The mosquito has long been known as a carrier of deadly diseases such as dengue, yellow fever, Zika, and malaria, causing millions of deaths worldwide each year. Female mosquitoes, in particular, require blood for egg development and have been extensively studied for over a century to understand how they locate their hosts. Researchers at UC Santa Barbara have added a new sense to the mosquito’s repertoire: infrared detection. By exposing mosquitoes to infrared radiation from a source that mimics human skin temperature, the researchers found that the insects’ host-seeking behavior doubled when combined with CO2 and human odor. This study sheds new light on how mosquitoes are so effective at finding human hosts.
Mosquitoes like Aedes aegypti utilize multiple cues such as CO2, odors, heat, and humidity to locate hosts from a distance. However, each of these cues has its limitations, especially in terms of accuracy and reliability. The researchers were interested in investigating whether mosquitoes could detect a more reliable directional cue, such as infrared radiation. By exposing female mosquitoes to infrared radiation from a skin temperature source, they observed a significant increase in host-seeking activity. This highlights the importance of infrared radiation as a newly documented sense that mosquitoes use to locate hosts efficiently.
Detecting thermal infrared radiation is a complex process for mosquitoes as the energy of IR is too low to activate the proteins responsible for visible light detection in their eyes. The researchers discovered that mosquitoes detect infrared radiation indirectly through their antennae, specifically the tips which contain heat-sensing neurons. Removing the tips of the antennae resulted in the mosquitoes losing their ability to detect infrared radiation. The team identified a temperature-sensitive protein called TRPA1 located at the end of the antenna, which plays a crucial role in detecting IR along with other rhodopsin proteins expressed in the same antennal neurons.
Further experiments revealed that more intense thermal infrared directly activates TRPA1, while other rhodopsin proteins, Op1 and Op2, can indirectly trigger TRPA1 at lower levels of thermal infrared. This intricate mechanism strategically extends the range of the mosquito’s infrared sensor to around 2.5 feet. The study provides valuable insights into how mosquitoes can effectively locate human hosts using multiple sensory cues, including newly discovered infrared radiation detection. Understanding these mechanisms could lead to more effective methods for controlling mosquito populations and preventing the transmission of deadly diseases.
The implications of this research are significant, considering that over half of the world’s population is at risk of mosquito-borne diseases, with approximately one billion people getting infected yearly. The spread of mosquitoes such as Aedes aegypti beyond tropical regions due to climate change and global travel poses a serious threat to public health. The researchers’ discovery of mosquitoes’ ability to sense infrared radiation could be utilized to improve mosquito control methods, such as incorporating thermal IR in traps to increase their efficacy. Additionally, understanding how mosquitoes target humans could lead to new strategies for preventing mosquito-borne diseases and reducing their impact on public health.
Overall, this study provides a groundbreaking insight into the complex sensory mechanisms that mosquitoes employ to locate and feed on human hosts. By identifying infrared radiation as a crucial sense used by mosquitoes for host-seeking behavior, the researchers have opened up new possibilities for understanding and controlling mosquito-borne diseases. With the threat of these diseases becoming more widespread due to climate change and globalization, innovative research like this is essential for developing effective strategies to combat the deadliest animal on the planet.
