The completion of this thesis would not have been possible without the support and guidance of many wonderful individuals. With his support and encouragement, I ultimately decided to pursue a doctorate in the biological sciences. Aimee Bernard for allowing me to serve as a genetics teaching assistant, where I began to learn the fundamentals of pedagogy and the value of sharing a passion for learning with others.
Zwiebel, and the various members of my thesis committee, for always advocating science of the highest quality and integrity. Denise Due-Goodwin and Nathan Seaman for their many fascinating experiences teaching zoology, as well as the opportunity to further my training as a science teacher. Finally, I am also grateful for my friends and colleagues who all embarked on this graduate school journey together.
My dissertation work was conducted with the generous financial support of Vanderbilt University, the Gisela Mosig Travel Fund, the Howard Hughes Medical Institute, and the National Institutes of Health.
Olfactory genomics of eusociality within the Hymenoptera
Scott et al. 2001), where projection neurons then transmit information to the mushroom body (MB) and lateral horn (LH). There is a similarly large number of glomeruli in the antennal lobe, which corresponds to a large expansion of chemoreceptors (Nakanishi et al. The female-specific sensilla basiconica projects to the T6 cluster in ants (McKenzie et al. 2016) and the T3 cluster in the honey bee (Kropf et al. 2014) .
This may correspond to the increased levels of foraging observed in juveniles compared to juveniles (Simola et al. 2016). The role of biogenic amines in the regulation of aggression is also conserved in non-insect arthropods (Huber et al. 1997). In bees, receptors for linalool (AmelOr151) and other floral compounds (AmelOr152) have been identified (Claudianos et al. 2014).
Second, the profound changes in the neuroanatomical development of the antennal lobe of orco-/- mutants represent a significant confounding variable (Yan et al.
Functional characterization odorant receptors in the ponerine ant, Harpegnathos
Previous work has strongly implicated a nine-exon subfamily of ORs that accounts for nearly 30% of the 347 putative Or genes in H. Within these parameters, HsOrs that lie phylogenetically outside the nine-exon subfamily were favored based on the functional characterization of 22 members of this HsOr subfamily in a parallel study (Pask et al. 2017). Notably, this gene is the only known member of the ant OR subfamily B in H.
Of these receptors, HsOr271 exhibited a strong response (60 spots per s, Figure II-3) to 13,23-dimethyl-C37, which has been implicated as part of the fertility signal in H. We attribute this response to the establishment of near-distal glass recording electrode. Indeed, the wide range of significant inhibitory responses extended to all HsOs tested.
The response of the nine-exon receptor HsOr271 to the queen pheromone 13,23-dimethyl-C37 is also noteworthy, although it is also possible that there.
Odor coding of nestmate recognition in the eusocial ant Camponotus floridanus
Trible et al. 2017) demonstrated the value of applying new genetic and molecular techniques that have limited availability in the study of humans and other social primates. The formicine ant Camponotus floridanus lives in colonies founded by a single reproductive queen (Hölldobler and Wilson 1990; Gadau et al. 1996). Although it was initially proposed that ants accept individuals if they have desirable cues (D-present) or if they do not have undesirable cues (U-absent), to the exclusion of all others (Sherman, Reeve and Pfennig 1997), more recent evidence on that. that ants actively detect enemies but not friends through the detection of nNM odor cues (simple U-present model) (Guerrieri et al. 2009).
Importantly, however, discrimination can also occur when crucial components of the CHC profile are missing (Neupert et al. 2018). This was an essential aspect of our approach in light of the broad neuroanatomical changes recently observed in the development of the antennal lobes of Orco mutants in two ant species (Trible et al. 2017; however, because removal of the antennae disrupts a wide range of both mechanoreceptors and chemoreceptors (Nakanishi et al. 2009), a more targeted approach was needed to assess the specific function of OR-dependent chemoreceptor signaling in this context.
Using a modified aggression bioassay, based on previous methods described in (Guerrieri and d'Ettorre 2008) and (Gospocic et al. 2017), individual ants were challenged with a chemically neutral mechanical stimulus (i.e. a clean Von Frey filament ) and then scored for bite responses and wide opening of the mandibles as indicators of aggression. Although it is clear that these aggressive responses are mediated by the detection of chemical signals at the cuticle (Morel, Vandermeer, and Lavine 1988; Guerrieri et al. 2009; Leonhardt, Brandstaetter, and Kleineidam 2007; Neupert et al. 2018), the precise molecular mechanisms responsible for the detection and encoding of that information within the olfactory system have remained ambiguous.
Previous studies have shown that the antennae are necessary to elicit aggressive behavior towards nNMs (Wang et al. 2016; Forel 1928). Due to the broad developmental defects resulting from the loss of Orco in other ant systems (Trible et al. 2017; Yan et al. 2017), these pharmacological tools provide a unique opportunity to acutely investigate the role of OR-based signaling. investigated a wild-type adult nervous system.
As previously observed in other contexts (Sharma et al. 2015), VUANT1 antagonist treatment effectively silences all Orco/OR complexes and prevents the generation of any interpretable signal (Figure III-2). These results are consistent with previous literature suggesting that aggression-mediated NM recognition might be more appropriately described as nNM recognition (Guerrieri et al. 2009; van Zweden and d'Ettorre 2010).
Olfactory Changes Associated with an Age Polyethism in the Eusocial Ant
Group dynamics, such as the number of available workers or the current proportion of the workforce engaged in a particular task, can also influence decision making (Wilson 1984; Gordon 1987). Information in this context is communicated through an olfactory-dependent process such that successful foragers are identified based on their cuticular hydrocarbon profile and the odor profile of the food (Greene, Pinter-Wollman and Gordon 2013). Taken together, these results suggest that baseline antennal responsiveness is higher in older minor workers compared to older minor and major workers, regardless of the odorant compounds tested.
Comparison of the mean olfactory response to each of the 36 odor mixtures (two-way ANOVA with Tukey's correction for multiple comparisons, P < N = 36) (A). Comparison of normalized responses to the TETQ positive control (column factor (minor vs. major) was significant and characterized by A versus PCA analysis of the different chemical classes analyzed together with the percentage of variance explained by PC1 and PC2 (B–C).
Consistent with our focused examination of the unit compounds in compound 26, we found that nurses were significantly more responsive to 3-methylindole compared to foragers (Two-Way ANOVA with Tukey's correction for multiple comparisons, P < 0.0141, N = 7) ( Figure IV-6B ), suggesting that this connection may be responsible for task-related differences in behavior. Importantly, these behavioral transitions are accompanied by a dramatic shift in the workers' chemical and ecological environment. To prevent unwanted movement of the ant that could otherwise interfere with the quality of the recording, the ant's head and mandibles were restrained with wax beyond the right antennae.
Because of the ant's armor-like exoskeleton, a 30-gauge needle was required to puncture the right eye before inserting the reference electrode. Videos were then analyzed posthoc and the number of ants on each piece of paper was recorded every 30 seconds and averaged over the duration of the experiment. A small square of mesh secured with double-sided tape was placed over the top of this hole to allow ventilation of the arena.
Before starting the bioassay, a single ant was placed under a small cover (35 mm in diameter) in the Petri dish arena and allowed to acclimatize for 10 min. A two-way ANOVA with Tukey's correction for multiple comparisons was used to analyze the raw responses to the various odor mixtures (Figure IV-3A), the normalized responses to TETQ between minors and majors (Figure IV-3C), the unitary odorant responses of Blend 26 (Figure IV-5C and Figure IV-6B), and the movement and location data derived from EthoVision for individual responses to 3-methylene indole (Figure IV-6D-F).
Advances in the Study of Olfaction in Eusocial Ants
Of particular interest would be the development of a topographical map of the antennal lobe in ants, as is done in bees. Beginning with the publication of the first two ant genomes (Bonasio et al. 2010), considerable progress has been made in the field of olfactory myrmecology. Antennal Lobe Organization in the Queen Honey Bee, Apis-Mellifera L (Hymenoptera, Apidae)', International Journal of Insect Morphology & Embryology.
Comparative study of the antennal lobes and their afferent pathway in the worker bee and the drone (Apis-Mellifera), cell and tissue research. Distinct projections from two populations of olfactory receptor axons in the antennal lobe of the sphinx moth Manduca sexta', Chem Senses. Localization of short-term memory in the brain of the bee, Apis mellifera', Physiological Entomology, 5: 343-58.
Antennal olfaction physiology and male behavior of the Ponerine ant Harpegnathos saltator', Journal of Chemical Ecology. Multiple olfactory receptor neurons and their axonal projections in the antennal lobe of the honeybee Apis mellifera.', J Comp Neurol. Identification of Undecane as an Alarm Pheromone of the Ant Formica argentea', Journal of Insect Behavior.
A neural template remodeling process for cues for kin recognition in the carpenter ant Camponotus floridanus, J Comp Physiol A Neuroethol Sens Neural Behav Physiol. The chemoreceptor superfamily in the honey bee, Apis mellifera: expansion of the receptor family for smell but not for taste, Genome Res. A massive expansion of the chemosensory gene repertoire in the omnivorous German cockroach Blattella germanica, Journal of experimental zoology.
Odor-evoked responses to queen pheromone components and to plant odors using optical imaging in the drone antennal lobe of the honeybee Apis mellifera L.', Journal of Experimental Biology. Social interactions affect dopamine and octopamine homeostasis in the brain of the ant Formica japonica', Journal of Experimental Biology. Chemosensory coding by neurons in the coeloconic sensilla of the Drosophila antenna', Journal of Neuroscience, 25: 8359.
Organization of the olfactory pathway and odor processing in the antennal lobe of the ant Camponotus floridanus, J Comp Neurol.
