<p> Chapter 1-4 focuses on investigating whether forced copulations occur in teneral females, and how the female responds. There has only been one paper to report mating in newly eclosed (teneral) female matings in fruit flies (Drosophila melanogaster), and it was suggested to be forced. The focus of this thesis is to determine whether teneral matings are forced and how this may affect the future remating and reproductive success of females. Within the thesis, chapter 1 and 4 results suggest that teneral matings occur in both Canton-S and wild caught females, and occur in females less than 30 minutes post eclosion. Chapter 3 compared the male/female interaction of teneral females vs. immature females that successfully reject male mating attempts. Males were more aggressive with teneral females, and females displayed more rejection behaviours during courtship and mating. Chapter 4, was aimed at investigating what the reproductive consequences are, and results suggest that a teneral mating yields less progeny than a mature mating, and 68% of tenerally mated females remate at maturity.</p> <p> Chapter 5 and 6 focuses on investigating whether situational caffeine tolerance can be developed in fruit flies. Chapter 5 results indicate that caffeine causes a rest disruption, and a general tolerance to the rest disrupting effects can be gained over 6 days of repeated administration. The experiments in chapter 6 used various protocols to investigate whether a situational tolerance will develop, using odours and colours as associative cues. No conclusive results were found.</p> / Thesis / Master of Science (MSc)

Understanding the biological basis of behavior is crucial for gaining insights into human nature, treating behavioral disorders and improving overall well-being. Efforts to understand the biological basis of behavior have largely emphasized the role of neurons. However, examples across life show that behavior can occur in lieu of or in cell types outside of neurons. This thesis presents work exploring the mechanisms underlying multiple behaviors using the model system Drosophila melanogaster. Chapter 2 provides evidence for the influence of glia on courtship, aggression, and sleep. Chapter 3 characterizes a Drosophila model of autism spectrum disorder, finding that genetic neuronal manipulation of a single gene can cause pathologies beyond the nervous system. Chapter 4 investigates the connection between sleep behavior and oxidative stress response, demonstrating metabolism as a probable mediator of this relationship. Altogether, this work supports a wider definition for the biological basis of behavior.

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There has been a significant increase in the amount of connectomics data available at the level of single neurons and single synapses in the last few years. This increase enabled investigations into the structure and function of neural circuits in much greater detail than ever before. Thus, the next step in our quest to understand the brain's functional logic is the development of tools and methods to enable us to extract data from and model these new connectomics datasets, and their use to start to examine the brain computationally. Specifically, for Drosophila melanogaster, the fruit fly, a large amount of data on the connectome have become available in the last few years. In this dissertation, we start by introducing the tools we have built to extract information from the Drosophila connectome and to create spiking models of neuropils using this information to model sensory processing and associative learning circuits at single-synapse scale. We then use the toolkit we have introduced to explore sensory processing and associative learning in the brain. First, we introduce FlyBrainLab, an interactive computing environment designed to accelerate the discovery of functional logic of the Drosophila brain. Then, we propose a programmable ontology that expands the scope of the current Drosophila brain anatomy ontologies to encompass the functional logic of the fly brain, providing a language not only for modeling circuit motifs but also for programmatically exploring their functional logic; we introduce the FeedbackCircuits library for exploring the functional logic of the massive number of feedback loops (motifs) in the fruit fly brain, and NeuroNLP++, an application that supports free-form English queries for constructing functional brain circuits fully anchored on the available connectome/synaptome datasets. Thirdly, following up on the second, we explore the construction of antennal lobe circuits using models of glomeruli. We explore the composability of the connectivity of glomeruli with local neuron feedback loops, and quantitatively characterize the I/O of the AL as a function of feedback loop motifs in the one-glomerulus, two-glomerulus and 23-glomerulus scenarios. Lastly, in the final chapter, we consider the modeling of the mushroom body, a second order olfactory neuropil and a center of associative learning, to demonstrate how the architecture of the circuit interacts with the circuit mechanisms by which sensory inputs are represented and memories are updated. Thus, in this dissertation we introduce an approach for the analysis and modeling of neural circuits based on connectomics data, and apply this approach to neural circuits spanning multiple neuropils to extract and analyze the principles of computation in the brain. The methodology described here is designed to be applied to different sensory systems and organisms to infer the functional logic of connectome-based neural circuits.

<p>Recent observations illustrate fruit fly larval attraction to the distinct odour emanating from food occupied by other larvae. Growing evidence of bacteria as influential microorganisms of hosts suggested the closer examination of host-microbial interactions. We investigated the origin of the volatiles that are attractive to flies. Focal larvae showed no difference in attraction to axenic used food with axenic larvae and axenic fresh food. Additionally, mated females showed no difference in attraction to axenic used food with axenic larvae and axenic fresh food. When we supplemented the axenic disks with <em>L. brevis</em>, larvae showed a significant preference for the axenic used food with axenic larvae and <em>L. brevis </em>over axenic fresh food. Also, the supplementation of <em>L. plantarum</em> to axenic disks also resulted in larvae showing a significant preference for the axenic used food with axenic larvae and <em>L. plantarum </em>over axenic fresh food. Focal larvae showed a significant preference for <em>L. brevis</em> on scratched MRS agar and axenic used food with axenic larvae, but did not show a significant preference for <em>L. brevis</em> on scratched axenic food. In a learning experiment, focal larvae showed no preference for novel odours previously paired with standard used food over novel odours previously paired with axenic used food. In order to test whether <em>L. brevis</em> improves food quality, the three fitness parameters observed, larval development rate, egg-to-adult survival, and adult body mass, revealed inexplicable findings. These results provide evidence for the role of bacterial volatiles in mediating the social attraction observed in fruit flies.</p> / Master of Science (MSc)

The sex comb an array of specialized bristles on the foreleg, is a highly variable male trait of Drosophila that provides an ideal system for integrative studies of morphological evolution. Here, studies of the genetic and developmental architecture of sex comb bristle number variation in Drosophila melanogaster are described. Analysis of the response to twenty-four generations of divergent artificial selection indicated high genetic variance underlying this trait, and demonstrated a weak relationship with other, developmentally related non-sex bristle systems. I also present evidence showing bristle number is associated with mating success. Manipulation of diet in full-sib families confirmed that this trait is condition dependent, and that there is a genetic basis for condition dependence. Further partitioning of variance components using a half-sib mating design revealed a strong maternal, dominance and/or X chromosome effect on sex comb bristle number variation. Finally, sex comb bristle number was not correlated with comb orientation in wild type, High and Low artificial selection lines, or the mutant strain bric a brac PR72. Analysis of patterns of variation in comb orientation over ontogeny in these lines showed that this aspect of the sex comb phenotype is highly canalized. This body of work provides important insight into D. melanogaster sex comb evolvability, and represents a timely approach to bridging the gap between population genetics and development in studies of phenotypic evolution. / Thesis / Doctor of Philosophy (PhD)

Malpighian (renal) tubules of the fruit fly Drosophila melanogaster consist of three functional domains: a non-secretory distal segment, a secretory main segment and a reabsorptive lower segment. In this study a computer-controlled micropositioning system and a self-referencing K^+ microelectrode were used to measure K^+ concentration gradients of extracellular unstirred layers associated with specific epithelial domains. K^+ fluxes were calculated from the measured gradients. This is the first time: that an accurate assessment of the concentration gradients of the unstirred layer of Drosophila melanogaster could be assessed due to the enhanced sensitivity of this self-referencing technique over conventional ion-selective microelectrodes. The technique permits high resolution spatial and temporal mapping of the flux patterns in response to stimulation or inhibition of ion transport. Variations in K^+ transport over time and at different sites suggest that transport is non-uniform within any one functional domain. / Thesis / Master of Science (MSc)