In dark fishing spiders, males’ postmating nap is permanent

Once is apparently enough for male dark fishing spiders. After delivering only half of their available sperm to a single female, males curl up and wait for death.

In the considerable annals of spider sex ending badly, male Dolomedes tenebrosus suffer a fate not described before, says behavioral ecologist Steven K. Schwartz of the University of Nebraska-Lincoln. Males of this widespread North American species prepare sperm for two matings but spontaneously fall into a spidery version of a coma during the first one. Their legs crumple and their bodies hang terminally motionless without any sign of the female having injured them, Schwartz and his colleagues report June 18 in Biology Letters.
Male spiders deliver sperm via a pair of boxing-glove shaped projections, or pedipalps. Male dark fishing spiders load both pedipalps with sperm, but in lab and outdoor matings, males used only one before curling into a deathlike posture. Even when protected from any female attack, males’ hearts stopped beating about two hours after mating, Schwartz says.

If females eat the inert male, his death may gain him especially abundant or healthy offspring, Schwartz speculates. Or a recently fed female may be less likely to mate with the next suitor that comes along.

As dark male fishing spiders prepare to mate, the male (smaller than the female) rocks the female’s body. When he finally inserts one of his sperm-delivery organs into one of her reproductive openings, he suddenly collapses. He no longer responds when researchers pick up or poke at him.
Credit: S.K. Schwartz

Hubble finds hints of a planet oddly far-flung from its star

A mysterious gap in a star’s dusty shell of debris could be the signature of a young planet circling its sun at twice the distance of Pluto’s orbit. If it does exist, the far-flung planet’s birth may be hard for astronomers to explain.

“If this is a planet, it is extremely challenging for existing planet formation theories,” says Katherine Kretke, an astronomer at the Southwest Research Institute in Boulder, Colo.

Most planets are thought to begin their lives as small clumps of hot, rapidly moving dust and gas within vast disks of debris that orbit newborn stars. As a planet grows it behaves like a snow plow, scooping up some material to bulk up while flinging other material away, until it has cleared a smooth orbital path.
John Debes, an astronomer at the Space Telescope Science Institute in Baltimore, used the Hubble Space Telescope to study a disk around TW Hydrae, a 10-million-year-old star located about 176 light-years from Earth.

Hubble images revealed an unmistakable gap 12 billion kilometers from the star, 80 times farther than Earth is from the sun. “It’s very striking,” says Phil Armitage, an astrophysicist at the University of Colorado Boulder. “It looks like what you’d expect from a forming planet.”

If the planet’s existence is confirmed, astronomers have their work cut out for them explaining how it got there. Compared with particles in tighter orbits, ones near that gap are less densely packed and move much more slowly, Kretke says. As a result, it would be difficult for a potential planet to accrue enough material to clear its own orbit.

An alternative theory of planet formation posits that clumps of gas within a disk can rapidly collapse together in a process similar to the one that forms stars. That could account for the outer bulky planets recently discovered around the star HR 8799 (SN Online: 12/3/10). But Kretke says that process is capable only of building worlds more massive than Jupiter, while this potential planet would be the size of Neptune or a large Earth.

“No matter how you look at it, if there’s a planet there it’s going to change theories of how planets form,” Debes says. His team’s results appear June 14 in the Astrophysical Journal.

The next step is to find the planet, Debes says, which will be no easy task. Just identifying the gap in TW Hydrae’s disk was akin to seeing a groove in an LP record from six kilometers away; now astronomers hope to find a speck hidden within that groove.

Debes notes that the Hubble photos were taken by a nearly 20-year-old instrument; he is confident that next-generation telescopes will see the planet if it exists.

Ebola thwarted in mice by drugs for infertility, cancer

Two drugs already on the market for other purposes can halt Ebola virus in mice. The findings open the way for further testing of the drugs, clomiphene and toremifene, against the deadly virus.

Scientists screened more than 2,000 drugs against Ebola, a process that required the highest level of safety precautions because the virus is so lethal. Several drugs called selective estrogen receptor modulators showed promise, including clomiphene, marketed as Clomid and prescribed to treat infertility, and toremifene, used to treat advanced breast cancer.
In the June 19 Science Translational Medicine, researchers report that each drug prevented Ebola virus from commandeering cells in lab-dish experiments. The researchers also injected mice with one form of the Ebola virus, and nine of 10 mice given clomiphene one hour after exposure survived a month-long observation period. Five of 10 mice getting toremifene died within 10 days, but the other five survived the month. All mice given the virus without the drugs died within a week.

The drugs bottled up Ebola in a cell compartment called an endosome, which the virus uses as a way station when it invades a cell. How the drugs thwart the virus there is unclear, says study coauthor Gene Olinger, a virologist at the U.S. Army Medical Research Institute of Infectious Diseases in Frederick, Md. But the results suggest that the drugs might stop other versions of the Ebola virus and the related Marburg virus, another deadly pathogen. In theory, the drugs would be given to patients and health care workers in an outbreak, he says.

“This is an interesting study, and it’s the way one wants to go with these viruses,” says Stephan Becker, a virologist at Philipps University in Marburg, Germany. Ebola burst on the scene in 1976 with deadly outbreaks in Zaire and Sudan. But it has been a sporadic menace, racking up about 2,300 victims worldwide. Despite a stunning mortality rate, Becker says, the small numbers suggest that the best strategy against Ebola is to repurpose drugs already cleared for other uses.

While testing an established drug for a new use is faster than starting from scratch, Olinger says, approval of these drugs for Ebola might still take five to 10 years. There is currently no cure for an Ebola infection.

Snails trace Stone Age trek from Iberia to Ireland

Stone Age people may have carried land snails on a voyage from the Pyrenees to Ireland, an examination of the snails’ DNA reveals.

Scientists have struggled to explain why Ireland shares some plant and animal species with the Iberian Peninsula, but not with the rest of Europe or the British Isles. For example, Cepaea nemoralis land snails on Ireland’s western coast and in the southern Pyrenees share unique white-lipped shells.

To find out if the two populations of white-lipped snails are related, Angus Davison and Adele Grindon of the University of Nottingham in England took DNA samples from the species all over Europe. The researchers found that snails in Ireland and the Pyrenees share a variation in one gene that distinguishes them from other European specimens.

The simplest explanation, Davison and Grindon report June 19 in PLOS ONE, is that humans journeying to Ireland about 8,000 years ago brought along escargot as a food source. “Other explanations get quite convoluted,” Davison says.

On the trail of a new virus

A new, deadly respiratory virus spreads easily in hospital settings, a team of investigators has found.

The virus, called the Middle East respiratory syndrome coronavirus, or MERS, reminds Johns Hopkins University epidemiologist Trish Perl of SARS. “The cases are eerily similar,” she says. Perl and two colleagues investigated a SARS outbreak in Toronto 10 years ago. This spring, they helped unravel the chain of infection of a MERS outbreak in Saudi Arabia.

By examining medical records and carefully tracking where patients and hospital personnel had been, Perl’s team discovered that dialysis clinics played an important role in the outbreak. One man, designated Patient C, infected seven others, six of whom had undergone dialysis at the same time he did, the team reports June 19 in the New England Journal of Medicine. Patient C caught MERS from patient A, who was staying in the hospital room next door. Patient A ended up transmitting the virus to three people in total.
Once a person has been infected, it takes an average of 5.2 days for symptoms to appear and 7.6 days for MERS to spread to the next victim, the researchers calculate. MERS seems to spread earlier in the infection than SARS did. It is also more deadly.

SARS infected 8,098 people and killed 9.5 percent of them, or 774 people, between November 2002 and July 2003. To date, MERS has infected 64 people worldwide, killing 38, or about 59 percent. In the Saudi outbreak, 65 percent of the 23 people confirmed to have caught the virus died; most were elderly and had other health problems.

Aerial radar sizes up ancient urban sprawl

Laser pulses beamed from a low-flying airplane into northwestern Cambodia’s dense jungles have revealed ancient remnants of extensive, carefully planned settlements of rice farmers. These settlements were part of Angkor, the capital of the region’s Khmer empire.

Angkor flourished from around 900 to 1500, but forests now obscure much of the city’s urban sprawl. Laser technology called lidar has now seen through the jungle to the ground. It shows that, starting around 1100, roadways and canals formed rectangular grids — much like modern city blocks — around Angkor’s central temples and royal palaces, say archaeologist Damian Evans of the University of Sydney and his colleagues. Similar grids containing villages, ponds and small temples spread out far into the countryside over the next few centuries, covering as many as 1,000 square kilometers, the researchers report June 17 in the Proceedings of the National Academy of Sciences.

New probes of Angkor’s landscape support an increasingly popular idea: The city grew so large that its canals and reservoirs could not provide enough water when severe droughts hit around 1400. Residents may have gradually abandoned Angkor for cities built near rivers, in the region of today’s Phnom Penh.

Cabbage circadian clocks tick even after picking

Cabbages with jet lag are less nutritious and more vulnerable to insect pests.
Fruits and vegetables have an internal clock that can be reset by a daily cycle of light and dark, but storing produce in darkened refrigerators could disrupt this natural rhythm, researchers report June 20 in Current Biology.

Plants, even after being cropped from the stalk, are much more responsive to their external environment than we give them credit for, says Janet Braam, a plant biologist at Rice University. “When we harvest them they’re still metabolizing,” she says. “They’re still alive.”
Braam normally studies circadian rhythms in plants that are growing, but an offhand comment by her son inspired her to turn to the grocery store for new research subjects.

She and her colleagues had previously found that the plant Arabidopsis thaliana schedules production of insect-repelling chemical defenses to match caterpillar feeding peaks. These defenses include compounds called glucosinolates, which are thought to have anticancer and antimicrobial properties in addition to their caterpillar-discouraging ones.

When Braam told her son about these experiments, he joked that now he knew the best time to eat his vegetables. She realized that cabbages — which also produce glucosinolates — might have similar daily cycles even after being picked, packed and shipped.

“So we went to the grocery store, bought some cabbage and put them under dark/light cycles that were either in phase or out of phase with our insects, and then asked whether the insects could tell the difference,” says Braam.

Like Arabidopsis, the cabbage leaves had daily glucosinolate cycles if the vegetables were exposed to alternating 12-hour periods of light and dark. Caterpillars on a cycle offset by 12 hours to the cabbages’ (so the cabbages’ dawn was the caterpillars’ dusk) ate about 20 times more than did caterpillars on a schedule synchronized to their food. Caterpillars also ate twice as much cabbage if the vegetable had been kept either in constant light or constant darkness.

It’s not just cabbages that adjust daily rhythm to better fend off caterpillars; the team found similar results for spinach, zucchini, sweet potatoes, carrots and blueberries. These fruits and vegetables don’t produce glucosinolates, so they must make some other kind of defenses on a daily cycle, says Braam.

The researchers suggest that we might improve the health benefits and pest resistance of fruits and vegetables by storing them under lighting conditions that mimic day and night. But Cathie Martin, a plant biologist at the John Innes Centre in England, is skeptical. She says most postharvest vegetable losses are from fungal infections, not the insects that eat vegetables in the field. And cabbages are sometimes cold-stored for months in the dark before being sold. Cabbages lose the clock-regulated pest resistance about a week after harvesting, the new study shows.

“But maybe I’ll be proven completely wrong,” says Martin. “Maybe one day we’ll all have little LEDs in the fridge.”

Human brain mapped in 3-D with high resolution

A new 3-D map of the brain is the best thing since sliced cold cuts, at least to some neuroscientists.
“It’s a remarkable tour-de-force to reconstruct an entire human brain with such accuracy,” says David Van Essen, a neuroscientist at Washington University in St. Louis.

Using a high-tech deli slicer and about 100,000 computer processors, researchers shaved a human brain into thousands of thin slivers and then digitally glued them together. The result is the most detailed brain atlas ever published. Dubbed BigBrain, the digital model has a resolution 50 times greater in each of the three spatial dimensions than currently available maps, researchers report in the June 21 Science.
The difference is like zooming from a satellite view of a city down to the street level, says coauthor Alan Evans, a neuroimaging scientist at McGill University in Montreal.

BigBrain allows researchers to navigate the landscape of the human cortex, the rugged outer layer of the brain. And unlike previous maps, the tool also lets scientists burrow beneath the surface, tunnel through the brain’s hemispheres and step slice-by-slice through high-res structural data.

Around 100 years ago, neuroscientists relied on thick slabs of brain tissue to crudely chart out neural regions. More recently, imaging tools such as MRI have let researchers take a more detailed look. But even the very best MRI maps are still a little fuzzy, says Hanchuan Peng, a computational biologist at the Allen Institute for Brain Science in Seattle.

In 2010, a team of Chinese researchers constructed a digital map of the mouse brain using techniques similar to the ones that produced BigBrain. But until now, no one had done it in humans. Because the human brain is thousands of times bigger than the mouse brain, Evans and colleagues had to massively scale up slicing and computing methods. First, Katrin Amunts and colleagues at the Jülich Research Center in Germany carved the donated brain of a 65-year-old woman into 7,404 ultrathin sheets, each about the thickness of plastic wrap.

Next, researchers stained the sheets to boost contrast, took pictures of each sheet with a flatbed scanner, and then harnessed the processing power from seven supercomputing facilities across Canada to digitally stitch together the images. In all, the researchers analyzed about one terabyte, or 1,000 gigabytes, of image data. That’s about the same amount of data as 250,000 MP3 songs.

“Your laptop would choke if it tried to run a typical image-processing program to look at this dataset,” Evans says.

His team designed a software program that lets researchers dig into BigBrain’s data. Users will be able to pick up the brain, rotate it in any direction and cut through any plane they want. “It’s like a video game,” he says.

Evans hopes BigBrain will provide a digital scaffold for other researchers to layer on different kinds of brain data. Scientists could stack on information about chemical concentrations or electrophysical signals, just as climate and traffic data can be layered onto a geographical map.

The 3-D map could also help researchers interpret data from lower-resolution brain-scanning techniques such as MRI and PET, study coauthor Karl Zilles of the Jülich Research Center said during a press briefing June 19. Overlaying images from these scans onto BigBrain might give neuroimagers a better idea of where exactly damaged tissue lies in diseased brains.

And neurosurgeons might use BigBrain to guide placement of electrodes during deep-brain stimulation for Alzheimer’s or Parkinson’s diseases, he said.

Though all human brains have largely similar architecture, Evans says, every person has subtle shape variations. As a result, he’d like to make maps of more brains for comparison.

Now that the teams have ironed out BigBrain’s technical kinks, the researchers think they can compile a second brain’s map in about a year. “The computational tools are all largely in place now,” Evans says.

Some infertile men have heightened cancer risk

Men who don’t produce sperm face nearly three times the risk of cancer compared with the male population average, researchers report June 20 in Fertility and Sterility.

About 4 million men in the United States are infertile, with a host of causes. Of them, about 600,000 men don’t deliver sperm from the testes to the semen at all.

Michael Eisenberg of Stanford University and his colleagues studied the medical records of Texas men who had visited a male health clinic between 1989 and 2009. The men averaged 36 years old when they were examined. Of 2,238 men found to be infertile, about one-fifth didn’t have any sperm in their semen.

Over an average follow-up time of 6.7 years, 10 of the 451 men who didn’t make sperm developed some kind of cancer, making them 2.9 times as likely as similar-aged men in the general Texas population to be diagnosed with cancer. The reason is unclear, the authors say. Men who were infertile for other reasons didn’t face an increased risk of cancer.

First four-quark particle may have been spotted

An exotic subatomic particle could be the first amalgamation of more than three quarks — a fundamental building block of atoms — to be produced experimentally. If it is what physicists think it is, the particle could provide clues about the force that holds nuclei together and perhaps about the earliest moments of the universe.

“We have very solid evidence of an unconventional particle,” says Ronald Poling, a physicist at the University of Minnesota in Minneapolis. “But it’s the interpretation — the possibility that it has four quarks — that makes it very exciting.” The details of the particle, inelegantly named Zc(3900), appear June 17 in Physical Review Letters.
Physicists have known since the 1960s that protons and neutrons are made up of quarks, as are hundreds of other particles. All of these particles can be divided into two categories: mesons, which contain two quarks, and baryons (including protons and neutrons), which contain three.

Over the last decade many physicists, including those at the Belle experiment in Japan and the BESIII experiment in China have fruitlessly searched for particles with more than three quarks. Probing a particle’s insides is tough because physicists can’t see quarks directly. Instead they have to measure all the properties they can for a given particle, such as its mass, charge and decay products, looking for unusual characteristics that can be explained only by a peculiar combination of quarks.

The Belle and BESIII teams were both studying an odd particle called Y(4260) when they realized that it decayed to make another interesting particle, Zc(3900). Its mass, says Poling, who is part of the BESIII team, suggests that it is an electrically neutral meson made up of two quarks with opposite charges, called charm and anticharm. But surprisingly, both teams found that Zc(3900) has an electrical charge.

In fact, Poling says no two-quark or three-quark combinations can explain Zc(3900)’s charge and mass. That is leading physicists to the more exotic and exciting conclusion that the particle consists of four quarks: a charm and an anticharm along with an up and an antidown, which are extremely light and create a net positive charge. “The particle’s charge makes it a smoking gun for a four-quark state,” says Tomasz Skwarnicki, a physicist at Syracuse University in New York.

Assuming the evidence for a four-quark arrangement holds up, the big question will be how those quarks are arranged. Zc(3900) could be a single entity of four quarks, Skwarnicki says, but it could also be a coupling of two mesons, analogous to two atoms linking up to form a molecule.

Poling says that understanding the particle’s internal structure could improve physicists’ understanding of the strong nuclear force, which dictates how quarks bond together to create protons, neutrons and other composite forms of matter.

In addition, physicists believe that just after the Big Bang, matter existed in the form of a hot soup of individual quarks and gluons, particles that carry the strong force. Perhaps, as the universe cooled, that soup solidified into exotic multiquark combinations such as Zc(3900) before breaking up into the particles observed today. “The more complete our picture of all the elementary particles and their interactions,” Poling says, “the better we’ll understand where we started out and how we got to where we are.”