A 3D Analysis of Flight Behavior of Anopheles gambiae sensu stricto Malaria Mosquitoes in Response to Human Odor and Heat

Abstract

Female mosquitoes use odor and heat as cues to navigate to a suitable landing site on their blood host. The way these cues affect flight behavior and modulate anemotactic responses, however, is poorly understood. We studied in-flight behavioral responses of females of the nocturnal malaria mosquito Anopheles gambiae sensu stricto to human odor and heat. Flight-path characteristics in a wind tunnel (flow 20 cm/s) were quantified in three dimensions. With wind as the only stimulus (control), short and close to straight upwind flights were recorded. With heat alone, flights were similarly short and direct. The presence of human odor, in contrast, caused prolonged and highly convoluted flight patterns. The combination of odor+heat resulted in longer flights with more landings on the source than to either cue alone. Flight speed was greatest (mean groundspeed 27.2 cm/s) for odor+heat. Odor alone resulted in decreased flight speed when mosquitoes arrived within 30 cm of the source whereas mosquitoes exposed to odor+heat maintained a high flight speed while flying in the odor plume, until they arrived within 15 cm of the source. Human odor evoked an increase in crosswind flights with an additive effect of heat at close range (<15 cm) to the source. This was found for both horizontal and vertical flight components. However, mosquitoes nevertheless made upwind progress when flying in the odor+heat generated plume, suggesting that mosquitoes scan their environment intensively while they progress upwind towards their host. These observations may help to improve the efficacy of trapping systems for malaria mosquitoes by (1) optimizing the site of odor release relative to trap entry and (2) adding a heat source which enhances a landing response.

Absence of Close-Range Excitorepellent Effects in Malaria Mosquitoes Exposed to Deltamethrin-Treated Bed Nets

“…50 The wind tunnel assay is more sensitive to reveal behavioral effects than the current WHO assays and could be considered as an additional method useful for investigating spatial repellent effects of current and new insecticidal compounds. 51 In the wind tunnel setup, in the presence of human host cues, it was found that both susceptible and resistant An.…”

Straightforward multi-object video tracking for quantification of mosquito flight activity

“…In experimental contexts where conditions cannot be reliably controlled (such as imaging of mosquitoes in their natural habitats), more complex algorithms for object definition and tracking, or indeed the use of 3D imagery, may be necessary to obtain meaningful data (Beeuwkes et al, 2008;Spitzen et al, 2013;Wu et al, 2009).…”

“…Single camera setups are a suitable solution, however they are unable to record the depth of observed objects, and therefore tracks are recorded in two dimensions (2D). For this reason dual or multi-camera setups are increasingly employed for the observation of insect flight, which permits the reconstruction of 3D tracks from multiple views of the insects (Beeuwkes et al, 2008;Butail et al, 2012;Spitzen et al, 2013). Although multicamera techniques remain essential for a complete description and analysis of complex individual interactions (El-Sayed et al, 2000;Khan et al, 2005;Wu et al, 2009), they have a number of drawbacks: they are prohibitively expensive for many laboratories, require precise imaging calibration for their correct installation, and use relatively complex and computationally demanding techniques for 3D position reconstruction.…”

BORIS: a free, versatile open‐source event‐logging software for video/audio coding and live observations

“…Traditionally, commercial software also had limitations regarding the computers suitable to run the programs and were useable on a limited number of operating systems (e.g. ; Observer XT, Noldus 2015;INTERACT, Mangold 2015), while usually offering a powerful set of analytical features (Adamson et al 2013;Spitzen et al 2013).…”