Researchers uncover previously unexplored details of mosquito’s specialized detection mechanisms
Biologists use cutting-edge imaging technology to probe anatomical adaptations designed to target carbon dioxide emitted by humans
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Researchers have captured unprecedented images of the mechanisms that allow mosquitoes, the world’s deadliest animal, to target our blood.
view moreCredit: Erik Jepsen, UC San Diego
It’s bound to happen at a summer picnic, a peaceful walk in the woods or simply sitting in your backyard… a mosquito targets your blood for its next meal. You’ve been bitten.
But how do mosquitoes find you?
Among several methods used to locate new hosts for blood sucking, mosquitoes feature a keen ability to detect carbon dioxide. As we breathe out, we emit CO2 into the air around us, which mosquitoes can sense. But how?
Scientists have been aware of the mosquito’s ability to detect our carbon dioxide expirations but the intricate underlying physiological structures enabling these capabilities largely have remained unclear.
University of California San Diego researchers in the School of Biological Sciences and School of Medicine have now uncovered the first elaborately detailed visualizations of these mechanisms. At UC San Diego’s National Center for Microscopy and Imaging Research, the researchers used serial block-face electron microscopy, a technique that repeatedly slices tissue and images with an electron beam to generate detailed serial pictures, to construct 3D nanoscale models of the mosquito’s carbon dioxide-detecting neurons.
The research, which was led by UC San Diego undergraduate student researchers Shadi Charara and Jonathan Choy in Neurobiology Department Professor Chih-Ying Su’s lab, is published in the Proceedings of the National Academy of Sciences.
“In the past people have speculated about these mosquito mechanisms but they were hard to appreciate,” said Su. “Now we have a realistic 3D morphological model that provides quantitative measurements of the sensory surface area. This is the first time we’re seeing this level of detail.”
Mosquitoes detect carbon dioxide through sensory hairs known as sensilla. These hairs contain olfactory receptor neurons, or ORNs, including neurons specialized for CO2 sensing. The researchers focused on these features in Aedes aegypti mosquitoes, which are known to spread yellow fever, dengue, chikungunya and Zika viruses. The new results provide key insights into the mosquito’s sensing mechanisms that have been evolutionarily adapted to seek blood sources, a feature that contributes to their status as the world’s deadliest animal.
The new 3D visualizations reveal several remarkable specialized structures. Within the hairs, the new images revealed anatomical adaptations along sensory dendrites, branches that project out of neurons. Within capitate peg or “cpA” neurons, the researchers found enlarged CO2-sensing surface areas and a unique axonal architecture enriched with mitochondria — the energy components within cells — suggesting a high-energy-demand area. Such features likely allow heightened sensitivity to carbon dioxide.
“These characteristics suggest that ORNs have evolved specific metabolic and structural adaptations to support their essential role in host-seeking,” the researchers write in their paper.
The researchers also compared their new visualizations with similar structures found in fruit flies. They found that the analogous area in fruit flies is much less prominent, highlighting key differences between the insects.
“Fruit flies also have a sensing area for carbon dioxide but it’s much smaller,” said Su. “Sensing chemical cues is important for all animals but in fruit flies it serves as an alarm signal — they avoid carbon dioxide. For mosquitoes, carbon dioxide is an arousal cue that helps them find us. It’s a trigger for their whole host-seeking behavior.”
The researchers hope the new findings will provide valuable new information to further science’s understanding of the mosquito’s unique anatomical structures and their functions in seeking new blood hosts.
Intricate dendrite sheets of specialized carbon dioxide-sensing neurons (foreground) aid the detection skills of a yellow fever mosquito, lurking in the background.
Credit
Hassan Tahini @ ScienceBrush
Journal
Proceedings of the National Academy of Sciences
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Morphological specializations of mosquito CO2-sensing olfactory receptor neurons
Article Publication Date
29-Oct-2025
When it comes to mating, female mosquitoes call the shots
Scientists discovered that a subtle behavior by the female mosquito dictates whether mating is successful.
Rockefeller University
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The external genitalia of a female Aedes aegypti.
view moreCredit: H. Amalia Pasolli and Anurag Sharma
A female mosquito only gets one shot to get reproduction right: She mates just a single time in her entire life. With the stakes so high, it would make sense for these insects to be quite choosey when it comes to selecting a mate. And yet a long-standing assumption in the field was that males controlled the process, and females were simply passive recipients of sperm.
“There’s an inherent contradiction in this assumption,” says Rockefeller University and Howard Hughes Medical Institute mosquito expert Leslie Vosshall. “If females have no say, then multiple males should be able to mate with them all the time. So how can a female mosquito both be a helpless creature but also the decision maker?”
Puzzled by the paradox, Vosshall and her team in the Laboratory of Neurogenetics and Behavior dove into the moment-by-moment, nuts-and-bolts of mosquito mating. The resulting study, recently published in Current Biology, uncovered the first evidence that scientists had it backwards: What makes mating possible is a subtle behavior of the female—a physical movement of her genitalia. Moreover, no subsequent physical pairings trigger this behavior again, regardless of how many males try, or how often they try—and they try a lot.
“It’s a very fast, very subtle change, but it entirely dictates whether mating occurs,” says lead author Leah Houri-Zeevi, a postdoctoral scientist in the lab. “If she makes this movement, it happens. If she doesn’t, it doesn’t matter what the male does—no successful mating will occur.”
Obscure mechanics
Depending on whether she’s living a short and dangerous life in the wild or a long and cushy one in the lab, a single female mosquito can produce up to 1,000 eggs in a single lifetime.
Following her lone mating, she stores the male’s sperm in internal reservoirs. Every 3–4 days, she feeds on the blood of a host, and once sated, draws from these sperm reservoirs to inseminate and lay her eggs in fresh water.
Despite studies on mosquito mating going back to the 1950s, the role of the female in the process remained obscure. The speed of the process—the interactions that lead to mating take 1–2 seconds—makes it challenging to capture, and might have been combined with hidden biases for what the female role in mating could be.
“There’s a long history in biology of assuming male agency and female passivity,” says Vosshall. “This study is a reminder that those assumptions can get in the way of seeing what’s actually happening, even in something as well-studied as mosquito mating.”
For the current study, the researchers investigated the mating practices of two of the most invasive mosquito species in the world: Aedes aegypti and Aedes albopictus, better known as the yellow fever mosquito and Asian tiger mosquito, respectively. Collectively, they can spread dozens of viruses to humans, including yellow fever, dengue, Zika, and Chikungunya.
They analyzed the step-by-step interactions of different mating pairs both within and between species, including female mosquitoes that had never previously mated and those that had.
A three-step process
Using high-speed, high-resolution cameras, deep learning, and transgenic mosquitoes with fluorescent sperm, Houri-Zeevi and her colleagues discovered that the same three-step process leading to a successful mating between a virgin female and a male occurred in both species. First, the male contacts the female genitalia with his genital tip. In response, the female chooses whether to elongate her tip to about twice its resting length. This behavior is critical for mating. If she doesn’t elongate her tip, mating cannot take place. If she does, the male’s internal genitalia interlocks with the female’s tip, and sperm transfers from one to the other.
The researchers found that the “key” to unlocking the critical female response in Aedes aegypti is rapidly evolving male structures, called gonostyli, that are inserted into the female genital tip and vibrate rapidly when the male attempts copulation.
Houri-Zeevi and the team also observed what occurred when a previously mated female and male attempted to interlock: Step two didn’t occur. That apparently prevents step three—successful insemination.
“After one successful mating, she will never elongate that tip again,” Houri-Zeevi notes.
Interspecies matings
They found this tip elongation mechanism in both species, demonstrating that female control over mating is shared in mosquitoes that diverged about 35 million years ago. However, they also noted differences between the two species, suggesting that within each species, there is a specific female lock and a specific male key.
That idea is bolstered by the fact that Asian tiger mosquitoes and yellow fever mosquitoes diverged from a common ancestor so long ago that they cannot produce viable offspring, so mating between these species is a genetic dead end for the female. However, that doesn’t stop the males from trying to mate with females of the other species. Houri-Zeevi and the team discovered that male Asian tiger mosquitoes—which have far larger gonostyli than their yellow fever mosquito counterparts—used their gonostyli to override the female mating control of yellow fever females, and mate with them without the female genital tip elongation behavior. This “lock picking” could only be done across species, and the Asian tiger mosquitoes could never override the female mating control of their own females.
That finding may help explain a striking pattern that entomologists in southern regions of the U.S. have observed: When Asian tiger mosquitoes move into an area, the population of yellow fever mosquitoes drops or vanishes.
It may also help improve methods of mosquito population control, some of which rely on ill-fated pairings between intentionally sterilized males and wild females. “It’s really important for people who work in an area to understand how the biology of females of a local wild population is going to interact with males from a genetically modified population,” notes Vosshall.
Going forward, the researchers will explore the finer details of the lock-and-key mating mechanism for each species. “We want to understand the neuronal code the female is using to sense male stimulation and then make her decision,” Vosshall says. “The question it comes down to is, how does she choose between different suitors given that it’s a once-in-a-lifetime choice?”
Journal
Current Biology
Article Title
Determination of Aedes mosquito mating success by a rapidly-evolving female-controlled lock-and-key mechanism
Article Publication Date
28-Oct-2025
Spotted lanternfly may use ‘toxic shield’ to fend off bird predators
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Entomologists in Penn State’s College of Agricultural Sciences examined the potential for birds to feed on spotted lanternflies.
view moreCredit: Anne Johnson / Penn State
UNIVERSITY PARK, Pa. — Spotted lanternflies may season themselves to the distaste of potential bird predators, according to a new study led by entomologists in Penn State’s College of Agricultural Sciences.
The findings, which were published in the Journal of Chemical Ecology, showed that several species of birds were less likely to eat spotted lanternflies that had fed on the pest’s preferred host, Ailanthus altissima, commonly known as tree of heaven. This suggests the pest stores nasty-tasting chemicals when they feed on the invasive plant that birds can detect, according to the research team.
Further, they said, the extent to which birds may play a role in pecking away at spotted lanternfly populations remains up in the air and depends on various factors.
Led by postdoctoral researcher Anne Johnson, the team investigated whether birds could serve as natural predators of the spotted lanternfly. This Asian planthopper causes damage to vineyards, orchards and the nursery industry.
The entomologists theorized that when the spotted lanternfly feeds on the plant, it stores toxic chemicals called quassinoids, which make the insect less appetizing to birds. These compounds are bitter and have a pungent smell to mammals; it is unknown if this is the case with birds.
“Like the spotted lanternfly, tree of heaven is an invasive species that originated in the same region of Asia as the insect,” said Johnson, who worked on the project under the guidance of co-author Kelli Hoover, professor of entomology. “We found that birds, including nesting house wrens, preferred to eat spotted lanternflies that had not fed on tree of heaven, suggesting that the insects that consume this plant are less tasty, thereby providing some chemical defenses against avian predators.”
To investigate the possibility that birds are deterred from feeding on spotted lanternflies that had stored toxic chemicals from tree of heaven, Johnson and Hoover reared different life stages of spotted lanternflies in controlled environments — some with access to the tree of heaven and others without. Chemical analyses confirmed that spotted lanternflies accumulated quassinoids from the tree of heaven in their bodies, with the highest concentrations in adults.
The researchers presented the insects to birds in two experiments: one involving feeding tests with house wrens in nest boxes. The team worked with two groups of lanternflies — one reared with access to tree of heaven and another that had never fed on it. Johnson used adult insects from each group to create two batches of suet cakes: one containing pieces of lanternflies that had fed on tree of heaven and the other containing lanternflies that had not. These suet cakes then were offered to attract various bird species, which the researchers observed.
The most common species visiting the suet feeders included three types of woodpeckers, black-capped chickadees, white-breasted nuthatches and Carolina wrens.
Hoover said that most bird species in the tests preferred lanternflies that had not been exposed to the tree of heaven. Additionally, the nesting wrens ate — or fed to their young — larger quantities of the spotted lanternflies that were not exposed to the tree of heaven.
“Interestingly, we observed that, of the immature spotted lanternflies that were used by house wrens, the parents often ate both spotted lanternflies reared with and without access to tree of heaven but only fed their chicks nymphs reared without access to the tree of heaven,” Johnson said. “This could indicate that parent birds were less willing to tolerate quassinoids in spotted lanternfly prey for their offspring than they were for themselves.”
The researchers also found quassinoids in the eggs of the spotted lanternflies, indicating they likely inherited these toxins from the mothers. The scientists said this suggests that by passing these toxins to their eggs, adult lanternflies potentially are protecting the next generation.
The researchers noted that understanding the role of plant-derived toxins in the spotted lanternfly’s survival could help inform effective management strategies for this pest. While some birds may help control pest populations, their effectiveness may be limited by the insects’ toxic defenses. However, predation by birds does occur in the field; a community science project led by Johnson and Hoover in 2023 reported numerous observations of birds feeding on lanternflies in nature.
In addition to birds, other animals prey on the spotted lanternfly, and Johnson and Hoover have investigated how they might be impacted by lanternfly diet.
“Some insect predators show promise for this approach, as our previous research found that, unlike birds, they do not favor lanternflies that were raised on grapevines without ever feeding on tree of heaven,” Johnson said.
The researchers said the next step may be to explore whether birds or insect predators could help reduce populations of this serious pest.
Study collaborators included Allison Cornell, assistant professor of biology at Penn State Altoona; Fang Zhu, associate professor of entomology; Ashley Shay, director of the Metabolomics Core Facility at the Huck Institutes of Life Sciences; and Gabrielle Davis, a Penn State alumna who will be attending graduate school at the University of Michigan.
A U.S. Department of Agriculture McIntire-Stennis grant and the Pennsylvania Department of Agriculture supported this research.
For more information on spotted lanternfly research and management strategies, visit the Penn State Extension website.
Journal
Journal of Chemical Ecology
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Sequestration of plant defenses by spotted lanternfly (Lycorma delicatula) and effects on avian predators
Article Publication Date
23-Oct-2025
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