Tag Archives: #night

Does Bacteria Have Internal Clocks Like Us? (Biology)

Humans have them, so do other animals and plants. Now research reveals that bacteria too have internal clocks that align with the 24-hour cycle of life on Earth.

Shining a light on internal clocks – the bacterium Bacillus subtilis © Professor Ákos Kovács, Technical University of Denmark

The research answers a long-standing biological question and could have implications for the timing of drug delivery, biotechnology, and how we develop timely solutions for crop protection.

Biological clocks or circadian rhythms are exquisite internal timing mechanisms that are widespread across nature enabling living organisms to cope with the major changes that occur from day to night, even across seasons.

Existing inside cells, these molecular rhythms use external cues such as daylight and temperature to synchronise biological clocks to their environment. It is why we experience the jarring effects of jet lag as our internal clocks are temporarily mismatched before aligning to the new cycle of light and dark at our travel destination.

A growing body of research in the past two decades has demonstrated the importance of these molecular metronomes to essential processes, for example sleep and cognitive functioning in humans, and water regulation and photosynthesis in plants.

Although bacteria represent 12% biomass of the planet and are important for health, ecology, and industrial biotechnology, little is known of their 24hr biological clocks.

Previous studies have shown that photosynthetic bacteria which require light to make energy have biological clocks.

But free-living non photosynthetic bacteria have remained a mystery in this regard.

In this international study researchers detected free running circadian rhythms in the non-photosynthetic soil bacterium Bacillus subtilis.

The team applied a technique called luciferase reporting, which involves adding an enzyme that produces bioluminescence that allows researchers to visualise how active a gene is inside an organism.

They focused on two genes: firstly, a gene called ytvA which encodes a blue light photoreceptor and secondly an enzyme called KinC that is involved in inducing formation of biofilms and spores in the bacterium.

They observed the levels of the genes in constant dark in comparison to cycles of 12 hours of light and 12 hours of dark. They found that the pattern of ytvA levels were adjusted to the light and dark cycle, with levels increasing during the dark and decreasing in the light. A cycle was still observed in constant darkness.

Researchers observed how it took several days for a stable pattern to appear and that the pattern could be reversed if the conditions were inverted. These two observations are common features of circadian rhythms and their ability to “entrain” to environmental cues.

They carried out similar experiments using daily temperature changes; for example, increasing the length or strength of the daily cycle, and found the rhythms of ytvA and kinC adjusted in a way consistent with circadian rhythms, and not just simply switching on and off in response to the temperature.

“We’ve found for the first time that non-photosynthetic bacteria can tell the time,” says lead author Professor Martha Merrow, of LMU (Ludwig Maximilians University) Munich. “They adapt their molecular workings to the time of day by reading the cycles in the light or in the temperature environment.”

“In addition to medical and ecological questions we wish to use bacteria as a model system to understand circadian clock mechanisms. The lab tools for this bacterium are outstanding and should allow us to make rapid progress,” she added.

This research could be used to help address such questions as: is the time of day of bacterial exposure important for infection? Can industrial biotechnological processes be optimised by taking the time of day into account? And is the time of day of anti-bacterial treatment important?

“Our study opens doors to investigate circadian rhythms across bacteria. Now that we have established that bacteria can tell the time we need to find out the processes that cause these rhythms to occur and understand why having a rhythm provides bacteria with an advantage,” says author Dr Antony Dodd from the John Innes Centre.

Professor Ákos Kovács, co-author from the Technical University of Denmark adds that “Bacillus subtilis is used in various applications from laundry detergent production to crop protection, besides recently exploiting as human and animal probiotics, thus engineering a biological clock in this bacterium will culminate in diverse biotechnological areas.”

Reference: Zheng Eelderink-Chen, Jasper Bosman, Francesca Sartor, Antony N. Dodd, Ákos T. Kovács, Martha Merrow, “A circadian clock in a non-photosynthetic prokaryote”, Science Advances, Vol. 7, no. 2, eabe2086 DOI: 10.1126/sciadv.abe2086 (https://doi.org/10.1126/sciadv.abe2086) https://advances.sciencemag.org/content/7/2/eabe2086

Provided by John Innes Center

Scientists Discover Why the Heart Slows Down at Night (Biology)

A consensus more than 90-years-old on the mechanisms which regulate the day-night rhythm in heart rate has been fundamentally challenged by an international team of scientists from Manchester, London, Milan, Maastricht, Trondheim and Montpellier.

The vagus nerve—one of the nerves of the autonomic nervous system which supplies internal organs including the heart—has long been thought to be responsible for the slower night-time heart rates.

But the University of Manchester-led study on mice and rats discovered that the vagus nerve is unlikely to be directly involved and instead, the sinus node—the heart’s natural pacemaker—has its own biological clock.

The sinus node, they find, knows when it is night and slows the heart rate accordingly.

The British Heart Foundation funded findings, published in Heart Rhythm, shine new light on this fundamental biological question of why the heart rate is slower at night and why dangerously slow heart rates—called bradyarrhythmias—can occur when we’re asleep.

The team behind the study demonstrated that changes in the ‘funny channel’ – also known as HCN4, a key protein that controls the heart rate—at different times of the day and night can explain the changes in heart rate.

The team found that blocking the funny channel with ivabradine, an angina treatment, removed the difference in heart rate between day and night.

The team found a role for the clock gene called BMAL1 as a regulator of the funny channel and this could one day lead to a treatment for dangerous bradyarrhythmias when we’re asleep.

Though the research was carried out in mice and rats, funny channels and clock genes play similar roles in all mammals—including humans—which is why the research has a universal significance.

Lead author Dr. Alicia D’Souza, a British Heart Foundation Intermediate Fellow from The University of Manchester said: “The heart slows down when we sleep and there can even be pauses between heart beats. Strangely, this is especially true in elite athletes. The longest documented pause is 15 seconds—a very long time to wait for your next heartbeat!

“For the very first time, we have tested an alternative hypothesis that there is a circadian rhythm in the intrinsic pacemaker of the heart—the sinus node. Our study shows that in mice, this is indeed the case and that explains why the heart rate is slower at night. These basic mechanisms of heart rate regulation are conserved in mammals—including humans—and therefore widely accepted concepts that are taught in schools may one day need to be revised.”

The sinus node—sometimes known as the sinoatrial node—generates electrical impulses which cause the heart to beat. It consists of a cluster of cells in the upper part of the right upper chamber of the heart.

Previous assumptions about the vagus nerve’s impact on the heart were based on a technique-called ‘heart rate variability.”

There are over 26,000 scientific papers based on heart rate variability published over 60 years. But the team’s previous British Heart Foundation-funded work demonstrated that heart rate variability is fundamentally flawed and says nothing about the vagus nerve.

In the present study the authors used a range of measurements to assess electrical activity and genes in the heart’s pacemaker. These included studying heart rhythm and activity levels and further exploration of ionic currents, proteins and regulatory proteins called transcription factors.

Cali Anderson, a British Heart Foundation-funded Ph.D. student and co-author added: “It is well known that the resting heart rate in humans varies over 24 hours and is higher during the day than at night. But for over 90 years, the daily changes in our heart rate has been—and we believe over simplistically—assumed to be the result of a more active vagus nerve at night. In the future these findings could have important therapeutic potential in the way we are able to understand and treat heart rhythm disturbances.”

Dr. Noel Faherty, Senior Research Advisor at the BHF, said: “This research challenges a near century old consensus on how heart rate is regulated. “A slower heart rate at night by itself is quite normal in most people, but understanding the mechanisms that govern the heart’s basic functions are crucial building blocks for tackling more complicated questions about heart rhythm disturbances. Worryingly, our ability to fund research like this in the future is threatened by the devastating fall in income caused by coronavirus. It is more important than ever that the public continue to support our work so that we can continue to make progress in treating and preventing heart and circulatory disease in the UK.”

“A circadian clock in the sinus node mediates day-night rhythms in Hcn4 and heart rate” is published in Heart Rhythm.

References: Alicia D’Souza et al. A circadian clock in the sinus node mediates day-night rhythms in Hcn4 and heart rate, Heart Rhythm (2020). DOI: 10.1016/j.hrthm.2020.11.026 https://www.research.manchester.ac.uk/portal/en/publications/a-circadian-clock-in-the-sinus-node-mediates-daynight-rhythms-in-hcn4-and-heart-rate(477ca573-af33-4427-a6e0-052950213849).html

Provided by University of Manchester

Airplane Noise at Night can Trigger Cardiovascular Death (Medicine)

For the first time, a study demonstrated that loud night-time noise from airplanes can trigger a cardiovascular death within two hours. Researchers from the University of Basel, the Swiss Tropical and Public Health Institute (Swiss TPH) and partners compared mortality data with acute night-time noise exposure around Zurich airport between 2000 and 2015. The results of the study have been published in the European Heart Journal.

Airplane noise can trigger cardiovascular death, new study finds. (Image: khunaspix/123RF)

Most studies on transportation noise and cardiovascular mortality have focused on long-term exposure to noise. These studies demonstrated that chronic noise exposure is a risk factor for cardiovascular mortality. Across Europe, 48,000 cases of ischemic heart disease per year can be attributed to noise exposure, in particular to road traffic noise.

For the first time, a study led by researchers at Swiss TPH found that acute noise from airplanes during the night can trigger cardiovascular deaths within two hours of aircraft noise exposure. The study published today in the European Heart Journal found that the risk of a cardiovascular death increases by 33% for night-time noise levels between 40 and 50 decibels and 44% for levels above 55 decibels.

“We found that aircraft noise contributed to about 800 out of 25,000 cardiovascular deaths that occurred between 2000 and 2015 in the vicinity of Zurich airport. This represents three percent of all observed cardiovascular deaths,” said Martin Röösli, Professor of Environmental Epidemiology at the University of Basel and Head of the Environmental Exposures and Health unit at Swiss TPH.

According to Röösli, the results are similar to the effects that emotions such as anger or excitement have on cardiovascular mortality. “This is not so surprising, as we know night-time noise causes stress and affects sleep,” he added. The night-time noise effect was more pronounced in quiet areas with little railway and road traffic background noise and for people living in older houses, which often have less insulation and are thus more noise-prone.

The Zurich airport has a flight curfew from 23:30 to 6:00. “Based on our study results, we can deduce that this night-time flight ban prevents additional cardiovascular deaths,” said Röösli.

Innovative study design to exclude confounding factors

The study used a case-crossover design to evaluate whether aircraft noise exposure at the time of a death was unusually high compared to randomly chosen control time periods. “This study design is very useful to study acute effects of noise exposure with high day-to-day variability such as for airplane noise, given changing weather conditions or flight delays,” said PhD student Apolline Saucy, first author of the study. ”With this temporal analysis approach, we can isolate the effect of unusually high or low levels of noise on mortality from other factors. Lifestyle characteristics such as smoking or diet cannot be a bias in this study design.”

Noise exposure was modelled using a list of all aircraft movements at Zurich Airport between 2000 and 2015 and linking with pre-existing outdoor aircraft noise exposure calculations, specific for aircraft type, air route, time of day and year.

References: Apolline Saucy, Beat Schäffer, Louise Tangermann, Danielle Vienneau, Jean-Marc Wunderli, Martin Röösli, “Does nighttime aircraft noise trigger mortality? A case-crossover study on 24,886 cardiovascual deaths“, European Heart Journal (2020), doi: 10.1093/eurheartj/ehaa957 https://academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehaa957/6007462

Provided by University of Basel

First Image Of AMICal Sat! (Astronomy)

Launched on the night of September 3 at 1:51 am UT (3:51 am French time) on Arianespace’s Vega 16 flight, AMICal SaT, the first nanosatellite of the Grenoble University Space Center (CSUG – UGA/Grenoble INP-UGA), transmitted its first image of dawn to the ground. The first of a long series that will improve knowledge of the polar aurora and help us better understand how solar flares can affect our technological systems.
After a takeoff delayed by many elements, AMICal Sat has been flying at 530km from the Earth for 2 months at a rate of about 15 orbits per day. This time was necessary to test the various functions of the satellite. The satellite works quite well despite a software problem still under investigation concerning the orientation system.

For several weeks now, the operation of the payload (a very bright camera) has been tested, proving that the Grenoble students involved in the project were able, with their supervisors, to produce a space instrument that works.

This is a great success for them, for the CSUG and for all the partners and sponsors brought together by the UGA Foundation!

“The days of October 21 and 22 were periods of moderate geomagnetic activity but we were able to take pictures of polar auroras. 17 photos were taken between 9pm UT (11pm French time) and 10am UT (12pm French time). The pictures were transmitted uncompressed to Earth by the radio link at a fairly high speed (S-band at 2.4 GHz) in several times. After a decoding which takes time, we were able, thanks to the help of the amateur radio community, especially in Grenoble, to process this image. The aurora is weak, the picture required a lot of work: reconstruction of the colors of the scattered RGB matrix and then increasing the contrast. Other photos are currently being processed for further scientific exploitation,” explains Mathieu Barthelemy, Director of the CSUG.

He added: “We would like to especially thank Vladimir Kalegaev (MSU SINP, Russia) who has been working with us since the beginning, as well as Sergei Krasnopeev (NILAKT, Russia), Julien Nicolas (F4HVX, ADRI38, Grenoble, France) and Daniel Estévez (EA4GPZ, Spain) for their help in decoding the radio links. We would also like to thank the whole amateur radio community for the more than 30,000 recovered data packets.”

The black or colored dots on the image are missing data (poor quality radio link at the time of these transmissions).

Picture date: 22 Oct at 8:53 am UTC. The position of the satellite: 141.2° W, 62.9° S close to the Antarctic continent above the Pacific Ocean. Exposure time: 5s

This is only the first of a long series that will improve our knowledge of the polar aurora and, thanks to the modeling work of PhD students, will lead to a better understanding of the impacts of solar activity on our technological systems such as radio communications, power grids and even the satellites themselves.

Provided by UGA

Europa Glows: Radiation Does A Bright Number On Jupiter’s moon (Planetary Science)

As the icy, ocean-filled moon Europa orbits Jupiter, it withstands a relentless pummeling of radiation. Jupiter zaps Europa’s surface night and day with electrons and other particles, bathing it in high-energy radiation. But as these particles pound the moon’s surface, they may also be doing something otherworldly: making Europa glow in the dark.

This illustration of Jupiter’s moon Europa shows how the icy surface may glow on its nightside, the side facing away from the Sun. Variations in the glow and the color of the glow itself could reveal information about the composition of ice on Europa’s surface. Credit: NASA/JPL-Caltech

New research from scientists at NASA’s Jet Propulsion Laboratory in Southern California details for the first time what the glow would look like, and what it could reveal about the composition of ice on Europa’s surface. Different salty compounds react differently to the radiation and emit their own unique glimmer. To the naked eye, this glow would look sometimes slightly green, sometimes slightly blue or white and with varying degrees of brightness, depending on what material it is.

Scientists use a spectrometer to separate the light into wavelengths and connect the distinct “signatures,” or spectra, to different compositions of ice. Most observations using a spectrometer on a moon like Europa are taken using reflected sunlight on the moon’s dayside, but these new results illuminate what Europa would look like in the dark.

“We were able to predict that this nightside ice glow could provide additional information on Europa’s surface composition. How that composition varies could give us clues about whether Europa harbors conditions suitable for life,” said JPL’s Murthy Gudipati, lead author of the work published Nov. 9 in Nature Astronomy.

That’s because Europa holds a massive, global interior ocean that could percolate to the surface through the moon’s thick crust of ice. By analyzing the surface, scientists can learn more about what lies beneath.

Shining a Light

Scientists have inferred from prior observations that Europa’s surface could be made of a mix of ice and commonly known salts on Earth, such as magnesium sulfate (Epsom salt) and sodium chloride (table salt). The new research shows that incorporating those salts into water ice under Europa-like conditions and blasting it with radiation produces a glow.

That much was not a surprise. It’s easy to imagine an irradiated surface glowing. Scientists know the shine is caused by energetic electrons penetrating the surface, energizing the molecules underneath. When those molecules relax, they release energy as visible light.

“But we never imagined that we would see what we ended up seeing,” said JPL’s Bryana Henderson, who co-authored the research. “When we tried new ice compositions, the glow looked different. And we all just stared at it for a while and then said, ‘This is new, right? This is definitely a different glow?’ So we pointed a spectrometer at it, and each type of ice had a different spectrum.”

To study a laboratory mockup of Europa’s surface, the JPL team built a unique instrument called Ice Chamber for Europa’s High-Energy Electron and Radiation Environment Testing (ICE-HEART). They took ICE-HEART to a high-energy electron beam facility in Gaithersburg, Maryland, and started the experiments with an entirely different study in mind: to see how organic material under Europa ice would react to blasts of radiation.

They didn’t expect to see variations in the glow itself tied to different ice compositions. It was—as the authors called it—serendipity.

“Seeing the sodium chloride brine with a significantly lower level of glow was the ‘aha’ moment that changed the course of the research,” said Fred Bateman, co-author of the paper. He helped conduct the experiment and delivered radiation beams to the ice samples at the Medical Industrial Radiation Facility at the National Institute of Standards and Technology in Maryland.

A moon that’s visible in a dark sky may not seem unusual; we see our own Moon because it reflects sunlight. But Europa’s glow is caused by an entirely different mechanism, the scientists said. Imagine a moon that glows continuously, even on its nightside—the side facing away from the Sun.

“If Europa weren’t under this radiation, it would look the way our moon looks to us—dark on the shadowed side,” Gudipati said. “But because it’s bombarded by the radiation from Jupiter, it glows in the dark.”

Set to launch in the mid-2020s, NASA’s upcoming flagship mission Europa Clipper will observe the moon’s surface in multiple flybys while orbiting Jupiter. Mission scientists are reviewing the authors’ findings to evaluate if a glow would be detectable by the spacecraft’s science instruments. It’s possible that information gathered by the spacecraft could be matched with the measurements in the new research to identify the salty components on the moon’s surface or narrow down what they might be.

“It’s not often that you’re in a lab and say, ‘We might find this when we get there,'” Gudipati said. “Usually it’s the other way around—you go there and find something and try to explain it in the lab. But our prediction goes back to a simple observation, and that’s what science is about.”

Missions such as Europa Clipper help contribute to the field of astrobiology, the interdisciplinary research on the variables and conditions of distant worlds that could harbor life as we know it. While Europa Clipper is not a life-detection mission, it will conduct detailed reconnaissance of Europa and investigate whether the icy moon, with its subsurface ocean, has the capability to support life. Understanding Europa’s habitability will help scientists better understand how life developed on Earth and the potential for finding life beyond our planet.

References: Gudipati, M.S., Henderson, B.L. & Bateman, F.B. Laboratory predictions for the night-side surface ice glow of Europa. Nat Astron (2020). https://doi.org/10.1038/s41550-020-01248-1 link: https://www.nature.com/articles/s41550-020-01248-1

Provided by NASA

Are You More Likely to Meet Dark Personalities at Night? (Psychology)

Research reveals why some people prefer to operate after hours.

“Nothing good happens past midnight,” your parents may have warned you, in attempting to rationalize your curfew as a teenager. While that (generous) time restriction might have seemed onerous in retrospect, consider the wisdom behind the words. Researchers have corroborated this parental advice regarding the types of people you are likely to meet after hours.

Dispositional Features of Creatures of the Night

Peter K. Jonason et al. in a piece aptly entitled “Creatures of the Night” (2013) studied the Dark Triad personality and night- versus day-time chronotypes. Recognizing the Dark Triad personality as narcissism, psychopathy, and Machiavellianism, they explored whether in furtherance of what they referred to as a “cheater strategy,” people with high levels of Dark Triad traits would have optimal cognitive performance later in the day, and consequently, a night-time chronotype.

Ultimately, they found the Dark Triad composite to be associated with an evening disposition, particularly with the darker factors of the Dark Triad: secondary (or hostile/reactive) psychopathy, Machiavellianism, and exploitive narcissism.

A Certain Breed of Night Owls

Jonason et al. define chronotype as the propensity to go to bed early or late at night, and to wake up early or late in the morning. Some people are early risers who experience optimal cognitive functioning earlier in the day, while others perform cognitively better late at night. Recognizing that people have the ability for both orientations, Jonason et al. suggest Dark Triad personalities might represent a specialized adaptation for nocturnal living.

Acknowledging prior research, they note that an evening chronotype has been linked to short-term mating success, risk-taking, impulsivity, and extraversion. They also note that an evening chronotype is more commonly linked with individualistic predispositions as opposed to other-oriented, collectivistic dispositions. Regarding gender differences, Jonason et al. found that although men may score higher than women on Dark Triad traits, they found no sex differences in chronotype.

Operating Under the Cover of Darkness

Jonason et al. recognize theoretically, a possible link between the Dark Triad and a night-time chronotype in order to avoid “cheater detection.” They recognize that the Dark Triad traits are characterized by “entitlement, superiority, dominance (i.e., narcissism), glib social charm, manipulativeness (i.e., Machiavellianism), callous social attitudes, impulsivity, and interpersonal antagonism (i.e., psychopathy).” They note that such traits could be adaptive by predisposing people to exploit the advantages of the evening’s cover of darkness. Considering there are fewer people awake, less light, and diminished cognitive processing of people who have a morning disposition, the authors note it is easier to facilitate a “cheater strategy” while avoiding detection.

Consistent with this observation, they note that both sexual and criminal activity reach the highest levels at night. They suggest that Dark Triad individuals who enjoy greater cognitive functioning at night are able to outthink others who would seek to detect and punish them, and would also be less likely to have their activities detected due to “fewer vigilant eyes.”

They conclude that Dark Triad individuals pursuing a “fast life strategy” might find it adaptive to exploit a low-light environment while other people are asleep and experiencing less cognitive functioning. Specifically, they note that nighttime may facilitate Dark Triad-trait-related goals of mate-poaching, casual sex, and risk-taking.

Illuminating Advice After Hours

Does this mean you won’t meet nice people at night? Certainly not. There are plenty of night owls who simply do their best work after hours, and a host of night-shift workers keeping society running while most people are asleep. The key appears to be noticing what type of activities people engage in at night. Are they drinking at a bar or studying at the library? Working at the office or walking the streets? Because around the clock, actions speak louder than words.

References: Jonason, Peter K., Amy Jones, and Minna Lyons. 2013. “Creatures of the Night: Chronotypes and the Dark Triad Traits.” Personality and Individual Differences 55 (5): 538–41. doi:10.1016/j.paid.2013.05.001.

This article is republished here from psychology today under common creative licenses.

Glowing Mice “PKAchu” Shine Light On Night Vision (Biology)

Publishing in PNAS, biologists at Kyoto University report on a previously unknown mechanism in the retina that will perhaps lead to a better understanding of how our eyes see at night. The finding was made possible thanks to mice engineered to change fluorescence when a specific molecule — protein kinase A, or PKA — is activated.

Retinal cells from PKAchu. PKA is activated by darkness only in the stimulated area (Kyoto University/Matsuda Lab)

These ‘PKAchu’ mice were developed to provide researchers with a way of visualizing the activation of one of the body’s most essential and widely studied proteins.

“PKA is found in many cells and is involved in a wide variety of biological processes. It’s natural that researchers would find a way to observe its activities,” explains first author Shinya Sato of the Graduate School of Biostudies.

“PKAchu mice were developed in 2012 — ‘chu’ being Japanese for ‘squeak’— to allow us to closely monitor how PKA acts during specific biological processes. I decided to apply this to my work in retina biology.”

The team first developed a method for recording high resolution, microscopic images of living retinal tissue. They then observed how PKA reacts to light stimulation. Knowing the pathways involved, the team hypothesized that light would deactivate PKA.

But to their surprise, the exact opposite happened.

“We started with a six-second illumination of the tissue. Incredibly, this activated PKA in the selected area for nearly 15 minutes,” continues Sato. “We then did a ten-minute illumination, during which PKA was inactive. But when the lights were turned off, PKA kicked into gear. It was as if the darkness had activated it.”

Single-cell level analysis revealed that this lights-off PKA activation occurred only in rod cells, which are indispensable for our night vision.

Sato hypothesizes that this previously unknown mechanism of rod-specific PKA activation may be a key in boosting light sensitivity in our eyes, contributing to our night vision. Rod-type photoreceptor cells are thought to have evolved from color-sensing cone cells. PKA activation, it now appears, is rod-specific.

Michiyuki Matsuda, the study’s senior author, concludes: “We have not only uncovered many interesting aspects of retinal cells, but the further utility of PKAchu mice as well. We are excited to uncover the mechanisms and purpose behind these new findings, and perhaps illuminate our understanding of conditions such as night blindness.”

References: Shinya Sato, Takahiro Yamashita, and Michiyuki Matsuda (2020). Rhodopsin-mediated light-off-induced protein kinase A activation in mouse rod photoreceptor cells. Proceedings of the National Academy of Sciences of the United States of America. DOI】https://doi.org/10.1073/pnas.2009164117

Provided by Kyoto University

DNA In Fringe-lipped Bat Poop Reveals Unexpected Eating Habits (Biology)

Poop is full of secrets. For scientists, digging into feces provides insights into animal diets and is particularly useful for understanding nocturnal or rare species. When animals eat, prey DNA travels all the way through animal digestive tracts and comes out again. Poop contains very precise information about the prey species consumed. At the Smithsonian Tropical Research Institute (STRI), a team explored the eating habits of the fringe-lipped bat (Trachops cirrhosus) by examining its poop.

Hypothesized approach of a sleeping white-necked jacobin, Florisuga mellivora, by the fringe-lipped bat, Trachops cirrhosus. ©Illustration by Amy Koehler.

Bats hunt at night. This makes it challenging to observe their foraging behavior in nature. Analyzing DNA traces in bat guano offers a more specific way to explore how bats feed in the wild and to study how bat behavior changes depending on their eating habits.

“Because bats forage at night, and in the dense forest, you can’t observe what they are eating the way you can with a diurnal bird or mammal,” said Patricia Jones, former STRI fellow, assistant professor of biology at Bowdoin College and main author of the study. “It feels so momentous, therefore, to have a glimpse into the diet of this species that we thought we knew so much about, to discover they are eating prey we had no idea were part of their diet.”

The fringe-lipped bat, also known as the frog-eating bat, is well adjusted to hunting frogs. The bats’ hearing is adapted to their low-frequency mating calls, and their salivary glands may neutralize the toxins in the skin of poisonous prey. Fringed-lipped bats also feed on insects, small reptiles or birds and other bats. Researchers knew that these bats often find their prey by eavesdropping on mating calls, but it was unknown if they could find prey that was silent.

As expected, most of the DNA recovered from the poop samples in the study belonged to frog species and plenty of lizards, but researchers also found evidence that the bats were eating other bats and even a hummingbird. In additional experiments, wild-caught fringe-lipped bats exposed to recordings of prey sounds and stationary prey models were able to detect silent, motionless prey, as well as prey that made sounds. This led researchers to conclude that the fringe-lipped bat is more capable of locating prey by echolocation than previously thought.

Most of the DNA recovered from the poop samples in the study belonged to frog species and plenty of lizards, but researchers also found evidence that the bats were eating other bats and even a hummingbird. ©Marcos Guerra.

“This is interesting because we didn’t know that these bats were able to detect silent, still prey,” said May Dixon, STRI fellow, doctoral student at the University of Texas at Austin and co-author of the study. “Detecting silent, still prey in the cluttered jungle is thought to be a really hard task for echolocation. This is because when the bats echolocate in the jungle, the echoes of all the leaves and branches bounce back along with the echoes of their prey, and they ‘mask’ the prey.”

These results may offer a new line of research on the sensory abilities and foraging ecology of T. cirrhosus. It also adds to a growing body of work that suggests that, in the tropics, bats may be important nocturnal predators on sleeping animals like birds. The team also found unexpected frog species among its common prey.

“We found T. cirrhosus were often eating frogs in the genus Pristimantis,” Jones said. “I think this will open new avenues of research with T. cirrhosus, because Pristimantis call from the canopy and their calls are hard to localize, so if T. cirrhosus are consuming them it means that they are foraging differently than we understood before.”

Going forward, this novel combination of dietary DNA analysis with behavioral experiments may be used by other ecologists interested in the foraging behaviors of a wide range of animal species.

“It’s really exciting to see the doors that open when animal behavior is combined with metabarcoding,” said STRI staff scientist Rachel Page. “Even though we have studied Trachops intensely for decades, we actually know very little about its behavior in the wild. It was completely surprising to see prey items show up in the diet that we never anticipated, such as frog species whose mating calls seemed to lack acoustic parameters helpful for localization and, more surprising, prey that it seems the bats must have detected by echolocation alone, like hummingbirds. This work makes us rethink the sensory mechanisms underlying this bat’s foraging behavior, and it opens all kinds of new doors for future questions.”

References: Patricia L Jones, Timothy J Divoll, M May Dixon, Dineilys Aparicio, Gregg Cohen, Ulrich G Mueller, Michael J Ryan, Rachel A Page, Sensory ecology of the frog-eating bat, Trachops cirrhosus, from DNA metabarcoding and behavior, Behavioral Ecology, , araa100, https://doi.org/10.1093/beheco/araa100 link: https://academic.oup.com/beheco/advance-article-abstract/doi/10.1093/beheco/araa100/5934110?redirectedFrom=fulltext

Provided by Smithsonian Tropical Research Institute

Sleep Deprivation Eats Your Brain (Neuroscience)

Did you sleep last night? Or did you toss and turn the night away? Or maybe it was school work that kept you up, or cramming for a final. Or maybe you just threw the most epic party the numismatics club had ever seen. Whatever kept you up last night, it didn’t do your brain any favors. Turns out the brain goes full-zombie on itself if it doesn’t get enough sleep.

We’ve already told you sleeping is how your brain tidies up, clipping away unnecessary memories to make room for the next day’s events. But surprisingly, not getting enough sleep doesn’t prevent that trim from occurring. It takes the brakes off it. Astrocytes are the brain cells responsible for that clean-up, and a team of researchers from Italy’s Marche Polytechnic University found that when their mice were deprived of sleep, their astrocytes went into overdrive.

Some mice were given a nightly eight hours of sleep, and some were periodically interrupted to keep them from snoozing too deeply. Some were kept awake for an entire night, and some poor little rodents were forced to stay up five nights straight. The less the mice slept, the more active their astrocytes became. What’s more, the astrocytes in the good-sleep and interrupted-sleep mice stuck to the business of eating brain waste, those in the sleep-deprived category ate parts of working synapses instead. No wonder they say driving without sleep is as bad as driving drunk.

Your brain eating itself is pretty bad news. That kind of damage can lead to some serious problems in the long run. This activity might be a key explanation for diseases like Alzheimer’s, which has already been linked with highly active microglial cells — the same type of cells as astrocytes. As a matter of fact, a lack of sleep is strongly associated with the disease as well. If that’s not a good enough reason to practice good sleep hygiene, we don’t know what is. Here’s a quick primer on healthy sleep habits to help you beat insomnia:

Limit your naps to 30 minutes. Who doesn’t love naps? But they don’t take the place of a good night’s sleep, and might get in the way of one.
Get some exercise. You don’t want to get yourself too energized right before bed. But sometime during the day, try to work up a sweat.
Enjoy natural light. Exposure to sunlight during the day and darkness at night regulates your body clock and gets you sleepy on schedule.
Cut out the screens. Try putting down the phone, stepping away from the computer, and leaving the TV off an hour before bed. It could do wonders.