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The occurrence of D. weischeri Chizhov, Borisov & Subbotin, a newly described stem nematode species of creeping thistle (Cirsium arvense L.), and D. dipsaci (Kühn) Filipjev, a pest of garlic and quarantine parasitic species of many crops, has been reported in Canada. This research was conducted to determine if D. weischeri is a pest of agricultural crops, especially yellow pea (Pisum sativum L.) in the Canadian Prairies. Significant (P < 0.05) slight reproduction (1 < ratio of final to initial population < 2) of D. weischeri occurred on two (Agassiz and Golden) of five varieties of yellow pea examined. Other annual pulse and non-pulse crops, including common bean, chickpea, lentil, spring wheat, canola, and garlic were non-hosts for D. weischeri. Conversely, a range of reproduction responses to D. dipsaci was observed with all pulse crops being a host of the nematode. Ditylenchus weischeri was not a seed-borne parasite of yellow pea, unlike, D. dipsaci which was recovered from seed. Conversely, D. weischeri and not D. dipsaci was recovered from creeping thistle seeds. In callused carrot disks, with no addition of medium, an increase of 54 and 244 times the addition density of 80 nematodes was obtained for D. weischeri and D. dipsaci, respectively, after 90 days. Temperature had a significant influence on the development of D. weischeri and D. dipsaci in yellow pea. Development of D. weischeri did not proceed past adult stage at 17 and 22°C whereas a minimum generation time of 30 days was apparent at 27°C with the associated accumulated growing degree-days of 720 degree-days (above a base temperature of 3°C). The minimum generation time for D. dipsaci was 24, 18 and 22 days with 336, 342 and 528 degree-days at 17, 22 and 27°C, respectively. In field microplots, grain yield of yellow pea were not significantly affected by addition density of D. weischeri. At harvest, the total number of recovered nematodes per plant was not significantly different than the added at the start. The results of these studies confirm that D. weischeri is unlikely to be a pest of yellow pea for weather conditions of the Canadian Prairies. / October 2016

Ticks are obligate haematophagous arthropods that represent a major economic drain upon the world's livestock as well being a significant medical and veterinary risk through the transmission of tick-borne pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. The tick-host relationship is a function of both ecological and physiological factors. Successful feeding requires the effective acquisition and digestion of a bloodmeal by the tick. Acquisition relies upon the ability of the tick to counteract host immune responses induced by the extended feeding periods of ixodid ticks (up to 2 weeks). The host response to tick infestation and the consequent countermeasures employed by the tick, constitute the tick-host interface. The immune response of hosts to Ixodes ricinus infestations was examined through antigenic profiling. The antigens exposed to the host were shown to vary throughout the feeding period and differed between the different development stages of I. ricinus. It was also shown that different host species infested with I. ricinus recognised different antigens. This was true of both natural and non-natural hosts, and even closely related species. Anti-complement activity was investigated in the salivary glands of Ixodes ticks. This activity was shown to inhibit some host species but not others. The pattern of inhibitory activity varied between the tick species tested in a way that was consistent with known tick host-preferences. The mechanisms of anti-complement activity in I. ricinus salivary glands were explored. The alternative but not the classical pathway of complement was inhibited. Activity was present in unfed ticks and throughout the feeding period. Three targets of the complement system were identified as being modulated by the tick. Digestion of the bloodmeal was explored and a haemolytic activity was associated with the salivary glands of I. ricinus ticks. The activity was demonstrated to be Mg²⁺- dependent. In addition, a subtractive cDNA library enriched for saliva-associated transcripts was successfully produced. Random sampling identified putative differentially expressed genes. The results of this thesis illustrate the complexity of tick-host interactions at the molecular level. It is apparent that the research described poses many more questions than answers.

One of the major aims of this thesis was to identify novel regulators that drive C. albicans adaptation during growth under different nutrient and temperature conditions. The classical stress response cascades have been previously characterised under standardized, but physiologically irrelevant growth conditions (YPD at 30°C). In this study these pathways and other regulators were examined under more physiologically relevant inputs because metabolic plasticity and thermo-tolerance have been shown to affect stress adaptation (Arguelles et al., 1999; Brown et al., 2014; Cowen, 2009; Diezmann et al., 2014). In this study, we characterized 18.5% of the functional C. albicans ORFeome under 144 different stress conditions by employing a standardized system of robotic screening (Chapter 3). These screens highlighted extensive carbon and temperature-conditional regulators in C. albicans. We identified carbon-conditional contributions of the transcriptional regulators Sfp1 and Rtg3 to stress adaptation in this pathogenic fungus (Chapter 4). Sfp1 was found to regulate the expression of key stress regulators during growth on glucose, whereas Rtg3 induced the expression of these stress genes during growth on lactate. Our screens also revealed a distinct set of transcription factors, Hap43, Swi4, Sfp1, Cap1 and Zcf31, that control regulators of cell wall integrity and that promote antifungal drug resistance in a temperature dependent and yet Hsp90- independent manner. The screens also provided new information about a relatively obscure group of transcriptional regulators in C. albicans; the zinc cluster proteins with focus on Zcf3 and Zcf18 which we further pursued with RNA-sequencing to establish them as modulators of cell cycle, stress resistance and virulence in C. albicans. Lastly, our screens reveal a network of regulators that are homologous to human oncogenes and control fungal growth via modulation of TOR signaling. In conclusion, this thesis has revealed many novel targets for possible antifungal drug development and highlighted the extensive and intricate cross-talk between stress response modules facilitated by physiologically relevant nutrient sources and ambient temperatures.

This paper explores the various relationships found in John Steinbeck's "Of Mice and Men," Tennessee Williams's "A Streetcar Named Desire," Franz Kafka's "The Metamorphosis," and F. Scott Fitzgerald's "Tender is the Night." The exploration of each demonstrates the common theme of parasitic relations and the toll this dynamic takes on the persons involved.