The search for neutron stars has intensified because of a relatively small area, low in the northern midnight sky, from which the strangest radio signals yet received on Earth are being detected. If the signals come from a star, the source broadcasting the radio waves is very likely the first neutron star ever detected. — Science News, March 16, 1968

Update
That first known neutron star’s odd pulsating signature earned it the name “pulsar.” The finding garnered a Nobel Prize just six years after its 1968 announcement — although one of the pulsar’s discoverers, astrophysicist Jocelyn Bell Burnell, was famously excluded. Since then, astronomers have found thousands of these blinking collapsed stars, which have confirmed Einstein’s theory of gravity and have been proposed as a kind of GPS for spacecraft (SN: 2/3/18, p. 7).

Adult mice and other rodents sprout new nerve cells in memory-related parts of their brains. People, not so much. That’s the surprising conclusion of a series of experiments on human brains of various ages first described at a meeting in November (SN: 12/9/17, p. 10). A more complete description of the finding, published online March 7 in Nature, gives heft to the controversial result, as well as ammo to researchers looking for reasons to be skeptical of the findings.

In contrast to earlier prominent studies, Shawn Sorrells of the University of California, San Francisco and his colleagues failed to find newborn nerve cells in the memory-related hippocampi of adult brains. The team looked for these cells in nonliving brain samples in two ways: molecular markers that tag dividing cells and young nerve cells, and telltale shapes of newborn cells. Using these metrics, the researchers saw signs of newborn nerve cells in fetal brains and brains from the first year of life, but they became rarer in older children. And the brains of adults had none.

There is no surefire way to spot new nerve cells, particularly in live brains; each way comes with caveats. “These findings are certain to stir up controversy,” neuroscientist Jason Snyder of the University of British Columbia writes in an accompanying commentary in the same issue of Nature.

THE WOODLANDS, Texas — Venus’ crust is broken up into chunks that shuffle, jostle and rotate on a global scale, researchers reported in two talks March 20 at the Lunar and Planetary Science Conference.

New maps of the rocky planet’s surface, based on images taken in the 1990s by NASA’s Magellan spacecraft, show that Venus’ low-lying plains are surrounded by a complex network of ridges and faults. Similar features on Earth correspond to tectonic plates crunching together, sometimes creating mountain ranges, or pulling apart. Even more intriguing, the edges of the Venusian plains show signs of rubbing against each other, also suggesting these blocks of crust have moved, the researchers say.
“This is a new way of looking at the surface of Venus,” says planetary geologist Paul Byrne of North Carolina State University in Raleigh.

Geologists generally thought rocky planets could have only two forms of crust: a stagnant lid as on the moon or Mars — where the whole crust is one continuous piece — or a planet with plate tectonics as on Earth, where the surface is split into giant moving blocks that sink beneath or collide with each other. Venus was thought to have one solid lid (SN: 12/3/11, p. 26).

Instead, those options may be two ends of a spectrum. “Venus may be somewhere in between,” Byrne said. “It’s not plate tectonics, but it ain’t not plate tectonics.”

While Earth’s plates move independently like icebergs, Venus’ blocks jangle together like chaotic sea ice, said planetary scientist Richard Ghail of Imperial College London in a supporting talk.
Ghail showed similar ridges and faults around two specific regions on Venus that resemble continental interiors on Earth, such as the Tarim and Sichuan basins in China. He named the two Venusian plains the Nuwa Campus and Lada Campus. (The Latin word campus translates as a field or plain, especially one bound by a fence, so he thought it was fitting.)
Crustal motion may be possible on Venus because the surface is scorching hot (SN: 3/3/18, p. 14). “Those rocks already have to be kind of gooey” from the high temperatures, Byrne said. That means it wouldn’t take a lot of force to move them. Venus’ interior is also probably still hot, like Earth’s, so convection in the mantle could help push the blocks around.

“It’s a bit of a paradigm shift,” says planetary scientist Lori Glaze of NASA’s Goddard Space Flight Center, who was not involved in the new work. “People have always wanted Venus to be active. We believe it to be active, but being able to identify these features gives us more of a sense that it is.”

The work may have implications for astronomers trying to figure out which Earth-sized planets in other solar systems are habitable (SN: 4/30/16, p. 36). Venus is almost the same size and mass as the Earth. But no known life exists on Venus, where the average surface temperature is 462° Celsius and the atmosphere is acidic. Scientists have long speculated that the planet’s apparent lack of plate tectonics might play a role in making the planet so seemingly uninhabitable.

What’s more, the work also underlines the possibility that planets go through phases of plate tectonics (SN: 6/25/16, p. 8). Venus could have had plate tectonics like Earth 1 billion or 2 billion years ago, according to a simulation presented at the meeting by geophysicist Matthew Weller of the University of Texas at Austin.

“As Venus goes, does that predict where the Earth is going in the relatively near future?” he wondered.

“Pop” goes the knuckle — but why?

Scientists disagree over why cracking your knuckles makes noise. Now, a new mathematical explanation suggests the sound results from the partial collapse of tiny gas bubbles in the joints’ fluid.

Most explanations of knuckle noise involve bubbles, which form under the low pressures induced by finger manipulations that separate the joint. While some studies pinpoint a bubble’s implosion as the sound’s source, a paper in 2015 showed that the bubbles don’t fully implode. Instead, they persist in the joints up to 20 minutes after cracking, suggesting it’s not the bubble’s collapse that creates noise, but its formation (SN: 5/16/15, p. 16).
But it wasn’t clear how a bubble’s debut could make sounds that are audible across a room. So two engineers from Stanford University and École Polytechnique in Palaiseau, France, took another crack at solving the mystery.

The sound may come from bubbles that collapse only partway, the two researchers report March 29 in Scientific Reports. A mathematical simulation of a partial bubble collapse explained both the dominant frequency of the sound and its volume. That finding would also explain why bubbles have been observed sticking around in the fluid.

Shimmering, gelatinous comb jellies wouldn’t appear to have much to hide. But their mostly see-through bodies cloak a nervous system unlike that of any other known animal, researchers report in the April 21 Science.

In the nervous systems of everything from anemones to aardvarks, electrical impulses pass between nerve cells, allowing for signals to move from one cell to the next. But the ctenophores’ cobweb of neurons, called a nerve net, is missing these distinct connection spots, or synapses. Instead, the nerve net is fused together, with long, stringy neurons sharing a cell membrane, a new 3-D map of its structure shows.
While the nerve net has been described before, no one had generated a high-resolution, detailed picture of it.

It’s possible the bizarre tissue represents a second, independent evolutionary origin of a nervous system, say Pawel Burkhardt, a comparative neurobiologist at the University of Bergen in Norway, and colleagues.

Superficially similar to jellyfish, ctenophores are often called comb jellies because they swim using rows of beating, hairlike combs. The enigmatic phylum is considered one of the earliest to branch off the animal tree of life. So ctenophores’ possession of a simple nervous system has been of particular interest to scientists interested in how such systems evolved.

Previous genetics research had hinted at the strangeness of the ctenophore nervous system. For instance, a 2018 study couldn’t find a cell type in ctenophores with a genetic signature that corresponded to recognizable neurons, Burkhardt says.

Burkhardt, along with neurobiologist Maike Kittelmann of Oxford Brookes University in England and colleagues, examined young sea walnuts (Mnemiopsis leidyi) using electron microscopes, compiling many images to reconstruct the entire net structure. Their 3-D map of a 1-day-old sea walnut revealed the funky synapse-free fusion between the five sprawling neurons that made up the tiny ctenophore’s net.
The conventional view is that neurons and the rest of the nervous system evolved once in animal evolutionary history. But given this “unique architecture” and ctenophores’ ancient position in the animal kingdom, it raises the possibility that nerve cells actually evolved twice, Burkhardt says. “I think that’s exciting.”

But he adds that further work — especially on the development of these neurons — is needed to help verify their evolutionary origin.

The origins of the animal nervous system is a murky area of research. Sponges — the traditional competitors for the title of most ancient animal — don’t have a nervous system, or muscles or fundamental vision proteins called opsins, for that matter. But there’s been mounting evidence to suggest that ctenophores are actually the most ancient animal group, older even than sponges (SN: 12/12/13).

If ctenophores arose first, it “implies that either sponges have lost a massive number of features, or that the ctenophores effectively evolved them all independently,” says Graham Budd, a paleobiologist at Uppsala University in Sweden who was not involved in the research.

If sponges emerged first, it’s still possible that ctenophores evolved their nerve net independently rather than inheriting it from a neuron-bearing ancestor, Burkhardt says. Ctenophores have other neurons outside the nerve net, such as mesogleal neurons embedded in a ctenophore’s gelatinous body layer and sensory cells, the latter of which may communicate with the nerve net to adjust the beating of the combs. So, it’s possible they’re a mosaic of two nervous systems of differing evolutionary origins.

But Joseph Ryan, a bioinformatician at the University of Florida in Gainesville, doesn’t think the results necessarily point to the parallel evolution of a nervous system. Given how long ctenophores have been around — especially if they are older than sponges — the ancestral nervous system may have had plenty of time to evolve into something weird and highly-specialized, says Ryan, who was not part of the study. “We’re dealing with close to a billion years of evolution. We’re going to expect strange things to happen.”

The findings are “one more bit of the jigsaw puzzle,” Budd says. “There’s a whole bunch we don’t know about these rather common and rather well-known animals.”

For instance, it’s unclear how the nerve net works. Our neurons use rapid changes in voltage across their cell membranes to send signals, but the nerve net might work quite differently, Burkhardt says.

There are reports of potentially similar systems in other animals, such as by-the-wind-sailor jellies (Velella velella). Studying them in detail, along with nerve nets in other ctenophore species, could determine just how unusual this synapse-less nervous system is.

Northern elephant seals are the true masters of the power nap.

On long trips out to sea, the seals snooze less than 20 minutes at a time, researchers report in the April 21 Science. The animals average just two hours of shut-eye per day while swimming offshore for months — rivaling African elephants for the least sleep measured among mammals (SN: 3/1/17).

“It’s important to map these extremes of [sleep behavior] across the animal kingdom to get a better sense of the evolution and the function of sleep for all mammals, including humans,” says Jessica Kendall-Bar, an ecophysiologist at the University of California, San Diego. Knowing how seals catch their z’s could also guide conservation efforts to protect places where they sleep.
Northern elephant seals (Mirounga angustirostris) spend most of the year out in the Pacific Ocean. On these odysseys, the animals forage around the clock for fish, squid and other food to sustain their enormous bodies, which can be as hefty as a car (SN: 2/4/22). Because northern elephant seals are most vulnerable to sharks and killer whales at the surface, they come up for air only a couple minutes at a time between 10- to 30-minute deep dives (SN: 9/28/02).

“People had known that these seals dive almost all the time when they’re out in the ocean, but it wasn’t known if and how they sleep,” says Niels Rattenborg, a neurobiologist at the Max Planck Institute for Biological Intelligence in Seewiesen, Germany, who was not involved in the study.

To find out if the seals sleep while diving, Kendall-Bar and her colleagues developed a watertight EEG cap for the animals. Using the cap and other sensors, the team tracked the brain waves, heart rates and 3-D motion of 13 young female seals, including five at a lab and six hanging out at coastal Año Nuevo State Park north of Santa Cruz, Calif. EEG data recorded while seals were slumbering revealed what the animals’ naptime brain waves looked like.

Kendall-Bar’s team also took two sensor-strapped seals from Año Nuevo and released them at another beach about 60 kilometers south. To swim home, the seals had to cross the deep Monterey Canyon — a locale similar to the deep, predator-fraught waters frequented by seals on months-long foraging trips. Matching the seals’ EEG readings to their diving motions on this journey showed how northern elephant seals sleep on long voyages.

The animals first swim 60 to 100 meters below the surface, then relax into a glide, Kendall-Bar says. As they nod off into slow-wave sleep, the animals keep holding themselves upright for several minutes. But as REM sleep sets in, so does sleep paralysis. The animals flip upside-down and drift in gentle spirals toward the seafloor. Seals can descend hundreds of meters deep during these naps — far below where their predators normally prowl. When the seals wake after five to 10 minutes of sleep, they swim up to the surface. The whole routine takes about 20 minutes.

Looking for that distinct sleep dive motion, the researchers could pick out naps in the dive records of 334 adult seals that had been outfitted with tracking tags from 2004 to 2019. Those sleep patterns revealed that northern elephant seals conk out, on average, around two hours per day while on months-long foraging missions. But the seals sleep nearly 11 hours per day while on land to mate and molt, where they can indulge in long, beachside siestas without worrying about predators.
“What the seals are doing might be something like what we do when we sleep in on the weekend, but it’s on a much longer timescale,” Rattenborg says. He and his colleagues have found a similar feast-and-famine style of sleep in great frigate birds, which fly over the ocean (SN: 6/30/16). “Although they can sleep while they’re flying,” he says, “they sleep less than an hour a day for up to a week at a time, and once back on land, they sleep over 12 hours a day.”

Curiously, northern elephant seals’ sleep habits are quite different from how other marine mammals have been seen sleeping in labs. “Many of them … sleep in just half of their brain at a time,” Kendall-Bar says. That half-awake state allows dolphins, fur seals and sea lions to practice constant vigilance, literally sleeping with one eye open.

“I think it’s pretty cool that elephant seals are doing this without [one-sided] sleep,” Kendall-Bar says. “They’re shutting off both halves of their brain completely and leaving themselves vulnerable.” It seems the key to enjoying such deep sleep is sleeping deep in the sea.

MINNEAPOLIS — Bubbles of radiation billowing from the galactic center may have started as a stream of electrons and their antimatter counterparts, positrons, new observations suggest. An excess of positrons zipping past Earth suggests that the bubbles are the result of a burp from our galaxy’s supermassive black hole after a meal millions of years ago.

For over a decade, scientists have known about bubbles of gas, or Fermi bubbles, extending above and below the Milky Way’s center (SN: 11/9/10). Other observations have since spotted the bubbles in microwave radiation and X-rays (SN: 12/9/20). But astronomers still aren’t quite sure how they formed.
A jet of high-energy electrons and positrons, emitted by the supermassive black hole in one big burst, could explain the bubbles’ multi-wavelength light, physicist Ilias Cholis reported April 18 at the American Physical Society meeting.

In the initial burst, most of the particles would have been launched along jets aimed perpendicular to the galaxy’s disk. As the particles interacted with other galactic matter, they would lose energy and cause the emission of different wavelengths of light.

Those jets would have been aimed away from Earth, so those particles can never be detected. But some of the particles could have escaped along the galactic disk, perpendicular to the bubbles, and end up passing Earth. “It could be that just now, some of those positrons are hitting us,” says Cholis, of Oakland University in Rochester, Mich.

So Cholis and Iason Krommydas of Rice University in Houston analyzed positrons detected by the Alpha Magnetic Spectrometer on the International Space Station. The pair found an excess of positrons whose present-day energies could correspond to a burst of activity from the galactic center between 3 million and 10 million years ago, right around when the Fermi bubbles are thought to have formed, Cholis said at the meeting.

The result, Cholis said, supports the idea that the Fermi bubbles came from a time when the galaxy’s central black hole was busier than it is today.

Since early 2022, sea urchins have been mysteriously dying off across the Caribbean. Now scientists say they have identified the main culprit: a type of relatively large, single-celled marine microorganism called a scuticociliate.

The discovery is a little surprising given that “ciliates are not normally seen as agents of mass mortality,” says Ian Hewson, a marine microbial ecologist at Cornell University. But the evidence, described April 19 in Science Advances, all points to the organism, Philaster apodigitiformis, infecting the urchins, he says. “In all of my years of investigating marine diseases, this is the one which we are 100 percent confident about.”
Scuticociliates are found across the world’s oceans. Given their ubiquity, it’s unknown what conditions may have allowed P. apodigitiformis to become so detrimental to the urchins. It’s also unclear how it causes infection.

While there are no available treatments for the disease, knowing the pathogen’s identity allows for the development of possible options.
Long-spined sea urchins (Diadema antillarum) play a crucial role in Caribbean coral reefs, grazing algae that would otherwise smother corals (SN: 9/27/22). In the 1980s, the urchins nearly disappeared during a massive die-off, the cause of which remains unknown (SN: 6/16/84).

Decades of restoration efforts had made some progress when an alarmingly similar mortality event began to spread in January 2022, wiping out thousands of urchins. This time, scientists across the United States and the Caribbean sprang into action.

Three teams independently reached the same conclusion about P. apodigitiformis, using different approaches. Hewson’s team compared the entire set of active genes, or the transcriptome, of healthy and sick urchins from 23 sites across the Caribbean. The researchers noticed that some of the active genes in the sick urchins’ transcriptomes weren’t from the urchins but from the microorganism. Meanwhile, teams in Florida and Hawaii observed the scuticociliates in the tissues and fluids of sick urchins, reinforcing the genetic finding.

Upon a closer look, the scuticociliates tended to cluster in the sick urchins’ body walls and at the base of their spines. The microorganisms were absent from healthy urchins.
The next step was to isolate the pathogen and infect healthy urchins. Four days after infection, six of 10 infected urchins lost many spines — a common symptom of sick urchins. None of the uninfected urchins lost spines.

“It was really exciting to see,” says Michael Sweet, a marine disease ecologist at the University of Derby in England, who wasn’t involved in the study. “Scary, but also exciting to see the [ciliate’s] name mentioned in a different context because Philaster has never been related to urchin diseases before.” His research points to the involvement of the genus in several coral diseases.

While the scuticociliate clearly plays a pivotal role, Sweet says, there are almost certainly other factors at play, such as other microorganisms or environmental stressors, that could help explain what triggered the start of the recent die-off.

For now, it’s unknown if the same pathogen was involved in the 1980s die-off. Hewson’s team hopes to answer that question by looking at museum specimens from the period.

The classical view of how the human brain controls voluntary movement might not tell the whole story.

That map of the primary motor cortex — the motor homunculus — shows how this brain region is divided into sections assigned to each body part that can be controlled voluntarily (SN: 6/16/15). It puts your toes next to your ankle, and your neck next to your thumb. The space each part takes up on the cortex is also proportional to how much control one has over that part. Each finger, for example, takes up more space than a whole thigh.
A new map reveals that in addition to having regions devoted to specific body parts, three newfound areas control integrative, whole-body actions. And representations of where specific body parts fall on this map are organized differently than previously thought, researchers report April 19 in Nature.

Research in monkeys had hinted at this. “There is a whole cohort of people who have known for 50 years that the homunculus isn’t quite right,” says Evan Gordon, a neuroscientist at Washington University School of Medicine in St. Louis. But ever since pioneering brain-mapping work by neurosurgeon Wilder Penfield starting in the 1930s, the homunculus has reigned supreme in neuroscience.

Gordon and his colleagues study synchronized activity and communication between different brain regions. They noticed some spots in the primary motor cortex were linked to unexpected areas involved in action control and pain perception. Because that didn’t fit with the homunculus map, they wrote it off as a result of imperfect data. “But we kept seeing it, and it kept bugging us,” Gordon says.

So the team gathered functional MRI data on volunteers as they performed various tasks.

Two participants completed simple movements like moving just their eyebrows or toes, as well as complex tasks like simultaneously rotating their wrist and moving their foot from side to side.

The fMRI data revealed which parts of the brain activated at the same time as each task was done, allowing the researchers to trace which regions were functionally connected to one another. Seven more participants were recorded while not doing any particular task in order to look at how brain areas communicate during rest.

Testing only a few participants, each for many hours, offers unique insights into neural connectivity, Gordon says. “When we collect this much data in individuals, we constantly start seeing things that people have never really noticed before.”
The team discovered that while the brain-body part connections vaguely follow the pattern discovered by Penfield, the primary motor cortex is organized into three distinct sections. Each represents different body regions: lower body, torso and arms, and head.

Within each of these sections, the outermost body part of that region is mapped to the center of that section. For example, the area of the primary motor cortex assigned to the lower body has the toes in the middle with other leg parts radiating out in each direction from it. As a result, the entire section is organized like this: hip, knee, ankle, toes, ankle, knee, hip.
The team also unexpectedly found three mysterious spots not linked to a specific body part. Dubbed intereffector regions, they connect to an external network involved in action control and the sensing of pain. These regions alternate with the sections devoted to specific body parts. The team suspects that intereffector regions may integrate action goals and body movements involving multiple body parts, while the spaces in between are used for precise movements of isolated body parts.

Using previous data from three large fMRI studies, which include data from around 50,000 people, the team verified that this organization was consistent across a wide swath of people. Similar patterns also appeared in existing datasets from macaque monkeys, children and clinical populations.

“I think it was just easy to miss anything that seemed anomalous — must be noise,” says Michael Graziano, a neuroscientist at Princeton University who was not involved in the research. But with access to these huge datasets, “you get these vast numbers of subjects, and the pattern is crystal clear, and you can’t ignore it …. This is really the best example I’ve seen in a long, long time of looking at humans and trying to figure out at a detailed level what is the organization.”

Gordon’s team now plans to see whether these intereffector regions play a role in certain kinds of pain. More broadly, the team hopes their findings will prompt more in-depth research of what specific areas of the brain do. With new techniques and equipment, there is much left to explore, Gordon says. “Brain mapping isn’t dead.”

An animal bone fragment full of human-made pits hints at how prehistoric people in Western Europe may have crafted clothing.

The nearly 40,000-year-old artifact probably served as a punch board for leatherwork, researchers report April 12 in Science Advances. They suggest that the bone fragment rested beneath animal hide while an artisan pricked holes in the material, possibly for seams. If so, it’s the earliest-known tool of its kind and predates eyed needles in the region by about 15,000 years.
Found at an archaeological site south of Barcelona, the roughly 11-centimeter-long bone fragment contains 28 punctures scattered across one flat side, with 10 of them aligned and fairly evenly spaced.

The marks don’t seem to have been a notation system or decoration, given that some holes are hard to see and the bone fragment wasn’t otherwise shaped, says archaeologist Luc Doyon of the University of Bordeaux in France. He thought leatherwork could have made the marks. But it wasn’t until he visited a cobbler shop and saw one of the artisan’s tools that the hypothesis solidified, guiding Doyon’s next steps.

He and colleagues attempted to re-create the artifact’s holes by puncturing cattle rib bones with tools including sharpened flint, horns and antlers. Piercing leather atop bone with a burin — a pointed stone chisel — by tapping it with a hammerlike tool created pits that resemble those on the bone fragment.

Further experiments suggested the artifact’s 10 orderly punctures were made by the same tool and intentionally aligned and regularly spaced. This hints that holes were created in the leather to make a seam sewn with a threading tool.

Scientists knew that humans wore clothing long before the oldest-known eyed needles existed (SN: 4/20/10). “What [the new finding] tells us is that the first modern humans who lived in Europe had the technology in their toolkit for making fitted clothes,” Doyon says.