No evidence for long-range male sex pheromones in two malaria mosquitoes

Abstract

Cues involved in mate seeking and recognition prevent hybridization and can be involved in speciation processes. In malaria mosquitoes, females of the two sibling species Anopheles gambiae s.s. and An. coluzzii mate in monospecific male swarms and hybrids are rare. Long-range sex pheromones driving this behavior have been debated in literature but to date, no study has proven their existence or their absence. Here, we attempted to bring to light their existence. To put all the odds in our favor, we used different chemical ecology methods such as behavioral and electrophysiological assays as well chemical analyses, and we worked with mosquitoes at their optimal physiological mating state i.e. with swarming males during their natural swarming windows. Despite all our efforts, our results support the absence of long-range sex pheromones involved in swarm detection and recognition by females. We briefly discuss the implications of this finding in ecology, evolution and for control strategies.

Spatial and temporal characteristics of laboratory-inducedAnopheles coluzziiswarms: shape, structure and flight kinematics

“…On the assumption that both male and female mosquitoes use swarm markers to find and join mating sites [20,21,23], we suggest that at the start of sunset, the non-swarming flight continues until the mosquito find an appropriate visual ground marker. Then, the male mosquito initiates a stationary pseudo-looping flight above the marker until it detects a potential mate.…”

Swarm formation as backward diffusion

“…We show how emergence of confining potential wells (Okubo 1986, Kelley andOuellette 2013), a hallmark of insect swarms, can be attributed to individuals undergoing fission-fusion processes (described below), mirroring the case of stable swarms (Okubo 1986, Kelley andOuellette 2013). The new mechanism is distinctly different from aggregation due to either attractive pheromones, visual cues or acoustic cues, contentious processes in the context of insect swarms (Feugére et al 2021, Poda et al 2022 which in themselves do not result in the formation of potential wells and in the emergence of collective behaviour.…”

Oviposition site selection in mosquitoes : the role of conspecific larvae, heterospecific larvae and microbes

“…Mosquitoes use both auditory (Feugere et al, 2021(Feugere et al, , 2022 and may or may not use chemical cues to attract both sexes to mate in a swarm (Fawaz et al, 2014;Mozuraitis et al, 2020;Poda et al, 2022;Wang et al, 2021Wang et al, , 2023. Both sexes are sensitive to auditory cues and swarm in the air to mate (Feugere et al, 2021;Su et al, 2018).…”