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Tag Archives: Mate
A ‘cataclysmic’ celestial couple gone wrong — a star eats its mate
An artist’s illustration shows a white dwarf and larger, sun-like star forming a “cataclysmic” binary system. (M.Weiss,Center for Astrophysics, Harvard and Smithsonian via Reuters)
Estimated read time: 3-4 minutes
WASHINGTON — Unlike the lonely sun, about half the stars in our Milky Way galaxy are in a long-term committed relationship with another star, orbiting each another in a celestial marriage called a binary system.
Researchers this week described one of these marriages gone wrong — a twosome that borders on the extreme, with the pair whirling around each other every 51 minutes in the fastest such orbital period known for a rare class of binary stars. As part of the drama, one star is eating its companion.
The two stars are located about 3,000 light years from Earth in the direction of the constellation Hercules. A light year is the distance light travels in a year, 5.9 trillion miles.
The system belongs to a class of binary stars known as “cataclysmic variables” in which a star similar to our sun orbits close to what is called a white dwarf, basically a hot and compact core of a burned-out star. Variable just means that their combined brightness varies over time when viewed from Earth. Cataclysmic refers to the fact that this luminosity changes dramatically — by a factor of 10,000 or more in some cases.
Over millions of years, the distance between these two stars has narrowed to the point that they now are closer together than the moon is to Earth.
“Imagine if the moon zipped across the sky 10 times a night. That’s the kind of speed we are talking about,” said Massachusetts Institute of Technology astrophysicist Kevin Burdge, lead author of the study published this week in the journal Nature.
Being close does not mean they are being nice to each other, though — the white dwarf is mercilessly siphoning material from its partner.
This larger star is about the same temperature as the sun but has been stripped down to just about 10% of the sun’s diameter — leaving it about the size of Jupiter, our solar system’s largest planet. The white dwarf has a mass about 56% that of our sun but is densely packed, with a diameter about 1.5 times that of Earth.
“It’s an old pair of stars, where one of the two moved on — when stars die of old age they become white dwarfs — but then this remnant began to eat its companion,” Burdge said.
“Basically, they were bound together for 8 billion years in a binary orbit. And now, right before the second one could end its stellar life cycle and become a white dwarf in the way that stars normally do — by evolving into a type of star called a red giant — the leftover white dwarf remnant of the first star interrupted the end of the companion’s lifecycle and started slowly consuming it,” Burdge said..
The researchers used data from the Palomar Observatory in California and telescopes in Hawaii and the Canary Islands.
Most stars are composed primarily of hydrogen, with lesser amounts of helium and other elements. The larger of the two stars in this binary — already growing old — is unusually helium-rich, not only because its companion has snacked on hydrogen from its outer layers but because it has lots of this element in its core through the slow process of fusing hydrogen atoms into helium in its thermonuclear cauldron.
This binary system periodically brightens and fades in part because the larger star is being physically deformed into a teardrop shape, rather than spherical, by the white dwarf’s gravitational tug.
There are more than a thousand known cataclysmic variables, though only a dozen have orbital periods below 75 minutes. While this binary system’s 51 minutes is speedy, it is not a record when compared to other classes of binaries. The fastest-known orbital period among binaries is just 5 minutes and 21 seconds, with two white dwarfs orbiting one another.
“There is tons of wild stuff going on in space,” Burdge said.
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Cancer warning: Mate tea increases risk
What’s more, a review article published in the BMJ cited research which found drinking “scalding hot” mate was associated with an increased risk of oesophageal cancer.
The research, published in the journal American Association for Cancer Research, was based on two case studies: a 1988 to 2005 Uruguay study and a 1986 to 1992 multinational study in Argentina, Brazil, Paraguay, and Uruguay, including 1,400 cases and 3,229 controls.
However, unlike the previous research, intensity of drinking mate did not influence cancer risk.
But the “strength of association increased with higher maté temperatures”, the researchers concluded.
“Black widow” neutron star devoured its mate to become heaviest found yet
Enlarge / A spinning neutron star periodically swings its radio (green) and gamma-ray (magenta) beams past Eart. A black widow pulsar heats the facing side of its stellar partner to temperatures twice as hot as the Sun’s surface and slowly evaporates it.
NASA’s Goddard Space Flight Center
Astronomers have determined the heaviest neutron star known to date, weighing in at 2.35 solar masses, according to a recent paper published in the Astrophysical Journal Letters. How did it get so large? Most likely by devouring a companion star—the celestial equivalent of a black widow spider devouring its mate. The work helps establish an upper limit on just how large neutron stars can become, with implications for our understanding of the quantum state of the matter at their cores.
Neutron stars are the remnants of supernovae. As Ars Science Editor John Timmer wrote last month:
The matter that forms neutron stars starts out as ionized atoms near the core of a massive star. Once the star’s fusion reactions stop producing enough energy to counteract the draw of gravity, this matter contracts, experiencing ever-greater pressures. The crushing force is enough to eliminate the borders between atomic nuclei, creating a giant soup of protons and neutrons. Eventually, even the electrons in the region get forced into many of the protons, converting them to neutrons.
This finally provides a force to push back against the crushing power of gravity. Quantum mechanics prevent neutrons from occupying the same energy state in close proximity, and this prevents the neutrons from getting any closer and so blocks the collapse into a black hole. But it’s possible that there’s an intermediate state between a blob of neutrons and a black hole, one where the boundaries between neutrons start to break down, resulting in odd combinations of their constituent quarks.
Short of black holes, the cores of neutron stars are the densest known objects in the Universe, and because they are hidden behind an event horizon, they are difficult to study. “We know roughly how matter behaves at nuclear densities, like in the nucleus of a uranium atom,” said Alex Filippenko, an astronomer at the University of California, Berkeley and co-author of the new paper. “A neutron star is like one giant nucleus, but when you have 1.5 solar masses of this stuff, which is about 500,000 Earth masses of nuclei all clinging together, it’s not at all clear how they will behave.”
This animation shows a black widow pulsar together with its small stellar companion. Powerful radiation and the pulsar’s “wind”—an outflow of high-energy particles—strongly heat the facing side of the companion, evaporating it over time.
The neutron star featured in this latest paper is a pulsar, PSR J0952-0607—or J0952 for short—located in the constellation Sextans between 3,200 and 5,700 light-years away from Earth. Neutron stars are born spinning, and the rotating magnetic field emits beams of light in the form of radio waves, X-rays, or gamma rays. Astronomers can spot pulsars when their beams sweep across Earth. J0952 was discovered in 2017 thanks to the Low-Frequency Array (LOFAR) radio telescope, following up on data on mysterious gamma ray sources collected by NASA’s Fermi Gamma-ray Space Telescope.
Your average pulsar spins at roughly one rotation per second, or 60 per minute. But J0952 is spinning at a whopping 42,000 revolutions per minute, making it the second-fastest-known pulsar thus far. The current favored hypothesis is that these kinds of pulsars were once part of binary systems, gradually stripping down their companion stars until the latter evaporated away. That’s why such stars are known as black widow pulsars—what Filippenko calls a “case of cosmic ingratitude”:
The evolutionary pathway is absolutely fascinating. Double exclamation point. As the companion star evolves and starts becoming a red giant, material spills over to the neutron star, and that spins up the neutron star. By spinning up, it now becomes incredibly energized, and a wind of particles starts coming out from the neutron star. That wind then hits the donor star and starts stripping material off, and over time, the donor star’s mass decreases to that of a planet, and if even more time passes, it disappears altogether. So, that’s how lone millisecond pulsars could be formed. They weren’t all alone to begin with—they had to be in a binary pair—but they gradually evaporated away their companions, and now they’re solitary.
This process would explain how J0952 became so heavy. And such systems are a boon to scientists like Filippenko and his colleagues keen to weigh neutron stars precisely. The trick is to find neutron star binary systems in which the companion star is small but not too small to detect. Of the dozen or so black widow pulsars the team has studied over the years, only six met that criteria.
Enlarge / Astronomers measured the velocity of a faint star (green circle) that has been stripped of nearly its entire mass by an invisible companion, a neutron star and millisecond pulsar that they determined to be the most massive yet found and perhaps the upper limit for neutron stars.
W. M. Keck Observatory, Roger W. Romani, Alex Filippenko
J0952’s companion star is 20 times the mass of Jupiter and tidally locked in orbit with the pulsar. The side facing J0952 is thus quite hot, reaching temperatures of 6,200 Kelvin (10,700° F), making it bright enough to be spotted with a large telescope.
Fillipenko et al. spent the last four years making six observations of J0952 with the 10-meter Keck telescope in Hawaii to catch the companion star at specific points in its 6.4-hour orbit around the pulsar. They then compared the resulting spectra to the spectra of similar Sun-like stars to determine the orbital velocity. This, in turn, allowed them to calculate the mass of the pulsar.
Finding even more such systems would help place further constraints on the upper limit to how large neutron stars can become before collapsing into black holes, as well as winnowing down competing theories on the nature of the quark soup at their cores. “We can keep looking for black widows and similar neutron stars that skate even closer to the black hole brink,” Filippenko said. “But if we don’t find any, it tightens the argument that 2.3 solar masses is the true limit, beyond which they become black holes.”
DOI: Astrophysical Journal Letters, 2022. 10.3847/2041-8213/ac8007 (About DOIs).
Heaviest Neutron Star Ever Discovered Is a “Black Widow” Devouring Its Mate
A spinning neutron star periodically swings its radio (green) and gamma-ray (magenta) beams past Earth in this artist’s concept of a black widow pulsar. The pulsar heats the facing side of its stellar partner to temperatures twice as hot as the sun’s surface and slowly evaporates it. Credit: NASA’s Goddard Space Flight Center/Cruz deWilde
Observations of faint, planet-size star help weigh its millisecond pulsar companion.
A dense, collapsed star has shredded and consumed nearly the entire mass of its stellar companion and, in the process, grown into the heaviest
“We know roughly how matter behaves at nuclear densities, like in the nucleus of a uranium 
Astronomers measured the velocity of a faint star (green circle) that has been stripped of nearly its entire mass by an invisible companion, a neutron star and millisecond pulsar that they determined to be the most massive yet found and perhaps the upper limit for neutron stars. The objects are in the constellation Sextans. Credit: W. M. Keck Observatory, Roger W. Romani, Alex Filippenko
The extreme sensitivity of the 10-meter Keck I telescope on Maunakea in Hawai’i was what made it possible to measure of the neutron star’s mass. It recorded a spectrum of visible light from the hotly glowing companion star, which is now reduced to the size of a large gaseous planet. Located in the direction of the constellation Sextans, the stars are about 3,000 light-years from Earth.
Discovered in 2017, PSR J0952-0607 is referred to as a “black widow” pulsar. Their name is an analogy to the tendency of female black widow spiders to consume the much smaller male after mating. Hoping to establish the upper limit on how large neutron stars/pulsars can grow, Filippenko and Romani have been studying black widow systems for more than a decade.
“By combining this measurement with those of several other black widows, we show that neutron stars must reach at least this mass, 2.35 plus or minus 0.17 solar masses,” said Romani, who is a professor of physics in Stanford’s School of Humanities and Sciences and member of the Kavli Institute for Particle Astrophysics and Cosmology. “In turn, this provides some of the strongest constraints on the property of matter at several times the density seen in atomic nuclei. Indeed, many otherwise popular models of dense-matter physics are excluded by this result.”
If 2.35 solar masses is close to the upper limit of neutron stars, the astronomers say, then the interior is likely to be a soup of neutrons as well as up and down quarks — the constituents of normal protons and neutrons — but not exotic matter, such as “strange” quarks or kaons, which are particles that contain a strange quark.
“A high maximum mass for neutron stars suggests that it is a mixture of nuclei and their dissolved up and down quarks all the way to the core,” Romani said. “This excludes many proposed states of matter, especially those with exotic interior composition.”
Romani, Filippenko and Stanford graduate student Dinesh Kandel are co-authors of a paper describing the team’s results that were published today (July 26, 2022) in The Astrophysical Journal Letters.
How large can they grow?
Astrophysicists generally agree that when a star with a core larger than about 1.4 solar masses collapses at the end of its life, it forms a dense, compact object with an interior under such high pressure that all atoms are smashed together to form a sea of neutrons and their subnuclear constituents, quarks. These neutron stars are born spinning, and though too dim to be seen in visible light, reveal themselves as pulsars, emitting beams of light — radio waves, X-rays or even gamma rays — that flash Earth as they spin, much like the rotating beam of a lighthouse.
“Ordinary” pulsars spin and flash about once per second, on average, a speed that can easily be explained given the normal rotation of a star before it collapses. But some pulsars repeat hundreds or up to 1,000 times per second, which is hard to explain unless matter has fallen onto the neutron star and spun it up. But for some millisecond pulsars, no companion is visible.
One possible explanation for isolated millisecond pulsars is that each did once have a companion, but it stripped it down to nothing.
“The evolutionary pathway is absolutely fascinating. Double exclamation point,” Filippenko said. “As the companion star evolves and starts becoming a red giant, material spills over to the neutron star, and that spins up the neutron star. By spinning up, it now becomes incredibly energized, and a wind of particles starts coming out from the neutron star. That wind then hits the donor star and starts stripping material off, and over time, the donor star’s mass decreases to that of a planet, and if even more time passes, it disappears altogether. So, that’s how lone millisecond pulsars could be formed. They weren’t all alone to begin with — they had to be in a binary pair — but they gradually evaporated away their companions, and now they’re solitary.”
The pulsar PSR J0952-0607 and its faint companion star support this origin story for millisecond pulsars.
“These planet-like objects are the dregs of normal stars which have contributed mass and angular momentum, spinning up their pulsar mates to millisecond periods and increasing their mass in the process,” Romani said.
“In a case of cosmic ingratitude, the black widow pulsar, which has devoured a large part of its mate, now heats and evaporates the companion down to planetary masses and perhaps complete annihilation,” said Filippenko.
Spider pulsars include redbacks and tidarrens
Finding black widow pulsars in which the companion is small, but not too small to detect, is one of few ways to weigh neutron stars. In the case of this binary system, the companion star — now only 20 times the mass of
“We can keep looking for black widows and similar neutron stars that skate even closer to the black hole brink. But if we don’t find any, it tightens the argument that 2.3 solar masses is the true limit, beyond which they become black holes,” Filippenko said.
“This is right at the limit of what the Keck telescope can do, so barring fantastic observing conditions, tightening the measurement of PSR J0952-0607 likely awaits the 30-meter telescope era,” added Romani.
Reference: “PSR J0952-0607: The Fastest and Heaviest Known Galactic Neutron Star” by Roger W. Romani, D. Kandel, Alexei V. Filippenko, Thomas G. Brink and WeiKang Zheng, 26 July 2022, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ac8007
Other co-authors of the ApJ Letters paper are UC Berkeley researchers Thomas Brink and WeiKang Zheng. The work was supported by the National Aeronautics and Space Administration (80NSSC17K0024, 80NSSC17K0502), the Christopher R. Redlich Fund, the TABASGO Foundation, and UC Berkeley’s Miller Institute for Basic Research in Science.
This Horrifying Zombie Fungus Forces Males to Mate With The Dead. Now We Know How
The fungus Entomophthora muscae has a survival strategy that’s both fascinating and potentially going to put you off your next meal: it infects and ‘zombifies’ female houseflies before sending out irresistible chemical signals encouraging male houseflies into necrophilia.
By luring these male flies into mating with zombified females, the fungus can transfer to the male fly and, in theory, have a better chance of further dispersal. The unlucky male fly is then taken over by E. muscae in the same way.
Crucial to the process is the release of sesquiterpenes, or chemical messages, which are synthesized in the female cadaver and sent out as a seductive signal. Based on the experiments carried out by the researchers, the longer the corpse has been dead, the more attractive it appears to be to the males.
“The chemical signals act as pheromones that bewitch male flies and cause an incredible urge for them to mate with lifeless female carcasses,” says evolutionary biologist Henrik H. De Fine Licht, from the University of Copenhagen in Denmark.
Once E. muscae has infected a female fly with its spores, it starts to multiply. After around six days, it can control the behavior of the insect, sending it up to the highest possible point (on a wall or a plant) before it dies. Fungus spores are then sent out from the dead fly, hoping to land on another.
But as this new study shows, by enticing a male over, E. muscae can ensure it passes into at least one more host, which will carry its spores far and wide again.
The team used a variety of chemical analysis and genetic sequencing techniques to figure out exactly what the fungus was doing, as well as exposing male flies to female partners at different stages of fungal infection, or that had died from other causes.
“Our observations suggest that this is a very deliberate strategy for the fungus,” says H. De Fine Licht. “It is a true master of manipulation – and this is incredibly fascinating.”
Tests showed that female fly corpses that had been dead for 3-8 hours attracted 15 percent of male flies, whereas with corpses that had been dead for 25-30 hours, that figure shot up to 73 percent. The more time that passed, the more chemical signals were released.
This isn’t the only time that scientists have observed sesquiterpenes being used to attract the attention of insects. As chemical signals go, it appears to be one of the most effective at manipulating these tiny creatures.
There are plenty of opportunities for further research here, not least into effective fly repellents – flies can infect humans with various diseases, and sesquiterpenes could be used to lure flies away from certain areas, such as where food is being prepared.
“This is where the Entomophthora muscae fungus may prove useful,” says H. De Fine Licht. “It might be possible for us to use these same fungal fragrances as a biological pest control that attracts healthy males to a fly trap instead of a corpse.”
The research has been published in the ISME Journal.
2022 French Grand Prix FP2 report and highlights: Sainz leads Ferrari team mate Leclerc by 0.1s in second French GP practice session
Ferrari stamped their authority on the French Grand Prix weekend as Carlos Sainz beat team mate Charles Leclerc to the quickest time, with Red Bull’s Max Verstappen more than 0.5s off the pace.
Before teams turned their attention to long runs and judging how long the tyres will last in warm conditions, they sent their respective drivers out on soft tyres and low fuel in the search of performance.
Sainz clock a 1m 32.527s on the sixth lap on the same set of soft tyres to edge out Leclerc by 0.101s, however he won’t be in the fight for pole after taking a new engine component that triggers a 10-place grid penalty.
READ MORE: Sainz set for 10-place grid penalty in France after taking new engine component
The Ferrari duo made an improvement of between 0-8-1.0s when they moved from the medium tyres to the softest rubber.
Championship leader Verstappen complained of understeer in the first sector and, while he offered the greatest threat to the red cars, he wasn’t quick enough to give the Italian team too much cause for concern.
|
1 Carlos Sainz SAI Ferrari |
1:32.527 |
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2 Charles Leclerc LEC Ferrari |
+0.101s |
|
3 Max Verstappen VER Red Bull Racing |
+0.550s |
|
4 George Russell RUS Mercedes |
+0.764s |
|
5 Lewis Hamilton HAM Mercedes |
+0.990s |
Mercedes, running an updated package in France, continued their upward trajectory, with George Russell fourth best 0.76s off the pace, with Lewis Hamilton getting his first run of the weekend – having let reserve Nyck de Vries borrow his car in FP1 – fifth a couple of tenths further back.
Lando Norris, running McLaren’s sizeable update, was sixth – one second off the pace – with his team mate Daniel Ricciardo half a second back in ninth. Betyween them was the heavily updated AlphaTauri of home favourite Pierre Gasly and the Haas of Kevin Magnussen, who made a big step in form from FP1 to FP2.
Red Bull’s Sergio Perez left it late to do his soft tyre run but it wasn’t spectacular, the Mexican slotting into 10th, a second behind his team mate Verstappen.
READ MORE: ‘There’s unfinished business’ – Why Daniel Ricciardo looks like a man on a mission ahead of the French Grand Prix
2022 French GP FP2: Schumacher takes huge spin in second practice
Fernando Alonso was the leading Alpine in 11th, his team mate Esteban Ocon competing in his home grand prix down in 18th, with Valtteri Bottas getting his first running of the day after Robert Kubica used his Alfa Romeo in FP1. The Finn was 12th.
Sebastian Vettel was the lead Aston Martin in 13th, ahead of Yuki Tsunoda – who was given the AlphaTauri update for the second session after initial data gathering on Gasly’s car in FP1 was deemed a success.
MUST-SEE: Sebastian Vettel pilots a 100-year-old slice of Aston Martin history around the Circuit Paul Ricard
Aston Martin’s Lance Stroll was 15th, ahead of Williams’ Alex Albon and Alfa Romeo’s Zhou Guanyu.
Mick Schumacher flat-spotted a set of medium tyres when he ran wide at Turn 11 on the mediums and was 19th overall, as Nicholas Latifi running the updated Williams package for the first time, two races after Albon got it, propping up the timesheets.
Who’s going to score in the 2022 French Grand Prix? Pick your dream team before qualifying and take on the world to win huge prizes with the Official Formula 1 Fantasy game. Sign up, join leagues and manage your squad here.
Zombie fly fungus lures healthy male flies to mate with female corpses
Entomophthora muscae is a widespread, pathogenic fungus that survives by infecting common houseflies with deadly spores. Now, research shows that the fungus has a unique tactic to ensure its survival. The fungus “bewitches” male houseflies and drives them to necrophilia with the fungal-infected corpses of dead females.
After having infected a female fly with its spores, the fungus spreads until its host has slowly been consumed alive from within. After roughly six days, the fungus takes over the behavior of the female fly and forces it to the highest point, whether upon vegetation or a wall, where the fly then dies. When the fungus has killed the zombie female, it begins to release chemical signals known as sesquiterpenes.
“The chemical signals act as pheromones that bewitch male flies and cause an incredible urge for them to mate with lifeless female carcasses,” explains Henrik H. De Fine Licht, an associate professor at the University of Copenhagen’s Department of Environment and Plant Sciences and one of the study’s authors.
As male flies copulate with dead females, the fungal spores are showered onto the males, who then suffer the same gruesome fate. In this way, Entomophthora muscae spreads its spores to new victims and ensures for its survival.
This is the conclusion of a new study conducted by researchers at the University of Copenhagen and Swedish University of Agriculture Sciences in Alnarp.
“Our observations suggest that this is a very deliberate strategy for the fungus. It is a true master of manipulation—and this is incredibly fascinating,” says Henrik H. De Fine Licht.
Fly corpses become more attractive as the hours pass
Tracking fly behavior also let the researchers demonstrate that dead female flies become more attractive as time passes.
Specifically, 73 percent of the male flies in the study mated with female fly carcasses that had died from the fungal infection between 25–30 hours earlier. Only 15 percent of the males mated with female corpses that had been dead for 3–8 hours.
“We see that the longer a female fly has been dead, the more alluring it becomes to males. This is because the number of fungal spores increases with time, which enhances the seductive fragrances,” explains Henrik H. De Fine Licht.
Besides the insight into nature’s fascinating mechanisms, the study provides new knowledge that may lead to effective fly repellents in the future. Henrik H. De Fine Licht adds:
“Flies are quite unhygienic and can sicken humans and animals by spreading coli bacteria and any diseases that they are carrying. So, there is an incentive to limit housefly populations, in areas where food is being produced for example. This is where the Entomophthora muscae fungus may prove useful. It might be possible for us to use these same fungal fragrances as a biological pest control that attracts healthy males to a fly trap instead of a corpse,” he concludes.
The research was published in The ISME Journal.
The research explained
- The researchers used an array of methods. These included the chemical analysis of fragrances emitted by the fungus and amplified in dead female flies, as well as by studying the fungus’ genetics via RNA sequencing.
- They also studied the sexual habits of male flies through behavioral experiments that exposed them to dead female flies which were at various stages of fungal infection, as well as females that had died from other causes. Here, researcher observations demonstrated that male flies preferred mating with fungus-infected females that had been dead for quite some time.
More about the zombie fly fungus
- Entomophthora muscae is a fungus that survives by taking control of and infecting its host, namely flies.
- The fungus secretes special enzymes that break a fly’s body down over the course of about seven days. The fungus can eject its infected spores at up to 10 meters a second, which is among the fastest of nature’s movements.
A fungus that uses chemicals to trick male flies into mating with infected dead females
More information:
Andreas Naundrup et al, Pathogenic fungus uses volatiles to entice male flies into fatal matings with infected female cadavers, The ISME Journal (2022). DOI: 10.1038/s41396-022-01284-x
Andreas Naundrup et al, Pathogenic fungus uses volatiles to entice male flies into fatal matings with infected female cadavers, The ISME Journal (2022). DOI: 10.1038/s41396-022-01284-x
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Microscopic Mites That Mate on Our Faces at Night May Soon Become One With Humans
Image showing Demodex folliculorum mite on skin under Hirox microscope. Credit: University of Reading
The secret lives of mites in the skin of our faces.
First ever full
Image shows the unusually-positioned penis of a Demodex folliculorum mite. Credit: University of Reading
The mites are passed on during birth and are carried by almost every human, with numbers peaking in adults as the pores grow bigger. They measure around 0.3mm long, are found in the hair follicles on the face and nipples, including the eyelashes, and eat the sebum naturally released by cells in the pores. They become active at night and move between follicles looking to mate.
The first ever genome sequencing study of the D. folliculorum mite found that their isolated existence and resulting inbreeding is causing them to shed unnecessary genes and cells and move towards a transition from external parasites to internal symbionts.
Microscope image of the posterior end of the anus of a Demodex folliculorum mite. The presence of an anus on this mite had been wrongly overlooked by some previously, but this study confirmed its presence. Credit: University of Reading
Dr. Alejandra Perotti, Associate Professor in Invertebrate Biology at the University of Reading, who co-led the research, said: “We found these mites have a different arrangement of body part genes to other similar species due to them adapting to a sheltered life inside pores. These changes to their DNA have resulted in some unusual body features and behaviors.”
The in-depth study of the Demodex folliculorum DNA revealed:
- Due to their isolated existence, with no exposure to external threats, no competition to infest hosts, and no encounters with other mites with different genes, genetic reduction has caused them to become extremely simple organisms with tiny legs powered by just 3 single cell muscles. They survive with the minimum repertoire of proteins – the lowest number ever seen in this and related species.
- This gene reduction is the reason for their nocturnal behavior too. The mites lack UV protection and have lost the gene that causes animals to be awakened by daylight. They have also been left unable to produce melatonin – a compound that makes small invertebrates active at night – however, they are able to fuel their all-night mating sessions using the melatonin secreted by human skin at dusk.
- Their unique gene arrangement also results in the mites’ unusual mating habits. Their reproductive organs have moved anteriorly, and males have a penis that protrudes upwards from the front of their body meaning they have to position themselves underneath the female when mating, and copulate as they both cling onto the human hair.
- One of their genes has inverted, giving them a particular arrangement of mouth appendages extra protruding for gathering food. This aids their survival at a young age.
- The mites have many more cells at a young age compared to their adult stage. This counters the previous assumption that parasitic animals reduce their cell numbers early in development. The researchers argue this is the first step toward the mites becoming symbionts.
- The lack of exposure to potential mates that could add new genes to their offspring may have set the mites on course for an evolutionary dead end, and potential extinction. This has been observed in bacteria living inside cells before, but never in an animal.
- Some researchers had assumed the mites do not have an anus and therefore must accumulate all their feces through their lifetimes before releasing it when they die, causing skin inflammation. The new study, however, confirmed they do have anuses and so have been unfairly blamed for many skin conditions.
Demodex folliculorum mite under a microscope walking. Credit: University of Reading
The research was led by Bangor University and the University of Reading, in collaboration with the University of Valencia, University of Vienna and National University of San Juan. It is published in the journal Molecular Biology and Evolution.
Dr. Henk Braig, co-lead author from Bangor University and the National University of San Juan, said: “Mites have been blamed for a lot of things. The long association with humans might suggest that they also could have simple but important beneficial roles, for example, in keeping the pores in our face unplugged.”
Reference: “Human follicular mites: Ectoparasites becoming symbionts” by Gilbert Smith, Alejandro Manzano Marín, Mariana Reyes-Prieto, Cátia Sofia Ribeiro Antunes, Victoria Ashworth, Obed Nanjul Goselle, Abdulhalem Abdulsamad A. Jan, Andrés Moya, Amparo Latorre, M. Alejandra Perotti and Henk R Braig, 21 June 2022, Molecular Biology and Evolution.
DOI: 10.1093/molbev/msac125
Skin Mites That Mate on Our Faces at Night Are Slowly Merging With Humans
If you are reading this, you are probably not alone.
Most people on Earth are habitats for mites that spend the majority of their brief lives burrowed, head-first, in our hair follicles, primarily of the face. In fact, humans are the only habitat for Demodex folliculorum. They are born on us, they feed on us, they mate on us, and they die on us.
Their entire life cycle revolves around munching your dead skin cells before kicking the teeny tiny bucket.
So reliant is D. folliculorum on humans for their survival, new research suggests, that the microscopic mites are in the process of evolving from an ectoparasite into an internal symbiont – and one that shares a mutually beneficial relationship with its hosts (that’s us).
In other words, these mites are gradually merging with our bodies so that they now live permanently within us.
Scientists have now sequenced the genomes of these ubiquitous little beasts, and the results show that their human-centered existence could be wreaking changes not seen in other mite species.
“We found these mites have a different arrangement of body part genes to other similar species due to them adapting to a sheltered life inside pores,” explained invertebrate biologist Alejandra Perotti of the University of Reading in the UK.
“These changes to their DNA have resulted in some unusual body features and behaviors.”
D. folliculorum seen in a potassium hydroxide preparation of human skin. (K.V Santosh/Flickr, CC BY 2.0)
D. folliculorum is actually a fascinating little creature. Human skin detritus is its sole food source, and it spends the majority of its two-week lifespan in pursuit thereof.
The individuals emerge only at night, in the cover of darkness, to crawl painstakingly slowly across the skin to find a mate, and hopefully copulate before returning to the safe darkness of a follicle.
Their tiny bodies are just a third of a millimeter in length, with a cluster of tiny legs and a mouth at one end of a long, sausage-shaped body – just right for scooching down human hair follicles to get at the tasty noms therein.
The work on the genome of the mite, co-led by Marin and geneticist Gilbert Smith of Bangor University in the UK, revealed some of the fascinating genetic characteristics that drives this lifestyle.
Because their lives are so cruisy – they have no natural predators, no competition, and no exposure to other mites – their genome has reduced down to just the bare essentials.
Their legs are powered by three, single-cell muscles, and their bodies have the absolute minimum number of proteins, only what is needed for survival. It’s the smallest number ever seen in its wider group of related species.
This pared-down genome is the reason for some of D. folliculorum‘s other strange peccadilloes, too. For instance, the reason it only comes out at night. Among the genes lost are those responsible for protection against UV radiation, and those that wake animals up at daylight.
They are also unable to produce the hormone melatonin, found in most living organisms, with varying functions; in humans, melatonin is important for regulating the sleep cycle, but in small invertebrates, it induces mobility and reproduction.
This hasn’t seemed to have hindered D. folliculorum, however; it can harvest melatonin secreted by the skin of its host at dusk.
Unlike other mites, their reproductive organs of D. folliculorum have moved towards the front of their bodies, with male mites’ penises pointing forwards and upwards from their backs. This means he has to arrange himself underneath the female as they perch precariously on a hair for mating, which they do all night, AC/DC-style (presumably).
But although mating is pretty important, the potential gene pool is very small: there is very little opportunity for expanding genetic diversity. This could mean that the mites are on track for an evolutionary dead end.
Interestingly, the team also found that, at the nymph stage of development, between larva and adult, is when the mites have the greatest number of cells in their bodies. When they move on to the adult stage, they lose cells – the first evolutionary step, the researchers said, in the march of an arthropod species to a symbiotic lifestyle.
One might wonder what possible benefits humans can gain from these peculiar animals; something else the researchers found might partially hint at the answer. For years, scientists have thought that D. folliculorum doesn’t have an anus, instead accumulating waste in its body to explode out when the mite dies, and thus causing skin conditions.
The team found that this is simply not the case. The mites do indeed have tiny little buttholes; your face probably isn’t full of mite poop expelled posthumously.
“Mites have been blamed for a lot of things,” said zoologist Henk Braig of the University of Bangor and the National University of San Juan in Argentina. “The long association with humans might suggest that they also could have simple but important beneficial roles, for example, in keeping the pores in our face unplugged.”
The research has been published in Molecular Biology and Evolution.