Abstract
Attraction of female Aedes aegypti mosquitoes to 1-octen-3-ol (octenol), CO2, lactic acid, or ammonia emitted by vertebrate hosts is not only contingent on the presence of odorants in the environment, but is also influenced by the insect’s physiological state. For anautogenous mosquito species, like A. aegypti, newly emerged adult females neither respond to host odors nor engage in blood-feeding; the bases for these behaviors are poorly understood. Here we investigated detection of two components of an attractant blend emitted by vertebrate hosts, octenol, and CO2, by female A. aegypti mosquitoes using electrophysiological, behavioral, and molecular approaches. An increase in sensitivity of octenol olfactory receptor neurons (ORNs) was correlated with an increase in odorant receptor gene (Or) expression and octenol-mediated attractive behavior from day 1 to day 6 post-emergence. While the sensitivity of octenol ORNs was maintained through day 10, behavioral responses to octenol decreased as did the ability of females to discriminate between octenol and octenol + CO2. Our results show differing age-related roles for the peripheral receptors for octenol and higher order neural processing in the behavior of female mosquitoes.
Highlights
Female Aedes aegypti mosquitoes spread human pathogenic viruses that cause yellow fever, dengue fever, and Chikungunya
Detection of specific odorants, such as CO2, octenol, lactic acid, and ammonia, is carried out by receptor proteins located in the dendritic membrane of olfactory receptor neurons (ORNs); these receptors belong to the odorant receptor (OR), gustatory receptor (GR), and ionotropic receptor classes (Hansson and Stensmyr, 2011)
ELECTROPHYSIOLOGICAL RESPONSE OF OCTENOL-SENSITIVE NEURONS We recorded the electrical activity of the “C” neuron using the single-cell recording technique in 1, 6, and 10 days old adult female A. aegypti mosquitoes
Summary
Female Aedes aegypti mosquitoes spread human pathogenic viruses that cause yellow fever, dengue fever, and Chikungunya. Much of the struggle against these diseases has relied on a combination of prophylactic measures such as vector control including insecticides and odor-baited traps. These systems can be improved once we better understand the relationships between the A. aegypti olfactory system and odorants. Sensilla distributed on the antennae, maxillary palps, and proboscis of mosquitoes (Figure 1A) house ORNs that detect volatile chemicals and transduce these signals into electrical outputs for further processing within the central nervous system. Detection of specific odorants, such as CO2, octenol, lactic acid, and ammonia, is carried out by receptor proteins located in the dendritic membrane of ORNs; these receptors belong to the odorant receptor (OR), gustatory receptor (GR), and ionotropic receptor classes (Hansson and Stensmyr, 2011)
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