Blood-feeding mosquitoes, by transmitting parasites and viruses to their hosts, kill several hundred thousand people every year. Mosquito populations are currently developing raising levels of insecticide resistance, and there is a need for a better understanding of their behavior so that new control solutions can be imagined, and existing ones can be improved. There has been a vast number of studies examining the host seeking behavior of mosquitoes, however there is a lack of knowledge concerning how mosquitoes are evading the threats their hosts pose via their defensive behaviors. Female mosquitoes are indeed in this unique position where their fitness and reproduction depend on them being able to locate hosts as well as evade them. In order to do this, they rely on sensory cues that they must be able to continuously re-evaluate during host tracking to potentially decide to quickly escape at any point during these interactions. Host seeking is mediated by multiple sensory modalities such as vision, olfaction, and thermosensation. However, it is not clear whether mosquitoes may also be using some of these same cues to identify that their host is turning into a threat. Focusing solely on visual cues in the context of escape behavior, we used a looming stimulus to elicit escape responses from the Yellow Fever mosquito, Aedes aegypti. A virtual reality environment was adapted from previous work, to display the looming stimulus while the mosquito is in a variety of conditions (i.e., landed, in free or tethered flight). Results from these experiments allowed us to characterize the escape responses of mosquitoes, by determining the angles and distances to the stimuli that will most likely trigger an avoidance response. / Master of Science in Life Sciences / Mosquitoes are the deadliest animals in the world because of the several diseases they can transmit. Females are the only ones that bite, since they require a blood meal in order to produce offspring. The task of obtaining this blood meal from a mobile, and defensive host can be extremely dangerous. The females must find a host, approach it, land, feed, and flee without being killed so they can reproduce. At any point, the host might detect the mosquito and try to kill it, typically by swatting at it. For this reason, mosquitoes have evolved the ability to navigate in close proximity to the host, while assessing their level of defensiveness and avoiding these threats. Insects, in general, are well known to display escape behaviors in response to visual, predator-like, looming stimuli. However, in spite of great epidemiological importance, very little is known about the mechanisms that allow mosquitoes to evade their predators, as well as swatting from their hosts. Mosquitoes use visual, olfactory, and thermal cues to track their hosts but what kinds of sensory cues are being used to avoid threats? As a first step towards bridging this knowledge gap, we analyzed the behavioral responses of the Yellow Fever mosquito, Aedes aegypti, to looming visual stimuli. For this, we used a virtual-reality environment designed for mosquitoes, where we displayed looming squares to mosquitoes in a variety of conditions (for example: landed, in flight). Results from these experiments allowed us to characterize the escape responses of mosquitoes, by determining the angles and distances to the stimuli that will most likely trigger an avoidance response. Ultimately, better understanding mosquito vision in the context of their escape behavior, can help us improve the design of control tools, such as traps, to increase their efficiency.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/106748 |
| Date | 04 June 2020 |
| Creators | Wynne, Nicole Elizabeth |
| Contributors | Biochemistry, Vinauger, Clément, Socha, John J., Tu, Zhijian, Lahondère, Chloé |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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