Abstract
As one of the most notorious ectoparasites, bed bugs rely heavily on human or animal blood sources for survival, mating and reproduction. Chemoreception, mediated by the odorant receptors on the membrane of olfactory sensory neurons, plays a vital role in their host seeking and risk aversion processes. We investigated the responses of odorant receptors to a large spectrum of semiochemicals, including human odorants and plant-released volatiles and found that strong responses were sparse; aldehydes/ketones were the most efficient stimuli, while carboxylic acids and aliphatics/aromatics were comparatively less effective in eliciting responses from bed bug odorant receptors. In bed bugs, both the odorant identity and concentrations play important roles in determining the strength of these responses. The odor space constructed based on the responses from all the odorant receptors tested revealed that odorants within the same chemical group are widely dispersed while odorants from different groups are intermingled, suggesting the complexity of odorant encoding in the bed bug odorant receptors. This study provides a comprehensive picture of the olfactory coding mechanisms of bed bugs that will ultimately contribute to the design and development of novel olfactory-based strategies to reduce both the biting nuisance and disease transmission from bed bugs.
Highlights
Chemoreception is critical for insects as it plays a vital role in locating hosts, finding mates, identifying oviposition sites and avoiding natural enemies
Specific Odorant receptors (ORs) gene expansion was observed in both kissing bugs and stink bugs, with at least two branches of ORs evolved in stink bugs, which may be relevant to their phytophagy comparing to bed bugs and kissing bugs, and one branch of kissing bug ORs showed no close relatives from bed bugs or stink bugs
Human odorants were served as important cues for host seeking while chemical repellents, like compounds from alarm pheromone, delivered dangerous information for potential risks
Summary
Chemoreception is critical for insects as it plays a vital role in locating hosts, finding mates, identifying oviposition sites and avoiding natural enemies. Two previous studies using nearly the same panel of odorants to test the neuronal responses of bed bugs via single sensillum recording (SSR)[2,3], enabled us to directly compare the sensory spectra of ORNs and ORs. Unsurprisingly, most of the odorants (45 out of 67) eliciting active ORNs responses (≥50 spikes/s or 20% of the maximal responses) were very effective in activating the ORs (Fig. 3C).
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