PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Beetles under climate stress lay larger male eggs: Wolbachia infection drives adaptive reproduction strategy in response to rising temperature and CO₂

Researchers find that azuki bean beetles, a common pest, produce larger eggs yielding male offspring when infected with Wolbachia bacteria under elevated temperature and carbon dioxide conditions

2025-07-11
(Press-News.org)

Fukuoka, Japan—Researchers at Kyushu University have found that when azuki bean beetles infected with Wolbachia bacteria are exposed to a simulated climate change environment—characterized by elevated temperature and carbon dioxide—they tend to produce larger eggs to enhance the survivability of their offspring. Interestingly, these larger eggs gave rise exclusively to male larvae.

The study, published in Scientific Reports, demonstrates the benefits of Wolbachia infection under adverse environmental conditions in these beetles. It is also the first observation of sex-dependent changes in egg size in a species with chromosomal sex determination.

The azuki bean beetle (Callosobruchus chinensis) is a small insect, growing up to about 3 mm in length, and is a known pest of stored legume seeds. These beetles lay their eggs on the seed surface, and once hatched, the larvae bore into the seeds. Understanding their biology is therefore essential for mitigating the damage they cause.

“One characteristic we’ve observed in some insects, including these beetles, is that they increase egg size when exposed to environmental stress. Offspring hatched from larger eggs tend to survive better and develop more quickly during early stages. It’s a form of biological investment under stressful conditions” explains Professor Midori Tuda of Kyushu University’s Faculty of Agriculture, who led the study. “With human activities raising atmospheric CO₂ and global temperatures, it is critical to predict the future population dynamics of agricultural pests like the azuki bean beetle.”

Another factor influencing egg size in insects is infection by Wolbachia, one of the most common parasitic microbes in insects. It can cause a variety of effects across species. For example, in thrips and mites—where sex is determined by haplodiploidy (i.e., whether the offspring has a full or half set of chromosomes)—Wolbachia-infected parents have been shown to produce larger eggs, but only those that yield female offspring.

“We combined these two ideas to examine whether Wolbachia infection influences egg size under elevated temperature and CO₂ conditions, and whether this affects offspring sex,” continues Tuda. “In azuki bean beetles, sex is determined by X and Y sex chromosomes, just like in humans. To our knowledge, no one has previously investigated sex-specific changes in egg size under such conditions in organisms with this type of sex determination.”

Approximately 96% of natural azuki bean beetle populations are coinfected with two strains of Wolbachia: wBruCon (referred to as Con) and wBruOri (referred to as Ori). Single infections with either strain are rare: 1.6% of the population is infected only with Con, and 2.4% only with Ori.

The researchers exposed beetles to elevated temperature and CO₂ (denoted as eT&CO₂) for over two days during egg-laying. They found that beetles coinfected with both Wolbachia strains produced larger eggs, and all the larger eggs developed into male larvae. Egg size increases were observed only in beetles coinfected with both strains of Wolbachia.

Interestingly, the adult lifespan of the offspring was influenced not by egg size, but by environmental conditions, sex, Wolbachia infection, and development time. In fact, eT&CO₂ reduced male lifespan but had no significant effect on females.

This study is the first to demonstrate sex-specific egg size changes due to Wolbachia infection in a species with chromosomal sex determination. Further research is needed to elucidate the mechanisms driving this sex-dependent change aided by Wolbachia coinfection.

“From a pest control perspective, targeting Wolbachia may be a strategy worth exploring. However, because nearly half of all insect species are infected with Wolbachia, non-selective use of bactericides could threaten non-pest insects as well,” concludes Tuda. “A nature-positive approach is essential as we adapt to a changing climate.”

###

For more information about this research, see "Wolbachia infection facilitates adaptive increase in male egg size in response to environmental changes," Eloïse Leroy, Siyi Gao, Maya Gonzalez, Marie-Pierre Ellies-Oury, and Midori Tuda, Scientific Reports https://doi.org/10.1038/s41598-025-96680-6

About Kyushu University 
Founded in 1911, Kyushu University is one of Japan's leading research-oriented institutes of higher education, consistently ranking as one of the top ten Japanese universities in the Times Higher Education World University Rankings and the QS World Rankings. The university is one of the seven national universities in Japan, located in Fukuoka, on the island of Kyushu—the most southwestern of Japan’s four main islands with a population and land size slightly larger than Belgium. Kyushu U’s multiple campuses—home to around 19,000 students and 8000 faculty and staff—are located around Fukuoka City, a coastal metropolis that is frequently ranked among the world's most livable cities and historically known as Japan's gateway to Asia. Through its VISION 2030, Kyushu U will “drive social change with integrative knowledge.” By fusing the spectrum of knowledge, from the humanities and arts to engineering and medical sciences, Kyushu U will strengthen its research in the key areas of decarbonization, medicine and health, and environment and food, to tackle society’s most pressing issues.

END



ELSE PRESS RELEASES FROM THIS DATE:

Groundbreaking quantum study puts wave-particle duality to work

2025-07-11
Since its development 100 years ago, quantum mechanics has revolutionized our understanding of nature, revealing a bizarre world in which an object can act like both waves and particles, and behave differently depending on whether it is being watched.  In recent decades, researchers exploring this wave-particle duality have learned to measure the relative “wave-ness” and “particle-ness” of quantum objects, helping to explain how and when they veer between wave-like or particle-like behaviors. Now, in a paper ...

Weekly injection could be life changing for Parkinson’s patients

2025-07-11
A new weekly injectable drug could transform the lives of more than eight million people living with Parkinson’s disease, potentially replacing the need for multiple daily tablets. Scientists from the University of South Australia (UniSA) have developed a long-acting injectable formulation that delivers a steady dose of levodopa and carbidopa – two key medications for Parkinson’s – over an entire week. Their findings have been reported in the journal Drug Delivery and Translational Research. The biodegradable formulation is injected under the skin or into muscle tissue, where it gradually releases ...

Toxic metals linked to impaired growth in infants in Guatemala

2025-07-11
TUCSON, Ariz. — Research led by the University of Arizona Health Sciences found a potential link between growth problems among infants and high levels of toxic metals and other elements in the breast milk of Mayan women in Guatemala’s Lake Atitlán watershed region. The findings were reported in the journal Environmental Pollution.  Guatemala has the highest rate of impaired growth, or stunting, in the Western Hemisphere. Stunting is frequently attributed to poor nutrition and infections. Many studies have linked ...

Being consistently physically active in adulthood linked to 30–40% lower risk of death

2025-07-10
Being consistently physically active in adulthood is linked to a 30–40% lower risk of death from any cause in later life, while upping levels from below those recommended for health is still associated with a 20–25% lower risk, finds a pooled data analysis of the available evidence, published online in the British Journal of Sports Medicine. The findings prompt the researchers to conclude that switching to a more active lifestyle at any point in adult life may extend the lifespan, and that it’s never too late to start. Currently, it’s recommended that adults should aim for 150-300 weekly minutes of moderate intensity physical activity, or 75-150 ...

Nerve pain drug gabapentin linked to increased dementia, cognitive impairment risks

2025-07-10
Receiving six or more prescriptions of the drug gabapentin for low back pain is associated with significantly increased risks of developing dementia and mild cognitive impairment (MCI)--29% and 85%, respectively—finds a large medical records study published online in the journal Regional Anesthesia & Pain Medicine. What’s more, these risks were more than twice as high in those normally considered too young to develop either condition—18-64 year olds—the findings indicate. Unlike opioids, gabapentin has relatively low addictive potential, and it has become increasingly popular for the treatment ...

Children’s social care involvement common to nearly third of UK mums who died during perinatal period

2025-07-10
The involvement of children’s social care services was a common factor in nearly a third of UK maternal deaths occurring during, or within a year of, pregnancy between 2014 and 2022, finds research published in the open access journal BMJ Medicine. These women were at heightened risk of dying from psychiatric causes and being murdered, the findings indicate. But uncoordinated appointment schedules across a wide number of services added to the many disadvantages these women already faced. Changes to maternity care practice and policy are now urgently required, say the researchers. In the UK, children's social ...

‘Support, not judgement’: Study explores links between children’s social care involvement and maternal deaths

2025-07-10
A third of women who died during or in the year after pregnancy were known to Children’s Social Care – higher than previously reported, new research reveals. The authors say urgent changes are needed to prioritise and improve mothers’ care. The study is published today in BMJ Medicine and led by King’s College London, Oxford University and the charity Birth Companions, and funded by the National Institute for Health and Care Research. It is the first to detail the situations of the 1695 ...

Ethnic minority and poorer children more likely to die in intensive care

2025-07-10
SMC labelling: Peer-reviewed, Observational study, People Imperial College Academic Health Science Centre press release Under STRICT embargo until: Thursday 10 July 2025 23.30 GMT/ 18.30 Eastern Standard Time Ethnic minority and poorer children more likely to die in intensive care Children from ethnic minority backgrounds and those living in areas with higher levels of child poverty were more likely to die in intensive care than White children and those from the least deprived areas. Researchers ...

Major progress in fertility preservation after treatment for cancer of the lymphatic system

2025-07-10
Young patients with advanced Hodgkin’s lymphoma, a cancer of the lymphatic system, now have a better chance of having their own children after treatment. An international study led by the German Hodgkin Study Group (GHSG) at University Hospital Cologne and the University’s Faculty of Medicine has shown: The new BrECADD chemotherapy regimen preserves fertility significantly better than the previous standard eBEACOPP – without worsening the chances of recovery. The results were published under the title “Fertility in patients with advanced-stage classic Hodgkin lymphoma treated withBrECADD versus eBEACOPP: ...

Fewer complications after additional ultrasound in pregnant women who feel less fetal movement

2025-07-10
It can be difficult to decide whether to expedite birth when a woman in the final stage of pregnancy perceives less fetal movements. An additional ultrasound measurement to assess resistance infetal blood vessels can help make this decision more accurately, leading to fewer complications during delivery. This is the conclusion of a large international study led by gynaecologist Sanne Gordijn from the University Medical Center Groningen (UMCG), in collaboration with Wessel Ganzevoort from Amsterdam UMC. Reduced Fetal Movement Can Be Concerning Sometimes, ...

LAST 30 PRESS RELEASES:

‘Molecular shield’ placed in the nose may soon treat common hay fever trigger

Beetles under climate stress lay larger male eggs: Wolbachia infection drives adaptive reproduction strategy in response to rising temperature and CO₂

Groundbreaking quantum study puts wave-particle duality to work

Weekly injection could be life changing for Parkinson’s patients

Toxic metals linked to impaired growth in infants in Guatemala

Being consistently physically active in adulthood linked to 30–40% lower risk of death

Nerve pain drug gabapentin linked to increased dementia, cognitive impairment risks

Children’s social care involvement common to nearly third of UK mums who died during perinatal period

‘Support, not judgement’: Study explores links between children’s social care involvement and maternal deaths

Ethnic minority and poorer children more likely to die in intensive care

Major progress in fertility preservation after treatment for cancer of the lymphatic system

Fewer complications after additional ultrasound in pregnant women who feel less fetal movement

Environmental impact of common pesticides seriously underestimated

The Milky Way could be teeming with more satellite galaxies than previously thought

New study reveals surprising reproductive secrets of a cricket-hunting parasitoid fly

Media Tip Sheet: Symposia at ESA2025

NSF CAREER Award will power UVA engineer’s research to improve drug purification

Tiny parasitoid flies show how early-life competition shapes adult success

New coating for glass promises energy-saving windows

Green spaces boost children’s cognitive skills and strengthen family well-being

Ancient trees dying faster than expected in Eastern Oregon

Study findings help hone precision of proven CVD risk tool

Most patients with advanced melanoma who received pre-surgical immunotherapy remain alive and disease free four years later

Introducing BioEmu: A generative AI Model that enables high-speed and accurate prediction of protein structural ensembles

Replacing mutated microglia with healthy microglia halts progression of genetic neurological disease in mice and humans

New research shows how tropical plants manage rival insect tenants by giving them separate ‘flats’

Condo-style living helps keep the peace inside these ant plants

Climate change action could dramatically limit rising UK heatwave deaths

Annual heat-related deaths projected to increase significantly due to climate and population change

Researchers discover new way cells protect themselves from damage

[Press-News.org] Beetles under climate stress lay larger male eggs: Wolbachia infection drives adaptive reproduction strategy in response to rising temperature and CO₂
Researchers find that azuki bean beetles, a common pest, produce larger eggs yielding male offspring when infected with Wolbachia bacteria under elevated temperature and carbon dioxide conditions