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.

“We have no doubt that other ants with similar death-feigning behaviours will be discovered in Australia, but it is thrilling to be among the pioneers.”

The study found that warm water pollution increased growth rates but also death rates, resulting in a population of younger, but larger fish. The finding is at odds in part with general predictions of the effect of warming on natural ecosystems and highlights that these need to be tested in large-scale experiments.

As aquatic ecosystems become warmer, it is predicted that animals such as fish will grow faster at a young age but reach smaller body sizes as adults. This pattern has mainly been observed in small-scale experiments, and although some studies have tested this prediction in natural environments, these have mostly been carried out on fish species subjected to fishing, where the process of fishing itself can influence growth rates and body size.

“Studies into the effects of warming waters on fish from large-scale, semi-controlled experiments in natural settings are rare, yet they can provide unique insights,” says lead author Max Lindmark, researcher at the Swedish University of Agricultural Sciences, Department of Aquatic Resources, Lysekil, Sweden. “We used a unique study system to investigate how warm water pollution has changed the death rates, growth rates and size of fish over many generations.”

The team carried out their study in an enclosed coastal bay that has received cooling water from a nuclear power plant, making it 5-10°C warmer than the surrounding waters. They compared the fish species Eurasian perch from the enclosed bay and from a reference area in the adjacent archipelago over a 24-year time period. They combined data on catches with measurements of the fishes’ length-at-age (back-calculated throughout their life from “age rings” in hard structures), and then analysed these using statistical models to investigate how the warm water pollution affected the age and size of the fish populations, as well as their growth and death rates.

While the researchers found statistically notable differences in estimated growth rates, death rates and sizes of the fish populations between the heated and reference areas, not all of these changes were as they expected. Although female perch in the warm area grew faster, as the team anticipated, they continued to do so throughout life. These fish therefore reached a large size-at-age — approximately 7-11% larger in the heated area at any age, when compared with the reference area. Moreover, the authors say the increase in growth rate of younger fish due to warm water was so pronounced that even if death rates were higher because of warming, and resulted in a younger overall population of fish, the average size and relative abundance of larger fish was still higher in the heated area. This trend conflicts with the prediction that global warming would shrink fish over time, especially the large and old ones. In essence, ecosystem warming instead led to younger, but larger fish in this study.

“Our study provides strong evidence for warming-induced differences in growth and death rates among a natural population of an unexploited temperate fish species exposed to 5-10°C water temperature increases for more than two decades. These effects largely, but not completely, counteract each other — while the fish are younger, they are also larger on average,” says co-author Malin Karlsson, Water Manager at the Department of Nature and Environment, County Administrative board of Västmanland, Sweden.

“These findings highlight that generalised predictions based on theories such as the temperature-size rule may have limited use for predicting changes at a population level, and that both death rates and growth rates are important when studying temperature effects,” concludes senior author Anna Gårdmark, Professor at the Swedish University of Agricultural Sciences, Department of Aquatic Resources, Uppsala, Sweden. “Although we only studied a single species, this unique climate change experiment suggests the effects of heating at the scale of a whole ecosystem, making its findings highly relevant in the context of global warming.”

The research was done on Dungeness crabs and found that ocean acidification causes them to physically sniff less, impacts their ability to detect food odours and even decreases activity in the sensory nerves responsible for smell.

“This is the first study to look at the physiological effects of ocean acidification on the sense of smell in crabs,” says Cosima Porteus, an assistant professor in the department of biological sciences at U of T Scarborough and co-author of the study along with postdoc Andrea Durant.

Ocean acidification is the result of the Earth’s oceans becoming more acidic due to absorbing increasing amounts of carbon dioxide in the atmosphere. It’s a direct consequence of burning fossil fuels and carbon pollution, and several studies have shown it’s having an impact on the behaviour of marine wildlife.

Dungeness crabs are an economically important species found along the Pacific coast, stretching from California to Alaska. They are one of the most popular crabs to eat and their fishery was valued at more than $250 million in 2019.

Like most crabs, they have poor vision, so their sense of smell is crucial in finding food, mates, suitable habitats and avoiding predators, explains Porteus. They sniff through a process known as flicking, where they flick their antennules (small antenna) through the water to detect odours. Tiny neurons responsible for smell are located inside these antennules, which send electrical signals to the brain.

The researchers discovered two things when the crabs were exposed to ocean acidification: they were flicking less and their sensory neurons were 50 per cent less responsive to odours.

“Crabs increase their flicking rate when they detect an odour they are interested in, but in crabs that were exposed to ocean acidification, the odour had to be 10 times more concentrated before we saw an increase in flicking,” says Porteus.

There are a few potential reasons why ocean acidification seems to be impacting sense of smell in crabs. Porteus points to other research done at the University of Hull that showed ocean acidification disrupts odour molecules, which can impact how they bind to smell receptors in marine animals such as crabs.

For this study, published in the journal Global Change Biology, Porteus and Durant were able to test the electrical activity in the crabs’ sensory neurons to determine they were less responsive to odours. They also discovered that they had fewer receptors and their sensory neurons were physically shrinking by as much as 25 per cent in volume.

“These are active cells and if they aren’t detecting odours as much, they might be shrinking to conserve energy. It’s like a muscle that will shrink if you don’t use it,” she says.

Porteus says reduced food detection could have implications for other economically important species such as Alaskan king and snow crabs because their sense of smell functions the same way.

“Losing their sense of smell seems to be climate related, so this might partially explain some of the decline in their numbers,” says Porteus.

“If crabs are having trouble finding food, it stands to reason females won’t have as much energy to produce eggs.”

This research was supported by the Natural Sciences and Engineering Research Council of Canada. Some of the analysis was performed at U of T’s Centre for the Neurobiology of Stress.

The research represents a nearly-unprecedented feat of data analysis: From 2020 to 2022, the small army of mostly first- and second-year students examined the physics of more than 600 real solar flares — gigantic eruptions of energy from the sun’s roiling corona.

The researchers, including 995 undergraduate and graduate students, published their finding May 9 in The Astrophysical Journal. The results suggest that solar flares may not be responsible for superheating the sun’s corona, as a popular theory in astrophysics suggests.

“We really wanted to emphasize to these students that they were doing actual scientific research,” said James Mason, lead author of the study and an astrophysicist at the Johns Hopkins University Applied Physics Laboratory.

Study co-author Heather Lewandowski agreed, noting that the study wouldn’t be possible without the undergrads who contributed an estimated 56,000 hours of work to the project.

“It was a massive effort from everyone involved,” said Lewandowski, professor of physics and fellow of JILA, a joint research institute between CU Boulder and the National Institute of Standards and Technology (NIST).

Campfire physics

The study zeroes in on a mystery that has left even senior astrophysicists scratching their heads.

Telescope observations suggest that the sun’s corona sizzles at temperatures of millions of degrees Fahrenheit. The surface of the sun, in contrast, is much cooler, registering only in the thousands of degrees.

“That’s like standing right in front of a campfire, and as you back away, it gets a lot hotter,” Mason said. “It makes no sense.”

Some scientists suspect that especially tiny flares, or “nanoflares,” which are too small for even the most advanced telescopes to spot, may be responsible. If such events exist, they may pop up across the sun on a nearly constant basis. And, the theory goes, they could add up to make the corona toasty. Think of boiling a pot of water using thousands of individual matches.

The students’ results cast doubt on this theory, Mason said, although he thinks it’s too early to say for sure.

“I was hoping our result was going to be different. I still feel like nanoflares are an important driver of coronal heating,” Mason said. “But the evidence from our paper suggests the opposite. I’m a scientist. I have to go where the evidence is pointing.”

Peak pandemic times

The effort began at the height of the COVID-19 pandemic.

In spring 2020, CU Boulder, like most universities around the country, had moved its courses entirely online. Lewandowski, however, faced a predicament: She was teaching a class on hands-on research called “Experimental Physics I” that fall, and she had nothing for her students to do.

“This was peak pandemic times,” Lewandowski said. “It’s sometimes hard to remember back to what life was like then. These students were very isolated. They were really stressed.”

Mason, who was then a researcher at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder, offered an idea.

The scientist had long wanted to dig into the mathematics of solar flares. In particular, he had tried examining a dataset of thousands of flares that occurred between 2011 and 2018 and had been spotted by instruments in space. They included the National Oceanic and Atmospheric Administration’s Geostationary Operational Environmental Satellite (GOES) series and NASA’s Miniature X-ray Solar Spectrometer (MinXSS), a CubeSat mission designed and built at LASP.

The problem: There were just too many flares to examine on his own.

That’s when Mason and Lewandowski turned to the students for help.

Mason explained that you can infer details about the behavior of nanoflares by studying the physics of larger flares, which scientists have observed directly for decades.

To do just that, students split into groups of three or four and picked a normal flare they wanted to analyze over the course of the semester. Then, through a series of lengthy calculations, they added up how much heat could each of these events pour into the sun’s corona.

Their calculations painted a clear picture: The sum of the sun’s nanoflares likely wouldn’t be powerful enough to heat up its corona to millions of degrees Fahrenheit.

Educational experiences

What is making the corona so hot isn’t clear. A competing theory suggests that waves in the sun’s magnetic field carry energy from inside the sun to its atmosphere.

But the study’s actual findings aren’t its only important results. Lewandowski said her students were able to have opportunities that are rare for scientists and engineers so early in their careers — to learn first-hand about the collaborative and often-messy way that scientific research works in the real world.

“We still hear students talking about this course in the halls,” she said. “Our students were able to build a community and support each other at a time that was really tough.”

CU Boulder co-authors of the new study include Alexandra Werth, postdoctoral researcher at JILA; Colin West, teaching associate professor in physics; Allison Youngblood, astrophysicist at LASP now at the NASA Goddard Space Flight Center; Donald Woodraska, data systems team lead at LASP; and Courtney Peck, data systems software engineer at LASP and the Cooperative Institute for Research in Environmental Sciences (CIRES).

Funding for the research came from NASA through the MinXSS mission and the U.S. National Science Foundation through the STROBE Science & Technology Center and JILA Physics Frontier Center.

Tuberculosis infects more than 2 billion people in the world, and although tuberculosis is the most common co-infection in people living with HIV, previous studies have not examined how tuberculosis impacts HIV immune responses and virus characteristics.

This study suggest that tuberculosis may impact the efficacy of antibody based prevention and therapeutic strategies. Vaccines to elicit antibodies and antibodies are also being investigated as a means to treat and cure HIV. Higher prevalence of antibody resistant strains along with tuberculosis disease implies that these antibody-based interventions are more likely to in fail in these individuals.

“Tuberculosis is extremely common, especially in regions of the world with high levels of ongoing HIV transmission, and impacts both the immune responses and the characteristics of the circulating virus in people living with HIV so it is imperative we understand the relationship between the two,” said Manish Sagar, MD, an internist at Boston Medical Center and Professor of Medicine at Boston University Chobanian & Avedisian School of Medicine. “These studies have implications for HIV vaccines and antibody based HIV therapeutics.”

Researchers worked closely with investigators in Uganda and at the AIDS Clinical Trial Group (ACTG) to collect samples from people newly diagnosed with HIV that either did or did not have tuberculosis. From these individuals, they examined samples collected prior to and about 6 months after the start of HIV medications. Researchers compared antibodies, plasma inflammatory markers, and HIV sequences in the baseline and in treatment samples.

Tuberculosis disease is associated with higher prevalence of the some antibody resistant HIV. High ongoing HIV transmission in areas of the world with frequent tuberculosis disease suggest that a potential vaccine that elicits broad and potent antibodies may not work because these geographic regions are more likely to have antibody resistant strains.

Researchers highlight that this study has implications for HIV vaccine strategies as they aim to generate antibodies that can block the virus after exposure. Generating broad and potent HIV antibodies has not been accomplished and remains a monumental challenge. But Tuberculosis disease generates broadly potent antibody responses and dissecting biological pathways that provide insight into how tuberculosis enhances HIV antibody responses could be leveraged to develop novel strategies for eliciting broad and potent HIV antibodies.

Monitoring wildlife is one of the most costly and difficult aspects of conservation, and often depends on long-term observations in individual species.

But the study reveals a new and effective method.

It focusses on “interactions” between species, such as insects pollinating flowers or birds feeding on plants.

The results show that a small snapshot of interactions is a reliable indicator of the health of an entire community of species. Specifically, the study looked at whether these communities are “persistent” or not — meaning whether all species are fine or if any are declining to extinction.

The study was carried out by the University of Exeter, McGill University, the University of Toronto, Princeton University and MIT.

“All communities of plants and animals are supported by an underlying network of interactions between species,” said Dr Christopher Kaiser-Bunbury, from the Centre for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall.

“Our study — which combines theory, statistics and real-world data — shows that examining a few of these interactions can provide ‘big picture’ conclusions about ecosystem health.

“This information is essential for policymakers, scientists and societies, as we try to tackle the global biodiversity crisis.”

When environmental conditions change, interactions between species often change too — providing an early indicator of wider problems.

As such, the study’s method can identify patterns more quickly than some traditional conservation monitoring — which is vital given the rapid changes being caused by human activity.

“Using minimal resources, we can rapidly assess both the persistence of entire ecological networks and the expected success of restoration,” said Dr Benno Simmons, also from Exeter’s Centre for Ecology and Conservation.

“Our method is especially effective at identifying when an ecological community is not persistent — allowing for rapid detection of extinction risk.”