Cues of mosquito host finding and oviposition site selection

Abstract

The aim of this work was to study odor cues that affect mosquito host seeking and oviposition behavior. Due to the vastness (and sometimes contradictions) of mosquito oviposition cues available in literature, I started by reviewing these cues, their source in nature, and their role in mosquito oviposition. Then, I tested the oviposition response of Aedes aegypti towards the contradictory oviposition odor p-cresol and its isomer m-cresol in different situations.p-cresol showed an oviposition deterrent effect at a broad range of concentrations (10-8-103 ppm) and stimulant effect only at 10-10 ppm while m-cresol was deterrent at 103 ppm only. Mixing the two compounds at 102 ppm yielded an oviposition deterrent effect. In addition, when both odors were presented in separate cups but together in the same cage, m-cresol was also perceived as deterrent suggesting an interaction between the two odors when presented in the same place.Odors that influence mosquito host seeking could also affect oviposition. I confirmed the repellent effect of methyl N,N-dimethyl anthranilate and ethyl anthranilate on host seeking Aedes aegypti mosquitoes using a Y-tube olfactometer and showed that butyl anthranilate, which has been previously shown to be repellent, works only in still air situations. In addition, I showed that ethyl anthranilate and butyl anthranilate have an oviposition deterrent effect while methyl N,N-dimethyl anthranilate has no effect on Aedes aegypti oviposition.To study odor coding in the mosquito antennal lobe, I presented a calcium imaging method and showed that it works to some degree in staining the antennal lobe. I also showed glomerular response in few mosquitoes towards significant odors, and the response to one of them (2-phenylethanol) was consistently in similar positions within the antennal lobe of different mosquitoes. Afterwards, I tested the host seeking and oviposition response of Aedes aegypti mosquitoes towards 2-phenylethanol, the odor which elicited the most stable response in calcium imaging experiments.2-phenylethanol repelled host seeking mosquitoes at 10-3 and 10-2 and deterred oviposition at 10 and 100 ppm.Finally, I tested the effect of prior experience on mosquito oviposition preference towards different concentrations of the oviposition pheromone n-heneicosane. I showed that raising Aedes aegypti larvae in 100 ppm n-heneicosane until eclosion resulted in a preference of the gravid females towards 100 ppm n-heneicosane over the innately preferred concentration 10 ppm.