Graduate Theses & Dissertations

Effects of Opioids on the Development and Reproductive Capacity of Japanese Medaka, Oryzias latipes
Opioid drugs are among the microcontaminants that are discharged with domestic wastewater into the aquatic environment with the potential to affect the development and reproductive capacity of aquatic organisms. To study the effects of exposure of fish to opioid drugs, Japanese medaka (Oryzias latipes) were exposed over a full life cycle to environmentally relevant (i.e. ng/L) concentrations of two opioids, codeine and fentanyl. Acute exposure of early life stage (ELS) of medaka to codeine resulted in slightly extended times to hatch, but no increase in embryo mortalities or reduced hatching success. Chronic exposure to codeine at a nominal concentration of 25,000 ng/L over a full life cycle interfered with growth, reducing the weight of the fish at maturity. Life cycle treatments with codeine at all test concentrations resulted in a significant reduction in the number of eggs produced in reproductive trials, as well as a reduction in the numbers of mature oocytes in adult females. High treatments with codeine also increased the percentage of immature sperm cells in adult males. Life cycle exposures to codeine also resulted in reduced whole-body concentrations of several hypothalamic-pituitary-gonadal (HPG) axis hormones, including reduced levels of luteinizing hormone in male and female fish and a reduction in 11-ketotestosterone in males and 17β-estradiol in females. Fentanyl did not affect reproduction or HPG hormones at the exposure concentrations tested, but high fentanyl exposures increased the mortality rate among ELS’s of the F1 generation offspring from life cycle exposed adults. The results of this thesis contribute to the literature on the environmental impacts of microcontaminants of wastewater origin and, the potential for effects in fish exposed to opioids.Keywords: Opioids, microcontaminants, fentanyl, codeine, sexual development, reproduction. Author Keywords: codeine, fentanyl, microcontaminants, opioids, reproduction, sexual development
Effect of the neonicotinoid imidacloprid on embryogenesis and anuran survivorship in frog virus 3 infected tadpoles
Exposure of pre-metamorphic amphibians to neonicotinoid insecticides may be contributing to the global decline in amphibian populations. In this study, anuran embryos and tadpoles of the African clawed frog (Xenopus laevis) and the North American leopard frog (Lithobates pipiens) were used to determine the effects of embryonic exposure to neonicotinoids. In addition, Xenopus was used to determine if prolonged exposure to neonicotinoids influenced tadpole sensitivity to frog virus 3 (FV3). Exposure of anuran embryos to concentrations of the neonicotinoid insecticide, imidacloprid, ranging from 1 -20 ppm induced a concentration dependent increase in malformations of the retina in Xenopus embryos. However, similar responses were not observed with embryos of leopard frogs. Exposure of Xenopus tadpoles to 500 ppb concentration of imidacloprid followed by challenge with FV3 showed that pesticide exposure unexpectedly decreased the rates of mortality, although total mortalities by the end of the experiment were not significantly different from controls. This unexpected observation may be attributed to a reduced inflammatory response induced by exposure to imidacloprid. Despite the low acute toxicity of neonicotinoid insecticides to vertebrates, these studies indicate that exposure to this class of insecticides causes sublethal effects in anuran species during early life stages. Author Keywords: embryogenesis, Lithobates pipiens, neonicotinoid, ranavirus, tadpole, Xenopus laevis
Responses of Primary Producers and Grazers to Silver Nanoparticle Exposure
The increasing production and use of silver nanoparticles (AgNPs) raise concerns on environmental exposure and impact. A large scale in situ enclosure study was conducted at the Experimental Lakes Area to determine the effect of AgNPs on natural phytoplankton and zooplankton communities. This study investigated AgNPs of varying concentrations (4, 16 and 64 μg/L), dosing regimens (chronic vs. pulse), and capping agents (poly-vinyl pyrrolidone vs. citrate). Phytoplankton communities were influenced only by the natural limnological properties of the system signifying tolerance to AgNPs. Zooplankton community structure significantly changed with AgNP concentration and dosing regimen indicating AgNP sensitivity. A microcosm study investigating the effect of AgNPs and phosphorus-dosed periphyton before and after grazing by two benthic invertebrate species (snails and caddisfly larvae) showed reduced periphyton stoichiometry with AgNP exposure. Grazers foraged less on silver dosed periphyton indicating a preferential choice in food quality. Phosphorus reduced the detrimental effects of AgNPs across all conditions. These studies verify the need for in situ experimental designs to fully investigate the effects of AgNPs and their interaction with environmental factors, multiple species assemblages, and across trophic levels. Author Keywords: benthic invertebrate, Experimental Lakes Area, periphyton, phytoplankton, silver nanoparticles, zooplankton
Comparing Biological Responses to Contaminants in Darters (Etheostoma spp.) Collected from Rural and Urban Regions of the Grand River Watershed, Ontario
Urban and agricultural activities may introduce chemical stressors, including contaminants of emerging concern (CECs) and current use pesticides (CUPs) into riverine systems. The objective of this study was to determine if fish collected from sites in a river show biomarkers of exposure to these classes of contaminants, and if the biomarker patterns vary in fish collected from urbanized and agricultural sites. The watershed selected for this study was the Grand River in southern Ontario, which transitions from areas dominated by agricultural land use in the north to highly urbanized locations in the southern part of the watershed. Rainbow darters (Etheostoma caerluem) and fantail darters (Etheostoma flabellare) were collected from the Grand River in June, 2014 for biomarker analysis from two urbanized sites and three agricultural sites (n=20 per site). Over the same period of time, Polar Organic Chemical Integrative Samplers (POCIS) were deployed for 2 weeks at each site to monitor for the presence of CUPs and CECs. The amounts of the target compounds accumulated on POCIS, determined using LC-MS/MS were used to estimate the time weighted average concentrations of the contaminants at each site. Data on the liver somatic index for darters indicate site-specific differences in this condition factor (p<0.05). Significant differences in the concentrations of thiobarbituric acid reactive substances (TBARS) in gill tissue (p<0.05) indicate differences in oxidative stress in fish collected from the various sites. Measured concentrations of ethoxyresorufin-O-deethylase (EROD) in liver tissue were significantly different between sites (p<0.05), indicating differences in CYP1A metabolic activity. Finally, acetylcholinesterase (AChE) activity in brain tissue was significantly different between fish from rural and urban sites (p<0.05). The analysis of these biomarkers indicates that fish may be experiencing different levels of biological stress related to different land uses. These data may be useful in developing mitigation strategies to reduce impacts on fish and other aquatic organisms in the watershed. Author Keywords: AChE, Biomarker, Darter, EROD, POCIS, TBARS

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