A mosquito's perception of an individual: a detailed examination
Refresh Your Knowledge: How Mosquitoes Hunt Us Down
Get a shiver down your spine as you picture a human arm from a mosquito's perspective. Yes, those pesky bloodsuckers zero in on their next meal using thermal infrared, leaving you itchy and potentially sick.
In a study published this week in Nature, a team of scientists unveiled the infrared detector of the mosquito Aedes aegypti and the structures that support it, such as CO from our breath, odors, vision, heat from our skin, and humidity from our bodies. As explained by co-lead author Avinash Chandel, a biologist from UC Santa Barbara, "Each of these cues has its limitations."
But itchy welts aren't the only concern. Mosquito bites can transmit diseases like dengue, yellow fever, and Zika. The research team aimed to uncover the precise functions mosquitoes employ when seeking a tasty human meal.
Mosquitoes, with their poor vision, must rely on a fusion of senses to locate a host. A 2022 paper in Scientific Reports revealed that mosquitoes respond to visual and mechanical threats, like an open hand readying itself for a swat, while feeding.
Within approximately four inches from human skin, mosquitoes can detect thermal heat. They intensify their host-seeking behavior once they land on our skin due to their direct temperature perception. However, the new research indicates that mosquitoes also respond to thermal infrared.
To demonstrate, the researchers set up two zones, both suffused with human odors and CO2 at the same concentration we exhale. But, one zone was also exposed to thermal infrared from a source resembling human skin temperature. The researchers discovered that this increased the mosquitoes' host-seeking activity by a factor of two. With thermal infrared active, the mosquitoes' sensitivity to heat appears to extend to around 2.5 feet.
According to senior author Craig Montell of UCSB, "A single cue by itself doesn't stimulate host-seeking activity. It's only in the context of other cues, like elevated CO and human odor, that IR makes a difference."
The team hypothesizes that loose-fitting clothing offers a solid defense against mosquitoes, as it leaves room for thermal infrared to dissipate, making it harder for the insects to locate hosts.
These days, A. aegypti has expanded its range beyond its tropical and subtropical origins, spreading as far as California. Understanding mosquitoes' host-seeking strategies will aid researchers in discovering deterrent methods, thereby limiting the transmission of mosquito-borne diseases.
Insights on Mosquitoes’ Sensory Cues
Mosquitoes employ multiple sensory cues when locating a host, including thermal infrared, CO, odors, vision, and humidity. Here's a breakdown of how these cues contribute to their hunting behavior:
Contribution of Sensory Cues
- Thermal Infrared and Heat: Mosquitoes are drawn to warmth emitted by mammals, a sign of a potential host. Thermal infrared radiation helps them detect the heat signature of a host, guiding them towards their target. This sensitivity to heat is crucial for locating warm-blooded creatures like humans.
- CO (Carbon Dioxide): Mosquitoes can detect the elevated levels of CO2 produced by human respiration, which guides them towards a host. This cue is essential in environments where humans are present.
- Odors: Volatile organic compounds (VOCs), such as lactic acid and urea, from human sweat and breath, attract mosquitoes. Their olfactory system, mediated by odorant receptors, is essential for detecting these chemical signals.
- Vision: Although mosquitoes are not efficient visual hunters, they use visual cues to help orient themselves towards larger objects and movements that could indicate a potential host.
- Humidity: Humidity sensing is vital for mosquitoes as it helps them detect moisture gradients around potential hosts. High humidity encourages their activity and improves their ability to locate hosts effectively.
Thermal Infrared’s Specific Effects
- Sensitivity to Heat: Thermal infrared helps mosquitoes differentiate between warm-blooded hosts and other objects in the environment. This heightened sensitivity, combined with their ability to discern temperature differences, enables them to prefer warmer targets, typically indicative of mammals or birds.
- Host-Seeking Activity: The detection of thermal infrared radiation boosts mosquito activity and initiates host-seeking behavior. Thermal infrared serves to enhance their ability to pursue hosts effectively, especially in environments with competing sensory stimuli.
In conclusion, thermal infrared plays a vital role in guiding mosquitoes towards warm hosts, complementing other sensory cues such as CO2, odors, and humidity to facilitate efficient host-seeking behavior.
*Mosquitoes utilize multiple sensory cues to find hosts, including thermal infrared, Carbon Dioxide (CO), odors, vision, and humidity.* Thermal infrared radiation helps mosquitoes detect the heat signatures of potential hosts, guiding them towards their targets.* The heightened sensitivity to heat, combined with the ability to discern temperature differences, allows mosquitoes to prefer warmer targets, often indicative of mammals or birds.* The detection of thermal infrared boosts mosquito activity and initiates host-seeking behavior, enhancing their efficiency in pursuing hosts, especially in environments with competing sensory stimuli.
