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Mosquito Receptors Go Cold: How Extreme Heat Affects Insect Repellents

Hotter temperatures may render natural insect repellents less effective against mosquitoes, according to a new study.

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The way we keep mosquitoes at bay might be changing due to rising temperatures. Researchers have discovered that when it gets extremely hot, the natural insect repellents we rely on become less effective. This is because the pain receptors that help detect and avoid these chemicals are becoming desensitized.

In a recent study published in Pesticide Biochemistry and Physiology, Peter Piermarini and his team from Ohio State University investigated how mosquitoes respond to heat and insect repellents. They found that when temperatures reach above 32 degrees Celsius, the chemical cues that typically trigger mosquito avoidance behaviors become less potent.

The researchers focused on a pain receptor called TRPA1, which is responsible for detecting noxious heat and harmful chemicals in animals. In humans, this receptor can cause eye and skin irritation. Piermarini explained that “what we found was that the chemicals were not able to activate the mosquito wasabi receptor as effectively when temperatures exceeded the heat activation threshold.” This means that the mosquito would find certain repellents less irritating in hotter weather.

Typical insect repellents create a chemical barrier that discourages proximity and prevents mosquitoes from reaching their target. Yet, because their receptors are desensitized in warmer temperatures, natural substances like citronellal and catnip oil, known for their repellent properties, would be less effective. This could have serious implications as climate change leads to more extended breeding periods per season, worsen the spread of mosquito-borne disease.

The study was conducted by removing TRPA1 mosquito receptors and injecting them into frog egg cells, a technique often used for making receptor proteins in the lab. Then, they tested how the receptors would react to citronellal and catnip oil under normal and high temperatures. The results showed that the receptors were activated but less sensitive to the substances at higher temperatures.

In a second experiment, the researchers studied how fully grown female mosquitoes reacted when confronted with either repellent at different temperatures. When temperatures exceeded 32 degrees Celsius, the mosquitoes were less likely to avoid the substances, suggesting they might behave similarly in the wild.

Interestingly, the researchers found that synthetic mosquito repellents like DEET do not interact with the wasabi receptor and therefore remained effective even in high temperatures. “This suggests that during the hottest days of the year you’d probably want to stick with a more conventional synthetic repellent and avoid using a natural product with citronella or catnip oil,” said Piermarini.

The study highlights the importance of understanding how mosquito behavior changes under different environmental conditions, which can help inform strategies for controlling mosquito populations and preventing disease.

Animals

Flamingos’ Feeding Secrets Revealed: The Art of Water Tornadoes and Skimming

Flamingos have developed an amazing variety of techniques to create swirls and eddies in the water to concentrate and eat brine shrimp and other organisms, a biologist found. They stomp dance to stir organisms from the bottom and concentrate them in whorls. The organisms are then drawn upward by a head jerk that forms a vortex. Meanwhile, their beak is chattering underwater to create vortices that funnel prey into their mouths.

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The fascinating world of bird feeding behaviors has been further explored by researchers, who have discovered that Chilean flamingos use their unique beak and foot structure to create water tornados and skimming techniques to trap their prey.

Victor Ortega Jiménez, an assistant professor at the University of California, Berkeley, and his collaborators have published a study in the Proceedings of the National Academy of Sciences detailing how these birds employ various strategies to capture brine shrimp, a crucial food source for them.

One of the key findings is that flamingos use their floppy webbed feet to churn up the water and create vortices around their beaks. This allows them to concentrate particles of food and increase their chances of capturing prey.

Another technique employed by flamingos is skimming, which involves moving the lower beak in a rapid chattering motion to create symmetrical vortices on either side of the beak. This helps to recirculate particles in the water and bring them into the beak, making it easier for the bird to capture its prey.

The study also highlights the importance of fluid dynamics in understanding how flamingos feed. Researchers employed computational fluid dynamics to simulate the 3D flow around the beak and feet, confirming that the vortices do indeed concentrate particles, similar to experiments using a 3D-printed head in a flume.

This research has significant implications for our understanding of bird feeding behaviors and could potentially inform the design of robots that need to navigate water or muddy environments.

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Animals

Uncovering the Roots of Language: Chimpanzees’ Complex Communication System Reveals Insights into Human Origins

Wild chimpanzees alter the meaning of single calls when embedding them into diverse call combinations, mirroring linguistic operations in human language. Human language, however, allows an infinite generation of meaning by combining phonemes into words and words into sentences. This contrasts with the very few meaningful combinations reported in animals, leaving the mystery of human language evolution unresolved.

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The human capacity for language has long been considered unique to our species. However, recent studies have challenged this notion by revealing that chimpanzees possess a complex communication system that rivals that of humans in terms of its combinatorial potential. Researchers from the Max Planck Institutes for Evolutionary Anthropology and Cognitive and Brain Sciences, along with colleagues from the Cognitive Neuroscience Center Marc Jeannerod and Neuroscience Research Center in Lyon, France, have recorded thousands of vocalizations from wild chimpanzees in the Taï National Park in Ivory Coast.

Their findings reveal that chimpanzees employ four distinct methods to alter meanings when combining single calls into two-call combinations. These include compositional and non-compositional combinations, analogous to the key linguistic principles in human language. The study also highlights the versatility of these combinations, which are used in a wide range of contexts beyond mere predator alerts.

One of the most significant aspects of this research is that it suggests that chimpanzees’ complex communication system may be more similar to human language than previously thought. This has implications for our understanding of the origins of language and the evolutionary history of humans. The study’s authors propose that the capacity for complex combinatorial capacities was already present in the common ancestor of humans and great apes, challenging the views of the last century that communication in great apes is fixed and linked to emotional states.

This research opens up new avenues for investigation into the evolution of language and highlights the importance of studying the communicative capabilities of our closest living relatives. As Cédric Girard-Buttoz, first author on the study, notes, “Our findings suggest a highly generative vocal communication system, unprecedented in the animal kingdom… This changes the views of the last century which considered communication in the great apes to be fixed and linked to emotional states, and therefore unable to tell us anything about the evolution of language.”

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Animals

A “Roadmap” to Understanding the Fruit Fly Brain: Breakthrough Study Reveals Comprehensive Insights into Entire Nervous System

Researchers have gained comprehensive insights into the entire nervous system of the fruit fly (Drosophila melanogaster). The study describes in detail the neurons that span the entire nervous system of the adult fruit fly. The researchers also compared the complete set of neural connections (the connectome) in a female and a male specimen — and identified differences.

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The fruit fly (Drosophila melanogaster) has long been a model organism for scientists studying genetics, development, and behavior. However, despite its importance, the intricacies of the fruit fly’s nervous system have remained somewhat of a mystery – until now. Researchers at Leipzig University and other institutions have made a groundbreaking discovery, publishing a study in Nature that provides comprehensive insights into the entire nervous system of the adult fruit fly.

For the first time, scientists have mapped out the neural connections (the connectome) in a female and a male specimen, revealing differences between the two sexes. This breakthrough is a significant step forward in understanding the complex interactions within the fruit fly’s brain and nervous system.

The study, led by Dr. Katharina Eichler from Leipzig University, involved analyzing three connectomes: one female brain data set and two nerve cord data sets (one male, one female). The researchers used light microscopy to identify all neurons in the neck of the fruit fly that could be visualized using this technique.

This allowed them to analyze the circuits formed by these cells in their entirety. When comparing male and female neurons, the scientists identified sex-specific differences for the first time. They found previously unknown cells that exist only in one sex and are absent in the other.

One notable example is a descending neuron known as aSP22, which communicates with neurons present only in females. This finding provides an explanation for the behavioral differences observed when this neuron is active: female flies extend their abdomen to lay eggs, while males curl theirs forward to mate.

The study’s findings are significant not only because they provide a comprehensive overview of the fruit fly connectome but also because they offer a “roadmap” for future research. By understanding the intricate connections within the nervous system, scientists can design more intelligent experiments to investigate the function of individual neurons or entire circuits – saving time and resources.

As Eichler notes, now that the technical challenges in analyzing the fruit fly’s nervous system have been overcome, her research group is working on two new data sets covering the entire central nervous system of both a female and a male specimen. This continued research will undoubtedly shed more light on the complexities of the fruit fly brain and its implications for our understanding of nervous systems in general.

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