Mars once had salt lakes similar to those on Earth

Salt flat in Bolivia.

Mars once had salt lakes that are similar to those on Earth and has gone through wet and dry periods, according to an international team of scientists that includes a Texas A&M University College of Geosciences researcher.

Marion Nachon, a postdoctoral research associate in the Department of Geology and Geophysics at Texas A&M, and colleagues have had their work published in the current issue of Nature Geoscience.

The team examined Mars' geological terrains from Gale Crater, an immense 95-mile-wide rocky basin that is being explored with the NASA Curiosity rover since 2012 as part of the MSL (Mars Science Laboratory) mission.

The results show that the lake that was present in Gale Crater over 3 billion years ago underwent a drying episode, potentially linked to the global drying of Mars.

Gale Crater formed about 3.6 billion years ago when a meteor hit Mars and created its large impact crater.

"Since then, its geological terrains have recorded the history of Mars, and studies have shown Gale Crater reveals signs that liquid water was present over its history, which is a key ingredient of microbial life as we know it," Nachon said. "During these drying periods, salt ponds eventually formed. It is difficult to say exactly how large these ponds were, but the lake in Gale Crater was present for long periods of time -- from at least hundreds of years to perhaps tens of thousands of years," Nachon said.

So what happened to these salt lakes?

Nachon said that Mars probably became dryer over time, and the planet lost its planetary magnetic field, which left the atmosphere exposed to be stripped by solar wind and radiation over millions of years.

"With an atmosphere becoming thinner, the pressure at the surface became lesser, and the conditions for liquid water to be stable at the surface were not fulfilled anymore," Nachon said. "So liquid water became unsustainable and evaporated."

The salt ponds on Mars are believed to be similar to some found on Earth, especially those in a region called Altiplano, which is near the Bolivia-Peru border.

Nachon said the Altiplano is an arid, high-altitude plateau where rivers and streams from mountain ranges "do not flow to the sea but lead to closed basins, similar to what used to happen at Gale Crater on Mars," she said. "This hydrology creates lakes with water levels heavily influenced by climate. During the arid periods Altiplano lakes become shallow due to evaporation, and some even dry up entirely. The fact that the Atliplano is mostly vegetation free makes the region look even more like Mars," she said."

Nachon added that the study shows that the ancient lake in Gale Crater underwent at least one episode of drying before "recovering." It's also possible that the lake was segmented into separate ponds, where some of the ponds could have undergone more evaporation.

Because up to now only one location along the rover's path shows such a drying history, Nachon said it might give clues about how many drying episodes the lake underwent before Mars's climate became as dry as it is currently.

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Climate: Uncertainty in scientific predictions can help and harm credibility

The more specific climate scientists are about the uncertainties of global warming, the more the American public trusts their predictions, according to new research by Stanford scholars.

But scientists may want to tread carefully when talking about their predictions, the researchers say, because that trust falters when scientists acknowledge that other unknown factors could come into play.

In a new study published in Nature Climate Change, researchers examined how Americans respond to climate scientists' predictions about sea level rise. They found that when climate scientists include best-case and worst-case case scenarios in their statements, the American public is more trusting and accepting of their statements. But those messages may backfire when scientists also acknowledge they do not know exactly how climate change will unfold.

"Scientists who acknowledge that their predictions of the future cannot be exactly precise and instead acknowledge a likely range of possible futures may bolster their credibility and increase acceptance of their findings by non-experts," said Jon Krosnick, a Stanford professor of communication and of political science and a co-author on the paper. "But these gains may be nullified when scientists acknowledge that no matter how confidently they can make predictions about some specific change in the future, the full extent of the consequences of those predictions cannot be quantified."

Effects of communicating uncertainty

Predicting the future always comes with uncertainty, and climate scientists routinely recognize limitations in their predictions, note the researchers.

"In the context of global warming specifically, scientific uncertainty has been of great interest, in part because of concerted efforts by so-called 'merchants of doubt' to minimize public concern about the issue by explicitly labeling the science as 'uncertain,'" said Lauren Howe, who was a postdoctoral scholar at Stanford when she conducted the research with Krosnick and is first author on the paper.

"We thought that, especially in this critical context, it was important to understand whether expressing uncertainty would undermine persuasion, or whether the general public might instead recognize that the study of the future has to involve uncertainty and trust predictions where that uncertainty is openly acknowledged more than those where it is minimized," Howe said.

To better understand how the public reacts to scientists' messages about the uncertainties of climate change, the researchers presented a nationally representative sample of 1,174 American adults with a scientific statement about anticipated sea level rise.

Respondents were randomly assigned to read either a prediction of the most likely amount of future sea level rise, a prediction plus a worst-case scenario, or a robust prediction with worst-case and best-case scenarios, for example: "Scientists believe that, during the next 100 years, global warming will cause the surface of the oceans around the world to rise about 4 feet. However, sea level could rise as little as 1 foot, or it could rise by as much as 7 feet."

The researchers found that when predictions included a best-case and worst-case scenario, it increased the number of participants who reported high trust in scientists by 7.9 percentage points compared with participants who only read a most likely estimate of sea level rise.

Changes in environmental policies, human activities, new technologies and natural disasters make it difficult for climate scientists to quantify the long-term impact of a specific change -- which scientists often acknowledge in their predictions, the researchers said. They wanted to know if providing such well-intended, additional context and acknowledging complete uncertainty would help or hurt public confidence in scientific findings.

To find out, the researchers asked half of their respondents to read a second statement acknowledging that the full extent of likely future damage of sea level rise cannot be measured because of other forces, such as storm surge: "Storm surge could make the impacts of sea level rise worse in unpredictable ways."

The researchers found that this statement eliminated the persuasive power of the scientists' messages. When scientists acknowledged that storm surge makes the impact of sea level rise unpredictable, it decreased the number of participants who reported high trust in scientists by 4.9 percentage points compared with the participants who only read a most likely estimate of sea level rise.

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Limiting mealtimes may increase your motivation for exercise

Limiting access to food in mice increases levels of the hormone, ghrelin, which may also increase motivation to exercise, according to a study published in the Journal of Endocrinology. The study suggests that a surge in levels of appetite-promoting hormone, ghrelin, after a period of fasting prompted mice to initiate voluntary exercise. These novel findings indicate that better diet control, for example limiting food intake to mealtimes or fasting intermittently, could help overweight people maintain a more effective exercise routine, lose weight and avoid debilitating complications such as diabetes and heart disease.

Obesity is a costly and growing, global health epidemic that needs more effective intervention strategies to avoid serious complications including heart disease and diabetes. Food restriction and regular exercise are the two main cost-effective strategies to prevent and treat obesity; however the condition is often associated with a sedentary lifestyle and bad eating habits, such as snacking and binge eating. Consequently, adhering to a regular exercise regime can be difficult due to an inability to exercise for a prolonged period or a lack of motivation. Ghrelin, often referred to as the 'hunger hormone', stimulates appetite through actions on the brain reward circuitry that increase motivation to eat. It has also been reported to be essential for endurance exercise by increasing metabolism to meet the energy demands of prolonged exercise. Although previous studies have suggested a relationship between ghrelin and exercise, it is not known whether ghrelin levels have a direct effect on motivation to exercise.

In this study, Dr Yuji Tajiri and colleagues from Kurume University School of Medicine in Japan, investigated the relationship between exercise and ghrelin levels in mice. Food intake and wheel-running activity were compared in mice given free access to food and those fed only twice a day for a limited time. Although both groups ate a similar amount of food, the restricted mice ran significantly more. Mice genetically altered to have no ghrelin and on the restricted feeding diet ran less than the mice given free access, however, this could be reversed by administering ghrelin. Furthermore, mice given free access to food and given ghrelin also ran significantly more. These findings suggest that ghrelin may play an important role in the motivation for both feeding and exercise, in response to restricted eating plans.

Dr Tajiri comments, "Our findings suggest that hunger, which promotes ghrelin production, may also be involved in increasing motivation for voluntary exercise, when feeding is limited. Therefore, maintaining a healthy eating routine, with regular mealtimes or fasting, could also encourage motivation for exercise in overweight people."

However, Dr Tajiri cautions. "These findings and previous reports are based on animal studies; so much more work is needed to confirm that this ghrelin response is also present in people. If it can be established in clinical practice, it not only opens up new cost-effective diet and exercise strategies but may also indicate a new therapeutic application for ghrelin-mimicking drugs."

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Candidate Ebola vaccine still effective when highly diluted, macaque study finds

A single dose of a highly diluted VSV-Ebola virus (EBOV) vaccine -- approximately one-millionth of what is in the vaccine being used to help control the ongoing Ebola outbreak in the Democratic Republic of the Congo (DRC) -- remains fully protective against disease in experimentally infected monkeys, according to National Institutes of Health scientists. The NIH investigators completed the vaccine dosage study using cynomolgus macaques and an updated vaccine component to match the EBOV Makona strain that circulated in West Africa from 2014-16. The study appears in Lancet's EBioMedicine.

Nearly 250,000 people have received the investigational VSV-EBOV vaccine since August 2018 as part of a "ring vaccination" program to help stem the outbreak. The vaccine appears to be safe and highly effective. The manufacturer has announced that it has submitted a biologics license application to the U.S. Food and Drug Administration. VSV-EBOV is based on a live-attenuated vesicular stomatitis virus and delivers an EBOV protein to elicit protective immune responses. With the continued need to vaccinate individuals in the DRC and surrounding countries, a potential shortage of VSV-EBOV vaccine is a concern and further dose adjustment is a possible solution.

Scientists from NIH's Rocky Mountain Laboratories (RML), part of the National Institute of Allergy and Infectious Diseases, tested several dosage strengths, including one with 10 million plaque-forming units (PFU). They determined that a vaccine with 10 PFUs was just as effective as the highest dose tested (a dose which was still lower than the one currently in use in the DRC). They vaccinated macaques 28 days prior to infecting them with a lethal dose of EBOV and then monitored the animals for 42 days after infection. Even the macaques given the lowest dose appeared completely protected from disease due to EBOV.

The scientists say their study findings could help make more vaccine available for more people and may reduce adverse reactions to the vaccine because of the smaller amount of active ingredient. Such reactions can include injection site irritation, headache, fatigue, fever, chills, myalgia, and arthralgia. Demonstrating that the vaccine appears effective with adjusted dosing also could ease the burden on vaccine production.

The authors say that although results from preclinical and clinical studies can differ, these promising findings in macaques of complete protection with a lower-dose VSV-EBOV vaccine help support the possibility of similar clinical trials in people.

From Science Daily

A new discovery: How our memories stabilize while we sleep

Scientists at the Center for Interdisciplinary Research in Biology (CNRS/Collège de France/INSERM) have shown that delta waves emitted while we sleep are not generalized periods of silence during which the cortex rests, as has been described for decades in the scientific literature. Instead, they isolate assemblies of neurons that play an essential role in long-term memory formation. These results were published on 18 October 2019 in Science.

While we sleep, the hippocampus reactivates itself spontaneously by generating activity similar to that while we are awake. It sends information to the cortex, which reacts in turn. This exchange is often followed by a period of silence called a 'delta wave' then by rhythmic activity called a 'sleep spindle'. This is when the cortical circuits reorganize to form stable memories. However, the role of delta waves in the formation of new memories is still a puzzle: why does a period of silence interrupt the sequence of information exchanges between the hippocampus and the cortex, and the functional reorganisation of the cortex?

The authors here looked more closely at what happens during delta waves themselves. They discovered, surprisingly, that the cortex is not entirely silent but that a few neurons remain active and form assemblies, i.e. small, coactive sets that code information. This unexpected observation suggests that the small number of neurons that activate when all the others stay quiet can carry out important calculations while protected from possible disturbances. And the discoveries from this work go even further! Spontaneous reactivations of the hippocampus determine which cortical neurons remain active during the delta waves and reveal transmission of information between the two cerebral structures. In addition, the assemblies activated during the delta waves are formed of neurons that have participated in learning a spatial memory task during the day. Together these elements suggest that these processes are involved in memory consolidation. To demonstrate it, in rats the scientists caused artificial delta waves to isolate either neurons associated with reactivations in the hippocampus, or random neurons. Result: when the right neurons were isolated, the rats managed to stabilise their memories and succeed at the spatial test the next day.

These results substantially change how we understand the cortex. Delta waves are therefore a means of selectively isolating assemblies of chosen neurons, which send crucial information between the periods of hippocampo-cortical dialog and the reorganisation of cortical circuits, to form long-term memories.

From Science Daily

Lifestyle is a threat to gut bacteria: Ötzi proves it, study shows

Intestinal bacteria illustration

The intestinal microbiome is a delicate ecosystem made up of billions and billions of microorganisms, bacteria in particular, that support our immune system, protect us from viruses and pathogens, and help us absorb nutrients and produce energy.

The industrialization process in Western countries had a huge impact on its content. This was confirmed by a study on the bacteria found in the intestine of Ötzi, the Iceman who, in 1991, emerged from the ice of the Ötztal Alps, where Italy borders with Austria. Scientists of Eurac Research examined samples of the mummy's bacteria, confirming the findings of the researchers of the University of Trento who had analyzed the genome of intestinal microorganisms of over 6500 individuals from all continents.

Previous studies by the University of Trento had demonstrated that there is a connection between the microbiome's bacterial content and the increase, in Western countries, of obesity, autoimmune and gastrointestinal diseases, allergies and other complex conditions. In the study that appeared today in Cell Host & Microbe, researchers from Cibio of the University of Trento and Eurac in Bolzano/Bozen demonstrated that the differences between Western and non-Western or prehistoric microbiome lie in the decrease of some types of bacteria that process complex and vegetal fibers in the intestine.

That may have been caused by the Westernization process. Changes in diet, which is now higher in fat and low in fibers, a sedentary lifestyle in an urban setting, the development of new hygiene habits and the widespread use of antibiotics and other medical products have, with no doubt, made our life safer, but impacted the delicate balance of our microbiome.

About the study

The scientists of Eurac Research in Bolzano/Bozen sequenced the Iceman's DNA and were able to identify his set of bacteria, while the researchers of the University of Trento compared it with the microbiome of contemporary non-Westernized populations (from Tanzania and Ghana in particular), which are not used to processed food and have non-Westernized hygiene practices and lifestyle. Their findings were surprising.

The study focused, in particular, on Prevotella copri, a microbe that, when is found in our intestine, is usually the most represented. P. copri is present in 30% of Western individuals.

"First of all, we found out that P. copri it is not a monotypic species but is composed of four distinct but similar clades," explained Nicola Segata, coordinator of the study with Adrian Tett of Cibio of the University of Trento. "We then noticed that at least three of these four clades are almost always present in non-Westernized populations, but are much less prevalent in Westernized individuals. And when it is so, there usually is only one of the four clades. We postulated that the complex process of Westernization had a considerable impact on the gradual disappearance of this bacterium. Our hypothesis was confirmed by the analysis of ancient samples of DNA that were made available by Frank Maixner of the Institute for Mummy Studies at Eurac Research. The Iceman's guts contained three of the four clades of P. copri. And the four clades were also co-present in fossilized stool samples from Mexico that are more than one thousand years old. We still do not know what are the biomedical consequences of these changes of the microbiome which has evolved considerably in recent decades while the human body it colonizes has remained genetically practically unchanged for centuries,"

"Through these 'ancient' samples," continued Tett, "we were able to study the evolution of these clades and now we know that they genetically delineated with the human species and before the initial human migrations out of the African continent."

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Ancient stars shed light on Earth's similarities to other planets

Exoplanets illustration; elements furnished by NASA.

Earth-like planets may be common in the universe, a new UCLA study implies. The team of astrophysicists and geochemists presents new evidence that the Earth is not unique. The study was published in the journal Science on Oct. 18.

"We have just raised the probability that many rocky planets are like the Earth, and there's a very large number of rocky planets in the universe," said co-author Edward Young, UCLA professor of geochemistry and cosmochemistry.

The scientists, led by Alexandra Doyle, a UCLA graduate student of geochemistry and astrochemistry, developed a new method to analyze in detail the geochemistry of planets outside of our solar system. Doyle did so by analyzing the elements in rocks from asteroids or rocky planet fragments that orbited six white dwarf stars.

"We're studying geochemistry in rocks from other stars, which is almost unheard of," Young said.

"Learning the composition of planets outside our solar system is very difficult," said co-author Hilke Schlichting, UCLA associate professor of astrophysics and planetary science. "We used the only method possible -- a method we pioneered -- to determine the geochemistry of rocks outside of the solar system."

White dwarf stars are dense, burned-out remnants of normal stars. Their strong gravitational pull causes heavy elements like carbon, oxygen and nitrogen to sink rapidly into their interiors, where the heavy elements cannot be detected by telescopes. The closest white dwarf star Doyle studied is about 200 light-years from Earth and the farthest is 665 light-years away.

"By observing these white dwarfs and the elements present in their atmosphere, we are observing the elements that are in the body that orbited the white dwarf," Doyle said. The white dwarf's large gravitational pull shreds the asteroid or planet fragment that is orbiting it, and the material falls onto the white dwarf, she said. "Observing a white dwarf is like doing an autopsy on the contents of what it has gobbled in its solar system."

The data Doyle analyzed were collected by telescopes, mostly from the W.M. Keck Observatory in Hawaii, that space scientists had previously collected for other scientific purposes.

"If I were to just look at a white dwarf star, I would expect to see hydrogen and helium," Doyle said. "But in these data, I also see other materials, such as silicon, magnesium, carbon and oxygen -- material that accreted onto the white dwarfs from bodies that were orbiting them."

When iron is oxidized, it shares its electrons with oxygen, forming a chemical bond between them, Young said. "This is called oxidation, and you can see it when metal turns into rust," he said. "Oxygen steals electrons from iron, producing iron oxide rather than iron metal. We measured the amount of iron that got oxidized in these rocks that hit the white dwarf. We studied how much the metal rusts."

Rocks from the Earth, Mars and elsewhere in our solar system are similar in their chemical composition and contain a surprisingly high level of oxidized iron, Young said. "We measured the amount of iron that got oxidized in these rocks that hit the white dwarf," he said.

The sun is made mostly of hydrogen, which does the opposite of oxidizing -- hydrogen adds electrons.

The researchers said the oxidation of a rocky planet has a significant effect on its atmosphere, its core and the kind of rocks it makes on its surface. "All the chemistry that happens on the surface of the Earth can ultimately be traced back to the oxidation state of the planet," Young said. "The fact that we have oceans and all the ingredients necessary for life can be traced back to the planet being oxidized as it is. The rocks control the chemistry."

Until now, scientists have not known in any detail whether the chemistry of rocky exoplanets is similar to or very different from that of the Earth.

How similar are the rocks the UCLA team analyzed to rocks from the Earth and Mars?

"Very similar," Doyle said. "They are Earth-like and Mars-like in terms of their oxidized iron. We're finding that rocks are rocks everywhere, with very similar geophysics and geochemistry."

"It's always been a mystery why the rocks in our solar system are so oxidized," Young said. "It's not what you expect. A question was whether this would also be true around other stars. Our study says yes. That bodes really well for looking for Earth-like planets in the universe."

White dwarf stars are a rare environment for scientists to analyze.

The researchers studied the six most common elements in rock: iron, oxygen, silicon, magnesium, calcium and aluminum. They used mathematical calculations and formulas because scientists are unable to study actual rocks from white dwarfs. "We can determine the geochemistry of these rocks mathematically and compare these calculations with rocks that we do have from Earth and Mars," said Doyle, whose background is in geology and mathematics. "Understanding the rocks is crucial because they reveal the geochemistry and geophysics of the planet."

"If extraterrestrial rocks have a similar quantity of oxidation as the Earth has, then you can conclude the planet has similar plate tectonics and similar potential for magnetic fields as the Earth, which are widely believed to be key ingredients for life," Schlichting said. "This study is a leap forward in being able to make these inferences for bodies outside our own solar system and indicates it's very likely there are truly Earth analogs."

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Arthropods formed orderly lines 480 million years ago

Researchers studied fossilized Moroccan Ampyx trilobites, which lived 480 million years ago and showed that the trilobites had probably been buried in their positions -- all oriented in the same direction. Scientists deduced that these Ampyx processions may illustrate a kind of collective behavior adopted in response to cyclic environmental disturbances.

Though our understanding of the anatomy of the earliest animals is growing ever more precise, we know next to nothing about their behaviour. Did group behaviour arise recently or is it primeval? To answer this question, researchers from the CNRS, the University of Poitiers, UBO, Claude Bernard Lyon 1 University*, Cadi Ayyad University (Marrakech, Morocco), and the University of Lausanne (Switzerland) studied fossilized Moroccan Ampyx trilobites, which lived 480 million years ago. They showed that the trilobites had probably been buried in their positions -- all oriented in the same direction, in orderly lines, maintaining close contact with each other through their long spines -- during storms.

By comparing this observation with the behaviour of living animals such as North American spiny lobsters, the scientists deduced that these Ampyx processions may illustrate a similar kind of collective behaviour -- adopted in response to cyclic environmental disturbances like storms or to chemical signals associated with reproduction.

This example would seem to suggest that group behaviour is of ancient origin and, from an early date, likely conferred an evolutionary advantage on the first animals, allowing them to survive environmental stress and improve their reproductive chances.

*From the Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS / ENS de Lyon / Université Claude Bernard Lyon 1), the Laboratoire Géosciences Océan (CNRS / Université Bretagne Occidentale / Université Bretagne Sud), and the Institute of Chemistry of Materials and Media of Poitiers (IC2MP (CNRS / Université de Poitiers).

From Science Daily

Daily exposure to blue light may accelerate aging, even if it doesn't reach your eyes

Woman looking at blue light from at computer screen.

Prolonged exposure to blue light, such as that which emanates from your phone, computer and household fixtures, could be affecting your longevity, even if it's not shining in your eyes.

New research at Oregon State University suggests that the blue wavelengths produced by light-emitting diodes damage cells in the brain as well as retinas.

The study, published today in Aging and Mechanisms of Disease, involved a widely used organism, Drosophila melanogaster, the common fruit fly, an important model organism because of the cellular and developmental mechanisms it shares with other animals and humans.

Jaga Giebultowicz, a researcher in the OSU College of Science who studies biological clocks, led a research collaboration that examined how flies responded to daily 12-hour exposures to blue LED light -- similar to the prevalent blue wavelength in devices like phones and tablets -- and found that the light accelerated aging.

Flies subjected to daily cycles of 12 hours in light and 12 hours in darkness had shorter lives compared to flies kept in total darkness or those kept in light with the blue wavelengths filtered out. The flies exposed to blue light showed damage to their retinal cells and brain neurons and had impaired locomotion -- the flies' ability to climb the walls of their enclosures, a common behavior, was diminished.

Some of the flies in the experiment were mutants that do not develop eyes, and even those eyeless flies displayed brain damage and locomotion impairments, suggesting flies didn't have to see the light to be harmed by it.

"The fact that the light was accelerating aging in the flies was very surprising to us at first," said Giebultowicz, a professor of integrative biology. "We'd measured expression of some genes in old flies, and found that stress-response, protective genes were expressed if flies were kept in light. We hypothesized that light was regulating those genes. Then we started asking, what is it in the light that is harmful to them, and we looked at the spectrum of light. It was very clear cut that although light without blue slightly shortened their lifespan, just blue light alone shortened their lifespan very dramatically."

Natural light, Giebultowicz notes, is crucial for the body's circadian rhythm -- the 24-hour cycle of physiological processes such as brain wave activity, hormone production and cell regeneration that are important factors in feeding and sleeping patterns.

"But there is evidence suggesting that increased exposure to artificial light is a risk factor for sleep and circadian disorders," she said. "And with the prevalent use of LED lighting and device displays, humans are subjected to increasing amounts of light in the blue spectrum since commonly used LEDs emit a high fraction of blue light. But this technology, LED lighting, even in most developed countries, has not been used long enough to know its effects across the human lifespan."

Giebultowicz says that the flies, if given a choice, avoid blue light.

"We're going to test if the same signaling that causes them to escape blue light is involved in longevity," she said.

Eileen Chow, faculty research assistant in Giebultowicz's lab and co-first author of the study, notes that advances in technology and medicine could work together to address the damaging effects of light if this research eventually proves applicable to humans.

"Human lifespan has increased dramatically over the past century as we've found ways to treat diseases, and at the same time we have been spending more and more time with artificial light," she said. "As science looks for ways to help people be healthier as they live longer, designing a healthier spectrum of light might be a possibility, not just in terms of sleeping better but in terms of overall health."

In the meantime, there are a few things people can do to help themselves that don't involve sitting for hours in darkness, the researchers say. Eyeglasses with amber lenses will filter out the blue light and protect your retinas. And phones, laptops and other devices can be set to block blue emissions.

Read more at Science Daily

Phylogenetic analysis forces rethink of termite evolution

Despite their important ecological role as decomposers, termites are often overlooked in research. Evolutionary biologists at the Okinawa Institute of Science and Technology Graduate University (OIST) have constructed a new family tree for this unassuming insect brood, shedding unexpected light on its evolutionary history.

Writing in Current Biology, the team presents a new tree showing the relationship among termite families and subfamilies. Critically, they have managed to correctly place a subfamily of termites that has until now befuddled researchers. Through comprehensive analysis of termite RNA sequences, the team has now determined the proper position of termites within the Termitidae family.

The Termitidae make up around 80% of termite species and are important as decomposers. This is because, unlike in other families, many Termitidae have shifted their food source from wood to soil and decomposing plant matter -- an important change in diet that took place when they lost protist gut symbionts found in all other termite families. This loss was possibly triggered by new relationships with fungi and bacteria, which the Termitidae cultivate externally in complex sponge-like structures called combs.

The Sphaerotermitinae is one such comb-building subfamily. And while they have previously been difficult to place, the RNA analysis has confirmed that they are, in fact, a sister of the fungus growing Macrotermitinae subfamily -- within the Termitidae. Both subfamilies build combs inside their nests, and the new family tree explains how this behavior evolved.

"Cultivating fungi and bacteria in combs is a peculiar way of securing food," explains Dr. Aleš Bu?ek, a postdoctoral scholar in OIST's Evolutionary Genomics Unit. "It was previously thought that comb building led to the loss of protist gut symbionts in Termitidae. But the new family tree suggests that combs emerged in the ancestor of Sphaerotermitinae and Macrotermitinae -- not across the whole Termitidae family."

"It seems likely, therefore, that associations with new gut bacteria allowed for the loss of old symbionts."

Rethinking the termite family tree

When researchers construct a family tree, or phylogeny, they can do so using different genes. By looking at the differences in a gene between species, they can understand how closely-related those species are. Often, researchers construct a phylogeny using a single gene. This can, however, give an inaccurate picture of the relationship between species -- and can incorrectly place them.

Instead of relying on a single gene, the OIST team used up to 4065 genes from each termite species to construct the phylogeny. This provides a more reliable picture of how different species are related. They included 55 termite species from across the globe, representing all major lineages.

This tree indicated that the Sphaerotermitinae is, in fact, a sister of the comb building Macrotermitinae, a well-studied subfamily of termites. The two sisters both build combs, although only in the Macrotermitinae does this involve the cultivation of fungi for food. Sphaerotermitinae combs, meanwhile, appear to contain bacteria, although the species are not yet identified.

What the team can say, however, is that comb building emerged only once, several million years after the loss of gut symbionts in the ancestor of all Termitidae.

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