If you’ve ever felt the urge to tap along to music, this research may strike a chord.
Recognizing rhythms doesn’t involve just parts of the brain that process sound — it also relies on a brain region involved with movement, researchers report online January 18 in the Journal of Cognitive Neuroscience. When an area of the brain that plans movement was disabled temporarily, people struggled to detect changes in rhythms.
The study is the first to connect humans’ ability to detect rhythms to the posterior parietal cortex, a brain region associated with planning body movements as well as higher-level functions such as paying attention and perceiving three dimensions. “When you’re listening to a rhythm, you’re making predictions about how long the time interval is between the beats and where those sounds will fall,” says coauthor Jessica Ross, a neuroscience graduate student at the University of California, Merced. These predictions are part of a system scientists call relative timing, which helps the brain process repetitive sounds, like a musical rhythm.
“Music is basically sounds that have a structure in time,” says Sundeep Teki, a neuroscientist at the University of Oxford who was not involved with the study. Studies like this, which investigate where relative timing takes place in the brain, could be crucial to understanding how the brain deciphers music, he says.
Researchers found hints of the relative timing system in the 1980s, when observing that Parkinson’s patients with damaged areas of the brain that control motion also had trouble detecting rhythms. But it wasn’t clear that those regions were causing patients’ difficulty with timing — Parkinson’s disease can wreak havoc on many areas of the brain. Ross and her colleagues applied magnetic pulses to two different areas of the brain in 25 healthy adults. Those areas — the posterior parietal cortex and the supplementary motor area, which controls movement — were then unable to function properly for about an hour.
Suppressing activity in the supplementary motor area caused no significant change in participants’ ability to follow a beat. But when the posterior parietal cortex was suppressed, all of the adults had trouble keeping rhythm. For example, when listening to music overlaid with beeps that were on the beat as well as off the beat, participants frequently failed to differentiate between the two. This finding suggests the posterior parietal cortex is necessary for relative timing, the researchers say.
The brain has another timing system that was unaffected by the suppression of activity in either brain region: discrete timing, which keeps track of duration. Participants could distinguish between two notes held for different amounts of time. Ross says this suggests that discrete timing is governed by other parts of the brain. Adults also had no trouble differentiating fast and slow tempos, despite tempo’s connection to rhythm, which might imply the existence of a third timing system, Ross says.
Research into how the brain processes time, sound and movement has implications for understanding how humans listen to music and speech, as well as for treating diseases like Parkinson’s.
Still, many questions about the brain’s timing mechanisms remain (SN: 07/25/15, p. 20): What are the evolutionary origins of different timing mechanisms? How do they work in conjunction to create musical perception? And why do most other animals seem to lack a relative timing system?
Scientists are confident that they will have answers — all in good time.
Fishing has left a hefty footprint on Earth. Oceans cover more than two-thirds of the planet’s surface, and industrial fishing occurred across 55 percent of that ocean area in 2016, researchers report in the Feb. 23 Science. In comparison, only 34 percent of Earth’s land area is used for agriculture or grazing.
Previous efforts to quantify global fishing have relied on a hodgepodge of scant data culled from electronic monitoring systems on some vessels, logbooks and onboard observers. But over the last 15 years, most commercial-scale ships have been outfitted with automatic identification system (AIS) transceivers, a tracking system meant to help ships avoid collisions. In the new study, the researchers examined 22 billion AIS positions from 2012 through 2016. Using a computer trained with a type of machine learning, the team then identified more than 70,000 fishing vessels and tracked their activity.
Much of the fishing was concentrated in countries’ exclusive economic zones — ocean regions within about 370 kilometers of a nation’s coastline — and in certain hot spots farther out in the open ocean, the team found. Such hot spots included the northeastern Atlantic Ocean and the nutrient-rich upwelling regions off the coasts of South America and West Africa.
Surprisingly, just five countries — China, Spain, Taiwan, Japan and South Korea — accounted for nearly 85 percent of fishing efforts on the high seas, the regions outside of any country’s exclusive economic zone.
Tracking the fishing footprint in space and time, the researchers note, can help guide marine environmental protections and international conservation efforts for fish. That may be particularly important in a time of rapid change due to rising ocean temperatures and increasing human activity on the high seas.
THE WOODLANDS, Texas — Mars’ missing magnetic field may have drowned in the planet’s core.
An excess of hydrogen, split off from water molecules and stored in the Martian mantle, could have shut down convection, switching the magnetic field off forever, planetary scientist Joseph O’Rourke proposed March 21 at the Lunar and Planetary Science Conference.
Planetary scientists think magnetic fields are produced by the churning of a planet’s molten iron core. Convection relies on denser materials sinking into the core, and lighter stuff rising to the surface. The movement of iron, which can carry a charge, generates a strong magnetic field that can protect a planet’s atmosphere from being ravaged by solar wind (SN Online: 8/18/17). But if lighter material, like hydrogen, settles close to the iron core, it could block dense material from sinking deep enough to keep convection going, said O’Rourke, of Arizona State University in Tempe.
“Too much hydrogen and you can shut down convection entirely,” he said. “Hydrogen is a heartless killer.”
O’Rourke and his ASU colleague S.-H. Dan Shim suggested the hydrogen could come from water locked up in Martian minerals. Near the hot core, water would split into hydrogen and oxygen. The oxygen would form compounds with other elements and stay high in the mantle, but the hydrogen could sit atop the core and effectively suffocate the dynamo. The question is whether Mars’ minerals would have had what it took to deliver the hydrogen at the right time. Mars’ crust is rich in the mineral olivine, which does not bond well with water and so is relatively dry.
In the planet’s interior, pressure forces olivine to transform into the minerals wadsleyite and ringwoodite, which hold more water. Deeper still, the mineral turns into bridgmanite and becomes dry again. For a time, that bridgmanite layer could act as a buffer against water, allowing the core to keep convecting. But as the mantle cooled, the bridgmanite layer would shrink and eventually disappear, O’Rourke’s study suggests.
Whether Mars’ interior ever had that saving layer of bridgmanite depends on how big its core is — a property that may be tested by NASA’s InSight Mars lander, launching on May 5, O’Rourke said. Mars did have a magnetic field more than 4 billion years ago. Scientists have struggled to explain how it vanished, leaving the planet vulnerable to solar winds, which probably stripped away its atmosphere and surface water (SN: 12/12/15, p. 31).
If hydrogen shut down the planet’s generator, it would have had to act fast. Previous observations suggest the magnetic field disappeared relatively rapidly, over 100 million years.
Another theory by James Roberts of the Johns Hopkins Applied Physics Lab in Laurel, Md., suggests a large impact could have shut down the dynamo by heating the outermost core, which would have kept it from sinking.
“It’s actually a similar idea to O’Rourke’s,” Roberts says. It may take many more sophisticated Mars missions to figure out what really happened.
Honeybee royal jelly is food meant to be eaten on the ceiling. And it might also be glue that keeps a royal baby in an upside-down cradle.
These bees raise their queens in cells that can stay open at the bottom for days. A big blob of royal jelly, abundantly resupplied by worker bees, surrounds the larva at the ceiling. Before the food is deposited in the cell, it receives a last-minute jolt of acidity that triggers its proteins to thicken into goo, says Anja Buttstedt, a protein biochemist at Technische Universität Dresden in Germany. Basic larva-gripping tests suggest the jelly’s protein chemistry helps keep future queens from dropping out of their cells, Buttstedt and colleagues propose March 15 in Current Biology. Suspecting the stickiness of royal jelly might serve some function, researchers tweaked its acidity. They then filled small cups with royal jelly with different pH levels and gently turned the cups upside down. At a natural royal jelly acidity of about pH 4.0, all 10 larvae dangled from their gooey blobs upside down overnight. But in jelly boosted to pH 4.8 (and thinned in the process), four of the 10 larvae dropped from the cups. At pH 5.9, all of them dropped.
Honeybees build several forms of royally oversized cells for raising a queen. Those for queens who will swarm with their workers to a new home hang from the rim of an array of regular cells. A hole stays open at the bottom of the cell until the larva nears pupation from her fat grub shape into a queen with wings. That hole at the bottom is big enough for a royal larva to fall through, confirms insect physiologist Steven Cook at the honeybee research lab in Beltsville, Md., run by the U.S. Department of Agriculture’s Agricultural Research Service.
Buttstedt and colleagues propose that the stickiness of royal jelly may be what keeps the larva in place. The team worked out how the jelly’s proteins change as it is made, and how those changes affect its consistency.
Royal jelly is secreted as a brew of proteins from the glands above a worker bee’s brain. At that point, it has a neutral pH, around 7, like water’s. The worker bee then adds fatty acids from glands in her mouthparts, which take the pH to around 4. “It has a quite sour smell,” Buttstedt says. As for taste? “Really weird.” A steady diet of this jelly is what turns a larvae into a queen instead of a worker.
At pH 4, the jelly’s most common protein, MRJP1, goes complicated. When the protein leaves the glands above the brain, it’s clustered in groups of four along with smaller proteins called apisimins, the team found. When the acidity shifts, the MRJP1 foursomes and the apisimins hook together in slender fibers and get gluey.
“The most puzzling question,” Buttstedt says, is “why build upside-down queen cells in the first place?”
Delusional infestation de-LU-zhen-al in-fes-TAY-shun n. A deep conviction that one’s skin is contaminated with insects or other objects despite a lack of medical evidence.
She was certain her skin was infested: Insects were jumping off; fibers were poking out. Fearful her condition could spread to others, the 50-year-old patient told doctors at the Mayo Clinic in Rochester, Minn., that she was avoiding contact with her children and friends.
The patient had delusional infestation, explains Mayo Clinic dermatologist Mark Davis. Sufferers have an unshaking belief that pathogens or inanimate objects pollute their skin despite no medical evidence. Davis and colleagues report online April 4 in JAMA Dermatology that the disorder is not as rare as previously assumed. In the first population-based study of the disorder’s prevalence, the researchers identified 35 cases from 1976 to 2010 reported in Minnesota’s Olmsted County. Based on the findings, the authors estimate 27 out of every 100,000 people in the United States have delusional infestation. Due to the county’s lack of diversity — the population of about 150,000 is predominantly white — the researchers used only the nationwide white population to estimate prevalence, so the result may not be representative of other populations.
Delusional infestation has been recognized for decades, albeit under different names. Patients insist they’ve been overtaken with creatures, such as insects, worms or parasites, or inanimate materials like fibers — or both. “It’s like aliens have infested their skin,” Davis says. Some present bagged samples of the claimed culprits, which turn out to be such debris as sand, dander or, as in the case of the 50-year-old woman, bits of skin and scabs. When lab tests confirm no infestation, patients often seek another opinion rather than accept the findings. Some attempt risky self-treatments, such as bathing in kerosene or bleach, or tweezing or cutting the skin.
Schizophrenia, dementia or other psychiatric illnesses can trigger delusional infestation. So can such drugs as amphetamines or cocaine. But when no other illness is involved, patients often reject the notion that the issue is psychiatric and tend to refuse the antipsychotic medications that can help, Davis says.
As for the 50-year-old patient, upset with the doctors’ diagnosis, she no longer comes to the Mayo Clinic.
Scientists playing peekaboo with dark matter have entered a new stage of the game.
For the first time, physicists are snooping on some of the likeliest hiding places for hypothetical subatomic particles called axions, which could make up dark matter. So far, no traces of the particles have been found, scientists with the Axion Dark Matter Experiment, ADMX, report April 9 in Physical Review Letters. But the researchers have now shown that their equipment is sensitive enough to begin searching in earnest.
An ethereal substance that makes up much of the matter in the universe, dark matter is necessary to explain the motions of stars within galaxies, among other observations. Scientists don’t know what dark matter is, but axions, extremely lightweight particles that may permeate the cosmos, are one of the major contenders.
Most past searches for dark matter particles have focused on a different candidate particle, known as a weakly interacting massive particle, or WIMP. But those efforts have so far come up empty (SN: 11/12/16, p. 14). Now, the spotlight is on the underdog axions. “We have to make sure we are considering all the possibilities,” says theoretical physicist Matthew Buckley of Rutgers University in Piscataway, N.J., who was not involved with the new result. Axions, he says, are a plausible candidate for dark matter.
Axions would produce incredibly feeble signals, so pinning down evidence for the minuscule particles is no easy undertaking. But ADMX, located at the University of Washington in Seattle, is now up to the task, says ADMX member Aaron Chou, a physicist at Fermilab in Batavia, Ill. Previous experiments have searched for axions, but those efforts weren’t sensitive enough to have a good chance of detecting the particles.
“It’s an experimental tour de force; it’s amazing work,” says theoretical physicist Helen Quinn of SLAC National Accelerator Laboratory in Menlo Park, Calif., who was not involved with the research.
ADMX uses what is essentially a supersensitive radio, isolated from external sources of radio waves and cooled to temperatures near absolute zero (‒273.15° Celsius). Scientists use the apparatus to search for axions converting into radio waves in a strong magnetic field. If axions exist, they are expected to interact with photons, particles of light, from the magnetic field. In the process, they would produce radio waves at a frequency that depends on the axion’s mass, which is unknown. Like scanning the dial for a good oldies station, scientists will gradually change the frequency at which they search, trying to “listen in” on the axion signal.
While the new study came up empty, scientists scanned only a small range of frequencies, ruling out some possible masses for axions, from 2.66 to 2.81 microelectron volts. Those tiny masses are less than a billionth of an electron’s mass. In the future, ADMX will study other possible masses. “There’ll be a lot of excitement in the next few years,” Chou says. “A discovery could come at any time.”
Using the precise position and brightness of almost 1.7 billion stars, the Gaia spacecraft has created the most precise 3-D map of the Milky Way yet.
On April 25, the European Space Agency’s Gaia team released the spacecraft’s second batch of data, gathered from July 2014 to May 2016, used to create the map. The tally includes measurements of half a million quasars — the active black holes at the centers of distant galaxies — and 14,099 known solar system objects (mostly asteroids), observations of other nearby galaxies and the amount of dust in between Earth and 87 million stars (SN: 4/14/18, p. 27).The spacecraft also measures the distances and motions of stars by taking advantage of Earth’s motion around the sun, a technique called parallax. As Earth moves, stars appear to trace a small ellipse, whose size is related to the stars’ distance. Measuring the wavelengths of light the stars emit tells how fast they are moving toward or away from the sun. Combining Gaia’s measurements with earlier sky surveys let astronomers track stars’ motions.
Gaia launched in 2013, and released its first batch of data in September 2016 (SN: 10/15/16, p. 16). Those data included distances and motions of roughly 2 million stars; the new data up that number to 1.3 billion.
Knowing those distances will allow astronomers to decipher details about the Milky Way’s shape and history. Already the second data release suggests that the galaxy contains two distinct populations of stars that may have different origins. The stars’ chemistry and motions suggest that some could have originated in a different galaxy that the Milky Way cannibalized long ago.
“With Gaia, we can reconstruct the whole history of the Milky Way,” ESA science director Günther Hasinger said in a news conference April 25.
In Finland, 88 percent of people have a genetic variation that increases their risk for migraines. But in people of Nigerian descent, that number drops to 5 percent.
Coincidence? Maybe. But a new study suggests that, thousands of years ago, that particular genetic mutation increased in frequency in northern populations because it somehow made people better suited to handle cold temperatures. That change may have had the unfortunate consequence of raising the prevalence of these severe headaches in certain populations, researchers report May 3 in PLOS Genetics. The mutation is in a stretch of DNA that controls the behavior of TRPM8, a protein that responds to cold sensation. People with the older version of this DNA snippet seems less susceptible to migraines than people with the mutated version, previous studies have shown.
Using a global database of human genetic information, evolutionary geneticist Aida Andres and her colleagues showed a correlation between the frequency of the mutation in a given population and that population’s latitude. It’s rare in Africa, for example, but fairly common across Europe.
Differences in temperature may have led to this variation, though scientists still aren’t sure exactly how the mutation affects TRPM8. Perhaps the mutation conferred some benefit to early humans who moved north from Africa, says Andres, of University College London. The connection to migraine appears to be a side effect.
The researchers acknowledge, however, that the science of migraines isn’t so simple. One variant can’t fully explain why these headaches are more common in certain populations. Migraine risk is “very complex,” Andres says. “It’s highly heritable, but other things impact it, too.” Plus, there’s still a lot to learn about TRPM8. “We don’t even really know how the entirely normal [protein], with no mutations, contributes to migraine,” says Greg Dussor, a neurobiologist at the University of Texas at Dallas who wasn’t part of the study.
Even the link between migraine and temperature is muddy: While cold temperatures can trigger migraines in some people, heat sets others off.
Choose wisely because in this fantasy you’ll transform into the creature and duel against one of your own. If you care about survival, go for the muscular, multispiked stag roaring at a rival. Never, ever pick the wingless male fig wasp. Way too dangerous.
This advice sounds exactly wrong. But that’s because many stereotypes of animal conflict get the real biology backward. All-out fighting to the death is the rule only for certain specialized creatures. Whether a species is bigger than a breadbox has little to do with lethal ferocity.
Many creatures that routinely kill their own kind would be terrifying, if they were larger than a jelly bean. Certain male fig wasps unable to leave the fruit they hatch in have become textbook examples, says Mark Briffa, who studies animal combat. Stranded for life in one fig, these males grow “big mouthparts like a pair of scissors,” he says, and “decapitate as many other males as they possibly can.” The last he-wasp crawling has no competition to mate with all the females in his own private fruit palace. In contrast, big mammals that inspire sports-team mascots mostly use antlers, horns and other outsize male weaponry for posing, feinting and strength testing. Duels to the death are rare.
“In the vast majority of cases, what we think of as fights are solved without any injuries at all,” says Briffa, of Plymouth University in England.
Evolution has produced a full rainbow of conflict styles, from the routine killers to animals that never touch an adversary. Working out how various species in that spectrum assess when it’s worth their while to go head-to-head has become a challenging research puzzle.“In the vast majority of cases, what we think of as fights are solved without any injuries at all,” says Briffa, of Plymouth University in England.
To untangle the rules of engagement, researchers are turning to animals that live large in small bodies but don’t have sports teams named after them. At least not yet. Deadliest matches It’s hard to imagine nematodes fighting at all. There’s little, if any, weaponry visible on the see-through, micronoodle body of the species called Steinernema longicaudum. Yet in Christine Griffin’s lab at Maynooth University in Ireland, a graduate student offered a rare hermaphrodite to a male as a possible mate. Instead of mating, the male went in for the kill. “We thought, well, poor hermaphrodite, she’s not used to mating, so maybe it’s just some kind of accident,” says Griffin, whose lab specializes in nematodes as pest control for insects. When the grad student, Kathryn O’Callaghan, offered females of another species, males killed some of those females too. When given a chance, males also readily killed each other. That’s how nematodes, in 2014, joined the list of kill-your-own-kind animals, Griffin says. Killing another nematode is an accomplishment for a skinny thread of an animal with just two thin, protruding prongs. The male S. longicaudum slays by repurposing his mating moves.
When he encounters a female of his own species, the male coils his tail around her and positions the prongs, known as spicules, to hold open the entrance to her reproductive tract. To kill, a male just coils his tail around another male, or a female of a different species, and squeezes extra hard. Pressure ruptures internal organs; sometimes spicules even punch a hole during the fatal embrace. The grip lasts from a few seconds to several minutes. Of those worms paralyzed by the attack, most are dead the next day.
Other nematodes live in labs around the world without murdering each other. So why does S. longicaudum, for one, lean toward extreme violence? Its lifestyle of colonizing the innards of an insect inclines it to kill, Griffin suggests. An insect larva is a prize one male worm can monopolize, not to mention the only place he can have sex.
These nematodes lurk in soil without reproducing or even feeding until they find a promising target, such as the pale fat larva of a black vine weevil. Nematodes wriggle in through any opening: the larva’s mouth, breathing pores, anus. If a male kills all rivals inside his new home, he becomes the nematode Adam for generations of offspring perhaps totaling in the hundreds of thousands, Griffin says. Territorial female slayers A defendable bonanza like a weevil larva, or a fig, has become a theme in the evolution of lethal fighting. Biologists have studied violence in certain male fig wasps for decades, but more recent research has revealed that some females kill each other too.
When a female Pegoscapus wasp, a bit longer than a poppy seed, chooses one particular pea-sized sac of flowers, a fig-to-be, she’s deciding her destiny. That sac is most likely her only chance at laying eggs, and will probably be the fruit she will die in, says evolutionary ecologist Charlotte Jandér of Harvard University.
Shortleaf fig trees (Ficus citrifolia) have “a delicate flowery smell,” Jandér says, but the blooms are hidden inside the little green-skinned sacs. To reach these inner riches and lay one egg per flower in as many flowers as she can, the wasp must push through a tight tunnel. The squeeze can take roughly half an hour and rip her wings and antennae. Reaching the inner cavity carpeted in whitish flowers, “there is plenty of space for one wasp to move around,” Jandér says. But more than one gets cramped, and conflicts get desperate.
In a Panamanian wasp species that Jandér has watched, females “can lock on to each other’s jaws for hours and push back and forth,” she says. In a Brazilian species, 31 females were found decapitated among 84 wasps, reported Jandér, Rodrigo A.S. Pereira of the University of São Paulo and colleagues in 2015. That was the first documented female-to-female killing in fig wasps.
Walk away From bellowing red deer stags to confrontational male stalk-eyed flies, many animal species have ways to back off rather than fight to the death. Searching for dynamics of less-than-deadly discord, Briffa studies sea anemones. And yes, anemones fight. Beadlet sea anemones (
Actinia equina
) release sperm and eggs into open seawater, so the animals don’t need to argue over mates. For a prime bit of tide pool rock, however, tensions rise.
Below a beadlet’s pinkish, swaying food-catcher tentacles are what often look like “little blue beads,” Briffa says. These are fighting tentacles, or acrorhagi. When combat looms, the anemone inflates them. “Imagine someone pulling out their bottom lip to make a funny face,” he says.
It’s no joke for an impertinent neighbor. Anemones, distant relatives of stinging jellies, carry harpoon-shooting, toxin-injecting capsules in the acrorhagi. Combatants rake stinger acrorhagi down each other’s soft flesh. “It almost looks like they’re punching each other,” Briffa says. “When one of the anemones decides it’s had enough and wants to quit the contest, it actually actively walks away.”
“Walk” is used loosely here, says Sarah Lane, a postdoc in Briffa’s lab, as she alternately arches her hand and flattens it in a measured trip across the Skype screen. “Like a cartoon caterpillar?” she says, trying to describe the gait. “A concertina?” When placed side by side in the lab for fighting tests, anemones concertina away or otherwise resolve the tension without any acrorhagi swipes about a third of the time. De-escalating makes sense considering that a full exchange “looks quite vicious,” Lane says. Strikes leave behind bluish fragments of acrorhagi full of stinging capsules, which kill tissue on the recipient. The attacker isn’t unscathed either; close-ups show open wounds where acrorhagi tissue was pulled out. An anemone “literally can’t hurt an opponent without ripping parts of itself off,” she says.
Injuries to an attacker from swiping, biting or other acts of aggression get overlooked in theorizing over how animals weigh the costs and benefits of dueling, Lane and Briffa argued in the April 2017 Animal Behaviour. The sea anemones may be an extreme example of self-harm from a strike, but they’re not the only one.
Humans can hurt themselves when they attack, and decision making around fighting has had some unintended consequences, Lane points out. In a bare-handed punch at somebody’s head, little bones in the hand crack — called boxer’s fractures — before the skull does. With the introduction of gloves around 1897, boxer’s fractures basically disappeared from match records, Lane says. Before gloves, however, records show no reported deaths in professional matches. Once gloves lessened the costs of delivering high-impact punches, deaths began appearing in the records.
Worth the fight? Sea anemones don’t have a brain or centralized nervous system, yet costs and benefits of fighting somehow still matter. The animals clearly pick their fights, escalating some blobby sting matches and creeping away from others.
Just how anemones choose, or how any animal chooses when to fight and when to back down, turns out to be a rich vein for research. Theorists have proposed versions of two basic approaches. One, called mutual assessment, “is sussing out when you’re weaker and giving up as soon as you know — that’s the smart way,” Briffa says. Yet the evidence Briffa has so far, he says with perhaps a touch of wistfulness, suggests anemones use “the dumb way of giving up.”
Animals resort to this “dumb” option, called self-assessment, when they can’t compare their opponent’s odds of winning with their own. Maybe they fight in shadowy, murky places. Maybe they don’t have the neural capacity for that kind of comparison. For whatever reason, they’re stuck with “keep going until you can’t keep going anymore,” he says. Never mind if the fight is hopeless from the beginning.
The odds of fighting “smart” look better for the animals that Patrick Green of Duke University studies. Those creatures have a brainlike ganglion and come close to fighting with superpowers. He’s working with, of course, mantis shrimp.
The high-powered smashers among these small crustaceans flick out a club that can accelerate as fast as a bullet shooting out of a .22 caliber pistol. When the clubs wham a tasty snail, the bounce back creates a low-pressure zone that vaporizes water. “I always feel weird saying this because it seems just goofy, but that does release heat equivalent to the surface of the sun,” Green says. But only for a fraction of a microsecond.
When smasher mantis shrimp — male or female — fight each other, they don’t supernova rivals into oblivion. The reality, arguably stranger, is that they superpunch each other. But the blows land on an area that can withstand the force: the telson, a bumpy shield covering the rump (SN: 7/11/15, p. 13).
In Caribbean rock mantis shrimp (Neogonodactylus bredini), the battle is often over after just one to five blows too fast for the human eye to see. With combatants of equal size, the winner is not the animal that lands the most forceful blow, but the one that gets in the most punches. Then, with no visible gore, one dueler just gives up. Now Green and Sheila Patek, also of Duke, propose that telson sparring, as they call it,
permits genuine mutual assessment, the smart way of losing a fight
. It’s difficult to figure out what lurks in the neural circuits of an arthropod, but the researchers presented multiple lines of evidence in the Jan. 31
Proceedings of the Royal Society B.
One strong clue came from matches Green staged between mantis shrimp of different sizes. He didn’t see a trend of smaller ones pointlessly pounding telsons as the lightweights fought bigger animals. Those bigger animals were going to win anyway, and it seemed as if the smaller ones got it, suggesting something more than self-assessment is going on, Green and Patek propose.
Researchers think they have seen mutual assessment in other animals too, among wrestling male New Zealand giraffe weevils (SN: 10/4/14, p. 4) and male jumping spiders that flip up banded legs in “Goal!” position to intimidate rivals. Analyzing assessment gets tricky. Game theorists have weighed in, but there’s debate over what kind of biological evidence truly distinguishes one form of assessment from another. And research in new directions is bringing more biological realism to the discussion of conflicts. Human scientists, dazzled by the sights and sounds that our own sensory world emphasizes, may be underestimating chemical cues. Among crawfish, “part of their fight is squirting urine in one another’s faces,” Briffa says.
Paradoxically peaceful Many of the scariest-looking weapons end up causing little bodily harm. Some are specialized for combat that’s more strategic than gory. Other weapons look so scary they hardly ever get used.
Among the tools for odd but not life-threatening combat are the horns of the male Asian rhinoceros beetles studied by Erin McCullough, now at the University of Western Australia in Perth. Male Trypoxylus dichotomus compete furiously with each other and grow forked horns on their heads that stretch nearly two-thirds the beetle’s body length. The horns are surprisingly lightweight, but look cumbersome. “Like a Styrofoam leg sticking out of your forehead,” she says. She watched the beetles in action on a muggy summer night lurking around ash trees at a university in Taiwan. Hardly blending in with the students, she decked out in leather gloves and a head lamp, making sure her shirts had the collars pulled way up. “You shouldn’t wear mosquito repellant when you’re working with insects,” she says.
The scene was “really messy and chaotic,” she recalls. Beetles flying out of the dark fought to dominate cracks in ash tree bark that oozed sap and attracted females. A dominant beetle would grip the bark and use his horn to flick incoming challengers off the branch left and right — until he was usurped. Getting thrown off the limb doesn’t kill losers; often they buzz right back for another try.
Yet evolutionarily speaking, a male prevented from mating might as well be dead, so the tactic was consequential. Males with longer horns are better at flicking off other males, but longer horns are more likely to snap, McCullough concluded. A broken horn doesn’t grow back, so the extravagant tool needs to be a pry bar of the right length, lightness and strength. Pristine horns on male beetles just starting their fighting careers have about four times the strength the horns need to resist cracking, about the safety factor that engineers build into bridges but less than the standard for elevator cables, she says.
Horns or antlers on male mammals often can kill, yet fatal fights may be rare. One of his favorite studies from decades-old literature, says Douglas Emlen of the University of Montana in Missoula, looked at about 1,308 sparring matches between male caribou in Alaska. With all this glaring, snorting and rushing, only six matches escalated into violent, bloody fights.
The caribou fit one of the paradoxical phases of the evolution of animal weaponry that Emlen studies. Usually evolution doesn’t favor extremes in teeth, horns or other such fighting body parts. Certain forms of sexual rivalry, however, can escape such stabilizing forces and expand extravagantly in a body-part arms race. There are common patterns to such arms races, he says, including some cheating.
Among the conditions that favor an arms race are rivalries playing out in one-on-one duels, he says. Imagine a magnificently endowed dung beetle in a tunnel, a female in the depths behind him, as he fends off rivals one by one for her attention. Growing bigger and bigger horns for an arms race becomes biologically expensive. Eventually, only an animal with the best nutrition, genes and luck can spare the resources to grow a truly commanding horn. At that point, horn size honestly signals a male that can overpower just about all rivals. Only if he confronts another supermale will he need to fight all out. The rest of the time, the signal value of his prodigious weaponry keeps the peace with barely a bump or a bruise.
Yet this is “a very unstable situation,” Emlen says. “It creates incentives for males to cheat.” Or maybe the word is “innovate.” He found that big-horned male dung beetles defending their tunnels could be outmaneuvered by small rivals who dug bypass tunnels around the guard zone and mated with the supposedly defended female. Beetle horns may not be the best analogy for human nuclear arsenals, but, Emlen notes, the innovations of cyberattacks have certainly bypassed hugely expensive national defense systems.
At the far extreme of animal rivalries are some species that blur the meaning of fights. Some butterflies, such as the speckled wood butterfly, “fight” without physical contact. Males compete for a little sunlit dapple on the forest floor by flying furious circles around each other until one gives up and scrams. No gore, but probably really exhausting.
Pity the protons: Those little particles are under a lot of pressure. Protons’ innards are squeezed harder than any other substance we have measured, a new study finds.
“It’s really the highest pressure we have ever seen,” says physicist Volker Burkert, a coauthor of the study, published in the May 17 Nature. Protons break the pressure record set by neutron stars, the incredibly dense dead stars that can form when a massive star explodes and its core collapses, squeezing more mass than the sun’s into a remnant the size of a city. The pressure in the proton’s center averages a million trillion trillion times the strength of Earth’s atmospheric pressure, report Burkert and colleagues, from Thomas Jefferson National Accelerator Facility in Newport News, Va. That’s around 10 times the pressure found inside a neutron star. Previously, scientists had theoretically predicted that such pressures might occur inside protons, but the new result is the first experimental proton pressure gauge.
In proton research, the particle’s internal pressure distribution has been a largely unexplored frontier, even though pressure is one of the proton’s fundamental properties. “It’s as important as electric charge or mass,” says physicist Peter Schweitzer of the University of Connecticut in Storrs, but was unknown until now.
Protons are made up of smaller particles including quarks, which are electrically charged, and gluons, which transmit the strong nuclear force that holds protons together (SN: 4/29/17, p. 22). In the center of this ball of particles, Burkert and colleagues report, an intense pressure pushes outward. But this record-breaking outward force is kept in check by an inward pressure from the outer regions of the particle.
This pressure pattern parallels what happens in much larger objects: “In some sense, it’s looking like a star,” says physicist Oleg Teryaev of the Joint Institute for Nuclear Research in Dubna, Russia. Stars also have pressures that push outward in their centers, which counteract the inward pull of gravity. Protons are held together by the strong force, just as stars are held together by gravity. But the tiny protons are a different beast. So “it’s natural, but it’s not completely trivial” that the two objects would have similarities pressure-wise, Teryaev says. To quantify the proton’s squeeze, the researchers used data from a particle detector known as CLAS, short for the Continuous Electron Beam Accelerator Facility Large Acceptance Spectrometer, located at Jefferson Lab. In experiments with CLAS, scientists shot electrons at liquid hydrogen, a plentiful source of protons, and watched what happened as electrons interacted with the protons’ constituents and ricocheted away. The new measurement is based on data from 2015 that was analyzed for the first time using a technique that could tease out the proton’s pressure.
The experiment, however, studied the quarks in protons, but not gluons, because the energy of the electrons — 6 billion electron volts — was not enough for the electrons to fully probe the protons. To make their pressure estimate, the researchers assumed that the gluons’ pressure contribution was the same as the quarks’, which is in line with some theoretical predictions.
Future particle accelerators, such as the planned Electron-Ion Collider, would allow for gauging the gluons’ contribution to provide a better estimate of the crushing pressure protons endure.
