UC Riverside

In the field of insect chemosensation, knowledge of basic principles has come from the model organism, Drosophila melanogaster. However, the different life histories of Culicids result in behaviors that are unique to mosquitoes. In hematophagous species, these behaviors facilitate the transmission of mosquito-borne diseases that pose grave threats to humans. Currently, we have a better understanding of the olfactory system despite many critical taste-driven behaviors such as blood-feeding. To better understand the role of the taste system and how it helps guide taste-driven behaviors, we aimed to characterize the neuronal responses of the mosquito labellum. A comprehensive survey was carried out on the labellar sensilla of the yellow fever mosquito Aedes aegypti using a panel of different categories of compounds (sweet, bitter, salt, water, and amino acids). The qualitative and quantitative differences observed across the different taste categories revealed five functional groups. Our survey showed that in addition to sweet, bitter, water, and salt taste responses, mosquito labellar sensilla exhibit neuronal sensitivity to amino acids. Analysis of responses to mixtures suggests that amino acid sensitivity maps to a neuron distinct from those that respond to the other four taste categories. We then investigated whether the sensitivity of the peripheral taste organs is modulated by physiological changes that the female mosquito undergoes throughout the gonotrophic cycle using a diagnostic panel of tastants. We first measured and compared the sensitivity of non-mated females to that of mated females and found that sensillar sensitivity to sucrose correlates to the meal preference during both states. We then measured labellar sensitivity before a blood meal and 18-20 hours after obtaining a blood meal. Lastly, we measured the sensitivity of male mosquitoes and compared them to the female response. We found that the male sensitivities are higher than the mated females but more similar to non-mated female labellar sensitivities. Overall, this dissertation presents the first map of the functional organization of taste sensilla of the labellum for a major mosquito vector. Our results raise the possibility that alterations in peripheral taste sensitivity underlie shifts in feeding preference during a female’s gonotrophic cycle.