Influence of Chromobacteriumanophelis bacteria on Anopheles coluzzii mosquito swarming behavior and its reproductive potential

Microbial symbionts are increasingly recognized as promising tools for the biological control of mosquito vectors. Chromobacterium anophelis , an entomopathogenic bacterium isolated from malaria mosquitoes, has demonstrated both larvicidal and adulticidal effects under laboratory conditions. However, its influence on mosquito reproductive behavior and survival under semi-field conditions remains insufficiently explored. We evaluated the effects of C. anophelis and its cell-free supernatant (Sup) on Anopheles coluzzii using a semi-field experimental design. Mosquitoes were exposed to varying concentrations of bacterial suspensions (Ca) or supernatant through sugar feeding. Survival probability was monitored daily for 14 days. Behavioral and reproductive parameters including swarm size, number of mating couples, and insemination rate were recorded during dusk swarming events. Statistical analyses included Kaplan–Meier survival estimates, analysis of variance (ANOVA), and behavioral comparisons across seven treatment groups. Exposure to both Ca and Sup significantly reduced mosquito survival, with complete mortality observed within 10 days in the highest-dose treatment groups. Swarm size was markedly reduced in Ca_10p6 and Sup_30% treatments, indicating strong behavioral impairment. Mating attempts and insemination rates were also substantially lower in these high-exposure groups. In some cases, males were observed to participate in swarms and attempt mating but failed to inseminate females, suggesting physiological disruption beyond simple behavioral suppression. In contrast, control and low-dose treatments (Sup_10% and Ca_10p5) maintained relatively high survival and reproductive performance. Chromobacterium anophelis and its metabolites significantly impair both survival and reproductive success in An. coluzzii through a combination of lethal and sublethal effects. These findings highlight the potential of microbial agents to disrupt mosquito reproductive behavior and reduce vector population replacement. Our data suggest that C. anophelis and its cell-free supernatant are candidates for further evaluation as complementary tools for mosquito vector control.