Semi-field and indoor setups to study malaria mosquito swarming behavior

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Résumé

Background: The recent resurgence of interest in sterile insect techniques to control vector mosquitoes has
renewed interest in novel methods for observing mating behavior. Malarial vectors of the Anopheles gambiae complex are known to mate in swarms at specific locations at dawn and dusk. Most knowledge of mosquito swarming
behavior is derived from field observations and a few experimental studies designed to assess critical parameters that
affect mosquito swarming. However, such studies are difficult to implement in the field because of uncontrollable
environmental factors and mosquito conditions. Here, we present two experimental setups specifically designed to
analyze mosquito swarming behavior and provide evidence that swarming behavior of mosquitoes can be generated
and accurately assessed under both semi-field and laboratory conditions.
Methods: The Mosquito Ecology Research Facility setup is a semi-field enclosure made of 12 compartments
(10.0×6.0×4.5 m L×W×H each) exposed to ambient meteorological and lighting conditions. The laboratory setup
consists of a windowless room (5.1×4.7×3.0 m) in which both environmental and mosquito conditions can be
controlled. In the two setups, 300 3–6-days-old An. coluzzii virgin males were released and some swarm characteristics
were recorded such as the time at which the swarm started, the number of mosquitoes in the swarm and the height.
Climatic conditions in the semi-field setup were also recorded.
Results: In both setups, An. coluzzii males displayed stereotyped and consistent swarming behavior day after day;
males gradually gather into a swarm over a ground marker at sunset, flying in loops in relation to specific visual
features on the ground. Although semi-field climatic conditions were slightly different from outdoors conditions, they
did not impede swarming behavior and swarm characteristics were similar to those observed in the field.
Conclusions: Swarm characteristics and their consistency across days provide evidences that these facilities can be
used confidently to study swarming behavior. These facilities come to complement existing semi-field setups and
pave the way for new experimental studies which will enhance our understanding of mating behavior but also mosquito ecology and evolution, a prerequisite for application of genetic approaches to malaria control.
Keywords: Anopheles, Burkina Faso, Mating behavior, Mosquito ecology research facility, Swarming room

Mots-clés

Anopheles, Burkina Faso, Mating behavior, Mosquito ecology research facility, Swarming room