Biological Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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Bacteria-delivered RNA interference strategies to silence genes related to vector competence of Aedes aegypti

Author: 
Date created: 
2018-05-29
Abstract: 

Dengue infection is a devastating mosquito-borne disease, and the principal vector is the mosquito, Aedes aegypti. Current vector control strategies are not working, hence the need for alternative strategies. Cathepsin B is a mosquito protein that dengue viruses require to establish and replicate within mosquitoes; knocking down cathepsin B using RNAi changes the phenotype from dengue susceptible to dengue refractory in Ae. aegypti. We engineered bacteria to express dsRNA against cathepsin B to develop an orally delivered RNAi system. Our data suggest inconsistencies in the alteration of gene expression that may be a result of the modified bacteria being digested, or a lower than required quantity of the RNAi constructs being expressed. Without a consistent knockdown, it is unlikely that we will be able to reduce vector competence predictably.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Carl Lowenberger
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.P.M.

The response of Agriotes obscurus click beetles to pheromone and its impact on the acquisition of a fungal pathogen

Date created: 
2018-04-19
Abstract: 

Wireworms, the larval stage of click beetles, are a pest of many root crops, and are a challenge to control due to their long, subterranean life style and tolerance to chemical insecticides. An alternative approach is to target the adults. Pheromones have primarily been used as aggregants in attract-and-kill pest management tactics. However, pheromones can also alter insect movement and social interactions in other ways. I investigated whether female sex pheromone can enhance the primary transmission of the fungal pathogen Metarhizium brunneum Petch in Agriotes obscurus L. click beetles. Using video tracking, I found sex pheromone increases beetle activity regardless of season, and different light and air movement conditions. Heightened activity resulted in 58% more male-to-male contacts in a small arena. Although beetles picked up significant numbers of spores from contact with conspecifics, and an environment contaminated by conspecifics, pheromone did not enhance the level of infection obtained through these pathways.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jenny Cory
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.P.M.

Hepatic proteome and toxic response of early-life stage rainbow trout (Oncorhynchus mykiss) to the aquatic herbicide, Reward®

Author: 
Date created: 
2018-05-07
Abstract: 

The objective of this study was to examine the acute toxicity and sub-lethal effects of the commercial formulation of diquat dibromide, Reward® Landscape and Aquatic Herbicide, on multiple early-life stages of rainbow trout exposed to environmentally relevant concentrations. The continuous exposure 96 h LC50 derived for juvenile feeding fry aged 85 d post-hatch was 9.8 mg/L. Rainbow trout eyed embryos and juvenile feeding fry were also exposed to concentrations of Reward® ranging from 0.12 to 10 mg/L during two 24 h pulse exposures separated by 14 d of rearing in fresh water to mimic the manufacturers instructions for direct applications to water bodies. Effects on growth and development were evident at 9.25 mg/L during the embryo/alevin exposures, but not in feeding juveniles, indicating a higher sensitivity of the early life stage fish. Quantitative proteomic assessment and subnetwork enrichment analyses were conducted on hepatic proteins for both life stages to evaluate protein expression changes after 0.37 mg/L diquat via Reward® exposure. Unique cellular process expression profiles for pre-feeding swim-up fry and for feeding juvenile fish were observed, reflecting differences between the two life stages in sub-cellular responses after diquat dibromide exposure. Hepatic proteome effects were more dramatic in the pre-feeding swim-up fry with 315 proteins significantly different between the control and fish exposed to Reward®, while in the later life stage feeding fry, only 84 proteins were significantly different after Reward® exposure. This study is the first to report the sub-cellular and whole organism level effects of diquat dibromide in a commercial formulation and demonstrates that numerous changes at the protein level occur at environmentally relevant concentrations based on aquatic application rates.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Vicki Marlatt
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Characterization of present biological conditions in the intertidal community across Howe Sound, British Columbia

Date created: 
2018-04-25
Abstract: 

Howe Sound is a Pacific Northwest fjord located north of Vancouver, British Columbia. This fjord has been impacted by effluents from several industries including two pulp mills and a copper mine. After Environment Canada undertook more stringent enforcement on environmental standards in the 1980s, the Britannia copper mine and the Woodfibre pulp and paper mill were shut down. Historical data from the intertidal community indicate that recovery of the ecosystems in these areas has been minimal, particularly at sites in close proximity to industrial activities. The goal of this study was to begin a characterization of several present biological conditions in the intertidal community across Howe Sound. Six sites were selected and grouped based on degree of exposure to industrial activities. High exposure sites included Britannia Beach, Darrell Bay and Port Mellon, while moderate exposure sites included Porteau Cove and Lions Bay. Chaster bay was selected as a reference site for this study. Two biomarkers of exposure; ethoxyresorufin-O-deethylase (EROD) and metallothionein (MT) were measured in mussels to assess the availability of polyaromatic hydrocarbons and metals at these sites. When compared to the Chaster Bay reference site, EROD activity was significantly higher in mussels collected from the two high exposure sites (Britannia Beach (~2.1 increase) and Port Mellon (~1.5 increase)) and the two moderate exposure sites (Porteau Cove (~1.8 increase) and Lions Bay (~1.6 increase). MT levels were significantly higher in mussels from the Britannia Beach (~4.2 increase), Darrell Bay (~2.8 increase) and Porteau Cove (~2.4 increase). Results from another ecological bioindicator (giant kelp) showed that germination rates were significantly lower at Lions Bay, Port Mellon and Darrel Bay (> 60% reduction compared to the reference site). A 16% reduction in germination rate was also noted for Britannia Beach. Germination tube length were only found to be significantly reduced at Lions Bay (~20 % decrease), Darrell Bay (~37% decrease) and Britannia Beach (~10% decrease). Finally, in an intertidal community assessment using species richness as an index, Chaster Bay contributed 39.94% to the total species richness, a range of 17.78% - 19.02% for moderate exposure sites and 4.50% - 12.79% for the high exposure sites.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Chris Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Effects of farming practices and landscape composition on wild invertebrate pollinator and bird abundance, richness and health

Date created: 
2018-04-11
Abstract: 

Wildlife biodiversity is threatened by agricultural intensification, which reduces and fragments natural habitat. I examine how farming practices and landscape composition influence wild pollinators and birds that inhabit these ecosystems. I also assess pollen foraging preferences of wild bumble bees and the effect of foraging preferences on their health. Forest cover was the main predictor of wild pollinator and bird abundance and richness, and floral resource availability also increased the abundance and richness of pollinators. There was no effect of farm management type (organic vs. conventional) on abundance or diversity of either pollinators or birds. Bumble bees showed a strong foraging preference for flowers not found on farms, and those collected in natural areas had higher body fat content than bees collected on farms. These results emphasize the importance of the conservation of natural habitat adjacent to agricultural areas for biodiversity, and of floral resources in natural areas for pollinator health.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Elizabeth Elle
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Characterization of suppressors of fat-like cadherin CDH-4 in context of axon guidance during embryonic development

Author: 
Date created: 
2018-04-10
Abstract: 

Developing the nervous system requires axons to grow and connect to specific targets, forming neuronal circuits, through axon navigation. One of the genes controlling axon navigation is the fat-like cadherin CDH-4, a member of the cadherin superfamily. To identify genes acting together with cdh-4, mutants suppressing the axon guidance defects of cdh-4 mutants were isolated previously. The goal of this thesis was to characterize and identify these suppressor genes. Five suppressors were studied in detail. They partially suppressed axon guidance and movement defects observed in the cdh-4 mutants. Three suppressor genes were identified: math-48, a functionally uncharacterized gene, prp-6 and prp-8, both encoding components of the spliceosome. A previous study documented changes in expression of several hundred genes when prp-6 or prp-8 are partially inactivated. This suggests that the suppression effect might be mediated by upregulation of one or more genes, compensating for the loss of CDH-4.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Harald Hutter
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Viability, growth, development, and performance of juvenile sockeye salmon (Oncorhynchus nerka) exposed to neonicotinoid pesticides

Author: 
Date created: 
2018-04-10
Abstract: 

The effects of the neonicotinoid insecticide imidacloprid on sockeye salmon (Oncorhynchus nerka) exposed from 1 h post-fertilization to the swim-up fry developmental stage were evaluated using a gravel-bed flume incubator designed to simulate a natural streambed environment. This chronic exposure tested nominal imidacloprid concentrations of 0.15, 1.5, 15, and 150 µg/L to investigate the effects on hatching success and timing, deformity rates and growth. The effects of the neonicotinoid insecticides thiamethoxam, imidacloprid, and clothianidin, and mixtures of all three on burst swimming performance and routine metabolism in sockeye salmon (Oncorhynchus nerka) were also examined after acute 96-h exposures. There was no evidence that chronic exposures impacted growth, development, hatch timing and success or survival in sockeye salmon during the embryonic pre-hatch and post-hatch alevin developmental stages. There was also no evidence that acute exposures to environmentally relevant concentrations of neonicotinoids impacted swim performance or routine metabolism in swim-up fry.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Chris Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Lethal and non-lethal effects of exposure to methylmercury in the Zebra Finch (Taeniopygia guttata) during development

Author: 
Date created: 
2018-02-20
Abstract: 

Methylmercury is an environmental contaminant that bioaccumulates, and has multiple toxic modes of action. Aquatic species have traditionally been the focus of wildlife toxicological research on mercury, but terrestrial receptors, including passerines, may also be exposed to similarly elevated levels of methylmercury. In this study we exposed a model passerine, the Zebra Finch (Taeniopygia guttata), to methylmercury in-ovo (embryonic exposure, pre-hatching), only as a chick (post-hatching exposure), and with a combined in-ovo chick treatment (embryonic and post-hatching exposure). Exposure to methylmercury in-ovo resulted in a significant reduction in hatching success, but there was no significant difference in behavioural or reproductive outcomes for the individuals that survived to maturity. Birds dosed both in-ovo and as chicks had reduced numbers of females surviving to maturity and altered male courtship behaviours. Birds dosed only as chicks had reduced survival rates. No long-term effects were seen on male courtship in the birds dosed only as chicks. Continuous exposure of chicks during embryogenesis and chick development had a deleterious effect on bird survival and fertility. Passerines may be able to withstand exposure to elevated levels of methylmercury during development at the nestling stage, but chronic exposure may reduce survival and fertility.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Tony Williams
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Behavioural and physiological responses of prey fish to an invasive predator

Date created: 
2017-12-12
Abstract: 

Local predator density should affect prey responses to predators by influencing predator recognition and/or general risk avoidance amongst prey. I investigated whether behavioural and physiological responses of juvenile striped parrotfish (Scarus iseri) to predatory invasive Indo-Pacific lionfish (Pterois sp.) varied with local native and invasive predator density. Parrotfish exhibited evasive behavioural changes in response to visual and chemical stimuli from a native predator (Epinephelus striatus) but not to lionfish stimuli. However, parrotfish from reefs with high compared to low predator densities exhibited more evasive behaviour and colouration responses overall. Parrotfish from reefs with high predator densities also had higher survival rates in encounters with lionfish. Steroid hormone reactivity did not vary across parrotfish groups. Selective predation by lionfish of risk-taking prey fish could be resulting in greater cautiousness in some prey populations. This heightened risk avoidance ultimately aids prey fish evasion of invasive lionfish in the absence of predator recognition.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Isabelle Cote
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Evaluating the role of zoos and ex situ conservation in global amphibian recovery

Date created: 
2017-10-12
Abstract: 

Amphibians are declining worldwide, and ex situ approaches (e.g. captive breeding and reintroduction) are increasingly incorporated into recovery strategies. Nonetheless, it is unclear whether these approaches are helping mitigate losses. To investigate this, I examine the conservation value of captive collections. I find that collections do not reflect the species of likeliest greatest concern in the future but that non-traditional zoos and conservation-focused breeding programs are bolstering the representation of threatened amphibians held ex situ. Next, I examine the reproductive success of captive breeding programs in relation to species’ biological traits and extrinsic traits of the program. Based on 285 programs, I find that not all species are breeding in captivity, yet success is not correlated to the suite of tested predictors. Overall, ex situ approaches are playing a potentially important role in amphibian conservation, but we must work to improve the representation of threatened amphibians in zoos and husbandry expertise.

Document type: 
Thesis
Senior supervisor: 
Arne Mooers
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.