Ants recognize infected wounds and treat them with antibiotics

The Matabele ants (Megaponera analis), which are widespread south of the Sahara, have a narrow diet: They only eat termites. Their hunting expeditions are dangerous because termite soldiers defend their conspecifics -- and use their powerful mandibles to do so. It is therefore common for the ants to be injured while hunting.

If the wounds become infected, there is a significant survival risk.

However, Matabele ants have developed a sophisticated healthcare system: they can distinguish between non-infected and infected wounds and treat the latter efficiently with antibiotics they produce themselves.

This is reported by a team led by Dr Erik Frank from Julius-Maximilians-Universität (JMU) Würzburg and Professor Laurent Keller from the University of Lausanne in the journal Nature Communications.

Treatment Drastically Reduces Mortality

"Chemical analyses in cooperation with JMU Professor Thomas Schmitt have shown that the hydrocarbon profile of the ant cuticle changes as a result of a wound infection," says Erik Frank.

It is precisely this change that the ants are able to recognise and thus diagnose the infection status of injured nestmates.

For treatment, they then apply antimicrobial compounds and proteins to the infected wounds.

They take these antibiotics from the metapleural gland, which is located on the side of their thorax.

Its secretion contains 112 components, half of which have an antimicrobial or wound-healing effect.

And the therapy is highly effective: the mortality rate of infected individuals is reduced by 90 per cent, as the research group discovered.

Analysis of Ant Antibiotics is Planned

"With the exception of humans, I know of no other living creature that can carry out such sophisticated medical wound treatments," says Erik Frank.

Laurent Keller also adds that these findings "have medical implications because the primary pathogen in ant's wounds, Pseudomonas aeruginosa, is also a leading cause of infection in humans, with several strains being resistant to antibiotics."

Are Matabele ants really unique in this respect? The Würzburg researcher now wants to explore wound care behaviours in other ant species and other social animals.

He also wants to identify and analyse the antibiotics used by Matabele ants in cooperation with chemistry research groups.

This may lead to the discovery of new antibiotics that could also be used in humans.

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Brain-altering parasite turns ants into zombies at dawn and dusk

It takes over the brains of ants, causing them to cling to the tops of blades of grass where they can be eaten by cattle and deer. The common liver fluke has an exceptional life cycle as it moves through snails, ants and grass-grazing herbivores. And now, researchers from the University of Copenhagen know a bit more about the workings of this tiny parasite. The new knowledge adds to our understanding of parasites, which could be the most widespread life form on Earth.

Imagine coming-to, jaws gripping the top of a swaying blade of grass, unaware of how you got there. That's the reality for ants infected with the lancet liver fluke, a tiny parasitic flatworm. Liver flukes have a complicated, almost insanely conceived life cycle, which begins with the hijacking of the ant's brain. The unsuspecting ant climbs up and clamps its powerful jaws onto the top of a blade of grass, making it more likely to be eaten by grazers such as cattle and deer.

Researchers from the University of Copenhagen's Department of Plant and Environmental Sciences have discovered that the parasite's ability to control the ant is even more cunning than previously believed. Impressively, the parasite can even get the ant to crawl back down the blade of grass when it gets too hot.

"Getting the ants high up in the grass for when cattle or deer graze during the cool morning and evening hours, and then down again to avoid the sun's deadly rays, is quite smart. Our discovery reveals a parasite that is more sophisticated than we originally believed it to be," explains Associate Professor Brian Lund Fredensborg, who conducted the study together with former graduate student Simone Nordstrand Gasque, now a PhD student at Wageningen University in the Netherlands.

Zombie "on/off switch"

The researchers tagged several hundred infected ants in the Bidstrup Forests near Roskilde, Denmark.

"It took some dexterity to glue colors and numbers onto the rear segments of the ants, but it allowed us to keep track of them for longer periods of time," says Brian Lund Fredensborg.

They then observed the infected ants' behavior in relation to light, humidity, time of day and temperature. It was clear that temperature had an effect on ant behavior. When the temperature was low, the ants were more likely to be attached to the top of a blade of grass. When the temperature rose, the ants relinquished the grass and crawled back down.

"We found a clear correlation between temperature and ant behavior. We joked about having found the ants' zombie switch," says Brian Lund Fredensborg.

Trojan horse

Once the liver fluke infects the ant, several hundred parasites invade the ant's body. But only one makes its way to the brain, where it can influence the ant's behavior. The rest of the liver flukes conceal themselves in the ant's abdomen.

"Here, there can be hundreds of liver flukes waiting for the ant to get them into their next host. They are wrapped in a capsule which protects them from the consequent host's stomach acid, while the liver fluke that took control of the ant, dies. You could say that it sacrifices itself for the others," explains Brian Lund Fredensborg.

Animals infected with many liver flukes can suffer liver damage as the parasite moves around the host's liver and bile ducts.

Nature's biggest influencer

Brian Lund Fredensborg notes that there are many other examples of parasites that alter animal behavior. As such, parasites that hijack their host'sbehavior have a greater hand in the food chain than many might think. According to Fredensborg, this new study sheds light on an extremely underrated group of creatures.

"Historically, parasites have never really been focused on that much, despite there being scientific sources which say that parasitism is the most widespread life form. This is in part due to the fact that parasites are quite difficult to study. Nevertheless, the hidden world of parasites forms a significant part of biodiversity, and by changing the host's behavior, they can help determine who eats what in nature. That's why they're important for us to understand," he says.

The tiny liver fluke is widespread in Denmark, and other temperate regions worldwide. The researcher and his colleagues will continue to investigate the parasite, and excactly how it takes over an ant's brain.

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Desert ant increase the visibility of their nest entrances in the absence of landmarks

Desert ants have outstanding navigational skills. They live in the saltpans of North Africa, an extremely inhospitable environment. To find food for their nest mates, foraging ants have to walk far into the desert. Once they have found food, for example a dead insect, their actual problem begins: How do they find their way back to their nest as quickly as possible in the extremely hot and barren environment? "The desert ant Cataglyphis fortis stands out due its remarkable ability to successfully navigate and forage in even the harshest environments, making it an excellent subject for studying the intricacies of navigation. With an innate navigation mechanism called path integration, these ants use both a sun compass and a step counter to measure the distances they cover. In addition, they possess the ability to learn and utilize visible and olfactory cues. We believe that this extremely harsh habitat has led, during evolution, to a navigation system of unsurpassed precision," said Marilia Freire, the study's lead author, summarizing what is known so far about the amazing orientation skills of these small animals.

The scientists had noticed during previous studies in Tunisia that the nests in the center of the saltpans, where there are hardly any visible landmarks, had high mounds at the nest entrances. In contrast, nest hills near the shrub-covered edges of the saltpans were lower or barely noticeable. So the research team has wondered for some time if these visible differences serve a purpose in helping the ants better find their way home. "It's always hard to tell whether an animal does something on purpose or not. The high nest mounds in the middle of the saltpans could have been a side effect of differences in soil structure or wind conditions. However, crucial for our study was the idea to remove the mounds and to provide some nests with artificial landmarks and others not, and to observe what would happen," Markus Knaden, head of the Project Group Odor-guided Behavior in the Department of Evolutionary Neuroethology, explains the goal of the study.

For their experiments, the researchers followed the ants with a GPS device. This allowed them to track the ants on their way to the saltpan and back home. "We observed that desert ants are capable of traveling much greater distances than previously reported. The farthest distance a single animal traveled was more than two kilometers. However, we also observed an unexpectedly high mortality rate. About 20% of foraging ants do not find their way back home after extremely long runs and died in front of our eyes, which explains the enormous selection pressure for even better orientation," says Marilia Freire.

Experiments in which ants could be tracked with particular accuracy during the last meters to the nest, thanks to a grid painted on the floor, showed that the nest hills are important visual cues. If they were removed, fewer ants found their way back to the nest, while their nest mates simultaneously began to rebuild nest mounds as quickly as possible. If, on the other hand, the scientists placed artificial landmarks in the form of small black cylinders near the nest entrances whose mounds they had previously removed, the ants did not invest in building new ones. Apparently, the cylinders were sufficient for orientation.

In ant nests, labor is divided. Ants that go foraging are usually older and more experienced nest members, while younger ants are busy building. Therefore, there must be some kind of information flow between the two groups. The researchers do not yet know exactly how this is achieved. "One possibility would be that ants in the nest somehow notice that fewer foragers return home, and as a result, hill-building activities at the nest entrance are increased," says Marilia Freire.

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Kangaroo Island ants 'play dead' to avoid predators

They're well known for their industrious work, but now a species of ant on Kangaroo Island is also showing that it is skilled at 'playing dead', a behaviour that University of South Australia researchers believe is a recorded world first.

Accidentally discovered as researchers were checking pygmy-possum and bat nest boxes on Kangaroo Island, a colony of Polyrhachis femorata ants appeared to be dead… until one moved.

Researchers believe the ants were 'playing dead' as a defensive strategy to avoid potential danger.

Published by CSIRO, this is the first time that a whole colony of ants has been recorded feigning death, and the first record of the Polyrhachis femorata ant species for South Australia.

Wildlife ecologist, UniSA's Associate Professor S. 'Topa' Petit, says she was surprised to discover a colony of what appeared to be dead ants in one of the nest boxes.

"The mimicry was perfect," Assoc Professor Petit says. "When we opened the box, we saw all these dead ants…and then one moved slightly.

"This sort of defensive immobility is known among only a few ant species -- in individuals or specific casts -- but we don't know of other instances when it's been observed for entire colonies.

"In some of the boxes containing colonies of Polyrhachis femorata, some individuals took a while to stop moving, and others didn't stop. The triggers for the behaviour are difficult to understand."

Assoc Prof Petit says that nest boxes may present an opportunity to study the ants' death-feigning behaviours, which are of great interest to many behavioural ecologists investigating a diversity of animal species.

The discovery was made during the Kangaroo Island Nest Box Project, where 901 box cavities have been monitored across 13 diverse properties as part of wildlife recovery efforts following the devastating 2020 bushfires.

Co-researcher at the Kangaroo Island Research Station, Peter Hammond, says that he used to call the Nest Box Project 'Friends of the Invertebrates', because invertebrates were often the only occupants of the bat and pygmy-possum nest boxes.

"We are learning a lot about invertebrates as well as targeted vertebrates," Hammond says.

"Most of our several hundred boxes are on burnt ground, but we also have some on unburnt properties as controls because our aim is to determine the value of nest boxes in bushfire recovery.

"Polyrhachis femorata is strongly associated with the critically endangered Narrow-Leaf Mallee community, where it colonised several boxes very quickly. However, we also have records for two other properties further west, indicating that the ants will use other habitats.

"We believe that the Polyrhachis femorata species was strongly affected by the bushfires."

Assoc Prof Petit says there is a lot to discover about this species.

"Polyrhachis femorata is a beautiful arboreal ant that tends to be quite shy, but little else is known about its ecology or behaviour," Assoc Prof Petit says.

"We have a relatively unknown world of ants under our feet and in the trees. Ants provide crucial ecosystem services and are a vital part of functional ecosystems on Kangaroo Island and elsewhere.

"It is very exciting that such an endearing species as Polyrhachis femorata is living on Kangaroo Island and we look forward to finding out more about its ecology.

Read more at Science Daily

Male yellow crazy ants are real-life chimeras

The yellow crazy ant, or Anoplolepis gracilipes, has the infamous distinction of being among the worst invasive species in the world. However, this is not the reason for which this particular ant is studied by a team of international researchers. What interests them is how the insects reproduce, because males of this ant have long perplexed scientists. "The results of previous genetic analyses of the yellow crazy ant have shown that the males of this species have two copies of each chromosome. This was highly unexpected, as males usually develop from unfertilized eggs in ants, bees, and wasps -- and thus should only have one maternal copy of each chromosome," explained Dr. Hugo Darras, Assistant Professor at Johannes Gutenberg University Mainz (JGU) and lead author of the corresponding article recently published in Science. "With this in view, we decided to investigate this puzzling phenomenon with subsequent experiments."

Two genomes in different cell clusters

The results were quite extraordinary. It had been assumed to date that the males of the yellow crazy ant carried the same two sets of chromosomes in all cells of their body. However, the team was able to demonstrate that this premise was anything but correct. "We discovered that the male ants have maternal and paternal genomes in different cells of their body and are thus chimeras. To put it another way, all males have two genomes, but each cell of their bodies contains only one or the other of the two genomes," summarized Darras. Normally, in a multicellular life form -- be this a human, a dog, or a bat -- all cells contain identical genetic material.

The research team concludes that male yellow crazy ants are chimeras: they develop from fertilized eggs in which the two parental gametes do not actually fuse. Instead, the maternal and paternal nuclei divide separately within the same egg, meaning that the resultant adult males have both parental DNA sequences but in different body cells. When the gametes do fuse, either a queen or a worker develops from the egg, depending on the genetic information carried by the sperm. It is yet unknown what mechanisms determine whether fusion of the parental gametes takes place or not.

Chimerism and the yellow crazy ant: A mode of reproduction previously unknown to science

Chimeras are individuals whose cells contain different genetic materials. They naturally occur in certain species, such as corals and angler fish, in which separate individuals can merge to become one. Chimerism can also be found in humans and other placenta mammals. During gestation, mother and fetus can exchange a small number of cells so the offspring usually has a few cells that contain the same genetic material as the mother. Such small-scale exchanges also occur between twins in the womb. "In contrast to these known cases, chimerism in the yellow crazy ant does not result from the fusion of two separate individuals or an exchange of cells between them. Instead, this process has its origin within a single fertilized egg. This is unique," concluded Darras. Hence, the development of the male yellow crazy ant appears to contravene one of the fundamental laws of biological inheritance in which all cells of an individual should contain the same genome.

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Reducing their natural signals: How sneaky germs hide from ants

Not only humans are social, ants are too. Group members are taking care of sick ones by providing collective hygiene measures. This presents germs with a task. They must circumvent the immunity of an individual ant and avoid the group's healthcare. A new study now published in Nature Ecology & Evolution reveals that germs develop a sneaky way to escape the ant colony's defense systems by reducing their detection cues.

Pathogens are disease-causing organisms. By natural selection, they develop evading mechanisms to outsmart the host's immune system and to get the upper hand. One way to support the immune system and fight back is medical intervention. However, this can lead to unwanted adaptions of pathogens as seen in antibiotic-resistant bacteria. Another strategy is social intervention. Some social groups like ants are trying to fight infection with "social immunity," the collective hygiene and health care measures to avoid spreading throughout the community. If and how pathogens can respond to this kind of group behavior, is still unknown.

The latest study by Professor Sylvia Cremer and her research team at the Institute of Science and Technology Austria (ISTA) shows the extraordinary effects of these kinds of host-parasite interactions. Together, with chemical ecologists at the University of Würzburg in Germany, the scientists took a close look at social ants, to see how pathogenic fungi respond to their hosts' social care intervention during infection. The results reveal that fungi reduce their chemical detection signals to outplay social immunity. The study is published today in Nature Ecology & Evolution.

More spores but less grooming

"Fungi infect the ants from the body surface and grow inside, but nestmates groom off many of the spores before they can even cause internal infection," explains Barbara Milutinović, one of the lead authors, former postdoc in the Cremer Group and now Marie Curie Sklodowska Fellow at Ruđer Bošković Institute in Croatia. The scientists set up an experiment where Argentine ants (Linepithemahumile) were infected with pathogenic Metarhizium fungi either in the absence or presence of caregiving colony members. "We found that the fungi fundamentally changed in response to the ant workers' caregiving," Milutinović continues. Over ten infection cycles, fungi which experienced grooming nestmate ants boosted their spore production compared to fungi accompanied by only individual ants. "Producing more spores will help the fungus counteract the spore-removal by helping nestmates. Yet, we were surprised to see that the ants showed less grooming against the spores," Sylvia Cremer adds. "This suggests, that the spores have become more difficult to detect by the ants."

Fungi lose their typical chemical profile

To check why ant workers had difficulties sensing fungi and to analyze possible fungal detection cues, the scientists teamed up with a chemical ecologist from the University of Würzburg. Local Professor Thomas Schmitt explains: "The fungi, that adapted to social hosts were perceived less strongly, due to a strong reduction of a fungi-specific compound called ergosterol." Ergosterol is an essential membrane compound, that all fungi have. By exposing the ants to pure fungal ergosterol or the slightly different non-fungal vertebrate equivalent, the researchers showed, that only the fungal compound induced intense grooming. Milutinović summarizes: "This demonstrates that fungal pathogens react to the presence of caregiving ants by reducing their characteristic fungal signals. They are no longer recognized as a disease threat and can escape the social immunity of the colony."

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Oldest army ant ever discovered reveals iconic predator once raided Europe

Their nomadic lifestyle and ravenous raiding have taken army ants (Dorylinae) to most continents on Earth, but a rare fossil discovery is now offering first evidence that the infamous predators once swarmed a land they are strikingly absent from today -- Europe.

In the journal Biology Letters, researchers at New Jersey Institute of Technology and Colorado State University have reported the discovery of the oldest army ant on record, preserved in Baltic amber dating to the Eocene (~35 million years ago).

The eyeless specimen Dissimulodorylus perseus (D. perseus) -- named after the mythical Greek hero Perseus who famously defeated Medusa with the limited use of sight -- marks just the second fossil army ant species ever described, and the first army ant fossil recovered from the Eastern Hemisphere.

Sized at roughly 3 millimeters in length, researchers say the ant fossil brings to light previously unknown army ant lineages that would have existed across Continental Europe before undergoing extinction in the past 50 million years.

Remarkably, the fossil had been kept in obscurity for nearly 100 years in the Museum of Comparative Zoology at Harvard University, before being identified by the paper's lead author and NJIT Ph.D. candidate, Christine Sosiak.

"The museum houses hundreds of drawers full of insect fossils, but I happened to come across a tiny specimen labeled as a common type of ant while gathering data for another project," said Sosiak. "Once I put the ant under the microscope, I immediately realized the label was inaccurate … I thought, this is something really different."

"This amber would have been excavated around or before the 1930s, so to now learn it contained a rare army ant is surprising enough, much less one that demonstrates these ants roamed Europe," said Phillip Barden, assistant professor of biology at NJIT and senior author of the paper. "From everything we know about army ants living today, there's no hint of such extinct diversity. … With this fossil now out of obscurity, we've gained a rare paleontological porthole into the history of these unique predators."

A Paleontological Porthole into a Unique Predator's History

Today, there are about 270 army ant species living in the Eastern Hemisphere, and roughly 150 across North and South America.

Based on X-ray and CT-scan analysis of the fossil, the NJIT team gathered phylogenetic and morphological data that places D. perseus as a close relative to eyeless species of army ants currently found in Africa and Southern Asia, called Dorylus.

"At the time the fossil formed, Europe was hotter and wetter than it is today and may have provided an ideal habitat for ancient army ants," said Barden. "Europe underwent several cooling cycles over tens of millions of years since the Eocene, however, which may have been inhospitable to these tropical-adapted species."

The team's analysis further revealed that the ant possessed an enlarged antibiotic gland, typically found in other army ants for sustaining life underground, suggesting the long-lost European army ant lineage was similarly suited to subterranean living.

It's a factor Sosiak says makes this fossil, and other fossil army ants, a rarity. Only one definitive fossil had been recorded until now, unearthed from the Caribbean (16 ~Ma.).

"This was an incredibly lucky find. Because this ant was probably subterranean like most army ants today, it was much less likely to come into contact with tree resin that forms such fossils," said Sosiak. "We have a very small window into the history of life on our planet, and unusual fossils such as this provide fresh insight."

Sosiak says D. perseus' anatomical traits -- including its sharply pointed mandibles and lack of eyes -- help classify the specimen as a worker ant in its colony, which would have been involved in carrying its queen's larvae and raiding for food with soldier ants when it was alive.

"Army ant workers participate in raiding swarms, hunting other insects and even vertebrates. Because these army ants are blind, they use chemical communication to stay coordinated with one another to take down large prey," explained Sosiak. "This worker may have strayed too far from its fellow hunters and into sticky tree resin, which eventually solidified and encased the ant as we see it today."

Army ants' distinct combination of behavior and traits is so unusual in the ant world, that it's warranted its own name -- army ant syndrome.

In contrast with other ant lineages, army ants have wingless queens capable of laying millions of eggs a day, while their nomadic colonies temporarily occupy nests between phases of travel that take the shape of bivouacs, sometimes involving millions of ants stretching for 100m.

The carnivores are perhaps best known for their highly coordinated foraging that can involve consuming upwards of 500,000 prey a day.

Barden says army ant syndrome is a case of convergent evolution that would have occurred twice -- once in the Neotropics and once in the Afrotropics.

"The discovery is the first physical evidence of the army ant syndrome in the Eocene, establishing that hallmarks of these specialized predators were in place even before the ancestors of certain army ants like Dorylus," said Barden.

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New global map of ant biodiversity reveals areas that may hide undiscovered species

They are hunters, farmers, harvesters, gliders, herders, weavers, and carpenters. They are ants, and they are a big part of our world, comprising over 14,000 species and a large fraction of animal biomass in most terrestrial ecosystems. Like other invertebrates, ants are important for the functioning of ecosystems. They play vital roles from aerating soil and dispersing seeds and nutrients, to scavenging and preying on other species. Yet a global view of their diversity is lacking. Now, researchers from the Biodiversity and Biocomplexity Unit at the Okinawa Institute of Science and Technology (OIST), in collaboration with multiple institutes around the world, have developed a high-resolution map that combines existing knowledge with machine learning to estimate and visualize the global diversity of ants. The maps and dataset were published in an article in Science Advances.

"This study helps to add ants, and terrestrial invertebrates in general, to the discussion on biodiversity conservation," said Prof. Evan Economo, who leads the Biodiversity and Biocomplexity Unit. "We need to know the locations of high diversity centers of invertebrates so that we know the areas that can be the focus of future research and environmental protection."

Prof. Economo added that the resource will also serve to answer a number of biological and evolutionary questions, such as how life diversified and how patterns in diversity arose.

This decade-long project began when study co-first author and former OIST postdoc Dr. Benoit Guénard (now at The University of Hong Kong), worked with Prof. Economo to create a database of occurrence records for different ant species from online repositories, museum collections, and around 10,000 scientific publications. Researchers around the world contributed and helped identify errors. More than 14,000 species were considered, which varied dramatically in the amount of data available.

However, the vast majority of these records, while containing a description of the sampled location, did not have the precise coordinates needed for mapping. To address this, coauthor Kenneth Dudley from OIST's Environmental Informatics Section built a computational workflow to estimate the coordinates from the available data, which also checked all the data for errors.

Then JSPS Postdoctoral Researcher and co-first author Dr. Jamie Kass, with Dudley and research technician Fumika Azuma, made different range estimates for each species of ant depending on how much data was available. For species with less data, they constructed shapes surrounding the data points. For species with more data, the researchers predicted the distribution of each species using statistical models that they tuned for optimal complexity.

The researchers brought these estimates together to form a global map, divided into a grid of 20 km by 20 km squares, that showed an estimate of the number of ant species per square (called the species richness). They also created a map that showed the number of ant species with very small ranges per square (called the species rarity). In general, species with small ranges are particularly vulnerable to environmental changes.

However, there was another problem to overcome -- sampling bias. "Some areas of the world that we expected to be centers of diversity were not showing up on our map, but ants in these regions were not well-studied," explained Dr. Kass. "Other areas were extremely well-sampled, for example parts of the USA and Europe, and this difference in sampling can impact our estimates of global diversity."

So, the researchers utilized machine learning to predict how their diversity would change if they sampled all areas around the world equally, and in doing so, identified areas where they estimate many unknown, unsampled species exist. Prof. Economo said, "This gives us a kind of 'treasure map', which can guide us to where we should explore next and look for new species with restricted ranges."

Okinawa, in southern Japan, was identified as a center for rarity, as many species endemic to these islands have very small ranges, around 1000 times smaller than species spread across North America and Europe. Thus, places like Okinawa are critical for environmental protection to conserve biodiversity.

When the researchers compared the rarity and richness of ant distributions to the comparatively well-studied amphibians, birds, mammals, and reptiles, they found that ants were about as different from these vertebrate groups as the vertebrate groups were from each other, which was unexpected given that ants are evolutionarily highly distant from vertebrates. This is important as it suggests that priority areas for vertebrate diversity may also have a high diversity of invertebrate species. But, at the same time, it is necessary to recognize that ant biodiversity patterns do have unique features. For example, the Mediterranean and East Asia show up as diversity centers for ants more than the vertebrates.

Finally, the researchers looked at how well-protected these areas of high ant diversity are. They found that it was a low percentage -- only 15% of the top 10% of ant rarity centers had some sort of legal protection, such as a national park or reserve, which is less than existing protection for vertebrates.

Read more at Science Daily