Wednesday July 18, 2018

Decoded: Why Mosquitoes Bite You

For the study, published in the journal Current Biology, the team placed mosquitoes in an insect flight simulator and exposing the mosquitoes to various smells, including human body odors, and observed how the insects, trained or not, reacted

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The study dopamine -- a brain chemical involved in reward learning -- is a key mediator of aversive learning in mosquitoes. Pixabay
The study dopamine -- a brain chemical involved in reward learning -- is a key mediator of aversive learning in mosquitoes. Pixabay
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  • People who swat at mosquitoes or perform other defensive behavior may be abandoned, no matter how sweet
  • The team placed mosquitoes in an insect flight simulator and exposing the mosquitoes to various smells for the study
  • The study was published in the journal Current Biology

Wonder why you receive more bug bites than others around you? It is because, mosquitoes can rapidly learn and remember the smells, researchers have found.

The study dopamine — a brain chemical involved in reward learning — is a key mediator of aversive learning in mosquitoes.

However, people who swat at mosquitoes or perform other defensive behavior may be abandoned, no matter how sweet.

Dopamine modulates the neural activity in the brain region where the information on smell in such a way that odors were easier to discriminate, and potentially learn, by the mosquitoes, the researchers said. Pixabay
Dopamine modulates the neural activity in the brain region where the information on smell in such a way that odors were easier to discriminate, and potentially learn, by the mosquitoes, the researchers said. Pixabay

ALSO READ: $18 Million Donation to Target Mosquito-borne Diseases like Zika in Colombia and Brazil

Mosquitoes exhibit a trait known as aversive learning by training female Aedes aegypti mosquitoes to associate odors (including human body odors) with unpleasant shocks and vibrations, said Clement Vinauger, Assistant Professor in Virginia Polytechnic Institute and State University or Virginia Tech.

For the study, published in the journal Current Biology, the team placed mosquitoes in an insect flight simulator and exposing the mosquitoes to various smells, including human body odors, and observed how the insects, trained or not, reacted.

“Unfortunately, there is no way of knowing exactly what attracts a mosquito to a particular human — individuals are made up of unique molecular cocktails that include combinations of more than 400 chemicals,” said Chloe Lahondere, Assistant Professor at the varsity.

“However, we now know that mosquitoes are able to learn odors emitted by their host and avoid those that were more defensive,” Lahondere added.

ALSO READ: Dengue stings Delhi as govt sleeps under an opaque mosquito net

Aedes aegypti mosquitoes are vectors for Zika fever, dengue fever, chikungunya, and yellow fever viruses, and can be found in tropical and subtropical regions throughout the world. Pixabay
Aedes aegypti mosquitoes are vectors for Zika fever, dengue fever, chikungunya, and yellow fever viruses, and can be found in tropical and subtropical regions throughout the world. Pixabay

 

“Understanding these mechanisms of mosquito learning and preferences may provide new tools for mosquito control,” Vinauger said.

“For example, we could target mosquitoes’ ability to learn and either impair it or exploit it to our advantage,” he noted. (IANS)

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Electric Fields Used By Spiders To Take Flight: Research

Charles Darwin remarked on the behavior when tiny spiders landed on the HMS Beagle, trailing lines of silk.

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A spider sits in her web. Researchers from England think spiders might be sensing and using electrostatic fields to become airborne.
A spider sits in her web. Researchers from England think spiders might be sensing and using electrostatic fields to become airborne. VOA

Since the 1800s, scientists have marveled at how spiders can take flight using their webbing. Charles Darwin remarked on the behavior when tiny spiders landed on the HMS Beagle, trailing lines of silk. He thought the arachnids might be using heat-generated updrafts to take to the sky, but new research shows a totally different cause may be at play.

Erica Morley and Daniel Robert from the University of Bristol in England were interested in exploring a second explanation for the spiders’ ability. They thought spiders might sense and use electrostatic fields in the air.

“There have been several studies looking at how air movement and wind can get spiders airborne, but the electrostatic hypothesis was never tested,” Morley told VOA.

Some observers suggested electrostatic fields might be the reason the multiple draglines some spiders use to float don’t get tangled with each other. Biologist Kimberley Sheldon from the University of Tennessee at Knoxville, who was not involved in the new research, pointed out that “though these spiders will have five or six draglines, those strands of silk do not get entangled. So we’ve known for a while that electrostatics probably [are] at least interacting with the spider, with the silk lines themselves, to keep them from getting tangled.”

Morley and Robert created a box with a grounded metal plate on the bottom and a plate on the top that they could pass an electrical current through. The scientists placed spiders in the box and turned on the voltage, watching as the creatures reacted to the electric field.

Reaction to current

When the electric field was on, the spiders lifted their abdomens into the air and started tiptoeing by raising up on the very ends of their legs. Morley told VOA that spiders only tiptoe right before they release silk draglines to fly away, in a process called ballooning.

And when the spiders did balloon and rise into the air, turning off the electric current caused them to drop.

Sheldon compared it to taking a balloon and rubbing it against your clothing. “If you hold the balloon [near your head], your hair stands on end. That’s kind of what’s happening with the spider silk.”

Spiders Use Electric Fields to Take Flight: Research
Spiders Use Electric Fields to Take Flight: Research. Pixabay

Clearly the spiders were able to sense the local electrostatic field and respond appropriately by releasing silk, but Morley and Robert wanted to know how.

“As a sensory biologist, I was keen to understand what sensory system they might use to detect electric fields,” said Morley. “We know that they have very sensitive hairs that are displaced by air movements or even sound. So I thought that it’s possible that they might be using these same hairs to detect electric fields.”

This was exactly what she observed. The small hairs along the spiders’ legs react not only to physical experiences like a breeze but also to the electric field. In nature, it makes sense for spiders to sense both the electrostatic field around them as well as wind conditions. Spiders probably use both when taking off and navigating the skies.

Mathematician Longhua Zhao from Case Western Reserve University in Cleveland has made computer models of how spiders balloon. She told VOA, “I think that both the electrical field and the fluid mechanics [of air flow] are important. They definitely play very important roles. However, we don’t know at this point which is the dominant factor.”

Also read: Did You Hear about the New Species of Spiders Named After Leonardo DiCaprio, Bernie Sanders and Barrack Obama?

Lead researcher Morley pointed out that spiders aren’t the only invertebrates to balloon. “Caterpillars and spider mites, which are arachnids but not spiders, balloon as well.” Morley hopes to see others follow up her research to see if these other animals respond in a way similar to the spiders. (VOA)