上海后花园1314

Some seals still eat like landlubbers.

Just like lions, tigers and bears, certain kinds of seals have claws that help the animals grasp prey and tear it apart. X-rays show that the bones in these seals’ forelimbs look like those found in the earliest seals, a new study finds.

Ancestors of these ancient seals transitioned from land to sea at some point, preserving clawed limbs useful for hunting on land. But clawed paws in these northern “true seals,” which include harbor and harp seals, seem to be more than just a holdover from ancient times, says David Hocking, a marine zoologist at Monash University in Melbourne, Australia. Instead, retaining the claws probably helps northern true seals catch a larger meal than they could with the stiff, slippery fins of other pinnipeds such as sea lions and fur seals, Hocking and his colleagues report April 18 in Royal Society Open Science.
Hocking and his colleagues spent 670 hours observing wild harbor and gray seals hunting salmon in Scotland. Tests with three captive seals, two harbor seals born in captivity and one spotted seal born in the wild allowed the team to observe eating behaviors at closer range.
While some of the captive seals seemed to prefer swallowing their prey whole, both the wild and captive animals relied heavily on their claws overall, the scientists found. The critters were frequently spotted using their slashers to hold onto prey and rip off smaller bites, much as a land animal like a wolverine or a bear might. Up-close observations revealed seals caught prey underwater, but ripped it apart at the surface. That probably lets them breathe while eating without inhaling gulps of seawater — a challenge when devouring a large meal underwater.
Northern true seals have flexible joints that allow the animals to curl their claws to grasp prey. These flexible joints are also seen on early pinnipeds such as Enaliarctos mealsi, a seal that lived 23 million years ago, Hocking and his colleagues found. Fur seals and sea lions, however, “have inflexible fingers that help them to maintain a stiff flipper,” Hocking says.

The evolution of flipperlike forelimbs helped some pinnipeds propel themselves through the water more efficiently. But slippery flippers aren’t as useful for grasping prey. That could explain why fur seals and sea lions tend to target smaller fish that they can swallow whole underwater without needing to grasp, Hocking says.

But this fully aquatic feeding style might have been a challenge for the earliest pinnipeds, who probably used their clawed paws to hunt more like today’s true seals, the researchers say. Catching prey underwater and then shredding it at the surface was probably a smaller behavioral leap from full-on land feeding than other aquatic hunting strategies.

Documenting seals using their paws to grasp food is a “nice observation,” says Frank Fish, a biologist at West Chester University in Pennsylvania. Without knowing what early seals ate, though, it’s hard to say for sure whether they actively used their claws to hold onto large prey, he says.

Other scientists have documented true seals using their pawlike forelimbs in stereotypically terrestrial ways, too, such as using the claws to dig out lairs in ice or uncovering buried fish from the seafloor.

When it comes to tiny ocean swimmers, the whole is much greater than the sum of its parts. Ocean turbulence stirred up by multitudes of creatures such as krill can be powerful enough to extend hundreds of meters down into the deep, a new study suggests.

Brine shrimp moving vertically in two different laboratory tanks created small eddies that aggregated into a jet roughly the size of the whole migrating group, researchers report online April 18 in Nature. With a fluid velocity of about 1 to 2 centimeters per second, the jet was also powerful enough to mix shallow waters with deeper, saltier waters. Without mixing, these waters of different densities would remain isolated in layers.
The shrimp represent centimeter-sized swimmers, including krill and shrimplike copepods, found throughout the world’s oceans that may together be capable of mixing ocean layers — and delivering nutrient-rich deep waters to phytoplankton, or microscopic marine plants, near the surface, the researchers suggest.
“The original thinking is that these animals would flap their appendages and create little eddies about the same size as their bodies,” says John Dabiri, an expert in fluid dynamics at Stanford University. Previous work, including acoustic measurements of krill migrations
in the ocean ( SN: 10/7/06, p. 238 ) and theoretical simulations of fluid flow around swimmers such as jellyfish and shrimplike copepods ( SN: 8/29/09, p. 14 ), had suggested that they may be stirring up more turbulence than thought.
In 2014, Dabiri coauthored a study that debuted the laboratory tank setup also used in the new research. That paper noted that migrating brine shrimp created jets and eddies much larger than themselves. “But there was skepticism about whether those lab results were relevant to the ocean,” Dabiri says. The 2014 study didn’t account for how ocean water stratifies into layers that don’t easily mix, due to differences in salinity or temperature. It wasn’t clear if shrimp-generated turbulence could be strong enough and extend deep enough to overcome the physical barriers and mix the layers.

The new research used a 1.2-meter-deep tank and a 2-meter-deep tank. Each held tens of thousands of wiggly brine shrimp in two layers of water of different densities. The researchers used LED lights to prompt the shrimp to migrate upward or downward, mimicking the massive daily, vertical migrations of krill, copepods and other ocean denizens. The shrimp migrated in close proximity to one another – and that helped to magnify their individual efforts, the scientists found.

“As one animal swims upward, it’s kicking backward,” Dabiri says. That parcel of water then gets kicked downward by another nearby animal, and then another. The result is a downward rush that gets stronger as the migration continues, and eventually extends about as deep as the entire migrating group. In the ocean, that could be as much as hundreds of meters.“At the heart of the investigation is the question about whether life in the ocean, as it moves about the environment, does any important ‘mixing,’ ” says William Dewar, an oceanographer at Florida State University in Tallahassee. “These results argue quite compellingly that they do, and strongly counter the concern that most marine life is simply too small in size to matter.”

The team’s finding opens the door to a host of interesting questions, Dewar adds. Ocean mixing is an important part of the global climate cycle: It churns up nutrients that feed phytoplankton blooms and aids the exchange of gases with the atmosphere. Adding biologically driven mixing to physical processes in the ocean makes the equation even more complex, he says.

The next step will be to try to observe the effect at sea, using shipboard measurements, Dabiri says. “Previous studies looked for turbulence or eddies on the scale of the animals’ size,” he says, instead of large downward jets. “This paper tells us for the first time what to look for.”

Shooting small rocks from a high-speed cannon showed that some asteroids could have brought water to the early Earth — without all the water boiling away on impact, a new study finds.

“We can’t bring an asteroid to Earth and crash it into the Earth, bad things would happen,” says planetary geologist R. Terik Daly, who did the research while a graduate student at Brown University in Providence, R.I. “So we went into the lab and tried to re-create the event as best we can.”
After the solar system formed about 4.6 billion years ago, Earth grew up relatively close to the sun, where it was too hot for water to condense out of the gas phase. And Earth was too small to hold on to much nearby gas anyway. So scientists think the pale blue dot may have received its water from somewhere else — although exactly how that happened is still up for debate (SN: 5/16/15, p. 18).

Daly, now at Johns Hopkins University, and Brown planetary scientist Peter Schultz made marble-sized pellets of antigorite, a mineral found in Japan that is similar to the kinds of rocks that may have brought water to Earth billions of years ago. To simulate a dry planetary surface, the team baked pumice at 850° Celsius for 90 minutes. Then the team shot the pellets at the pumice at about 5 kilometers per second using the NASA Ames Vertical Gun Range in California.
That speed is similar to those at which asteroids probably crashed into each other when the planets were forming, Daly says. Previous simulations suggested that all of an asteroid’s water would vaporize upon impact if the asteroid had been traveling faster than 3.1 kilometers per second. On a planet like the early Earth, which lacked an atmosphere, that water vapor would then have been lost to space.
But Daly and Schultz found that some of the water vapor released by the pellets’ impacts was captured within glass created from shocked rock, or conglomerates of “busted-up” rocks called breccias. Asteroids could have delivered up to 30 percent of their stored water to growing planets, the scientists conclude April 25 in Science Advances.
The next step is working out how the water could escape from rocks to create oceans and other water bodies, Daly says.

“I really like this work,” says planetary scientist Yang Liu of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who was not involved in the study. “The experimental setup is very clever.”

Liu studies water in lunar material, and one frequent question about her work is how the moon can have water at all (SN: 10/24/09, p. 10). Earth’s nearest celestial neighbor lacks a thick atmosphere where vapor can accumulate, which means the moon should have had an even harder time keeping impact-delivered water than the Earth did.

“This work demonstrates that this is feasible even for airless bodies,” she says. The finding even suggests a way for future crewed missions to find water on the moon: “Perhaps we should just look for impact melts to get the water we need.”

Animal experiments demonstrate for the first time that transplanted tumors release a chemical into the host’s bloodstream that causes the host to produce blood vessels to supply the tumor.… If such a factor can be identified in human cancers … it might be possible to prevent the vascularization of tumors. Since tumors above a certain small size require a blood supply to live, they might by this method be starved to death. — Science News, May 4, 1968

Update
By the 1990s, starving tumors had become a focus of cancer research. Several drugs available today limit a tumor’s blood supply. But the approach can actually drive some cancer cells to proliferate, researchers have found. For those cancers, scientists have proposed treatments that open up tumors’ gnarled blood vessels, letting more oxygen through. Boosting oxygen may thwart some cancer cell defenses and promote blood flow — allowing chemotherapy drugs and immune cells deeper access to tumors (SN: 3/4/17, p. 24).

The world tracked the New Horizons’ spacecraft with childlike glee as it flew by Pluto in 2015. The probe provided the first ever close-up of the place that many of us grew up considering the ninth planet. Pluto revealed itself as a fascinating world, with a shifting surface (SN: 12/26/15, p. 16), a hazy atmosphere (SN Online: 10/15/15) and a heart of nitrogen ice (SN Online: 9/23/16).
But the course of space exploration never did run smooth. In Chasing New Horizons, Alan Stern ­— New Horizons’ principal investigator and chief champion — and his coauthor, team member David Grinspoon, share their recollections of how a band of scrappy planetary scientists got a mission to the farthest reaches of the solar system off the ground. Over the course of a decade and a half, Stern and colleagues in the “Pluto Underground” fought first to get a Pluto mission taken seriously by NASA, then to keep it alive through budget woes, political battles, stiff competition from other mission proposals and outright cancellations.

Even if you followed the flyby closely and think you know this story, the book divulges details that will surprise you. Come for the sweeping tale of wonder and exploration; stay for the gaggle of planetary scientists celebrating on Bourbon Street once their mission finally got the green light.

Science News talked with Stern about the book, what it’s like to be “Mr. Pluto” and what’s next for New Horizons, which is currently in hibernation cruising through the Kuiper Belt. The interview that follows has been edited for length and clarity.
SN: Almost half of the book is about the fight to get the New Horizons mission approved. Why was it important for you to focus on that?
Stern: If you look at the 26-year span, from 1989 [the year the American Geophysical Union meeting devoted the first conference session to the subject of a Pluto mission] to 2015 when we got there, almost precisely half of that time was back and forth trying to get a mission to Pluto.

It’s rare for the public to get to see the behind the scenes of how difficult it is — how much competition there is, how many things come out of left field, how much scientists with a goal or objective in mind really have to have persistence to make it happen.

SN: You write that by the time the mission teams were being assembled, you were already known as Mr. Pluto. When did you start feeling like Mr. Pluto yourself?

Stern: Somewhere in the ʼ90s, when we were going through this maze of twists and turns to get a mission to Pluto. Every time we’d have a reversal, and I’d have to go fight for it again, I started to feel like I was putting on my Mr. Pluto hat.

I’m typecast that way now. You know, I’ve been on 29 different space missions, to almost every planet in the solar system. Only one of them was to Pluto, but that’s the one, maybe the only one, I’m known for. It’s like being on the cast of Gilligan’s Island, they only remember you for the one thing, no matter how much else you’ve done. Which is fine [laughs]. I love Pluto, no question, but it’s not like that’s all I did in the past three decades.

SN: What’s next for New Horizons?

Stern: We emerge from an almost six-month hibernation period on June 4. Our next flyby is taking place on New Year’s Eve and New Year’s Day with a small Kuiper Belt object that we’ve nicknamed Ultima Thule, which is a building block of planets like Pluto.

It’s going to just be spectacular, scientifically. And so our team is really up to our eyeballs in flyby planning and preparations.

SN: How long can the spacecraft keep going after that?

Stern: New Horizons has the fuel and power to go on for decades, and it’s very healthy. And there’s a lot more science to do in the Kuiper Belt. In fact, there is some science that the spacecraft is capable of doing that no other spacecraft can. There are some kinds of unique astrophysics that even the James Webb [Space Telescope, due to launch in 2020] and the Hubble can’t do, that we can do.

New Horizons is really is an amazing resource. There’s no other spacecraft planned to fly to these great distances again. So we want to make sure that science benefits to the maximum extent.

SN: There’s a scene in the book, right before the Pluto flyby, when a journalist asks how you’re going to feel at the end of the mission — will there be a sort of grief at the culmination of all this work. Now that you’re on the other side, how does it feel?

Stern: A lot of people in the mission team, as we were finally bearing down on Pluto, started to express that kind of concern. Frankly, we’d been so busy I didn’t have time to think philosophically about “what after.” I was thinking about catching up on my sleep, seeing my family more, what discoveries would we make. But I wasn’t thinking about, what do you do after your Apollo 11? What do you do after you’ve scaled your Everest?

As it turns out, a lot of those concerns just sort of washed away with the success of the flyby and the spectacular scientific discoveries at Pluto. Now I and other people on our team look back on it and say, “I was a part of something that really made a difference.” You can’t ask for much more than that.

Synthetic nanoparticles used to fight cancer could also heal sickly plants.

The particles, called liposomes, are nanosized, spherical pouches that can deliver drugs to specific parts of the body (SN: 12/16/06, p. 398). Now, researchers have filled these tiny care packages with fertilizing nutrients. The new liposomes, described online May 17 in Scientific Reports, soak into plant leaves more easily than naked nutrients. That allows the nanoparticles to give malnourished crops a more potent pick-me-up than the free-floating molecules in ordinary nutrient spray.
Each liposome is a hollow sphere about 100 nanometers across, and is made of fatty molecules extracted from soybean plants. Once a plant leaf absorbs these nanoparticles, the liposomes spread to cells in the plant’s other leaves and its roots, where the fatty envelopes break down and release their molecular cargo.
Researchers first exposed tomato plants to either liposomes packed with a rare earth metal called europium, or free-floating europium molecules. Europium doesn’t naturally exist in plants or soil, so it’s easy to trace how much of this element plants soaked up after treatment. Three days after exposure, plants treated with liposomes had absorbed up to 33 percent of the nanoparticles. Plants exposed to free-floating europium took in less than 0.1 percent of the molecules
The researchers then spritzed iron- and magnesium-deficient tomato plants with either a standard spray containing iron and magnesium, or a solution containing liposomes packed with those nutrients. Two weeks later, the leaves on plants treated with free-floating nutrients were still tinged yellow and curled. Plants that received liposome treatment sported healthy, green leaves.

Avi Schroeder, a chemical engineer at the Israel Institute of Technology in Haifa, and colleagues don’t know exactly why liposomes are more palatable to plants than plain nutrients. But sprays that contain nutrient-loaded liposomes could help farmers rejuvenate frail plants more efficiently than existing mixtures, Schroeder says.

Liposome-based spray would need to be tested on a variety of vegetation before it could enter widespread use, says Ramesh Raliya, a nanobiotechnology researcher at Washington University in St. Louis not involved in the work. That’s because the pores on leaves where liposomes are assumed to enter plants can range from 50 to 150 nanometers across. If a plant’s pores are smaller than 100 nanometers, the liposomes can’t squeeze inside.

Mariya Khodakovskaya, a biologist at the University of Arkansas at Little Rock, is wary of the potential cost of this new technique. Fashioning liposomes is expensive. That’s not a problem for making liposome-based medication, which requires only a small amount of nanoparticles. But for any new agricultural practice to take root, she says, “it has to be massive, and it has to be cheap.”

E. coli has a type and it isn’t pretty. The bacterium is more likely to cause severe diarrhea in people with type A blood.

An illness-causing strain of E. coli secretes a protein that gloms onto the sugar molecules that decorate type A blood cells, but not type B or O cells. These sugar molecules also decorate cells lining the intestines of people with type A blood and appear to provide a handle for the bacterium to latch onto before injecting its diarrhea-causing toxins, researchers report May 17 in the Journal of Clinical Investigation.
There were hints that blood type was linked to the severity of E. coli infection. But a clear connection was lacking until now, says a team led by researchers at Washington University School of Medicine in St. Louis.

Collaborators at Johns Hopkins University gave 106 healthy volunteers water laced with a strain of E. coli isolated from a person in Bangladesh with severe diarrhea. Within five days, 81 percent of the type A or AB volunteers developed moderate to severe diarrhea compared with roughly half the people with blood types O or B. (Everyone received antibiotics to clear the bacterium).

This discovery suggests that a vaccine targeting the bacterial protein — which is found in many E. coli strains — could be effective. That could help not only travelers but also children in the developing world, where repeated infections are linked to malnutrition and stunted growth. E. coli isn’t the only microbe that can cause severe diarrhea, though, making good hygiene — washing hands and purifying water — still the best defense.

Ancient colonizers of the Americas could have traveled down Alaska’s Pacific coast in canoes or other sea vessels around 17,000 years ago, a new study finds.

At that time, toward the end of the last ice age, glaciers had just receded from a cluster of southern Alaskan islands, say geologist Alia Lesnek of the University at Buffalo in New York and colleagues. Life-supporting habitats appeared soon after the ice melted, the scientists report May 30 in Science Advances.
The study is the latest to weigh in on the debate over how humans spread into the New World after arriving from Asia and reaching as far as Florida and South America
by 14,500 years ago ( SN: 6/11/16, p. 8 ; SN: 12/26/15, p. 10 ). Previous work has hinted that an inland, ice-free corridor from Alaska through what’s now British Columbia and into the United States may not have contained enough vegetation and wildlife to enable human travel before around 12,600 years ago ( SN Online: 8/10/16 ). New geologic evidence supports the idea of a coastal route, though Lesnek’s team found no human bones or artifacts on the islands.
Measures of chemicals that accumulate in rock due to cosmic radiation once glaciers retreat provided age estimates for when four Alaskan islands lost their ice coat. An open pathway for coastal travelers probably existed along the entire southeastern Alaskan coast roughly 17,000 years ago, the scientists say. Radiocarbon dates for a ringed seal’s remains found on a southern Alaskan island indicate that the seal lived about 17,000 years ago, suggesting the area became habitable soon after glaciers left.

A little animal that washed out to sea 240 million years ago off the coast of what’s now Italy turns out to be the oldest known fossil of a lizard.

The identification pushes back the fossil record of snakes and lizards by about 75 million years, says Tiago Simões of the University of Alberta in Edmonton, Canada. He and colleagues used observations of the fossil, called Megachirella wachtleri, and of related living and extinct species plus genetic data to reconstruct the evolutionary history of squamates, the reptile group that today includes snakes and lizards, the researchers report in the May 31 Nature.
“Understanding lizard and snake evolution has been a constant problem in paleontology,” says vertebrate paleontologist Stephanie Pierce of Harvard University who worked on the issue years ago but wasn’t involved in the new study. The trouble comes largely from a lack of relevant fossils, she says. That dearth isn’t just because little animals don’t fossilize as readily as big ones do. “Things like giant dinosaurs — they’re pretty easy to spot,” she says. “But if you’re looking for something that can fit in the palm of your hand, that makes it very challenging.”
A collector found M. wachtleri
almost 20 years ago in a part of the Italian Alps that had once been underwater. But researchers didn’t categorize it as a full member of the squamate branch of reptiles, until now. The sole specimen is partly embedded in rock, which obscured some of the creature’s telltale features. Now a CT scan has revealed previously unknown squamate details of its palate, braincase, limbs and shoulder, Simões says.
M. wachtleri was a small, terrestrial animal with teeth appropriate for snapping up insects, he says. Yet a catastrophe such as a tropical storm apparently swept it out to sea along with masses of leaves.

Besides taking a closer look at M. wachtleri, Simões and some colleagues traveled to 17 countries from Brazil to China to reexamine the other known squamate fossils. Combining all of the new fossil measurements with DNA data, the researchers reconstructed the evolutionary tree of squamates. Among the new insights: Geckos appear to be the most ancient of still-surviving lizards, the team found. And iguanas, a hard-to-place group on the tree, have a more recent origin than some other studies have found.

“The picture is coming together,” says study coauthor Oksana Vernygora, an evolutionary biologist also at the University of Alberta.

Previously, the oldest known squamate fossils dated back about to 168 million years ago. Adding M. wachtleri to the mix means that the squamates are so ancient that they arose before the mass extinction at the end of the Permian Period 252 million years ago, notes herpetologist and evolutionary biologist Jeff Streicher of the Natural History Museum in London who was not involved in the study. That cataclysm came the closest (yet) to wiping out life on Earth. How the ancestors of modern lizards and snakes made it is still a matter of debate.

The spacecraft fire that killed three Apollo astronauts and rocked the space agency a year and a half ago is still being felt.… Last week, after a series of delays … a major milestone was finally reached: the first manned tests of an Apollo spacecraft to include all the new equipment and safeguards incorporated since the fire. — Science News, June 8, 1968.

Update
Since that lunar program reboot, hundreds of NASA astronauts have made it to space, and 12 astronauts have walked on the surface of the moon. After NASA retired the U.S. Space Shuttle program in 2011, American astronauts have had to rely on Russia’s Soyuz spacecraft to reach the International Space Station (SN: 6/11/16, p. 4). Once again, U.S. spacecraft, from SpaceX and Boeing, are planned to take American astronauts into space, but delays have pushed those efforts back to late 2019 and 2020.