Fish microbiota repels ovipositing mosquitoes

The mere presence of predators causes prey organisms to enact predation-avoidance strategies. This presence is often reveled through predator-released kairomones. It was previously suggested that in many cases, the predator’s microbiota composition plays an important role in the release of these kairomones, however this mechanism is still poorly understood. Ovipositing mosquito females of several species are repelled by kairomones released from larvivorous fish. In this study we looked into the effects of the microbiota originated by Gambusia affinis (Baird and Girard) on the ovipisition behavior of gravid mosquito females in an outdoor mesocosm experiment. We show that interference with the fish microbiota significantly reduces its repellant effect. We further show that the bacterium Pantoea pleuroti isolated from the skin of the fish repels oviposition of Culex laticinctus (Edwards) and Culiseta longiareolata Macquart mosquitoes similarly to the effect of live fish. These results highlight the importance of bacteria in the interspecies interactions of their hosts and the potential conflict of interests in this system, where bacteria may benefit from the absence of the bacterivore mosquito larvae, but the fish loose access to prey.