Résumé
In the fight against malaria, the main vector control tools, which are insecticide-treated nets and indoor residual spraying, are currently encountering a limit of effectiveness due to the increased resistance of vectors to the used insecticides. Aware of this, the sterile insect technique (SIT) and genetically modified mosquitoes (GMMs) both based on mosquito mating, take up a key place as innovative, alternative or complementary strategies to existing tools. The success of these control strategies requires a better knowledge of the biology and ecology of mosquito reproduction. In order to contribute to a better knowledge of the mating behavior in malaria vectors, we initiated this PhD thesis which aimed to study the potential visual and chemical cues used at long range by Anopheles gambiae and Anopheles coluzzii females to search for and join the conspecific swarms. In order to reduce the influence of environmental factors, we performed our experiments under controlled conditions. To do so, we set up a laboratory allowing the swarming behavior stimulation of Anopheles under controlled conditions. A video-tracking system installed in this laboratory allowed us to acquire real time and three dimensional recordings and to reconstruct the flight trajectories of mosquitoes within swarms. Behavioral tests and chemical and electrophysiological analyses were performed in order to highlight the involvement of volatile sex pheromones in the mate seeking behavior. Our findings showed that both An. gambiae and An. coluzzii males use a ground visual marker to form and locate their swarms at the species-specific locations, An. coluzzii above and An. gambiae next to the marker. More notable, our results showed that virgin females also used the ground visual markers to reach the conspecific male swarming sites where they exhibited swarming behavior in the absence of males. Using the video-tracking system, we showed that swarming flight characteristics are distinct between the two species and between the sexes. Females fly faster and loop at higher frequencies than males, and An. coluzzii males fly faster than An. gambiae ones. Finally, despite different chemical ecology methods used and having worked with mosquitoes in their optimal physiological mating state, we failed to provide evidence of the volatile sex pheromones production in An. gambiae and An. coluzzii males. This thesis allowed improving our knowledge on Anopheles reproductive ecology and could contribute to improve the effectiveness of the control strategies based on SIT and GMMs. They also open new avenues for the development of innovative vector control tools. These results are of great importance in evolutionary ecology since they open avenues for a better understanding of the speciation mechanisms between An. gambiae and An. coluzzii, and the diversity within the An. gambiae complex.