Thesis (M.S.) in Natural Resources, Aquatic Toxicology--University of Wisconsin--Stevens Point, 2003. / Includes bibliographical references (leaves 75-82).

Determining the extent to which parasites influence natural populaions of hosts is a major focus of studies in parasitology. Addressing this issue requires host-parasite systems that can be monitored under natural conditions and can be manipulated in the laboratory. I study a model system involving the larval trematode Ornithodiplostomum ptychocheilus that encysts in the brains of its intermediate host, the fathead minnow (Pimephales promelas). This parasite was the most common and abundant of 13 other parasites found in minnows in four boreal lakes in Alberta, Canada. In two of these lakes, prevalence of infection reached 100% in most years and mean intensity ranged from 4 to 40 parasites/host. Field and laboratory experiments showed that the size, the rate of parasite development, and time to encystment were intensity-dependent. However, parasite intensity had no effect on host or parasite survival after a simulated winter in the laboratory. One effect of infection was that infected fish and significantly greater cranial heights and widths than controls. The expression of this parasite-induced alteration in host phenotype was dependent on the size of the fish at infection and on parasite intensity. The cranial distortion led to significantly higher mortality of fish maintained on poor diets and altered the host's phototactic response. / ix, 131 leaves : ill. (some col.), map ; 29 cm.

A wide variety of parasites are known to cause changes in host behaviour. The altered behaviours range from simple changes in features such as activity and phototaxis, to the creation of behaviours that are new, and often bizarre. In this study, I investigated the effect of a trematode parasite, Ornithodiplostomum ptychocheilus (Strigeidae; Diplostomidae), on the behaviour of its intermediate host, the fathead minnow (Pimephales promelas). The larval stage (metacercaria) of this parasite resides within the central nervous system, specifically the optic lobes. In fish, one of the main functions of the optic lobes is to receive visual stimuli from the retina and then coordinate the optomotor response (OMR). This response is an innate component of rheotaxis that plays an important role in motion detection, navigation and orientation. In an initial experiment, 16 wk-old metacercariae reduced minnow OMR by 42% compared to uninfected controls. However, in a follow-up experiment, it was 2- and 4- wk old metacercariae that caused the greater (39 and 41% respectively) decrease in OMR. Because 2- and 4-wk old metacercariae are not infective to birds (the next host in the life-cylce), alterations in minnow OMR at this time are unlikely to be a parasite adaptive. During this period, reduced OMR is more likely a result of pathology caused by developing larvae within the optic lobes. However, negative effects of infection on OMR performance persisted to 16 wk post-infection indicating the parasite-induced reduction in host performance could be an adaptive strategy to increase parasite transmission. Surprisingly, the magnitude of reduction in minnow OMR was only loosely linked to metacercarieae intensity. Although both low (<5 parasites/fish), and high intensities (>100) led to large decreases in OMR, intermediate intensities had only a small effect. Such non-linearity between intensity and the magnitude of host behavioural changes suggest that the mechanisms leading to altered host behaviours are varied, and complex. / vii, 79 leaves : ill. ; 29 cm.

The population dynamics and life histories of two larval parasites of fathead minnows were investigated, together with their effects on host reproduction in natural populations. In two lakes in northern Alberta, Canada, 100% of fathead minnows (Pimephales promelas) are infected with larval trematodes (Ornithodiplostomum ptychcocheilus and Posthodiplostomum minimum) that encyst in their brains and mesentaries, respectively. The numbers of parasites in individual adult minnows varied extensively between and within two different lakes. Parallel laboratory studies indicated that selection imposed by common hosts in the life cycles of these species have shaped broadly similar life histories. Field collections of male minnows indicated that early in the breeding season, breeding males were longer than non-breeding males. Furthermore, breeding males had larger girths (independent of total length) and contained fewer numbers of three of 4 common larval trematodes than non-breeding males throughout the breeding season. These parasites most likely affect a male's ability to compete for or defend a nest. / vi, 99 leaves : ill. ; 28 cm.

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 93-103).

Endocrine disrupting compounds are ubiquitous in aquatic environments. Exposure to these compounds may cause deiodination of thyroid hormones in fish and also affect certain behaviors. Behavioral change may be a useful indicator of deiodination on an organismal level, and may indicate effects to populations, especially if these behaviors affect reproduction. We exposed Pimephales promelas (Fathead Minnow) to effluent from a recently upgraded wastewater treatment facility. The effluent contained a matrix of low-level (< 1.0 µg/L) concentrations of endocrine disrupting compounds pre- and post-upgrade. We examined the behavior of adult Fathead Minnow exposed to treated wastewater for 90 days and the behavior of their offspring at 12-20 days old. There was no significant difference in 11 of the 12 behaviors we documented for adult fish in control and treatment tanks (p > 0.05). However, treatment fish were significantly more aggressive towards a decoy fish compared to control fish (p < 0.05). There was no significant difference found in the predator avoidance behaviors examined in the F1 generation. Although our results did not find any significant differences between control and treatment fish in regard to most behaviors we would typical associate with thyroid deiodination, such behaviors may have manifested following a longer exposure period or by having a larger sample size. Other future considerations should include looking at different behaviors (e.g. social behaviors) and further characterization of the finished effluent.

A commonly prescribed contraceptive, the synthetic progestin norethindrone (NET) inhibits ovulation in humans. However, ecotoxicological data are lacking. Preliminary tests produced an LC50 for NET of > 1.0 mg/L (96-hour, fathead minnow (FHM) and medaka) and a NOEC of 242.0 µg/L, a LOEC of 485.0 µg/L (7-day, growth for FHM and medaka). Reproductive testing revealed a LOEC for fecundity of 24.1 ng/L (21 days, medaka). Further testing confirmed the LOEC of 24.1 ng/L while defining a NOEC of 4.7 ng/L (28 days, medaka). Effect of NET in medaka life-cycle exposure at concentrations exceeding 4.7 ng/L was evident. Few females were present in the 24.7 ng/L exposure concentration, with none in the 104.6 ng/L. Egg production was significantly reduced at concentrations exceeding 4.7 ng/L. Additionally, weight, condition factor and somatic indices were significantly different in males exposed to concentrations exceeding 4.7 ng/L. For fecundity and sexual differentiation; the NOEC was 4.7 ng/L, the LOEC 24.6 ng/L; growth and somatic indices, the NOEC was more appropriately 0.9 ng/L, with effect evident at 4.7 ng/L. Sexual differentiation of the F1 population was similar to the F0. A defining result of this test was development of exceptionally large ovaries in NET- exposed female medaka, perhaps indicative of a threshold limit for exposure in these fish. Results of FHM life-cycle testing were similar, establishing a NOEC for fecundity of 0.9 ng/L, a LOEC of 4.8 ng/L. NET's inhibitory effect on gonadal development was obvious; GSI NOEC for males, 4.8 ng/L, and histological examination confirmed the presence of intersex development at elevated concentrations. Normal physical development and growth were impaired, generally at concentrations exceeding 24.1 ng/L. At exposure concentrations exceeding 4.8 ng/L, external sexual confirmation of fish was difficult; LOEC for finspot development in females, 4.8 ng/L. Sexual determination of the 97.1 ng/L exposure group was impossible; externally, all fish appeared male and internal examination revealed no gonadal development.

Current evidence suggests that thyroid hormones (THs) may impact development of the immune system. However, studies that explore the role of THs in immune development are limited, and the mechanisms leading to alterations in immune function are poorly understood. It is important to elucidate the role of THs in immune development given that many environmental contaminants have been shown to disrupt TH homeostasis and may also have negative impacts on the immune system. As such, the main goal of this study was to determine the long-term consequences of early life stage (ELS) hypothyroidism on immune function. To achieve this goal, it was first necessary to further characterize basic immune function in the selected model species, the fathead minnow (FHM, Pimephales promelas). Preliminary studies were conducted to describe the transcriptomic response to Yersinia ruckeri and adapt assays for the assessment of respiratory burst and phagocytic cell activity. To determine the long-term effects of ELS hypothyroidism, FHMs were exposed to the model thyroid suppressant propylthiouracil (PTU) from <1 to 30 days post hatch and reared under normal conditions. Upon reaching adulthood, ex vivo immune cell function and the in vivo immune response to Y. ruckeri were assessed. Fish exposed to PTU experienced significant alterations in gene networks associated with immune cell function as well as significant decreases in phagocytic cell activity. However, immune-related alterations at the molecular and cellular levels did not manifest themselves at higher levels of organization as ELS hypothyroidism did not affect any other immune-related endpoints, including pathogen resistance. To our knowledge, this is the first study to provide evidence that ELS hypothyroidism causes long-term effects on the immune system in fish.

Acclimation temperature had a significant effect on the lethality of copper to fathead minnows in replicated 96-hour lethality tests. Lowest median lethal copper concentrations (LC50) were recorded at 12 and 22°C, with LC50s at 5 and 32°C at least 140 μg/1 higher. This research found LC50 copper concentrations in the 300 to 500 μg/1 range and a polynomial relationship between LC50s and acclimation temperature. Following a 24-hour exposure to three sublethal concentrations of copper, critical thermal maxima (CTMax) were tested in minnows acclimated to four temperatures. Sublethal exposure to copper significantly decreased the CTMaxs relative to controls at three of the four temperatures. Control CTMaxs ranged from 28.6 to 40.4°C and increased 0.46°C for each 1°C increase in acclimation temperature.

The oil sands, located in north-eastern Alberta, are one of the largest deposits of oil worldwide. Because the Alberta Environmental Protection and Enhancement Act prohibits the release of oil sands process-affected material into the environment, industry is storing vast quantities of tailings on mine lease sites. The oil sands industry is currently accumulating tailings waste at a rate of >105 m3/day, for which reclamation strategies are being investigated. Naphthenic acids (NAs) have been identified as the most toxic component of oil sands tailings as they are considered acutely toxic to a variety of biota, and are therefore a target contaminant for tailings pond reclamation strategies. Current literature based on Microtox® assays (marine bacteria Vibrio fischeri) suggests that lower molecular weight NAs are more toxic than higher molecular weight NAs. The following thesis involves the utilization of NA fractions and their relative toxicities to determine if NA toxicity is related to NA molecular weight. A previous study generated an oil sands-derived naphthenic acid extract (NAE), which was fractionated by distillation at stepped temperatures, yielding five fractions with increasing median molecular weights (Daltons). In the present study, the same extract and five fractions were utilized. To expand on the earlier characterization which involved a low resolution electrospray ionization mass spectrometry (ESI-MS), the whole extract and five fractions were analysed using electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and synchronous fluorescence spectroscopy (SFS). Mean molecular weights were generated for each fraction, and an increase in molecular weight with increasing fraction number was confirmed. Respective mean Daltons and relative proportions for each fraction are as follows: 237 and 11.9 % (fraction 1), 240 and 32.3% (fraction 2), 257 and 33.4% (fraction 3), 308 and 16.8% (fraction 4), and 355 and 5.6% (fraction 5). When chemical analyses of fractions were compared, it was determined that structures contributing to increased molecular weight included increased cyclic structures (up to 7-ring structures), aromaticity (mono- and diaromatics), nitrogen, sulfur, and oxygen heteroatoms, and dihydroxy/dicarboxy compounds. In addition, characterization data suggested the presence of NAs exhibiting estrogenic structures. Following chemical characterization, NA fractions were subject to embryo/larval bioassays using two fish species: Oryzias latipes (Japanese medaka) and Pimephales promelas (fathead minnow). Endpoints evaluated were mortality, time to hatch, hatch length, and abnormalities. Results suggest that relative NA fraction toxicity is not related to molecular weight, as no trend relating mean Dalton weight to toxicity was observed for any endpoint in both species. Acute toxicity data indicated differences between fractions as high as 2-fold, although results were species-dependent. Fraction 1 displayed the lowest potency (highest LC50) for both Japanese medaka (0.291 mM) and fathead minnow (0.159 mM). Fractions 3 and 2 for Japanese medaka (0.149 and 0.157 mM, respectively), and fractions 5 and 2 for fathead minnow (0.061 and 0.080 mM, respectively) displayed the greatest potencies for mortality (lowest LC50). When fraction LC50s for Japanese medaka were compared to the whole NAE (0.143 mM), the mid molecular weight fractions (fractions 2 and 3) appeared most similar to the whole NA. . In terms of relative toxicity and proportion, constituents in the mid molecular range fractions (2 and 3) likely represent greater risk compared to other fractions, and further chemical and toxicological characterization of constituents within these fractions is warranted particularly for long-chained, monocarboxylic acids, with low aromaticity. Japanese medaka and fathead minnow varied in their sensitivity and their relative response to different fractions. In general, fathead minnow were more sensitive than Japanese medaka based on lower estimates of LC50 and threshold (growth) values in addition to the presence of developmental abnormalities (predominately yolk sac edema) associated with a few of the fractions. Compared to differences in toxicity between fractions for a given species (>2-fold for fathead minnow), there was more variability between species for a given fraction (> 3-fold for fraction 5). Also, the relative toxicity of fractions as indicated in the present study is contrary to the results generated using Vibrio fischeri for the same fractions. Thus, there is a need for multi- endpoint and species toxicity evaluations to assess the efficacy of remediation and reclamation options for reducing toxicity of oil sands tailings.