How slow and steady lionfish win the race against fast prey

Lionfish certainly aren’t the fastest predators on the reef, but new research suggests that they can catch swift prey through pure tenacity, gliding slowly in pursuit until the perfect moment to strike.

The finding may help explain part of the lionfish’s impact as an invasive species, and reveal a key hunting strategy that other relatively slow predators use, researchers report August 2 in Proceedings of the Royal Society B.

Festooned with long striped spines, lionfish can make their surreal silhouettes disappear against a coral reef backdrop long enough to stalk and ambush small fish. But the predators also feed in open water where they’re more visible.
Curious about how the predators hunt in plain view, Ashley Peterson, a comparative biomechanist at the University of California, Irvine, and her colleagues placed red lionfish (Pterois volitans) in a tank and recorded them as they chased down a green chromis (Chromis viridis), a small reef fish.

In 14 of the 23 trials, the lionfish successfully gulped down their prey. They also had a high rate of strike success, capturing the chromis in 74 percent of the trials where the lionfish made a strike attempt.

On average, the chromis swam about twice as fast as the lionfish. But many still fell victim to what Peterson and biomechanist Matthew McHenry, also at the University of California, Irvine, call a persistent-predation strategy — the lionfish swim toward a chromis, aiming for its current position, not the direction to intercept its path. And the lionfish’s pursuit is steady and incessant, the team found.

“If they’re interested in something and they want to try to eat it, they just seem to not give up,” Peterson says.

In contrast, the prey fish does bursts of fast swimming along with short pauses.

“Over time, all those pauses add up and allow this lionfish to get closer and closer and closer,” Peterson says. Then the slightest mistake or bit of distraction can doom the prey to the lionfish’s suction-creating jaws.

“This is a good example of ‘slow and steady wins the race,’” says Bridie Allan, a marine ecologist at the University of Otago in Dunedin, New Zealand who was not involved in the research. It would be interesting to see how the unwavering chase plays out in the wild, where there are no spatial restrictions like in a tank, she says.

If lionfish do use the strategy in the wild and prey react similarly, it’s possible that the tactic could contribute to the destructive potential of their invasion in the Caribbean, Western Atlantic and the Mediterranean, where the fish are devouring native ocean animals and disrupting food webs (SN: 7/6/16). But other factors, such as the lionfish’s huge appetite or prolific reproduction, could be more influential on invasiveness.

The persistent-predation strategy may not be exclusive to lionfish, Peterson says. Other predatory fish groups with sluggish swimmers — like straw-shaped trumpetfish (Aulostomus spp.) — could also use it.

In a natural setting, prey that are dodging lionfish and other slow swimmers may have more places to hide, Peterson says. But there are inherent risks in a busy, distracting environment too. “If you’re near a reef or up against the coral, you could get pinned if you aren’t really paying attention,” she says. That’s when determined and hungry slowpokes may have the upper hand.

Spinal stimulation gives some people with paralysis more freedom

By his count, Michel Roccati is on his third life, at least. In the first, he was a fit young man riding his motorcycle around Italy. A 2017 crash in the hills near Turin turned him into the second man, one with a severe spinal cord injury that left him paralyzed from the waist down. Today, the third Michel Roccati works out in his home gym in Turin, gets around with a walker and climbs stairs to visit a friend in a second-story apartment. Today, he says, his life is “completely different than it was before.”

Roccati, age 31, is one of three men who received experimental spinal cord stimulators as part of a clinical trial. All three had completely paralyzed lower bodies. The results have been a stunning success, just as Roccati had hoped. “I fixed in my mind how I was at the end of the project,” he says. “I saw myself in a standing position and walking. At the end, it was exactly what I expected.”
The technology that Roccati and others use, described in the February Nature Medicine, is an implanted array of electrodes that sits next to the spinal cord below the spot severed by the injury. Electrical signals from the device replace the missing signals from the brain, prompting muscles to move in ways that allow stepping, climbing stairs and even throwing down squats in the gym.

Today, Roccati spends time working at the consulting company he owns with his brother and sharing his ongoing physical accomplishments with researchers. “Every week we get a WhatsApp from Michel doing something new,” says study coauthor Robin Demesmaeker, a neural engineer at NeuroRestore, a research and treatment center in Lausanne, Switzerland.
These results and others prove that, with the right technology, people with severe spinal cord injury may be able to stand up and walk again. It’s a remarkable development.

But the really big news in this area goes far beyond walking. Many people with spinal cord injuries deal with problems that aren’t as obvious as paralysis. Low blood pressure, sexual dysfunction and trouble breathing or controlling hands, arms, bladder and bowels can all be huge challenges for people with paralysis as they navigate their daily lives. “These are the things that actually matter to people with spinal cord injuries,” says John Chernesky, who has a spinal cord injury. He works at the nonprofit Praxis Spinal Cord Institute in Vancouver, where he makes sure the priorities and voices of people living with spinal cord injuries are heard and addressed in research.

By figuring out the language of the spinal cord, researchers hope to learn how to precisely fill in the missing commands, bridging the gap left by the injury. The work may pave the way to treat many of these problems flagged by patients as important.

“The research field is changing … embracing all these other aspects,” says neuroscientist Kim Anderson Erisman of MetroHealth Medical Center and Case Western Reserve University in Cleveland. Already, early clinical trials are tackling the less obvious troubles that come with spinal cord injuries. Some of the same scientists that helped Roccati recently showed that similar spinal cord stimulation eased a man’s chronic low blood pressure. Other researchers are improving bladder and bowel function with stimulation. Still more work is focused on hand movements. The technology, and the understanding of how to use it to influence the nerves in the spinal cord, is moving quickly.

Not coincidentally, the way the research is being conducted is shifting, too, says Anderson Erisman, who has a spinal cord injury. “Scientists know the textbook things about spinal cord injuries,” she says. “But that’s not the same thing as living one day in the life with a spinal cord injury.” Involving people with such injuries in studies — as true partners and collaborators, not just subjects — is pushing research further and faster. Such collaboration, she says, “will only make your program stronger.”

These efforts are in the early stages. The stimulators are not available to the vast majority of people who might benefit from them. Only a handful of people have participated in these intense clinical trials so far. It’s unclear how well the results will hold up in larger trials with a greater diversity of volunteers. Also unclear is how attainable the technology will be for people who need it. For now, the research often requires large teams of experts, typically in big cities, with patients needing surgery and months of training the body to respond.

Still, the promise of spinal cord stimulation extends beyond spinal cord injuries. Stimulating nerves on the spinal cord could help people with symptoms from strokes, Parkinson’s disease, multiple sclerosis, cerebral palsy and other disorders in which signals between the brain and body get garbled. Initially, “hardly anyone wanted to believe these [improvements] were happening,” says V. Reggie Edgerton, an integrative biologist at the University of Southern California’s Neurorestoration Center and the Rancho Los Amigos Rehabilitation Center in Downey, Calif. “But now, they’re happening so regularly that it’s undeniable.”

A turnaround
Not so long ago, a serious spinal cord injury was a death sentence. “Prior to World War II, the life expectancy of a person with a spinal cord injury was measured in days or weeks,” Chernesky says. If the injury didn’t kill a person directly, they’d often succumb to respiratory distress or blood poisoning from a bladder infection. “If you lived six months, that was impressive,” he says.

The spinal cord ferries signals between brain and body. Signals from the brain tell leg muscles to contract for a step, blood vessels to expand and the bladder to hold steady until a bathroom is within reach. Signals from the body to the brain carry sensations of moving, pain and touch. When the spinal cord is injured, as it is for an estimated 18,000 or so people each year in the United States alone, these signals are blocked.
Researchers have long dreamed of repairing the damage by bridging the gap, perhaps with stem cells or growth factors that can beckon nerve cells to grow across the scar. The idea of using electricity to stimulate nerves below the site of the injury came, in part, from an accidental observation. In the mid-1970s, scientists were testing spinal cord stimulation as a treatment for severe and chronic pain. One participant happened to be a woman who was paralyzed from multiple sclerosis, a disease in which the body attacks its own nerves. With the device implanted on her spinal cord to ease pain, she was able to move again. That surprising discovery helped spark interest in spinal cord stimulation as a way to restore movement.

In 2011, researchers at the University of Louisville in Kentucky restored the ability to stand to a 23-year-old man with paraplegia. In 2018, that group and two others reported even greater strides in spinal stimulation: People with severe spinal cord injuries could step and walk with assistance (SN: 12/22/18 & 1/5/19, p. 30).

Earlier this year, Demesmaeker and his colleagues, including Grégoire Courtine of the Swiss Federal Institute of Technology in Lausanne, published the achievements of Roccati and two other men. All three men had been unable to move their lower limbs or feel any sensations there.

Most previous studies had relied on an electrode array designed and approved by the U.S. Food and Drug Administration to treat chronic pain. That device has electrodes that are implanted along the spinal cord, where their electrical jolts can ease long-term pain in the back and legs. But Roccati and the two other men received a specially designed device that was slightly longer and wider than that earlier device, able to cover more of the spinal cord’s nerve roots and provide more stimulation options.

Several weeks after surgery, the men visited the laboratory in Lausanne to start searching for the optimal stimulation settings. The timing, pattern and strength of the electrode signals were adjusted to allow Roccati to move. “We found a good sequence with the engineers that allowed me to stand up and see my body standing in the mirror in front of me,” Roccati says. “It was a very emotional moment. A standing ovation appeared from everyone in there.”

That first day, he took steps with the stimulation while being supported by a harness. That quick improvement is important, says biomedical engineer Ismael Seáñez of Washington University in St. Louis. “From day one, you can start training.” After months of intense practice (four to five sessions a week for one to three hours at a time), Roccati could walk without the harness, using only a walker.

The men in the trial have all been getting stronger, even when the stimulation is off. That suggests that there’s some sort of repair happening in the body, perhaps due to stronger neural pathways in the spinal cord. Just how the stimulation repairs the spinal cord is one of the big remaining mysteries.

“It’s exciting to see,” Seáñez says. “But it’s a first step in all of the different challenges faced by people with spinal cord injuries.”
Signaling blood vessels
One important problem with paralysis is low blood pressure. When the spinal cord is damaged, the signals that keep blood vessels constricted and blood pressure normal can get lost. Low blood pressure can leave people mentally foggy, exhausted and prone to fainting, not ideal conditions for physical rehab work. Blood pressure can also rise or fall quickly, upping the risk for stroke and heart attack. That’s a huge problem, says Aaron Phillips, who studies the physiology of the nervous system at the University of Calgary in Canada. “Blood pressure is one of the vital signs of life,” he says.

So Phillips, Courtine and colleagues decided to implant a spinal cord stimulator to see if it would help a man who had low blood pressure due to a spinal cord injury. When the machine was on, his blood pressure rose toward normal levels, the researchers reported last year in Nature. When the stimulation was turned off, the man’s blood pressure dropped.

The scientists homed in on an area in the mid-back, just around thoracic segment 11 in the human spine. That spot had the biggest effect on the man’s blood pressure. “We now know that there’s a key area in the spinal cord that, when stimulated, controls neural circuits and the connected blood vessels to elevate and decrease blood pressure,” Phillips says.

The system the researchers developed operated like a thermostat with a set point. In experiments with the man on a tilting table, monitors sensed low blood pressure when the table mimicked standing up. That triggered the stimulators, which in turn told the blood vessels to bring the pressure back up to an acceptable level.

The results represent “a huge pinnacle of my career,” Phillips says. But many challenges remain. The system used in the study in Nature needs tweaking, and the long-term effects of such stimulation aren’t known. Phillips and his colleagues hope to answer these questions. With funding from DARPA, a U.S. Department of Defense agency that invests in breakthrough technologies, the team is working on a wireless blood pressure monitor, and an upcoming clinical trial aims to enroll about 20 people with spinal cord injuries that affect their blood pressure.

Patient priorities
In 2004, Anderson Erisman and her colleagues asked people with spinal cord injuries to share their priorities for regaining function. For people with quadriplegia, who have impairments from the neck down, hand and arm function were most important. For people with paraplegia, who have use of their arms and upper body, sexual function was the highest priority. Both groups emphasized the desire for restored bladder and bowel function, Anderson Erisman and colleagues reported in the Journal of Neurotrauma. Walking was not at the top of either group’s wish list.

That’s no surprise to Chernesky, who uses a wheelchair. “The general population looks at people with spinal cord injuries rolling around in wheelchairs, and they say, ‘Oh, poor bugger. I bet he wishes he could walk,’ ” he says. “They have no idea that quite rapidly after an injury, walking becomes a lower priority.”

Chernesky himself recently participated in a clinical trial designed to externally stimulate the cervical spine, in his neck, to improve arm and hand movements. The device he tested sent signals to the spinal cord through the skin — a less invasive approach than surgery, but one that may sacrifice some specificity compared with implanted versions. Throughout that process, Chernesky noticed improvements in energy, sleep, strength, core stability and movement of both upper and lower limbs.
Other scientists are working on similar ways to externally stimulate the spinal cord to improve people’s autonomic nervous system. That system keeps your blood pressure steady, makes you sweat when it’s hot and tells you when you need to head to a bathroom.

In studies at the University of Southern California and elsewhere, Edgerton and colleagues have recently shown that external stimulation improved bowel function. He and others have also seen stimulators improve bladder function in people with spinal cord injuries and strokes. “We know some subjects can now feel when their bladder is full,” says Edgerton, who started a company called SpineX in 2019 to develop the technology further. That newfound sensation gives people enough time to get to the bathroom. “This doesn’t happen overnight, and it doesn’t happen in every individual,” he cautions. “But it happens a lot.”

Getting past the hype
The next phase of research will be boring — in the best possible way. Large, standardized studies will need to address some mundane but crucial questions, such as who might benefit from stimulation, how much improvement can be made for certain symptoms and whether the therapy causes any extra trouble for some people. “This type of technology will go from a very exciting proof of concept to standard clinical care,” Seáñez predicts.

Over his nearly 30 years of living with a spinal cord injury, Chernesky has witnessed enough so-called scientific breakthroughs to be skeptical. He’s immune to hype. But he admits that he’s excited by this moment. “Because now we can reverse paralysis,” he says. That doesn’t mean people are going to suddenly be tap dancing like Fred Astaire or playing a Chopin concerto anytime soon, he’s quick to add. “But every little bit matters.”

Roccati, for one, no longer has to recruit friends to carry him in his wheelchair up stairs to socialize. He feels more energetic. He is working on his summer six-pack abs. He has transformed, again, into someone new. “Now, after the implant, I am another type of person,” he says, a more optimistic version of himself.
This technology is still a long way from helping everyone who might benefit. Still, these stimulators hold great promise. “I am quite hopeful, almost certain, that these devices are going to become available, and there will be a lot of people buying them,” Chernesky says. “When you have nothing, and you can get a little bit back — how good is that?”

An hour after pigs’ deaths, an artificial system restored cellular life

Call it cellular life support for dead pigs. A complex web of pumps, sensors and artificial fluid can move oxygen, nutrients and drugs into pigs’ bodies, preserving cells in organs that would otherwise deteriorate after the heart stops pumping.

The finding, described August 3 in Nature, is preliminary, but it hints at new ways to keep organs in a body healthy until they can be used for transplantation.

In earlier work, scientists built a machine they named BrainEx, which kept aspects of cellular life chugging along in decapitated, oxygen-deprived pig brains (SN: 4/17/19). The new system, called OrganEx, pushes the approach to organs beyond the brain.
“We wanted to see if we could replicate our findings in other damaged organs across the body, and potentially open the door for future transplantation studies,” says Nenad Sestan, a neuroscientist at Yale University School of Medicine.

OrganEx aims to do the job of hearts and lungs by pumping an artificial fluid throughout pig bodies. Mixed in a 1–1 ratio with the animals’ own blood, the lab-made fluid has ingredients that provide fresh oxygen and nutrients, prevent clots and protect against inflammation and cell death.

Anesthetized pigs were put into cardiac arrest and then left alone for an hour. Then some pigs were placed on an existing medical system, called extracorporeal membrane oxygenation, or ECMO. This adds oxygen to the pigs’ own blood and pumps it into their body. Other pigs received the OrganEx treatment.

Compared with ECMO, OrganEx provided more fluid to tissues and organs, the researchers found. Fewer cells died, and some tissues, including kidneys, even showed cellular signs of repairing themselves from the damage done after the heart stopped.

A similar system might one day be useful for protecting human organs destined to be donated. But for now, “there is still lots of work to be done in our animal model,” Sestan says.

Mini-Neptunes may become super-Earths as the exoplanets lose their atmospheres

Mini-Neptunes and super-Earths may have a lot more in common than just being superlatives.

Four gaseous exoplanets, each a bit smaller than Neptune, seem to be evolving into super-Earths, rocky worlds up to 1.5 times the width of our home planet. That’s because the intense radiation of their stars appears to be pushing away the planets’ thick atmospheres, researchers report in a paper submitted July 26 at If the current rate of atmospheric loss keeps up, the team predicts, those puffy atmospheres will eventually vanish, leaving behind smaller planets of bare rock.
Studying how these worlds evolve and lose their atmospheres can help scientists understand how other exoplanets lose their atmospheres. And that, says astronomer Heather Knutson of Caltech, can provide intel on what types of planets might have habitable environments. “Because if you can’t keep an atmosphere,” she says, “you can’t be habitable.”

Knutson and her colleagues’ new study bolsters a previous suspicion. Earlier this year, the same researchers reported that helium seemed to be escaping the atmosphere of one these mini-Neptunes. But the team wasn’t sure if their discovery was a one-off. “Maybe we just got very lucky for this one planet, but every other planet is different,” says exoplanet researcher Michael Zhang, also of Caltech.

So the team looked at three more mini-Neptunes orbiting other stars and compared those worlds to the first planet they had observed. Each of these planets occasionally blocks some of the light from its star (SN: 7/21/21). Zhang, Knutson and colleagues tracked how long each planet blocked its stars’ light and how much of that starlight was absorbed by helium enveloping the planets. Together, these observations let the team measure the sizes and shapes of the planets’ atmospheres.

“When a planet is losing its atmosphere, you get this big, sort of cometlike tail of gas coming out from the planet,” Knutson says. If the gas instead is still bound to the planet — as is the case for Neptune in our solar system — the astronomers would have seen a circle. “We don’t fully understand all the shapes that we see in the outflows,” she says, “but we see they’re not spherical.”

In other words, each planet is steadily losing its helium. “I never would have guessed that every single planet we looked at, that we would see such a clear detection,” Knutson says.

The astronomers also calculated how much mass those exoplanets were losing (SN: 6/19/17). “This mass loss rate is high enough to strip the atmospheres of at least most of these planets, so that some of them, at least, will become super-Earths,” Zhang says.

These rates, though, are just snapshots in time, says Ian Crossfield, an exoplanet researcher at the University of Kansas in Lawrence who was not involved with this work. For each planet, “you don’t know exactly how it’s been losing atmosphere throughout its entire history and into the future,” he says. “All we know is what we see today.” Even with such open questions, he adds, the idea that mini-Neptunes turn into super-Earths “seems plausible.”

Theories and computer simulations of how planets form and lose their atmospheres can help fill in some of the blanks on individual planets, Crossfield says.

Measurements of more mini-Neptunes will also help. Zhang plans to observe another handful. In addition, “we’ve already looked at one more target, and that target also has a pretty strong escaping helium [signal],” he says. “Now we have five for five.”

Scientists mapped dark matter around galaxies in the early universe

Scientists have mapped out the dark matter around some of the earliest, most distant galaxies yet.

The 1.5 million galaxies appear as they were 12 billion years ago, or less than 2 billion years after the Big Bang. Those galaxies distort the cosmic microwave background — light emitted during an even earlier era of the universe — as seen from Earth. That distortion, called gravitational lensing, reveals the distribution of dark matter around those galaxies, scientists report in the Aug. 5 Physical Review Letters.
Understanding how dark matter collects around galaxies early in the universe’s history could tell scientists more about the mysterious substance. And in the future, this lensing technique could also help scientists unravel a mystery about how matter clumps together in the universe.

Dark matter is an unknown, massive substance that surrounds galaxies. Scientists have never directly detected dark matter, but they can observe its gravitational effects on the cosmos (SN: 7/22/22). One of those effects is gravitational lensing: When light passes by a galaxy, its mass bends the light like a lens. How much the light bends reveals the mass of the galaxy, including its dark matter.

It’s difficult to map dark matter around such distant galaxies, says cosmologist Hironao Miyatake of Nagoya University in Japan. That’s because scientists need a source of light that is farther away than the galaxy acting as the lens. Typically, scientists use even more distant galaxies as the source of that light. But when peering this deep into space, those galaxies are difficult to come by.

So instead, Miyatake and colleagues turned to the cosmic microwave background, the oldest light in the universe. The team used measurements of lensing of the cosmic microwave background from the Planck satellite, combined with a multitude of distant galaxies observed by the Subaru Telescope in Hawaii (SN: 7/24/18). “The gravitational lensing effect is very small, so we need a lot of lens galaxies,” Miyatake says. The distribution of dark matter around the galaxies matched expectations, the researchers report.

The researchers also estimated a quantity called sigma-8, a measure of how “clumpy” matter is in the cosmos. For years, scientists have found hints that different measurements of sigma-8 disagree with one another (SN: 8/10/20). That could be a hint that something is wrong with scientists’ theories of the universe. But the evidence isn’t conclusive.

“One of the most interesting things in cosmology right now is whether that tension is real or not,” says cosmologist Risa Wechsler of Stanford University, who was not involved with the study. “This is a really nice example of one of the techniques that will help shed light on that.”

Measuring sigma-8 using early, distant galaxies could help reveal what’s going on. “You want to measure this quantity, this sigma-8, from as many perspectives as possible,” says cosmologist Hendrik Hildebrandt of Ruhr University Bochum in Germany, who was not involved with the study.

If estimates from different eras of the universe disagree with one another, that might help physicists craft a new theory that could better explain the cosmos. While the new measurement of sigma-8 isn’t precise enough to settle the debate, future projects, such as the Rubin Observatory in Chile, could improve the estimate (SN: 1/10/20).

Relocated beavers helped mitigate some effects of climate change

In the upper reaches of the Skykomish River in Washington state, a pioneering team of civil engineers is keeping things cool. Relocated beavers boosted water storage and lowered stream temperatures, indicating such schemes could be an effective tool to mitigate some of the effects of climate change.

In just one year after their arrival, the new recruits brought average water temperatures down by about 2 degrees Celsius and raised water tables as much as about 30 centimeters, researchers report in the July Ecosphere. While researchers have discussed beaver dams as a means to restore streams and bulk up groundwater, the effects following a large, targeted relocation had been relatively unknown (SN: 3/26/21).
“That water storage is so critical during the drier periods, because that’s what can keep the ecosystem resilient to droughts and fires,” says Emily Fairfax, an ecohydrologist at California State University Channel Islands in Camarillo who was not involved with the study.

The Skykomish River flows down the west side of Washington’s Cascade Mountains. Climate change is already transforming the region’s hydrology: The snowpack is shrinking, and snowfall is turning to rain, which drains quickly. Waters are also warming, which is bad news for salmon populations that struggle to survive in hot water.

Beavers are known to tinker with hydrology too (SN: 7/27/18). They build dams, ponds and wetlands, deepening streams for their burrows and lodges (complete with underwater entrances). The dams slow the water, storing it upstream for longer, and cool it as it flows through the ground underneath.

From 2014 to 2016, aquatic ecologist Benjamin Dittbrenner and colleagues relocated 69 beavers (Castor canadensis) from lowland areas of the state to 13 upstream sites in the Skykomish River basin, some with relic beaver ponds and others untouched. As beavers are family-oriented, the team moved whole clans to increase the chances that they would stay put.

The researchers also matched singletons up with potential mates, which seemed to work well: “They were not picky at all,” says Dittbrenner, of Northeastern University in Boston. Fresh logs and wood cuttings got the beavers started in their new neighborhoods.

At the five sites that saw long-term construction, beavers built 14 dams. Thanks to those dams, the volume of surface water — streams, ponds, wetlands — increased to about 20 times that of streams with no new beaver activity. Meanwhile below ground, wells at three sites showed that after dam construction the amount of groundwater grew to more than twice that was stored on the surface in ponds. Stream temperatures downstream of the dams fell by 2.3 degrees C on average, while streams not subject to the beavers’ tinkering warmed by 0.8 degrees C. These changes all came within the first year after relocation.

“We’re achieving restoration objectives almost instantly, which is really cool,” Dittbrenner says.

Crucially, the dams lowered temperatures enough to almost completely take the streams out of the harmful range for salmon during a particularly hot summer. “These fish are also experiencing heat waves within the water system, and the beavers are protecting them from it,” Fairfax says. “That to me was huge.”

The study also found that small, shallow abandoned beaver ponds were actually warming streams, perhaps because the cooling system had broken down over time. Targeting these ponds as potential relocation sites could be the most effective way to bring temperatures down, the researchers say. When relocated populations establish and breed, young beavers leaving their homes could seek those abandoned spots out first, Dittbrenner says, as it uses less energy than starting from scratch. “If they find a relic pond, it’s game on.”

Herminia Pasantes discovered how taurine helps brain cells regulate their size

When Herminia Pasantes Ordóñez was about 14 years old, in 1950, she heard her mother tell her father that she would never find a husband. Pasantes had to wear thick glasses for her poor eyesight. In her mother’s eyes, those glasses meant her future as a “good woman” was doomed. “This made my life easier,” says Pasantes, “because it was already said that I was going to study.”

At a time when it was uncommon for women to become scientists, Pasantes studied biology at the National Autonomous University of Mexico in Mexico City, or UNAM. She was the first member of her family to go to college.
She became a neurobiologist and one of the most important Mexican scientists of her time. Her studies on the role of the chemical taurine in the brain offer deep insights into how cells maintain their size — essential to proper functioning. In 2001, she became the first woman to earn Mexico’s National Prize for Sciences and Arts in the area of physical, mathematical and natural sciences.

“We basically learned about cell volume regulation through the eyes and work of Herminia,” says Alexander Mongin, a Belarusian neuroscientist at Albany Medical College in New York.

Pasantes did get married, in 1965 while doing her master’s in biochemistry at UNAM. She had a daughter in 1966 and a son in 1967 before starting a Ph.D. in natural sciences in 1970 at the Center for Neurochemistry at the University of Strasbourg in France. There, she worked in the laboratory of Paul Mandel, a Polish pioneer in neurochemistry.

The lab was trying to find out everything there was to know about the retina, the layer of tissue at the back of the eye that is sensitive to light. Pasantes decided to test whether free amino acids, a group that aren’t incorporated into proteins, were present in the retinas and brain of mice. Her first chromatography — a lab technique that lets scientists separate and identify the components of a sample — showed an immense amount of taurine in both tissues. Taurine would drive the rest of her scientific career, including work in her own lab, which she started around 1975 at the Institute of Cellular Physiology at UNAM.

Taurine turns out to be widely distributed in animal tissues and has diverse biological functions, some of which were discovered by Pasantes. Her research found that taurine helps maintain cell volume in nerve cells, and that it protects brain, muscle, heart and retinal cells by preventing the death of stem cells, which give rise to all specialized cells in the body.
Contrary to what most scientists had believed at the time, taurine didn’t work as a neurotransmitter sending messages between nerve cells. Pasantes demonstrated for the first time that it worked as an osmolyte in the brain. Osmolytes help maintain the size and integrity of cells by opening up channels in their membranes to get water in or out.

Pasantes says she spent many years looking for an answer for why there is so much taurine in the brain. “When you ask nature a question, 80 to 90 percent of the time, it responds no,” she says. “But when it answers yes, it’s wonderful.”

Pasantes’ lab was one of the big four labs that did groundbreaking work on cell volume regulation in the brain, says Mongin.

Her work and that of others proved taurine has a protective effect; it’s the reason the chemical is today sprinkled in the containers that carry organs for transplants. Pasantes’ work was the foundation for our understanding of how to prevent and treat brain edema, a condition where the brain swells due to excessive accumulation of fluid, from head trauma or reduced blood supply, for example. She and other experts also reviewed the role of taurine for Red Bull, which added the chemical to its formula because of potentially protective effects in the heart.

Pasantes stopped doing research in 2019 and spends her time talking and writing about science. She hopes her story speaks to women around the world who wish to be scientists: “It is important to send the message that it is possible,” she says.

Years before she was accepted into Mandel’s lab, her application to a Ph.D. in biochemistry at the UNAM was rejected. Pasantes says the reason was that she had just had her daughter. Looking back, this moment was “one of the most wonderful things that could’ve happened to me,” Pasantes says, because she ended up in Strasbourg, where her potential as a researcher bloomed.

Rosa María González Victoria, a social scientist at the Autonomous University of the State of Hidalgo in Pachuca, Mexico, who specializes in gender studies, recently interviewed Pasantes for a book about Mexican women in science. González Victoria thinks Pasantes’ response to that early rejection speaks to the kind of person she is: “A woman that takes those no’s and turns them into yes’s.”

The heaviest neutron star on record is 2.35 times the mass of the sun

A fast-spinning neutron star south of the constellation Leo is the most massive of its kind seen so far, according to new observations.

The record-setting collapsed star, named PSR J0952-0607, weighs about 2.35 times as much as the sun, researchers report July 11 on “That’s the heaviest well-measured neutron star that has been found to date,” says study coauthor Roger Romani, an astrophysicist at Stanford University.

The previous record holder was a neutron star in the northern constellation Camelopardalis named PSR J0740+6620, which tipped the scales at about 2.08 times as massive as the sun. If a neutron star grows too massive, it collapses under its own weight and becomes a black hole. These measurements of hefty neutron stars are of interest because no one knows the exact mass boundary between neutron stars and black holes.
That dividing line drives the quest to find the most massive neutron stars and determine just how massive they can be, Romani says. “It’s defining the boundary between the visible things in the universe and the stuff that is forever hidden from us inside of a black hole,” he says. “A neutron star that’s on the hairy edge of becoming a black hole — just about heavy enough to collapse — has at its center the very densest material that we can access in the entire visible universe.”

PSR J0952-0607 is in the constellation Sextans, just south of Leo. It resides 20,000 light-years from Earth, far above the galaxy’s plane in the Milky Way’s halo. The neutron star emits a pulse of radio waves toward us each time it spins, so astronomers also classify the object as a pulsar. First reported in 2017, this pulsar spins every 1.41 milliseconds, faster than all but one other pulsar.

That’s why Romani and his colleagues chose to study it — the fast spin led them to suspect that the pulsar might be unusually heavy. That’s because another star orbits the pulsar, and just as water spilling over a water wheel spins it up, gas falling from that companion onto the pulsar could have sped up its rotation while also boosting its mass.

Observing the companion, Romani and his colleagues found that it whips around the pulsar quickly — at about 380 kilometers per second. Using the companion’s speed and its orbital period of about six and a half hours, the team calculated the pulsar’s mass to be more than twice the mass of the sun. That’s a lot heavier than the typical neutron star, which is only about 1.4 times as massive as the sun.

“It’s a terrific study,” says Emmanuel Fonseca, a radio astronomer at West Virginia University in Morgantown who measured the mass of the previous record holder but was not involved in the new work. “It helps nuclear physicists actually constrain the nature of matter within these extreme environments.”

Mammal ancestors’ shrinking inner ears may reveal when warm-bloodedness arose

Hot or not? Peeking inside an animal’s ear — even a fossilized one — may tell you whether it was warm- or cold-blooded. Using a novel method that analyzes the size and shape of the inner ear canals, researchers suggest that mammal ancestors abruptly became warm-blooded about 233 million years ago, the team reports in Nature July 20.

Warm-bloodedness, or endothermy, isn’t unique to mammals — birds, the only living dinosaurs, are warm-blooded, too. But endothermy is one of mammals’ key features, allowing the animals to regulate their internal body temperatures by controlling their metabolic rates. This feature allowed mammals to occupy environmental niches from pole to equator, and to weather the instability of ancient climates (SN: 6/7/22).
When endothermy evolved, however, has been a mystery. Based on fossil analyses of growth rates and oxygen isotopes in bones, researchers have proposed dates for its emergence as far back as 300 million years ago.

The inner ear structures of mammals and their ancestors hold the key to solving that mystery, says Ricardo Araújo, a vertebrate paleontologist at the University of Lisbon. In all vertebrates, the labyrinth of semicircular canals in the inner ear contains a fluid that responds to head movements, brushing against tiny hair cells in the ear and helping to maintain a sense of balance. That fluid can become thicker or thinner depending on body temperature.

“Mammals have very unique inner ears,” Araújo says. Compared with cold-blooded vertebrates of similar size, the dimensions of mammals’ semicircular canals — such as thickness, length and radius of curvature — is particularly small, he says. “The ducts are very thin and tend to be very circular compared with other animals.” By contrast, fish have the largest for their body size.

What if, Araújo and his colleagues hypothesized, the size and shape of the ear canals are related to the animal’s body temperature? In warm-blooded animals, the fluid becomes less viscous, and the canals may have shrunk to compensate. If so, it might be possible to trace how the shape of fossilized inner ear canals changed over time to discover when warm-bloodedness emerged in the mammal lineage.

To test that hypothesis, the researchers created a tool they call the “thermo-motility index” to link warm-bloodedness to those inner ear dimensions in 341 different vertebrates. Accounting for size differences, the value of this index turned out to closely track an animal’s body temperature, from fish to reptiles to mammals. Reptiles had low index values; mammals were high.

The team then applied this index to the fossilized ear canals of 56 extinct mammal ancestor species. To their surprise, the data showed a sharp change in inner ear morphology around 233 million years ago. That would correspond to an increase in body temperature of between 5 and 9 degrees Celsius — suggesting that endothermy evolved abruptly around that time, the team concludes.
“The fact that it is a sharp break in the data [suggests] the transition happened rapidly, within about a million years,” says coauthor Kenneth Angielczyk, a paleontologist at the Field Museum in Chicago.

It’s a clever study, says Stephen Brusatte, a paleontologist at the University of Edinburgh who was not involved in the work. “I’ve been using [computed tomography] data to study the shapes of inner ears for years, to try to infer how extinct species moved and how they could hear, and it never occurred to me that inner ear shape is related to metabolism and could be used to predict body temperatures of fossil species.”

However, Brusatte notes that there is a limit to what scientists can glean from fossilized ear canals alone, as they don’t reveal what soft tissues may have been present, such as the hair cells, or the actual viscosity of the ear fluid. “Shape alone may not always be sufficient to predict something as complex as body temperature or metabolic style.”

The timing of the purported shift, about 233 million years ago, corresponds to a geologically brief interlude of highly unstable climate known as the Carnian Pluvial Episode (SN: 9/30/21). “It was a time when global temperatures were changing a lot, and it was also a very wet, humid time,” Angielczyk says. “One of the benefits of endothermy is that it stabilizes the internal body environment, lets you operate independent of environmental conditions.”

The finding highlights how “the whole Triassic was a bit insane,” Araújo says. The start of the Triassic was epically hot, coming on the heels of the “Great Dying” mass extinction at the end of the Permian Period (SN: 12/6/18). Vertebrate species had just begun to recover from that event when they were hit with the Carnian Pluvial Episode. Yet the Triassic also saw the dawn of both mammals and dinosaurs — both of which managed to survive.

It was “a crucial time period in the history of life,” Araújo says. All of that instability may have armed both groups with the evolutionary tools they needed to weather yet another mass extinction at the end of the Triassic 201 million years ago (SN: 7/1/22).

A new technology uses human teardrops to spot disease

Human tears could carry a flood of useful information.

With just a few drops, a new technique can spot eye disease and even glimpse signs of diabetes, scientists report July 20 in ACS Nano.

“We wanted to demonstrate the potential of using tears to detect disease,” says Fei Liu, a biomedical engineer at Wenzhou Medical University in China. It’s possible the droplets could open a window for scientists to peer into the entire body, he says, and one day even let people quickly test their tears at home.
Like saliva and urine, tears contain tiny sacs stuffed with cellular messages (SN: 9/3/13). If scientists could intercept these microscopic mailbags, they could offer new intel on what’s happening inside the body. But collecting enough of these sacs, called exosomes, is tricky. Unlike fluid from other body parts, just a trickle of liquid leaks from the eyes.

So Liu’s team devised a new way to capture the sacs from tiny volumes of tears. First, the researchers collected tears from study participants. Then, the team added a solution containing the tears to a device with two nanoporous membranes, vibrated the membranes and sucked the solution through. Within minutes, the technique lets small molecules escape, leaving the sacs behind for analysis.

The results gave scientists an eyeful. Different types of dry-eye disease shed their own molecular fingerprints in people’s tears, the team found. What’s more, tears could potentially help doctors monitor how a patient’s diabetes is progressing.

Now, the scientists want to tap tears for evidence of other diseases as well as depression or emotional stress, says study coauthor Luke Lee, a bioengineer at Harvard Medical School. “This is just the beginning,” he says. “Tears express something that we haven’t really explored.”