Abstract
BackgroundMale Anopheles mosquitoes that swarm rely in part on features of the environment including visual stimuli to locate swarms. Swarming is believed to be the primary behaviour during which mating occurs in the field, but is not a common behaviour in the laboratory. Features that stimulate male Anopheles gambiae G3 strain swarming were created in novel large indoor cages.MethodsThe following visual features were tested in all combinations to determine which were important for swarm formation. Large cages and fading ceiling lights at dusk alone did not stimulate swarming while a dark foreground and contrasting illuminated background with a contrasting landmark stimulated and localized swarm formation during artificial twilight. Given the need to test transgenic strains in as natural a setting as possible, in this study it was investigated whether induced swarm behaviour and cage size would affect relative mating performance of wild-type and transgenic β2Ppo1 and β2Ppo2 A. gambiae sexually sterile males.ResultsEven using a mosquito colony that has been in laboratory culture for 39 years, swarming behaviour was induced by this novel arrangement. The presence of swarming stimuli was associated with an increase in insemination frequency from 74.3 to 97.7% in large cages. Transgenic males showed a lower competitiveness in large cages compared to small cages regardless of the presence of swarming stimuli.ConclusionsThe results of the present study are discussed in view of the progressive evaluation of genetically modified A. gambiae strains and the potential applications of reproducing swarms in controlled conditions to dissect the mating behaviour of this species and the mechanisms controlling it.
Highlights
Male Anopheles mosquitoes that swarm rely in part on features of the environment including visual stimuli to locate swarms
There are few publications describing A. gambiae swarms indoors: Charlwood and Jones stimulated male swarming in a 1.7 m3 cage [11]; Marchand determined that provision of an artificial horizon that contrasted with a bright artificial sky encouraged swarming of A. gambiae and Anopheles arabiensis in a
The ability to reliably stimulate swarming in the laboratory in large cages provides both insights and an opportunity to study questions related to factors controlling assortative mating, perception and the evaluation of strains being considered for field release
Summary
Male Anopheles mosquitoes that swarm rely in part on features of the environment including visual stimuli to locate swarms. Features that stimulate male Anopheles gambiae G3 strain swarming were created in novel large indoor cages. Swarming by males is a natural mating behaviour of many Diptera [1, 2], including a major malaria vector mosquito, Anopheles gambiae sensu lato (s.l.) [3]. Others [12,13,14,15] developed a large cage called a “mesocosm” where they studied effects of sugar on mating performance of A. gambiae. In their setting, A. gambiae males were observed to swarm but those studies did not focus on swarm behaviour nor on the stimuli inducing it. Clear evidence of swarming activity effects on female insemination rates has not been published
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