Tag Archives: #insects

Insect Evolution Was More Complex Than Previously Assumed (Biology)

Certain signalling proteins, which are responsible for the development of innate immune function in almost all animals are also required for the formation of the dorsal-ventral (back-belly) axis in insect embryos. A new study by researchers from the University of Cologne’s Institute of Zoology suggests that the relevance of these signalling proteins for insect axis formation has increased independently several times during evolution. For example, the research team found similar evolutionary patterns in the Mediterranean field cricket as in the fruit fly Drosophila, although the two insects are only very distantly related and previous observations suggested different evolutionary patterns. The new findings show that the evolution of axis formation in insects was actually much more complex than previously thought. The study has been published in eLife.

Signalling proteins play an important role in the early development of embryos. They are secreted by animal cells to influence the formation of other cells. The primary function of the so-called Toll signalling pathway is in the defence against pathogens (innate immune response). In insects, it is also involved in the division of the insect body along the dorsal-ventral body axis. Since the immune function has been found in almost all animals, but the axis formation function has only been found in insects, scientists wondered about the evolutionary history of this new role. Moreover, depending on the insect species, the significance of Toll for developmental processes differs. While axis formation in the fruit fly and flour beetle depend substantially on Toll, representatives of distantly related species, such as the wasp Nasonia and the milkweed bug Oncopeltus, rely more heavily on other signalling pathways. ‘Surprisingly, we found that the Toll signalling pathway plays a significant role in an insect that is separated by almost 400 million years from the species we studied so far,’ said Professor Dr Siegfried Roth from the Institute of Zoology. ‘The new study suggests that there might be several instances in which Toll independently acquired important functions in insect axis formation. For future studies, this means that our system allows us to explore mechanisms of parallel evolution.’

Featured image: University of Cologne scientists found out that the Toll signalling pathway is important not only for innate immune response, but also for axis formation in various insects. © Roth/Pechmann

Reference: Matthias Pechmann et al., “Striking parallels between dorsoventral patterning in Drosophila and Gryllus reveal a complex evolutionary history behind a model gene regulatory network”, Evolutionary Biology, 2021. DOI: 10.7554/eLife.68287

Provided by University of Cologne

Paleontologists Discover Major New Insect Group After Solving 150-year-old Mystery (Paleontology)

For more than 150 years, scientists have been incorrectly classifying a group of fossil insects as damselflies, the familiar cousins of dragonflies that flit around wetlands eating mosquitoes. While they are strikingly similar, these fossils have oddly shaped heads, which researchers have always attributed to distortion resulting from the fossilization process.

Now, however, a team of researchers led by Simon Fraser University (SFU) paleontologist Bruce Archibald has discovered they aren’t damselflies at all, but represent a major new insect group closely related to them.

The findings, published today in Zootaxa, show that the distinctive shape of the insect’s non-protruding, rounded eyes, set close to the head, are the defining features of a suborder related to damselflies and dragonflies that the researchers have named Cephalozygoptera.

 “When we began finding these fossils in British Columbia and Washington State, we also thought at first they must be damselflies,” says Archibald.

But on closer inspection, the team noticed they resembled a fossil that German paleontologist Hermann Hagen wrote about in 1858. Hagen set the precedent of linking the fossil to the damselfly suborder despite its different head shape, which didn’t fit with damselflies at all.

Wings of the new species Okanagrion threadgillae, from the Republic fossil site in northern Washington, a damselfly-like insect of the new suborder Cephalozygoptera. Copyright Zootaxa, used by permission.

Damselflies have short and wide heads with eyes distinctively protruding far to each side. Hagen’s fossil, however, had an oddly rounded head and eyes. But he assumed this difference was false, caused by distortion during fossilization.

“Paleontologists since Hagen had written that these were damselflies with distorted heads,” Archibald says. “A few hesitated, but still assigned them to the damselfly suborder.”

The SFU-led team, including Robert Cannings of the Royal British Columbia Museum, Robert Erickson and Seth Bybee of Brigham Young University and SFU’s Rolf Mathewes, sifted through 162 years of scientific papers and discovered that many similar specimens have been found since Hagen’s time.

They experienced a eureka moment when they realized the odd heads of their new fossils were, in fact, their true shape.

The researchers used the fossil’s defining head shape to name the new suborder Cephalozygoptera, meaning “head damselfly.”

The oldest known species of Cephalozygopteralived among dinosaurs in the Cretaceous age in China, and were last known to exist about 10 million years ago in France and Spain.

“They were important elements in food webs of wetlands in ancient British Columbia and Washington about 50 million years ago, after the extinction of the dinosaurs,” says Archibald. “Why they declined and went extinct remains a mystery.”

Paleontologist Bruce Archibald doing fieldwork at the McAbee fossil site in southern British Columbia, where many specimens were discovered of the new insect suborder Cephalozygoptera. Light coloured fossil-bearing sediments are exposed on the hillside behind him © Zootaxa

The team named 16 new species of Cephalozygoptera. Some of the fossils were found on the traditional land of the Colville Indian tribe of northern Washington, and so Archibald and his coauthors collaborated with tribal elders to name a new family of them. They called the family “Whetwhetaksidae,” from the word “whetwhetaks”, meaning dragonfly-like insects in the Colville people’s language.

Archibald has spent 30 years combing the fossil-rich deposits of southern British Columbia and northern interior Washington. To date, in collaboration with others, he has discovered and named more than 80 new species from the area.

Featured image: Wing of the new species Okanagrion hobani, from the McAbee fossil site in British Columbia, a damselfly-like insect of the new suborder Cephalozygoptera. Copyright Zootaxa, used by permission.

Reference: S. BRUCE ARCHIBALD, ROBERT A. CANNINGS, ROBERT J. ERICKSON, SETH M. BYBEE, ROLF W. MATHEWES, “The Cephalozygoptera, a new, extinct suborder of Odonata with new taxa from the early Eocene Okanagan Highlands, western North America”, Zootaxa, Vol 4934, No 1, 24 Feb. 2021. DOI: https://doi.org/10.11646/zootaxa.4934.1 https://www.mapress.com/j/zt/issue/view/zootaxa.4934.1

Provided by SFU

Amber-encased Fossil Shines Light on Evolution of Bioluminescent Insects (Paleontology)

Preserved with ‘life-like’ fidelity, beetle from the Cretaceous is fireflies’ missing fossil link.

Trapped in amber for ~100 million years, an exceptionally well-preserved, light-producing beetle sheds light on the diversification of bioluminescent beetles in the Cretaceous period and provides the missing fossil link between fireflies’ living relatives.

Artistic reconstruction of Cretophengodes azari male and female in the undergrowth of a Cretaceous rainforest. © Dinghua Yang

With over 3,500 described species, light-producing beetles are the most diverse bioluminescent terrestrial animals. Fireflies, fire beetles, glow-worm beetles and their kin use light to ward off predators, attract mates, and some females even use it to attract unsuspecting males to eat. Historically, despite their diversity, the evolution of bioluminescence in beetles has been poorly understood.

“Most light-producing beetles are soft-bodied and quite small, and so have a scant fossil record. However, this new fossil, found in amber from northern Myanmar, is exceptionally well-preserved, even the light organ on its abdomen is intact,” said Dr. Chenyang Cai, research fellow at the University of Bristol and associate professor at NIGPAS.

The presence of a light organ on the abdomen of the male provides direct evidence that that adults of Cretophengodes were capable of producing light, some 100 million years ago.

“The newly discovered fossil, preserved with life-like fidelity in amber, represents an extinct relative of the fireflies and the living families Rhagophthalmidae and Phengodidae,” says Yan-Da Li from the Nanjing Institute of Geology and Palaeontology (NIGP) and Peking University in China.

The majority of light-producing beetles fall into the giant superfamily Elateroidea with some 24 thousand known species and thousands more awaiting to be described. The discovery of this beetle, published in the Proceedings of the Royal Society B, provides the missing fossil link between living families and in doing so helps scientists understand how these beetles evolved and how they should be classified.

Cretophengodes azari, a fossil light-producing beetle from Cretaceous Burmese amber (~100 million years old). © Chenyang Cai

“Elateroidea is one of the most heterogeneous groups of beetles and that has always been very difficult for entomologists to deal with, particularly because important anatomical innovations evolved many times independently in unrelated groups. The discovery of a new extinct elateroid beetle family is significant because it helps shed light on the evolution of these fascinating beetles,” says Erik Tihelka from the School of Earth Sciences.

“We think that light production initially evolved in the beetle’s soft and vulnerable larvae as a defensive mechanism to ward off predators. The fossil shows that by the Cretaceous, light production was taken up by the adults as well. It could have than been co-opted to serve other functions such as locating mates,” says Robin Kundrata, an expert on elateroid beetles from Palacký University in the Czech Republic.

Light producing beetles often have unusual adaptations. One of the most striking ones is that the females often don’t look anything like their male counterparts and instead retain many larval features into adulthood.

“A good example of this is the trilobite beetle, where the females don’t look like beetles at all and instead superficially resemble trilobites. This means that females often get overlooked when collecting in the field. We want to focus on these unusual beetles when searching the fossil record in the years to come,” said Yan-Da Li.

The study was supported by the National Natural Science Foundation and the Chinese Academy of Sciences.

Reference: Yan-Da Li, Robin Kundrata, Erik Tihelka, Zhenhua Liu, Diying Huang and Chenyang Cai, ‘Cretophengodidae, a new Cretaceous beetle family sheds light on the evolution of bioluminescence,’ Proceedings of the Royal Society B, 2021. DOI: 10.1098/rspb.2020.2730 http://dx.doi.org/10.1098/rspb.2020.2730

Provided by University of Bristol

Aphids Suck: Invasive Aphid Found on Danish Apple Trees (Biology)

The spirea aphid, Aphis spiraecola, an invasive pest, has been discovered for the first time in Denmark by University of Copenhagen researchers. The extent of its current distribution remains unknown, but in time, it could prove to be a troublesome pest for Danish apple growers.

Whether the discovery of this aphid in Denmark is an isolated incident, or if the species has made itself at home due to a milder climate, remains unknown to the researchers. Closer investigation is needed. Photo: UCPH/Uni.Budapest

In a collaboration with colleagues at the University of Budapest, University of Copenhagen researchers have analysed and compared a number of samples of green aphids from apples around the world and discovered a new apple-loving pest in Denmark.

The bright greenish yellow spirea aphid—Aphis spiraecola— which most likely originates in East Asia, has gradually become a widespread pest in tropical and temperate regions around the planet. While it is especially problematic for citrus and apple trees, it can attack many other plant species. The aphid has been in the United States for the last 100 years and was discovered in Mediterranean countries in 1939. However, the spirea aphid has never been witnessed in the Nordic countries before.

“It is a serious pest that is more well known in countries a touch warmer than Denmark and is particularly harmful to citrus crops. It was identified in Germany in 2000, and the Baltic states a few years later. Now, it is here in Denmark. So, this is definitely something that we need to keep an eye on, as it could prove to be problematic for Danish apple growers,” warns Associate Professor Lene Sigsgaard of the University of Copenhagen’s Department of Plant and Environmental Sciences. For the past 20 years, Sigsgaard has researched natural predators and pest regulation in apple and other species.

Sucks nourishment out of the plants upon which it poos

Aphids have specialised mouth parts designed to pierce and suck nourishment from plants. Their liquid excrement, honeydew, is characterized by sticky areas on leaves and fruit. Sooty mold spores are captured by and can grow in the sticky honeydew coating a leaf, causing affected leaves to become dark, which blocks sunlight and reduces photosynthesis.

“Aphids can affect a plant in several ways. Among other things, they suck nourishment from plants, energy that would have otherwise been used to produce new shoots and fruits. This stresses plants and can reduce yields in both the current and following season,” explains Lene Sigsgaard. 

While the rosy apple aphid is currently enemy number one in Danish apple orchards, the bright green spiraea aphid could cause problems too. Only the future can tell what this little sucker’s ultimate impact will be.  

Virus spreaders

Aphis spiraecola is a virus vector on citrus fruit and can also spread plum pox virus, also called Sharka, which has yet to be observed in Denmark.

Whether the discovery of this aphid in Denmark is an isolated incident, or if the species has made itself at home due to a milder climate, remains unknown to the researchers. Closer investigation is needed.

Its natural predators, which typically keep aphid populations in check and limit damage, could help to regulate this invasive new aphid.

With increased biodiversity in and around orchards and fields, readily catalyzed by planting flowering hedges and flower rows, populations of natural predators such as ladybirds, green lacewings, spiders, kissing bugs and parasitoid wasps can be supported to combat and reduce aphid populations.

Fact Box

Species: Aphis spiraecola Patch, also known as the spirea aphid or green citrus aphid (Hemiptera, Aphididae)
Physical appearance: Bright greenish yellow to apple green aphid easily confused with the green apple aphid (Aphis pomi), yet with minor morphological differences. The aphid often occurs in mixed colonies of other aphids.
Origin: Probably East Asia
Distribution: Now widespread over tropical and temperate regions worldwide. Can be spread with plant material. Winged generations during spring and late summer allow the species to spread themselves.
Host plants: Spirea, citrus, and apples are primary hosts where eggs are laid. The species also attacks other seed fruits, stone fruits, etc., and in the tropics, species including cocoa. The aphid can live on at least 20 different plant genera, making it very polyphagous.
Life: Across most of its range, the species reproduces asexually year-round (females give birth to new females without mating). In Denmark, the vast majority of aphid species winter as eggs, except for the peach aphid. Whether this new species will winter in Denmark as eggs or aphids in large numbers is unknown.
Impact: Commonly attacks citrus and apple trees. Aphids suck nourishment from plants. Sooty mold growing in honeydew can decrease a plant’s ability to photosynthesize. The aphid causes apple leaves to curl and may cause the tips of branches to produce abnormally little growth. Severely-infested leaves become small, bright and may fall prematurely. Symptoms are similar to those caused by green apple aphids.
Viruses: The species is a virus vector for several species including CTV on citrus and plum pox virus.

Read the research article: https://static-curis.ku.dk/portal/files/253648977/108_2020_PPS.pdf

Provided by University of Copenhagen

How Insects Activate Muscles to Adapt to Limbs Removed? (Biology)

Adaptability explains why insects spread so widely and why they are the most abundant animal group on earth. Insects exhibit resilient and flexible locomotion, even with drastic changes in their body structure such as losing a limb.

A research group now understands more about adaptive locomotion in insects and the mechanisms underpinning it. This knowledge not only reveals intriguing information about the biology of insects, but it can also help to design more robust and resilient multi-legged robots that are able to adapt to similar physical damage.

The insect nervous system is comprised of approximately 105 to 106 neurons. Understanding the process behind this requires researchers to consider the role of the intrinsic neural circuits that influence the adaptions of insects under unfavorable circumstances and the sensory feedback mechanisms reflected in their body characteristics and physical interactions with the environment.

A research group comprising associate professor Dai Owaki from Tohoku University’s Department of Robotics at the Graduate School of Engineering and associate professor Hitoshi Aonuma from the Research Institute of Electronic Science at Hokkaido University simultaneously recorded the leg movements and muscle activation of crickets, both before and after middle leg amputation.

Intact cricket walking (top) and walking after both middle leg amputation (bottom). The left panels show the patterns of leg movements. The right panels show muscle activation patterns. After leg amputation, the middle leg muscle activation shifted from anti-phase to in-phase synchronization. ©Dai Owaki and Hitoshi Aonuma

Their findings showed that the walking manner of crickets shifted from a tetrapod/tripod gait to a four-legged trot after the middle leg had been removed.

Electromyogram (EMG) analysis of the muscles at the base of the middle leg revealed that the muscles were active in opposite phases when walking. Activation timing of the middle leg muscles synchronized in phase when both legs had been removed, whereas the activation timing showed anti-phase synchronization for crickets with all of their legs.

X-ray micro-computed tomography (microCT) imaging of the crickets. ©Dai Owaki and Hitoshi Aonuma

The findings demonstrated two things. First, an intrinsic contralateral connection exists within the mesothoracic ganglion, which generates in-phase synchronization of muscle activation. Second, mechanoreceptive informational feedback from the campaniform seensilla of the legs overrides the centrally generated patterns, resulting in the anti-phase leg movements of a normal gait.

“Our results will pave the way for the further understand of leg coordination mechanisms in insect locomotion,” said professor Dai Owaki. “It may also aid design principles for a decentralized controller that enables flexible and adaptive walking in an insect-like-six-legged robot.”

Reference: Leg amputation modifies coordinated activation of the middle leg muscles in the cricket Gryllus bimaculatus
Authors: Dai Owaki, Hitoshi Aonuma, Yasuhiro Sugimoto, and Akio Ishiguro
Journal: Scientific Reports
DOI: 10.1038/s41598-020-79319-6

Provided by Tohoku University

Unsure How to Help Reverse Insect Declines? Scientists Suggest Simple Ways (Entomology / Biology)

Entomologist Akito Kawahara’s message is straightforward: We can’t live without insects. They’re in trouble. And there’s something all of us can do to help.

Kawahara’s research has primarily focused on answering fundamental questions about moth and butterfly evolution. But he’s increasingly haunted by studies that sound the alarm about plummeting insect numbers and diversity.

Paper wasps play important roles as pollinators and predators of some plant pests, including caterpillars, cicadas and beetle larvae. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

Kawahara has witnessed the loss himself. As a child, he collected insects with his father every weekend, often traveling to a famous oak outside Tokyo whose dripping sap drew thousands of insects. It was there he first saw the national butterfly of Japan, the great purple emperor, Sasakia charonda. When he returned a few years ago, the oak had been replaced by a housing development. S. charonda numbers are in steep decline nationwide.

While scientists differ on the severity of the problem, many findings point to a general downward trend, with one study estimating 40% of insect species are vulnerable to extinction. In response, Kawahara has turned his attention to boosting people’s appreciation for some of the world’s most misunderstood animals.

“Insects provide so much to humankind,” said Kawahara, associate curator at the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity. “In the U.S. alone, wild insects contribute an estimated $70 billion to the economy every year through free services such as pollination and waste disposal. That’s incredible, and most people have no idea.”

Once abundant in in the greater Miami area and the Florida Keys, Schaus’ swallowtail butterfly is now a critically endangered species. It was the first insect listed under the Endangered Species Act, along with the Bahamian swallowtail. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE
Bees and butterflies aren’t the only pollinators. Flies, beetles, moths and other insects also play a key role in helping flowering plants reproduce. Here, a hummingbird hawk moth unfurls its long proboscis to feed. © FLORIDA MUSEUM PHOTO BY JEFF GAGE

Insects sustain flowering plants, the lynchpins of most land-based ecosystems, and provide food sources for birds, bats, freshwater fish and other animals. But they face a barrage of threats, including habitat loss, pesticides, pollution, invasive species and climate change. If human activities are driving the decline, Kawahara reasons, then people can also be a part of the solution.

In an opinion piece published in a special edition of the Proceedings of the National Academies of Science, Kawahara and his collaborators outline easy ways everyone can contribute to insect conservation.

Mow less

If you have a lawn, mowing less can give insect populations a boost. Kawahara suggests reserving 10% of a landscape for insects, either actively replacing a monoculture of grass with native plants or simply leaving the space unmown. These miniature nature preserves provide crucial habitat and food reservoirs for insects, he said, particularly if they remain free of chemical pesticides and herbicides. Benefits for lawn-maintainers include less yardwork and lower expenses.

Cultivating natural habitat provides a home for beneficial predators, such as this jagged ambush bug. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

“Even a tiny patch could be hugely important for insects as a place to nest and get resources,” Kawahara said. “It’s a stepping-stone they can use to get from one place to another. If every home, school and local park in the U.S. converted 10% of lawn into natural habitat, this would give insects an extra 4 million acres of habitat.”

If you don’t have a lawn, you can still help by cultivating native plants in pots in window boxes or on balconies and patios.

Dim the lights

Nighttime light pollution has spiked since the 1990s, doubling in some of the world’s most biodiverse places. Artificial lights are powerful attractants to nocturnal insects, which can exhaust themselves to death by circling bulbs or fall prey to predators that spot an easy target.

Akito Kawahara holds a hawk moth while filming a special segment of PBS’ “American Spring Live” highlighting the diversity of Florida’s nocturnal insects. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

You can give insects a hand – and reduce your electric bill – by turning off unnecessary lights after dark and using amber or red bulbs, which are less attractive to insects.

Florida is home to eight species of giant water bug, powerful aquatic predators of insects, small fish and other organisms. Frequently drawn to outdoor lights, they are sometimes known as “electric light bugs.” © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE
Beetles are the most diverse animals on the planet, comprising about 400,000 species – about 25% of all known animal Life forms. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

Use insect-friendly soaps and sealants

Chemical pollutants in soaps for washing cars and building exteriors and in coal-tar-based driveway sealants can harm a variety of insect life. Kawahara recommends swapping these out for biodegradable soaps and soy-based sealants. In winter, trading rock salt for salt-free formulations is safer for both insects and pets.

Become an insect ambassador

The majority of Earth’s more-than 3,000 mosquito species are not harmful to people. Toxorhynchites rutilus feeds on nectar as an adult. In its larval stage, it preys on other mosquitoes. PHOTO COURTESY OF LAWRENCE REEVES

In the U.S., insects have historically been depicted as devourers of crops, disease vectors and hallmarks of poor sanitation, even though the vast majority do not harm humans. Kawahara said rethinking your own stereotypes of insects and gaining a better understanding of their beauty, diversity and roles is a first step in helping others appreciate them, too.

He recalled leading schoolchildren on an insect-collecting trip during which a student found an elephant stag beetle, an enormous insect with massive jaws – “one of the coolest, most amazing bugs,” Kawahara said.

The student wanted to step on the beetle, thinking it was a cockroach.

“Other students were grossed out, too,” Kawahara said. “When I saw that, I was dumbfounded. If this was Japan, kids would be clamoring to be the first to get it and keep it as a pet. The juxtaposition of those cultural reactions was striking.”

He pointed to media characterizations of Asian giant hornets – which he grew up seeing drink sap from the oak tree outside of Tokyo – as “murder hornets” as another example of how framing insects as dangerous or disgusting has the power to evoke strong reactions from the public.

Positive early experiences with insects can help foster an appreciation for nature, Kawahara said. © FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

As antidotes to unfounded fears, walk outdoors to look for local insect life or adopt pet insects, a simple, inexpensive way to introduce children to science, Kawahara said. Documenting what you see on platforms such as iNaturalist not only helps you learn more about your finds, but also provides data for scientific research.

These small steps have the power to effect immediate changes for the planet’s insects, Kawahara said.

“The best way for change to happen quickly is for everyone to pitch in. As individuals, we can all do these kinds of activities right away.”

Co-authors of the article are Lawrence Reeves of the University of Florida, Jesse Barber of Boise State University and a Florida Museum research associate, and Scott Black of the Xerces Society for Invertebrate Conservation.

Some authors received funding from the National Science Foundation.

Reference: Akito Y. Kawahara, Lawrence E. Reeves, Jesse R. Barber, Scott H. Black, “Opinion: Eight simple actions that individuals can take to save insects from global declines”, Proceedings of the National Academy of Sciences Jan 2021, 118 (2) e2002547117; DOI: 10.1073/pnas.2002547117 https://www.pnas.org/content/118/2/e2002547117

Provided by Florida Museum

Charles Darwin Was Right About Why Insects are Losing The Ability to Fly (Biology)

Most insects can fly.

Yet scores of species have lost that extraordinary ability, particularly on islands.

On the small islands that lie halfway between Antarctica and continents like Australia, almost all the insects have done so.

Flies walk, moths crawl.

“Of course, Charles Darwin knew about this wing loss habit of island insects,” says PhD candidate Rachel Leihy, from the Monash University School of Biological Sciences.

“He and the famous botanist Joseph Hooker had a substantial argument about why this happens. Darwin’s position was deceptively simple. If you fly, you get blown out to sea. Those left on land to produce the next generation are those most reluctant to fly, and eventually evolution does the rest. Voilà.”

But since Hooker expressed his doubt, many other scientists have too.

In short, they have simply said Darwin got it wrong.

Yet almost all of these discussions have ignored the place that is the epitome of flight loss – those ‘sub-Antarctic’ islands. Lying in the ‘roaring forties’ and ‘furious fifties’, they’re some of the windiest places on Earth.

“If Darwin really got it wrong, then wind would not in any way explain why so many insects have lost their ability to fly on these islands,” said Rachel.

Using a large, new dataset on insects from sub-Antarctic and Arctic islands, Monash University researchers examined every idea proposed to account for flight loss in insects, including Darwin’s wind idea.

Reporting today in Proceedings of the Royal Society B, they show that Darwin was right for this ‘most windy of places’. None of the usual ideas (such as those proposed by Hooker) explain the extent of flight loss in sub-Antarctic insects, but Darwin’s idea does. Although in a slightly varied form, in keeping with modern ideas on how flight loss actually evolves.

Windy conditions make insect flight more difficult and energetically costly. Thus, insects stop investing in flight and its expensive underlying machinery (wings, wing muscles) and redirect the resources to reproduction.

“It’s remarkable that after 160 years, Darwin’s ideas continue to bring insight to ecology,” said Rachel, the lead author of the paper.

Professor Steven Chown, also from the School of Biological Sciences, added that the Antarctic region is an extraordinary laboratory in which to resolve some of the world’s most enduring mysteries and test some of its most important ideas.

Provided by Monash University

High Temperatures Threaten The Survival of Insects (Biology)

Insects have difficulties handling the higher temperatures brought on by climate change, and might risk overheating. The ability to reproduce is also strongly affected by rising temperatures, even in northern areas of the world, according to a new study from Lund University in Sweden.

Insects cannot regulate their own body temperature, which is instead strongly influenced by the temperature in their immediate environment. In the current study, the researchers studied two closely related species of damselflies in Sweden. The goal was to understand their robustness and ability to tolerate changes in temperature.

To study this, the researchers used a combination of field work in southern Sweden and infrared camera technology (thermography), a technology that makes it possible to measure body temperature in natural conditions. This information was then connected to the survival rates and reproductive success of the damselflies in their natural populations.

The results show that survivorship of these damselflies was high at relatively low temperatures, 15 – 20 C °. The reproductive capacity, on the other hand, was higher at temperatures between 20 and 30 C °, depending on the species.

“There is therefore a temperature-dependent conflict between survival on one hand and the ability to reproduce on the other”, says Erik Svensson, professor at the Department of Biology at Lund University, who led the study.

The study also shows that the damselflies ability to handle heat-related stress is limited. Insects are cold-blooded invertebrates, so they rely on external sources such as the sun or hot stones to raise their body temperature.

“Our results show that cold-blooded animals can suffer from overheating even if they live far up in the northern hemisphere, and that their ability to buffer their body temperature against rising external temperatures is limited. The results also challenge a popular theory that animals’ plasticity, i. e. their individual flexibility, can help them survive under harsher environmental conditions, such as during heat waves”, says Erik Svensson.

Provided by Lund University

When Plants Attack: Parasitic Plants Use Ethylene As A Host Invasion Signal (Botany)

Researchers from Nara Institute of Science and Technology find that the plant hormone ethylene mediates the invasion of hosts by parasitic plants.

Mutants that reveal the secrets of how plants attack? No, it’s not a scene from a science fiction movie, but you could be forgiven for thinking that. Instead, it’s a scene from real life:

Photo of the model parasitic plant, Phtheirospermum japonicum (left), and its haustorium (right). P: parasitic plant, H: host plant. The right lower photo shows xylem connection between a host and a parasite. Bar = 200 μm. ©Satoko Yoshida.

Researchers at Nara Institute of Science and Technology in Japan report in a new study in Science Advances that parasitic plants use the plant hormone ethylene as a signal to invade the roots of host plants.

To develop a successful parasitic relationship, parasitic plants form a specialized structure, the haustorium which attaches to and invades the host plant. The formation of haustoria is regulated by signal molecules derived from the host plant and allows the parasitic plant to absorb water, nutrients, and small materials from the host plant.

“To understand the genetic programs for haustorium development, we identified mutants that displayed haustorial defects on host invasion,” says lead author of the study Songkui Cui. “Genome sequencing showed that these mutants have defective ethylene signaling, and it turned out that ethylene signaling genes are crucial for the parasitic plant to infect its host plant.”

Ethylene is a gaseous plant hormone that is involved in fruit ripening, aging of leaves, and the formation of root nodules. Ethylene is also widely involved in plant interactions with viruses and numerous organisms, such as insects and bacteria, lending either resistance or susceptibility to plants depending on the types of pathogens.

“Our results indicate that ethylene mediates host recognition in parasitic plants for host invasion,” explains project leader Satoko Yoshida. “This is the first time that the mediation of host invasion by parasitic plant genes has been identified via forward genetics. Our findings offer a new understanding of how a parasitic plant uses the ethylene molecule to tweak haustorium development and host invasion.”

Forward genetics is used to identify genes, or sets of genes, that produce a particular characteristic in an organism. The model species used in this study is from a family of parasitic plants that includes destructive weeds. But the molecular basis for their parasitism has been largely unexplored until now.

“Our results suggest that parasitic plants have taken over ethylene signaling for parasitism at multiple stages of their life cycle, such as germination, haustorium growth termination, and host invasion. This knowledge could provide new ways to use ethylene and ethylene inhibitors to control a broader range of parasitic weeds, including those that don’t rely entirely on hosts to complete their life cycle, by manipulating haustorial function,” says Cui.

References: Songkui Cui, Tomoya Kubota, Tomoaki Nishiyama, Juliane K. Ishida, Shuji Shigenobu, Tomoko F. Shibata, Atsushi Toyoda, Mitsuyasu Hasebe, Ken Shirasu & Satoko Yoshida, “Ethylene signaling mediates host invasion by parasitic plants”, Science Advances, Vol. 6, no. 44, 2020. eabc2385 http://dx.doi.org/10.1126/sciadv.abc2385 DOI: 10.1126/sciadv.abc2385

Provided by Nara Institute Of Science and Technology