Female autodetection and plasticity of pheromone response in the corn earworm moth Helicoverpa zea
LE3 .A278 2017
Bachelor of Science
Most studies on insect olfaction have focused on males responding to female sex pheromones, in part due to assumptions that females were anosmic to sex pheromones. However, recently ‘autodetection’ (the ability for females to detect and respond to conspecific female sex pheromones) has been observed in female moths in the family Heliothinae. The objectives of this study were to examine the functional importance of autodetection in Helicoverpa zea by determining what chemicals and concentrations result in a physiological and behavioural response, the genetic basis correlating to response, and whether olfactory habituation contributes to compound sensitivity in females. Sensitivity to major and minor pheromone components was tested by behavioral bioassays and electroantennograms (EAG), and RT-PCR and qPCR techniques were used to determine and quantify the expression of olfactory receptors (ORs). All methods were carried out on two treatment groups; habituated, or ‘grouped’ females, and naïve, ‘ungrouped’ females. Behavioural trials suggest that females engaged in a ‘spacing behavior’ in response to two key compounds, with greater response in the ungrouped females. EAG responses showed statistically significant differences between concentrations of compounds, as well as grouped and ungrouped treatments. Finally, there is strong supporting evidence that there is greater expression of OR genes in the ungrouped treatment. Discovery that habituated females have a decreased peripheral sensitivity to compound due to down-regulation of their olfactory receptors could have major implications in how laboratory experiments are conducted, as well as providing additional knowledge for use of pheromone based mating disruption strategies.
The author grants permission to the University Librarian at Acadia University to reproduce, loan or distribute copies of my thesis in microform, paper or electronic formats on a non-profit basis. The author retains the copyright of the thesis.