as diverse as birds, reptiles, and insects can hang onto sperm and keep it fresh for days, weeks, or months?
Scientists studying this ability have been trying to figure out how females do it, and in a recent paper, researchers put forth evidence showing that the ladies may be arresting the aging process, by slowing down sperms’ metabolism.
These newly discovered filter feeders, named Siphusauctum gregarium by their discoverers, have been found in clumps of over 65, and appear to have fed by sucking water through their bodies and extracting food particles.
How a living material of cheese fungi sandwiched between plastic sheets works.
The crusty rind of cheeses like Camembert provide more than texture: they are miniature fortress walls, made of fungus, that protect the cheese’s creamy insides from bacterial invasions. Now, taking inspiration from this delicious snack, chemical engineers at ETH Zurich in Switzerland have shown that such a fungus can be enclosed in porous plastic and will digest spills, with implications for creating antibacterial surfaces from living material.
The team sandwiched a layer of Penicillium roqueforti—from, you guessed it, Roquefort cheese—between a plastic base and a top sheet of plastic with nanoscale pores that allowed gas and liquids to move through, but did not allow the fungus to spread. Then, they mimicked a kitchen spill by pouring sugary broth on the surface and watched as, over the course of two weeks, the captive fungus gradually consumed the entire spill, leaving the surface clean. As shown in the figure above, the fungi can go dormant when there is no food around, so if one had a countertop of such a material, you wouldn’t need to keep spilling sugar on it to keep the fungi happy. (more…)
An image of the Martian surface from NASA’s Viking 2
To eke out even the barest subsistence on Mars, a living thing would have to adapt to a formidable set of environmental challenges: an arid, often extremely cold landscape with miniscule amounts of oxygen in the atmosphere and no organic matter to eat. During a recent foray into a similarly inhospitable part of our own planet, scientists have discovered several species of bacteria that hint at what life on Mars, if it exists, might look like. These microbes survive on minerals in the surrounding rocks—minerals also found in the Martian surface.
If you live in the Northeast, chances are you’ve had a disappointingly balmy December so far (the snow seems to have taken a wrong turn somewhere and wound up over Texas instead). But when the air gets that snap and you reach for the wool socks, Emily Eggleston at Scientific American has a few factoids that promise to fascinate. Here’s why wool keeps you warm:
Wool keeps out the cold because it is an excellent insulator. Crimped and crisscrossed woolen fibers create tons of little air pockets. The tiny air masses within my socks have difficulty moving in and out of the fabric. Without convective heat transfer and contact with air of other temperatures, the spaces between wool fibers maintains a steady temperature.
In the form of brood parasites, the bird world has enough irresponsible moms to start a reality TV show: cowbirds, for instance, lay their eggs in other species’ nests, stab most of the hosts’ eggs to death, and then leave their offspring to be raised by the host parents. The standing explanation for this involves most host birds being not that sharp on the uptake (watch a tiny warbler fussing over a cuckoo chick ten times its size (above) and you’d think that too). But maybe, a new study suggests, it’s sometimes to the host’s benefit to let imposter eggs stay in their nests.
The researchers chose mockingbirds as their hosts and cowbirds as their parasites, because mockingbirds usually fight like crazy to keep cowbirds of their nests but get strangely quiescent once the invaders have laid their eggs, a behavior that piqued the researchers’ interest. Once all the birds in the sample population had laid, the researchers went around adding and removing eggs from nests to see whether having a certain number of cowbird eggs affected mockingbird survival. They found that mockingbird eggs that shared their digs with cowbird eggs and suffered repeated cowbird invasions were more likely to survive, apparently because when each cowbird arrived, it would stab a certain proportion of the eggs in the nest regardless of whether they were host eggs or the eggs of the previous cowbird. Letting the parasite’s eggs stay, then, means that more of the host eggs avoid getting stabbed. The researchers conclude that when there are a lot of cowbirds around and hence a high probability of multiple nest hijackings, it makes sense for mockingbird parents not to shove out the invaders’ eggs.
Nice. And with all this dubious parenting and wanton violence, it’s straight from an episode of Teen Mom meets Cops, no?
Spiders are covered with fine hairs that can detect the faint movements of an enemy creeping closer, or a prey insect moving nearby. Scientists had long thought that these hairs functioned like the hairs humans have in our ears, which each tremble in response to a specific frequency and have to work together for us to hear sounds. But a new experiment suggests that each individual hair on a spider is capable of responding to a whole spectrum of sound, thus acting as an ear all on its own. As Dave Mosher writes at Wired:
The hairs responded best to sounds between about 40 Hz, a low rumble of bass, and 600 Hz, a car horn (humans ears can detect between 20 Hz and 20,000 Hz). That they picked up such a wide range of frequencies at all could overturn previous assumptions about how trichobothria [as the hairs are called] work.
“They operate like band-pass filters or microphones, not like the hairs in a human ear,” Bathellier said. In effect, each hair is its own ear that filters out background noise and zeroes in on biologically relevant information, such as an unwary cricket’s hopping or a spider’s sneaking.
How all these tiny “ears” work together, though, is still a mystery—further studies will have to investigate how the hairs’ vibrations affect spiders’ nervous systems.
80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles on the day's most compelling topics.
80beats is written by Veronique Greenwood and Valerie Ross. This team darts through each day's science news faster than the ruby-throated hummingbird that beats its wings 80 times per second. Send ideas, tips, suggestions, and complaints to [azeeberg at discovermagazine dot com].
The researchers chose to examine the sperm of crickets, because, as with humans, you can get samples of it without having the male come into contact with a female first.
