Starling flocks, schools of fish, and clouds of insects all agree.
- Scientists discover that active particles take a pass on Newton's Second Law.
- Active particles exist in a "swirlonic" state of matter.
- Swirlonic behavior explains some of the more dazzling natural phenomena such as starling swarms and shape-shifting schools of fish.
It's likely you've seen some of the fascinating videos of starling murmurations, great swarms of birds mysteriously flying as if with a single mind. These gigantic shapes swoop and swirl, shapeshifting their way through the skies while maintaining miraculous integrity. Maybe you've seen schools of fish shifting together into new shapes in likewise dazzling displays of synchrony.
How do these things happen? Consider them super-sized examples of a newly described state of matter that scientists at the University of Leicester in the U.K. are calling "swirlons." And swirlons are something new: They stand in some ways outside Newtonian law.
Swirlons are described in a paper recently published in Scientific Reports.
Credit: Wikimedia Commons/Big Think
According to Newton's Second Law, the acceleration of an object depends on both the force acting upon it and the object's mass. Its acceleration increases in accordance with the force being exerted, and as its mass increases, the object's acceleration decreases. These things don't happen with swirlons.
It appears that the Second Law relates only to passive, non-living objects at small and large scales. Swirlons, however, are comprised of active, living matter that moves courtesy of its own internal force. In this context, individual starlings are analogous to self-propelled particles within the larger swirlonic object, their flock.
Spotting swirlonic motion
Credit: Johnny Chen/Unsplash
The scientists at Leicester, led by mathematician Nikolai Brilliantov, came upon swirlonic matter as they developed computer models of self-propelled particles similar to simple bacteria or nanoparticles. They were interested in better understanding the movement of human crowds evacuating a crowded space, and these particles served as human stand-ins.
The word "swirlonic" comes from the circular direction in which the scientists witnessed their particles milling about in clusters that operated together as larger quasi-particles.
"We were completely baffled," says Brilliantov, "to witness how these quasi-particles swirl within active matter, behaving like individual super-particles with surprising properties including not moving with acceleration when force is applied, and coalescing upon collision to form swirlons of a larger mass."
Brilliantov tells Live Science, "[They] just move with a constant velocity, which is absolutely surprising."
It's not the first time such behavior has been seen, but the first time it's been identified as a distinct state of matter. Says Brilliantov, "These patterns have previously been observed for animals at different evolution stages, ranging from plant-animal worms and insects to fish, but rather as singular structures, not as a phase which borders other phases, resembling gaseous and liquid phases of 'normal' matter."
The researchers also saw that swirlonic particles operate on a sort of "one for all, all for one" basis. With passive particles such as water, different individual particles can exist in different states: some may evaporate into gas as others remain as liquid. The models of active particles, on the other hand, stuck together in the same state as either a liquid, solid, or gas.
Moving forward, and back, or up, or down together
Brilliantov and his colleagues hope to explore swirlons further, moving beyond their simulation into real-world investigations and experiments.
The researchers are also developing more sophisticated models that mimic the behavior of swirlonic animals such as starlings, fish, and insects. In these models, the active particles will have information-processing capabilities that allow them to make movement decisions as living creatures presumably do. They hope these models will reveal some of the secrets behind flocking, schooling, and swarming.
Another future possibility is creating man-made active particles that can self-assemble. Other Leicester experts agree that this is reason alone to continue researching swirlons.
In any event, says study co-author Ivan Tyukin, "It is always exciting to consider deepening our understanding of novel phenomena and their guiding physical principles. What we know to date is so much less than what there is to know. The phenomenon of the 'swirlon' is part of the tip of the iceberg of hidden knowledge. It leaves us with the eternal question: 'what else don't we know'?"
It's like a little magnetic "nom, nom."
- Venus flytrap leaves shut in response to physical touch, salt water, or thermal stimuli.
- A team of scientists from Berlin have captured the magnetic charge that accompanies the closing of the plant's trap.
- Incredibly sensitive, non-invasive atomic magnetometers picked up the elusive signal.
For many children, the revelation that there's such a thing as a Venus Flytrap, Dionaea muscipula, is an amazing moment. The choppers of the sneaky plant predators are like something out of a fairy tale gone wrong. Adults can't help but be fascinated by them too, and now scientists at Johannes Gutenberg University Mainz (JSU) and the Helmholtz Institute Mainz in Germany have discovered something new that's surprising about these little demons: Every time they entrap prey, they give off a measurable magnetic charge.
"We have been able to demonstrate that action potentials in a multicellular plant system produce measurable magnetic fields, something that had never been confirmed before," says lead author Anne Fabricant.
Guilt as magnetically charged
The plants' bivalved snap trap (left), side view of a destained trap lobe (right)
Credit: Fabricant, et al./Scientific Reports
According to Fabricant, the finding isn't that much of a shock: "Wherever there is electrical activity, there should also be magnetic activity," she tells Live Science. And it is electrical activity in the form of action potentials that trigger its maw—really a pair of leaf lobes—to close when a hapless bug lands inside them, attracted by the nectar with which the plants bait their trap.
Along the inner surfaces of the lobes are trichomes, hair-like projections that cause the trap to close when they're disturbed by prey. One touch of a trichome is unlikely to cause the trap to shut — perhaps a mechanism that helps the plant avoid wasting energy on false alarms. A couple of touches, though, and it's chow time. The lobes come together as the bristles at their edges intertwine to help contain the prey. As the traps compress the trapped insect, its own secretions such as uric acid cause the trap to shut even more tightly, and then digestion begins.
In any event, just because the JSU researchers had reason to suspect the plant would give off a magnetic charge, catching it doing so was not a simple task.
Reading the Venus flytrap's magnetic output
Average action potential and corresponding magnetic signals
Credit: Fabricant, et al./Scientific Reports
"The problem," says Fabricant, "is that the magnetic signals in plants are very weak, which explains why it was extremely difficult to measure them with the help of older technologies." Still, where there's a will: "You could say the investigation is a little like performing an MRI scan in humans."
It's not just trichome flicks that trigger the trap — it will also close if triggered by salt-water, or with an application of either hot or cold thermal energy. The researchers applied heat via a purpose-built Peltier device that wouldn't introduce any background magnetic noise to mask or overwhelm the faint magnetic signal they were seeking. For the same reason, the experiments were conducted in a magnetically shielded room at Physikalisch-Technische Bundesanstalt (PTB) in Berlin.
The researchers used atomic magnetometers to measure the planets magnetic charges. The atomic magnetometer is a glass cell containing a vapor of rubidium atoms. When the traps were triggered, the magnetic charges released changed the spins of the atoms' electrons.
The researchers picked up magnetic signals at an amplitude of up to 0.5 picoteslas. "The signal magnitude recorded is similar to what is observed during surface measurements of nerve impulses in animals," says Fabricant. It's over a million times weaker than the Earth's own magnetic field.
Other researchers have detected magnetic charges coming the firing of animal nerves — including within our own brain. The phenomenon is referred to as "biomagnetism." Since other plants have action potentials, they may also generate biomagnetism, though less research has been done on them.
It's to other plants that the attention of the JSU team now turns, as they go looking for even smaller magnetic charges from other species. In addition to providing new understanding of nature's use of electricity, non-invasive detection technologies such as the one employed by the group could one day be utilized for more insightful monitoring of crops as they respond to thermal, pest, and chemical influences.
An intriguing theory explains animals' magnetic sense.
- Some animals can navigate via magnetism, though scientists aren't sure how.
- Research shows that some of these animals contain magnetotactic bacteria.
- These bacteria align themselves along the magnetic field's grid lines.
It's one of the more fascinating discoveries of the last several decades: the growing list of animals who can navigate the Earth's magnetic grid to get where they need to go. From birds to dogs, from fruit flies to lobsters, a number of species are somehow hooked into the planet's magnetic field — maybe even humans. The big unanswered question is how?
A new paper just published in Philosophical Transactions of the Royal Society B may have the answer: The creatures may have a symbiotic relationship with magnetotactic bacteria that orient them along global magnetic field lines.
While it's possible that the bacteria themselves are just one more magnetically sensitive organism, the paper presents evidence supporting the theory that their presence within other organisms endows their hosts with their magnetic navigational abilities.
Magnetotactic bacteria hosts
A right whale mother and calf
One of the paper's authors, Geneticist Robert Fitak, is affiliated with the biology department of the University of Central Florida in (UCF) Orlando. Prior to joining the department, he spent four years as a postdoctoral researcher at Duke University investigating the genomic mechanisms responsible for magnetic perception in fish and lobsters.
Fitak tells UFC Today, "The search for a mechanism has been proposed as one of the last major frontiers in sensory biology and described as if we are 'searching for a needle in a needle stack.'"
That metaphorical needle stack may well be the scientific community's largest database of microbes, the Metagenomic Rapid Annotations using Subsystems Technology database. It lists the animal samples in which magnetotactic bacteria have been found.
The primary use of the database, says Fitak, has been the measurement of bacterial diversity in entire phyla. An accounting of the appearance of magnetotactic bacteria in individual species is something that has previously be unexplored. "The presence of these magnetotactic bacteria had been largely overlooked, or 'lost in the mud' amongst the massive scale of these datasets," he reports.
Fitak dug into the database and discovered that magnetotactic bacteria have indeed been identified in a number of species known to navigate by magnetism, among them loggerhead sea turtles, Atlantic right whales, bats, and penguins. Candidatus Magnetobacterium bavaricum is regularly found in loggerheads and penguins, while Magnetospirillum and Magnetococcus are common among right whales and bats.
As for other magnetic-field-sensitive animals, he says, "I'm working with the co-authors and local UCF researchers to develop a genetic test for these bacteria, and we plan to subsequently screen various animals and specific tissues, such as in sea turtles, fish, spiny lobsters and birds."
The bacteria-host relationship
While the presence of the bacteria in these particular species is intriguing, further study is needed to be sure they're responsible for other animals' magnetic navigation. Their presence in these species could be just a coincidence.
Fitak also notes that he doesn't know at this point exactly where in the host animal the magnetotactic bacteria would reside, or other details of their symbiotic relationship. He suggests that they might be found in nervous tissue associated with navigation, such as that found in the brain or eye.
If confirmed, Fitak's hypothesis could suggest that our own sensitivity to the Earth's magnetic field might one day be enhanced via magnetotactic bacteria in our own individual microbiomes, should they be benign to us as hosts.
A new study finds that starlet sea anemones have the unique ability to grow more tentacles when they've got more to eat.
- These anemones belong to the Cnidaria phylum that continues developing through its lifespan.
- The starlet sea anemone may grow as many as 24 tentacles, providing there's enough food.
- When deprived of the chance to reproduce, they also grow more tentacles.
By now, you've probably worked out your personal go-to strategy for those times when you discover — a little bit too late — that you've eaten too much. Maybe you're the proactive type, arriving at the table in sweatpants. Otherwise, maybe a quick postprandial nap or a loosened belt is your thing. A new paper published in the journal Nature Communications describes the unique way that starlet sea anemones deal with extra food: They simply grow a pair of new tentacles, as if to make room.
Starlet sea anemone basics
Credit: Smithsonian Environmental Research Center/Flickr
The starlet sea anemone, or Nematostella vectensis, lives burrowed into the mud and silt of coastal salt marshes. Research suggests it's originally native to the east coast of North America, although it can also be found along the continent's west coast, around Nova Scotia, and in U.K. coastal marshes.
Being stationary creatures, starlet sea anemones have to reach out and grab nutrition floating by. Their natural diet is mainly copepods and midge larvae, though they're also perfectly happy eating brine shrimp in a laboratory setting. The anemones grab food with their tentacles whose cilia then wiggle the meal down to their mouths.
In the larval stage, the anemones have a quartet of tentacles, though they may develop up to 24 of them. A more typical amount is 16.
While the starlet sea anemone may grow larger in a lab setting, in the wild its clear, worm-like body typically extends from 10 to 19 millimeters (about three quarters of an inch) in length. Tentacles may add another 8 mm.
Members of the phylum to which the starlet sea anemone belongs, the Cnidaria phylum, have the unique ability to grow new body parts throughout their lives in response to environmental influences. Among these influences are fluctuations in the amount of available food. Nonetheless, no other animal has yet been seen growing new appendages when they get extra sustenance.
Tentacles budding, or not, under different feeding conditions
Credit: Ikmi, et al./Nature Briefing
Observations of starlet sea anemones in his lab prompted lead author of the paper, Aissam Ikmi of the European Molecular Biology Lab Heidelberg, to undertake the new research. He'd noticed what seemed to be an association between the amount of brine shrimp being consumed and the sprouting of new tentacles.
Ikmi and his team raised over 1,100 starlet sea anemone polyps to which they fed brine shrimp. Some of them began with 4 tentacles while the rest already had 16.
For over six months, the researchers varied the animals' food supply at cyclical intervals, feeding the anemones for a few days and then stopping for a few days.
The scientists tracked tentacle growth throughout the experiment, creating a spatio-temporal map that identified periods of tentacle growth in relation to feeding cycles.
They found that the anemones grew new tentacle pairs during feeding periods, and new tentacle production did indeed stop when their food supply was temporarily cut off. Tentacle-pair budding occurred at the same time as an anemone also doubled its body size.
"When food was available, however, primary polyps grew and sequentially initiated new tentacles in a nutrient-dependent manner, arresting at specific tentacle stages in response to food depletion." — Ikmi, et al.
Two ways to bud
In this illustration from the paper, development from 4 to 12 tentacles is characterized by trans budding. Cis budding is present beginning with 16 tentacles.
Credit: Ikmi, et al./Nature Briefing
The team identified two budding modalities, they named "cis" and "trans." In both modes, pairs of tentacles were produced, budding either simultaneously or consecutively. In:
- Trans budding — the two new tentacles budded on opposite sides of the anemone.
- Cis budding — the two new tentacles budded from within the same segment.
No, its not just to keep you warm with hair you don't have.
- A new study suggests that goosebumps are part of a larger system that not only keeps us warm, but also helps hair to heal.
- The sympathetic nerve system reacts to cold air with goose skin. If it stays on long enough, it orders new hair growth.
- The authors note that other, currently unknown, connections between this system and other parts of the body are likely to exist.
Everybody gets goosebumps, but have you ever wondered why? Until now, the leading hypothesis was that by elevating hair-follicles on the skin, goosebumps helped keep the body warm by providing more space for warm air to be collect near the body. However, many scientists have puzzled over this explanation, as the lack of body hair on modern humans leaves us with the ability to have goose skin but without the ability to benefit from it.
Evolutionarily, that makes little sense, if it really was that useless we'd expect more than a few people to not have the ability to get them by now.
A new study published in Cell suggests a different reason for this reaction. Its authors argue that the same cells that cause goosebumps might be responsible for helping hair growth in the first place, giving a reason for evolution to retain this familiar phenomenon.
A hair-raising study
In animals, many organs are made of three kinds of tissue: epithelium, mesenchyme, and nerve. In the skin, which is an organ, a nerve connects to muscle in the mesenchyme. This nerve is part of the sympathetic nervous system and helps maintain homeostasis. The muscle itself is connected to stem cells in the epithelium that heal wounds and regenerate hair follicles.
The researchers focused on mice, as is typical in these studies, but suggest that the findings are also applicable to humans given the similarity between our skin and hair cells.
The researchers examined the behavior and structure of the nerve under an electron microscope. To their surprise, the nerve was not only attached to the previously mentioned muscle tissue but also wrapped around hair follicle stem cells.
In normal conditions, the sympathetic nervous system is always operating at a low level. This keeps the body functioning normally. When the researchers observed this behavior, they noticed signals being sent by the nervous system to the stem cells in the hair follicles. These signals seem to keep the stem cells at the ready for potential use.
However, when the researchers exposed the tissues to the cold, the activity ramped up. A flood of neurotransmitters was released, and the stem cells activated. This prompted new hair growth to begin.
Another experiment dove into how the nerve reached the stem cells in the first place. Co-Author Yulia Shwartz explained the findings in a press release:
"We discovered that the signal comes from the developing hair follicle itself. It secretes a protein that regulates the formation of the smooth muscle, which then attracts the sympathetic nerve. Then in the adult, the interaction turns around, with the nerve and muscle together regulating the hair follicle stem cells to regenerate the new hair follicle. It's closing the whole circle -- the developing hair follicle is establishing its own niche."
Putting this together, it appears that goosebumps are part of a two-phased response to cold. In the first, the muscle below the skin is stimulated to form goosebumps. If this stimulation lasts long enough, the second phase kicks in, with the sympathetic nervous system calling for new hair growth and repairs for the old ones to be made in response to the cold.
This is interesting and all, but what possible application could this information have?
In their press release, the authors suggest that further research can focus on how the body repairs itself in response to environmental stimuli in various situations. The findings also imply that other currently unsuspected connections between the sympathetic nervous system and other parts of the body exist. These potential interactions will undoubtedly be searched for and examined.
Everybody gets goosebumps now and then. We've always assumed we knew why we still get them, even though the hypothesis had some holes. This study's findings show that the benefits of getting goosebumps are more complex than initially thought. It just goes to remind us that we still have much to learn about even the most mundane things.