爱上海后花园419论坛

A 36-million-year-old fossil skeleton is revealing a critical moment in the history of baleen whales: what happened when the ancestors of these modern-day filter feeders first began to distinguish themselves from their toothy, predatory predecessors. The fossil is the oldest known mysticete, a group that includes baleen whales, such as humpbacks, researchers report in the May 22 Current Biology.

Scientists have made predictions about what the first mysticetes might have looked like, but until now, haven’t had much fossil evidence to back up those ideas, says Nicholas Pyenson, a paleobiologist at the Smithsonian National Museum of Natural History in Washington, D.C. “Here, we have something we’ve been waiting for: a really old baleen whale ancestor.”
The earliest whales were predators with sharp teeth — a legacy carried on by today’s orcas, dolphins and other toothed whales. But at some point during whale history, the ancestors of modern mysticetes replaced teeth with baleen, fibrous plates that filter out small bits of food from seawater like a giant sieve. Such a huge lifestyle change didn’t happen overnight, though. And the new find, dubbed Mystacodon selenensis, shows the start of that transition, its discoverers say.

Mystacodon largely fits in well with what scientists have predicted from analyzing other whales, says Mark Uhen, a paleobiologist at George Mason University in Fairfax, Va. “It fleshes out this transition, rather than being something wacky and crazy we never thought of.”

Mystacodon was unearthed in a Peruvian desert by a team of European and Peruvian scientists. Like other early mysticetes, this one still had teeth — its name means “toothed mysticete.” The creature was probably close to 4 meters long, estimates study coauthor Olivier Lambert, a paleontologist at the Royal Belgian Institute of Natural Sciences in Brussels. That’s about the size of a pilot whale, and far smaller than today’s leviathan humpbacks.
The whale holds onto some features of primitive whales, Lambert says. For instance, it still had a bit of a protruding hip bone, suggesting the presence of tiny hind legs left over from when whales’ ancestors were four-legged, terrestrial creatures. “At this transition, scientists thought that this hind limb would be more or less gone,” Lambert says. But the new find suggests that completely losing those limbs took a little longer than previously believed. And the process probably happened independently in toothed whales, instead of one time in the common ancestor of baleen and toothed whales.
But Mystacodon also shows some more modern features. Its snout was flattened, just like in modern mysticetes. In the earliest whales, the joints in the front flippers — essentially elbows — could still be flexed, a relic of when those flippers were legs. Modern whales can’t move those joints, and neither could Mystacodon.
“This is the first indication of a locked elbow — the final step of the transition of the forelimbs into flippers,” Lambert says.

Wear patterns on Mystacodon’s teeth suggest that the whale was a suction feeder — vacuuming up its prey instead of chomping it. That could have been a step toward the filter-feeding strategies used by today’s baleen whales, Lambert suggests. (Other early mysticetes show similar wear, also suggesting suction-feeding tendencies.)

But the connection between suction feeding and filter feeding isn’t well-established, Pyenson says. Mysticetes didn’t become true filter feeders until millions of years later, he says. And scientists still don’t know what series of changes in the ocean environment and in mysticetes’ bodies led to the transformation. “I don’t think suction feeding alone is the primary step.”

Lambert and his colleagues will be looking for more ancient whales to further flesh out the story of early mysticetes. The region where the skeleton was found — the Pisco Basin on the southern coast of Peru — is a hot spot for evidence of ancient whales and dolphins that was overlooked for many years, Lambert says. “There is huge potential for the area where we excavated.”

Tubelip wrasses eat dangerously, daring to dine on sharp corals lined with stinging cells. New images reveal the fish’s secret to safe eating: lubing up and planting a big one on their dinner.

“It is like sucking dew off a stinging nettle. A thick layer of grease may help,” says David Bellwood, a marine biologist at James Cook University in Townsville, Australia, who snapped the shots with his colleague Victor Huertas.

Of roughly 6,000 fish species that roam reefs, just 128 consume corals. These corallivores specialize in different menus. Well-studied butterfly fish, for example, use their long, thin snouts to nip up coral polyps, the tiny animals that build corals. Tubelip wrasses such as Labropsis australis of the South Pacific are known for nibbling coral with their luscious lips, but until now, it was unclear what part of the coral the fish were eating or how they were eating it.
While the surface of the wrasse’s lips looks smooth to the naked eye, convoluted grooves appear under a scanning electron microscope, the team reports June 5 in Current Biology. Mucus-producing cells line each groove. In contrast, the lips of a wrasse species that doesn’t eat corals (Coris gaimard) are sleek and sport fewer slime-secreting cells.

Video footage of L. australis shows that the fish feeds by latching onto coral with its lips and sucking. The slime probably protects the fish’s lips from stinging cells that line the coral skeleton and also serves as a sealant, allowing the wrasse to get suction against the coral’s razorlike ridges.

“Their kiss is so hard it tears the coral’s flesh off its skeleton,” Bellwood says. The team suspects that the fish feed primarily on mucus layers and sometimes tissue that lines the sharp skeleton. So, essentially the fish are using their lip mucus to better harvest the coral’s mucus.
Mucus is, in general, a hot commodity in the marine ecosystem. Some fish use it as sunscreen, others for speed — it can reduce drag through the water. Cleaner wrasses even eat slime off the skin of other fish (SN: 8/2/03, p. 78).

Given the threats that coral reefs face from bleaching events and climate change, having fish that suck their flesh might seem a tad brutal. But whether the added stress of snot-eating fish serves as a mere nuisance or a serious threat remains to be studied.

Newly named fossils suggest that a weird and varied chapter in amphibian deep history isn’t totally over.

Small fossils about 220 million years old found along steep red slopes in Colorado represent a near-relative of modern animals called caecilians, says vertebrate paleontologist Adam Huttenlocker of the University of Southern California in Los Angeles.

Caecilians today have long wormy bodies with either shrunken legs or none at all. Yet the nearly 200 modern species of these toothy, burrow-dwelling tropical oddballs are genuine amphibians. The fossil creatures, newly named Chinlestegophis jenkinsi, still had legs but could be the oldest known near-relatives of caecilians, Huttenlocker and colleagues suggest.

A popular view of the amphibian family tree has put caecilians on their own long, peculiar branch beside the ancient frogs and salamanders. But a close look at the new fossils suggests a much earlier split from ancestral frogs and salamanders, the researchers propose June 19 in Proceedings of the National Academy of Sciences. The move puts the caecilians into “a strange but incredibly diverse” group, the stereospondyls, Huttenlocker says. These species included elongated, short-legged beasts with heads shaped like toilet lids.

Among the many stereospondyls, Huttenlocker speculates that caecilians came from “an aberrant branch of miniaturized forms that went subterranean.” And today’s legless burrowers could be this once-flourishing group’s sole survivors.

Like 1980s hair bands, male cockatoos woo females with flamboyant tresses and killer drum solos.

Male palm cockatoos (Probosciger aterrimus) in northern Australia refashion sticks and seedpods into tools that the animals use to bang against trees as part of an elaborate visual and auditory display designed to seduce females. These beats aren’t random, but truly rhythmic, researchers report online June 28 in Science Advances. Aside from humans, the birds are the only known animals to craft drumsticks and rock out.
“Palm cockatoos seem to have their own internalized notion of a regular beat, and that has become an important part of the display from males to females,” says Robert Heinsohn, an evolutionary biologist at the Australian National University in Canberra. In addition to drumming, mating displays entail fluffed up head crests, blushing red cheek feathers and vocalizations. A female mates only every two years, so the male engages in such grand gestures to convince her to put her eggs in his hollow tree nest.

Heinsohn and colleagues recorded more than 131 tree-tapping performances from 18 male palm cockatoos in rainforests on the Cape York Peninsula in northern Australia. Each had his own drumming signature. Some tapped faster or slower and added their own flourishes. But the beats were evenly spaced — meaning they constituted a rhythm rather than random noise.

From bonobos to sea lions, other species have shown a propensity for learning and recognizing beats. And chimps drum with their hands and feet, sometimes incorporating trees and stones, but they lack a regular beat.

The closest analogs to cockatoo drummers are human ones, Heinsohn says, though humans typically generate beats as part of a group rather than as soloists. Still, the similarity hints at the universal appeal of a solid beat that may underlie music’s origins.

A newly discovered particle is dishing out a double dose of charm.

The newcomer is a baryon, meaning that it’s composed of three smaller particles called quarks — in this case, two “charm” quarks and one “up” quark. Detected by the LHCb experiment at CERN, the European physics laboratory near Geneva, the baryon is the first to be discovered with two charm quarks, LHCb scientists reported July 6 at the European Physical Society Conference on High Energy Physics in Venice, Italy. Scientists produced the particle by ramming protons together at CERN’s Large Hadron Collider and sifting through the aftermath.
Baryons can be composed of a variety of quark combinations, two up quarks and one charm quark, for example, or one “strange” quark and two “down” quarks. Because the charm quarks are a particularly heavy variety of quark, scientists should be able to use the new particle to perform different types of tests of their theories of particle interactions.

Although the particle, called a doubly charmed Xi baryon, is the first of its kind, its appearance is no surprise — physicists’ theories predicted its existence. The particle’s mass — about four times that of the proton — agreed with expectations.

Data from a previous experiment had hinted at the presence of a similar doubly charmed particle, but the results were disputed. In 2002, scientists with the SELEX experiment, located at Fermilab in Batavia, Ill., reported that they had discovered a particle composed of two charm quarks and a down quark (SN: 7/6/02, p. 14). But the particle’s properties didn’t align with theoretical expectations, and other experiments couldn’t confirm the results. The new particle further casts doubt on SELEX’s results, because the two baryons should be close in mass, but instead they differ by a significant margin.

Carbon nanotubes may be the key to shrinking down transistors and squeezing more computer power into less space.

Historically, the number of transistors that can be crammed onto a computer chip has doubled every two years or so, a trend known as Moore’s law. But that rule seems to be nearing its limit: Today’s silicon transistors can’t get much smaller than they already are.

Carbon nanotubes may offer a sizable solution. In the June 30 Science, IBM researchers report a carbon-nanotube transistor with an overall width of 40 nanometers — the smallest ever. It’s about half the size of typical silicon transistors.

Researchers have created carbon-nanotube transistors with certain supersmall components before, but the whole package was still bulky, says study coauthor Qing Cao of IBM’s Thomas J. Watson Research Center in Yorktown Heights, N.Y. The new study confirms that, in terms of size, carbon-nanotube transistors can beat out silicon — and that’s no small feat.

Quantum particles can burrow through barriers that should be impenetrable — but they don’t do it instantaneously, a new experiment suggests.

The process, known as quantum tunneling, takes place extremely quickly, making it difficult to confirm whether it takes any time at all. Now, in a study of electrons escaping from their atoms, scientists have pinpointed how long the particles take to tunnel out: around 100 attoseconds, or 100 billionths of a billionth of a second, researchers report July 14 in Physical Review Letters.
In quantum tunneling, a particle passes through a barrier despite not having enough energy to cross it. It’s as if someone rolled a ball up a hill but didn’t give it a hard enough push to reach the top, and yet somehow the ball tunneled through to the other side.

Although scientists knew that particles could tunnel, until now, “it was not really clear how that happens, or what, precisely, the particle does,” says physicist Christoph Keitel of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Theoretical physicists have long debated between two possible options. In one model, the particle appears immediately on the other side of the barrier, with no initial momentum. In the other, the particle takes time to pass through, and it exits the tunnel with some momentum already built up.

Keitel and colleagues tested quantum tunneling by blasting argon and krypton gas with laser pulses. Normally, the pull of an atom’s positively charged nucleus keeps electrons tightly bound, creating an electromagnetic barrier to their escape. But, given a jolt from a laser, electrons can break free. That jolt weakens the electromagnetic barrier just enough that electrons can leave, but only by tunneling.

Although the scientists weren’t able to measure the tunneling time directly, they set up their experiment so that the angle at which the electrons flew away from the atom would reveal which of the two theories was correct. The laser’s light was circularly polarized — its electromagnetic waves rotated in time, changing the direction of the waves’ wiggles. If the electron escaped immediately, the laser would push it in one particular direction. But if tunneling took time, the laser’s direction would have rotated by the time the electron escaped, so the particle would be pushed in a different direction.

Comparing argon and krypton let the scientists cancel out experimental errors, leading to a more sensitive measurement that was able to distinguish between the two theories. The data matched predictions based on the theory that tunneling takes time.
The conclusion jibes with some physicists’ expectations. “I’m pretty sure that the tunneling time cannot be instantaneous, because at the end, in physics, nothing can be instantaneous,” says physicist Ursula Keller of ETH Zurich. The result, she says, agrees with an earlier experiment carried out by her team.

Other scientists still think instantaneous tunneling is possible. Physicist Olga Smirnova of the Max Born Institute in Berlin notes that Keitel and colleagues’ conclusions contradict previous research. In theoretical calculations of tunneling in very simple systems, Smirnova and colleagues found no evidence of tunneling time. The complexity of the atoms studied in the new experiment may have led to the discrepancy, Smirnova says. Still, the experiment is “very accurate and done with great care.”

Although quantum tunneling may seem an esoteric concept, scientists have harnessed it for practical purposes. Scanning tunneling microscopes, for instance, use tunneling electrons to image individual atoms. For such an important fundamental process, Keller says, physicists really have to be certain they understand it. “I don’t think we can close the chapter on the discussion yet,” she says.

Humans inhabited rainforests on the Indonesian island of Sumatra between 73,000 and 63,000 years ago — shortly before a massive eruption of the island’s Mount Toba volcano covered South Asia in ash, researchers say.

Two teeth previously unearthed in Sumatra’s Lida Ajer cave and assigned to the human genus, Homo, display features typical of Homo sapiens, report geoscientist Kira Westaway of Macquarie University in Sydney and her colleagues. By dating Lida Ajer sediment and formations, the scientists came up with age estimates for the human teeth and associated fossils of various rainforest animals excavated in the late 1800s, including orangutans.

Ancient DNA studies had already suggested that humans from Africa reached Southeast Asian islands before 60,000 years ago.

Humans migrating out of Africa 100,000 years ago or more may have followed coastlines to Southeast Asia and eaten plentiful seafood along the way (SN: 5/19/12, p. 14). But the Sumatran evidence shows that some of the earliest people to depart from Africa figured out how to survive in rainforests, where detailed planning and appropriate tools are needed to gather seasonal plants and hunt scarce, fat-rich prey animals, Westaway and colleagues report online August 9 in Nature.

The sun can’t keep its hands to itself. A constant flow of charged particles streams away from the sun at hundreds of kilometers per second, battering vulnerable planets in its path.

This barrage is called the solar wind, and it has had a direct role in shaping life in the solar system. It’s thought to have stripped away much of Mars’ atmosphere (SN: 4/29/17, p. 20). Earth is protected from a similar fate only by its strong magnetic field, which guides the solar wind around the planet.
But scientists don’t understand some key details of how the wind works. It originates in an area where the sun’s surface meets its atmosphere. Like winds on Earth, the solar wind is gusty — it travels at different speeds in different areas. It’s fastest in regions where the sun’s atmosphere, the corona, is dark. Winds whip past these coronal holes at 800 kilometers per second. But the wind whooshes at only around 300 kilometers per second over extended, pointy wisps called coronal streamers, which give the corona its crownlike appearance. No one knows why the wind is fickle.
The Aug. 21 solar eclipse gives astronomers an ideal opportunity to catch the solar wind in action in the inner corona. One group, Nat Gopalswamy of NASA’s Goddard Spaceflight Center in Greenbelt, Md., and his colleagues, will test a new version of an instrument called a polarimeter, built to measure the temperature and speed of electrons leaving the sun. Measurements will start close to the sun’s surface and extend out to around 5.6 million kilometers, or eight times the radius of the sun.

“We should be able to detect the baby solar wind,” Gopalswamy says.

Set up at a high school in Madras, Ore., the polarimeter will separate out light that has been polarized, or had its electric field organized in one direction, from light whose electric field oscillates in all sorts of directions. Because electrons scatter polarized light more than non-polarized light, that observation will give the scientists a bead on what the electrons are doing, and by extension, what the solar wind is doing — how fast it flows, how hot it is and even where it comes from.
Gopalswamy and colleagues will also take images in four different wavelengths of light, as another measurement of speed and temperature. Mapping the fast and slow solar winds close to the surface of the sun can give clues to how they are accelerated.
The team tried out an earlier version of this instrument during an eclipse in 1999 in Turkey. But that instrument required the researchers to flip through three different polarization filters to capture all the information that they wanted. Cycling through the filters using a hand-turned wheel was slow and clunky — a problem when totality, the period when the moon completely blocks the sun, only lasts about two minutes.
The team’s upgraded polarimeter is designed so it can simultaneously gather data through all three filters and in four wavelengths of light. “The main requirement is that we have to take these images as close in time as possible, so the corona doesn’t change from one period to the next,” Gopalswamy says. One exposure will take 2 to 4 seconds, plus a 6-second wait between filters. That will give the team about 36 images total.

Gopalswamy and his team first tested this instrument in Indonesia for the March 2016 solar eclipse. “That experiment failed because of noncooperation from nature,” Gopalswamy says. “Ten minutes before the eclipse, the rain started pouring down.”

This year, they chose Madras because, historically, it’s the least cloud-covered place on the eclipse path. But they’re still crossing their fingers for clear skies.

A genetic “crystal ball” can predict whether certain people will respond effectively to the flu vaccine.

Nine genes are associated with a strong immune response to the flu vaccine in those aged 35 and under, a new study finds. If these genes were highly active before vaccination, an individual would generate a high level of antibodies after vaccination, no matter the flu strain in the vaccine, researchers report online August 25 in Science Immunology. This response can help a person avoid getting the flu.

The research team also tried to find a predictive set of genes in people aged 60 and above — a group that includes those more likely to develop serious flu-related complications, such as pneumonia — but failed. Even so, the study is “a step in the right direction,” says Elias Haddad, an immunologist at Drexel University College of Medicine in Philadelphia, who did not participate in the research. “It could have implications in terms of identifying responders versus nonresponders by doing a simple test before a vaccination.”

The U.S. Centers for Disease Control and Prevention estimates that vaccination prevented 5.1 million flu illnesses in the 2015‒2016 season. Getting a flu shot is the best way to stay healthy, but “the problem is, we don’t know what makes a successful vaccination,” says Purvesh Khatri, a computational immunologist at Stanford University School of Medicine. “The immune system is very personal.”
Khatri and colleagues wondered if there was a certain immune state one needed to be in to respond effectively to the flu vaccine. So the researchers looked for a common genetic signal in blood samples from 175 people with different genetic backgrounds, from different locations in the United States, and who received the flu vaccine in different seasons. After identifying the set of predictive genes, the team used another collection of 82 samples to confirm that the crystal ball accurately predicted a strong flu response. Using such a variety of samples makes it more likely that the crystal ball will work for many different people in the real world, Khatri says.

The nine genes make proteins that have various jobs, including directing the movement of other proteins and providing structure to cells. Previous research on these genes has tied some of them to the immune system, but not others. Khatri expects the study will spur investigations into how the genes promote a successful vaccine response. And figuring out how to boost the genes may help those who don’t respond strongly to flu vaccine, he says.

As for finding a genetic crystal ball for older adults, “there’s still hope that we’ll be able to,” says team member Raphael Gottardo, a computational biologist at the Fred Hutchinson Cancer Research Center in Seattle. Older people are even more diverse in how they respond to the flu vaccine than younger people, he says, so it may take a larger group of samples to find a common genetic thread.

More research is also needed to learn whether the identified genes will predict an effective response for all vaccines, or just the flu, Haddad says. “There is a long way to go here.”