Biological Sciences Undergraduate Works

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Open Access
Acute effects of quinoline and 2-methylquinoline on electrical activity of great pond snail (Lymnaea stagnalis) neurons
(2025-04) Tramley, Cameron; Tomy, Gregg (Chemistry); Markham, John (Biological Sciences); Fry, Mark
Polycyclic aromatic compounds (PAC) are organic compounds found ubiquitously in the environment and originate naturally or anthropogenically. They are persistent, bioaccumulative, and toxic (PBT). PACs have been found to modulate voltage gated ion channels in fish cardiomyocytes. Many studies have examined PACs effects, however, there is growing concern about a less studied class of PACs: hetero-polycyclic aromatic compounds (HPACs). Quinoline and its derivative 2-methylquinoline are two-ringed HPACs found in high concentrations in sediment and tissues of fishes from the Great Lakes. Studies investigating synthetic quinoline derivatives used in the pharmaceutical industry have shown HPACs modulate voltage gated sodium, calcium and potassium ion channels in cardiomyocytes of fishes and mollusk neurons. We therefore designed a study investigating the acute neurobiological effects of quinoline and 2-methylquinoline on Great Pond Snail (Lymnaea stagnalis) neurons, a model with a large easily accessible central nervous system and well conserved ion channels. Electrophysiological characteristics were measured by performing suction electrode experiments on the right internal nerve of the right parietal Lymnaea stagnalis ganglion. Extracellular recordings before and after application of various quinoline or 2-methylquinoline concentrations were used to determine the frequency of right parietal nerve activity which we normalized as percent of control. The extracellular recordings revealed that quinoline affects right parietal nerve activity in a dose dependent manner. Quinoline caused a statistically significant effect on right parietal nerve activity at 1000 nM, but not 100 nM, and 10 nM, with mean percent of control values being 89.2 ± 4.3%, 103.9 ± 4.6% and 99.9 ± 3.5% respectively. 2-Methylquinoline had no statistically significant effect on right parietal nerve activity at 1000 nM. These experiments highlight the importance of understanding the neurobiological effect of PBT environmental contaminants quinoline and 2-methylquinoline, as well as demonstrate the utility of suction electrode recordings as an electrophysiology technique to evaluate acute neurotoxicity of environmental contaminants.
Open Access
Alternative BNIP3 splicing in alveolar rhabdomyosarcomal cells
(2023-04) Fernando, Amy; Whyard, Steve (Biological Sciences); Ghavami, Saeid (Human Anatomy and Cell Science); Gordon, Joseph; Wilkins, Olivia
Several cellular phenotypes drive tumorigenesis in alveolar rhabdomyosarcoma. These phenotypes may be attenuated via treatment with non-steroidal antiinflammatory drugs, like aspirin, tolfenamic acid, and indomethacin, which interfere with intracellular prostaglandin synthesis and induce cell death. Recent data suggest that this mechanism may be mediated by differential splicing of the cell death gene BNIP3, such that full-length BNIP3 could promote cell death, while short BNIP3 could inhibit it. Additional data indicate that oncogenic cytokines from the TGF-β family may also be involved in this mechanism. This honours thesis examines whether indomethacin alters cell death, BNIP3 splicing, and other alveolar rhabdomyosarcoma phenotypes. To assess this, RT-PCR and fluorescent imaging assays were performed on the RH30 cell line. Results of these experiments indicate that a 2.0 μM concentration of indomethacin alters the cell death phenotype. However, they also provide preliminary evidence that the expression levels of full-length and short BNIP3 are unchanged. Accordingly, drug treatments did not change calcium signalling pathways. Furthermore, this text examined the role of TGF-β cytokines in this molecular pathway. To help establish the role of TGF-β in alveolar rhabdomyosarcoma, a statistical analysis of a previously generated secretome dataset was performed. It determined that the three TGF-β isoforms are differentially secreted in alveolar and embryonal rhabdomyosarcoma. However, qRT-PCR results indicate that indomethacin exposure does not change TGF- β1 expression. Collectively, this thesis provides preliminary evidence that indomethacin exposure induces cell death in RH30s independently of alternative BNIP3 splicing.
Open Access
An Investigation of Knowledge Retention Using Two-Stage Exams in Undergraduate Biology
(2024-07-04) Judge, Abby
Although active learning is typically thought of as an in-class experience, this concept can be further applied to assessments as well. Two-stage exams allow for the unique experience of students working collaboratively during examinations, following the completion of the individual stage. Although two-stage exams have been shown to improve student learning gains, the effects of two-stage exams on retention of course content remains variable. I examined the effects of two-stage exams on knowledge retention at various Bloom’s level (Remember, Understand, and Apply) to determine whether two-stage exams promote knowledge retention at various levels of cognitive thinking. A two-stage in-class test followed by the re-testing of questions answered individually or in groups at subsequent time points (5, 48, and 85 days) allowed testing for knowledge retention. Our results indicate that group questions improve knowledge retention at relatively long time periods across all Bloom’s levels while also promoting retention at more complex Bloom’s levels at intermediate and relatively long time periods. Additionally, our analysis reveals that an average of 40% of individual only questions are forgotten by the final exam, while only an average of 19.5% of group questions are forgotten by the final exam. These results indicate that two-stage exams promote the ability to retain complex information at relatively long time periods.
Open Access
Arthropod Diversity Within The Three Sisters Cropping System
(2024-07-04) Ferch, Tessa; Roth, Jim (Biological Sciences); Markham, John (Biological Sciences); Bobiwash, Kyle; Worley, Anne
The Three Sisters is an indigenous cropping method that dates back hundreds of years. It is comprised of the simultaneous planting of corn, bean, squash, and sometimes sunflower. However, there has been no published research into arthropod communities and interactions with this cropping system. My study examined arthropod abundance and taxa to the family level at three areas: uncultivated, fields planted with The Three Sisters, and field edges. This was done at three sites in Manitoba: Ian N. Morrison Research Farm near Carman, Glenlea Research Station near Glenlea, and Brokenhead Ojibway First Nations Reserve. I placed 8 sticky cards within each area at each site starting in July 2023, and had 4 bi-weekly sampling rounds. The number of samples collected and processed was 288. I conducted a perMANOVA test, and ran multiple negative binomial generalized linear mixed models, testing the abundance and number of taxa present in relation to the site, area type, date, colour, and using trap number as a random effect. All sites were significantly different from each other. Glenlea had the highest diversity, and Carman had the least diversity. The uncultivated areas differed from both the field and edge areas, and the fields and edges also differed from each other at all sites. The field and edges had higher diversity than the uncultivated areas. The most important finding of my study was that The Three Sisters is an agricultural method that can allow for higher diversity of arthropods than uncultivated areas.
Open Access
Canopy-dependent environmental factors impact on nitrogen fixation in Shepherdia canadensis in the boreal forest and tundra
(2025-03) Tydings, Jason; Renault, Sylvie (Biological Sciences); Fraser, Kevin (Biological Sciences); Markham, John
Actinorhizal shrubs, plants that symbiotically associate with nitrogen-fixing bacteria and do not depend on soil nitrogen, can increase productivity and facilitate successional changes. High-latitude environments are characterized by harsh abiotic climatic conditions that limit nitrogen availability to plants. However, actinorhizal shrubs are less prevalent at higher latitudes, even though those environments are generally nitrogen-limited. Reduced year-round temperatures, water availability, and light availability are all thought to limit nitrogen fixation due to its energetic costs, making nitrogen fixation unfavourable at higher latitudes. Shepherdia canadensis (buffalo berry) is an actinorhizal shrub that is found in higher-latitude environments across Canada. We wanted to determine, within the northern edge of the boreal forest and tundra, how much nitrogen fixation is occurring in buffalo berry, and how it varies across naturally occurring habitat and canopy-dependent environmental factors. The natural abundance stable isotope technique was used to quantify nitrogen fixation, while canopy-dependent variables were measured using hemispherical image analysis. We found that buffalo berry shrubs were getting a majority of their nitrogen content through nitrogen fixation (55.32% - 94.74%) and that on average, fixation occurred at a higher rate in the forest (74.67%) compared to the tundra (68.00%). Notably, foliar δ13C values varied with canopy openness. Specifically, shrubs in more open areas and the tundra had higher δ13C values, which were interpreted to be a result of stomatal closure in response to reduced water availability. Nitrogen fixation was found to be sensitive to water availability, decreasing with canopy openness (17.99% – 99.79%). This limitation could reduce the productivity of nitrogen-fixing plants in response to warmer climate conditions.
Open Access
Characterization of the oxygen binding properties of hemoglobin from the ruby-throated hummingbird (Archilochus colubris)
(2024-07-04) Patel, Suchita; Signore, Anthony (Biological Sciences); Fraser, Kevin (Biological Sciences); Campbell, Kevin
Weighing only between 2.5 and 4.8 g, the ruby-throated hummingbird (A. colubris) has one of the highest known mass-specific metabolic rates among birds. Despite this, there is a lack of available data on the oxygen binding properties of their hemoglobin (Hb). Here I measured the effect of allosteric effectors, pH and temperature on the O2-affinity (defined as the O2 partial pressure required for 50% Hb O2 saturation; P50) of ruby-throated hummingbird Hb, while also estimating their Hb buffering capacity. A comparison of Hb-O2 affinity (i.e. P50 values) between A. colubris and its sole congener, the black-chinned hummingbird (A. alexandri), revealed differences likely attributed to two β-chain amino acid substitutions. Under treatment conditions resembling the natural physiological state of hummingbird blood, A. colubris exhibited a similar Bohr effect (-0.401) and buffering capacity (4.88 mol H+ mol Hb4-1 pH-1) to those of other hummingbird species, though both variables were among the lowest values previously reported for birds. Nonetheless, the low buffering capacity is modelled to enhance the efficiency of their (relatively low) Bohr effect and may enable a high blood [Hb], which together with a relatively low blood O2 affinity is shown to markedly increase tissue O2 delivery. I also found that O2 binding of A. colubris Hb was thermally insensitive under natural physiological conditions. This thermal insensitivity could help ensure adequate O2 delivery both during and upon arising from torpor, while minimize heat loss at the lungs. These findings highlight the various O2 binding properties of A. colubris that together facilitate the efficient delivery of O2 to the tissues irrespective of temperature.
Open Access
Circadian Patterns of Flight in a Long-Distance Migratory Songbird
(2024-07-05) White, Trina; Davoren, Gail (Biological Sciences); Fraser, Kevin
Migration is a common strategy in many different animal taxa, including birds. Most migratory songbirds migrate mainly at night (i.e., nocturnal migrants), with some species migrating primarily during daytime (i.e., diurnal migrants). Some birds can even combine nocturnal and diurnal flights, but these tend to be associated with barrier crossings (e.g., long overwater flights). Whether diurnally migrating songbirds also incorporate night flights into other periods of their spring migrations despite a lack of migration barriers has not been investigated. Further, we lack a precise understanding of the influence of specific environmental conditions on day or night flight behaviour. We investigated circadian patterns of flight in purple martins (Progne subis), a long-distance migratory songbird that journeys between nonbreeding areas in South America and breeding sites in eastern North America. We used direct-tracking (GPS loggers) of individual spring migrations to quantify the daily timing of flights, flight speed, flight distance, and altitude as well as whether these factors were associated with temperature. Birds were tagged with GPS loggers in Winnipeg, Canada, which collected location and altitude every two hours during spring migration. We used Movebank to align location data with average local temperature. We found that martins migrated mainly during daylight, but surprisingly, 15% of flights overland occurred during the night. The average speed for daytime and nighttime flights was similar. We found that neither temperature nor timing of flights influenced flight speed and distance travelled, but flights at higher altitudes were associated with longer flight distance and faster speeds. Our results suggest that a species classified as a diurnal migrant routinely makes night flights overland that are not associated with crossing known migratory barriers. Further studies could increase the sample size of birds and the number of usable GPS fixes, which would allow us to track birds as close to their breeding grounds in temperate areas as possible.
Open Access
Comparing the boldness and exploration of co-occurring invasive marine crabs (Hemigrapsus sanguineus and Carcinus maenas)
(2024-03) DeJaegher, Emily; Detwiler, Jillian (Biological Sciences); Davoren, Gail (Biological Sciences); Ramey-Balci, Patricia
Boldness (i.e., the propensity to take risks) and exploratory behaviours can influence an animal’s ability to acquire resources, thus affecting competitive success. The Asian shore crab, Hemigrapsus sanguineus, and European green crab, Carcinus maenas, co-occur as highly invasive species in coastal areas of the United States, and more recently, in Atlantic Canada. Both crabs use structurally complex rocky intertidal habitat and consume similar macroalgal and invertebrate prey, such that they likely compete for resources. Competitive interactions between co-invaders could influence the success of either species, affecting their impacts on the ecosystem. Yet, there is a gap in research comparing behaviours, such as boldness or exploration, between co-invaders such as these crabs. Here, the boldness of H. sanguineus and C. maenas are compared by investigating their tendencies to exit preferred rocky habitat with shelter to explore an open and brightly lit area. The crabs’ exploratory tendencies are also compared, by evaluating if the species spontaneously alternate (i.e., preferentially explore regions that they have least recently explored), an indicator of efficient exploration. The two species had similar latencies when exiting the sheltered habitat, but C. maenas spent more time in the open area overall. Both crabs also tended to spontaneously alternate, but H. sanguineus had a greater tendency to do so than C. maenas, revealing for the first time the existence of significant differences in spontaneous alternation behaviour between invasive species. If the strong exploration ability of H. sanguineus can improve the species’ ability to find resources, it may have a competitive advantage over C. maenas in regions where the crabs co-occur.
Open Access
Comparing the Rates of Adaptive Change in Species Across Biogeographic Gradients
(2023-04) Bourrier-Vince, Ava; Fraser, Kevin (Biological Sciences); Jeffries, Kenneth (Biological Sciences); Garroway, Colin
The process of adaptive evolution allows a species to persist with specific traits tailored to their environment. The rate at which a population adapts can change based on the varying environmental abiotic and biotic factors of their location. Environmental characteristics such as the amount of available energy, elevation, temperature and degree of human disturbance thus affect the rates of adaptive evolution across biogeographic gradients. In this study, I used data on adaptive rates for terrestrial species and aimed to determine if the rates of adaptive evolution showed patterns related to spatial biogeographic patterns and environmental factors such as elevation, evapotranspiration, precipitation and temperature. Additionally, I tested whether the rates of adaption changed based on these specific environmental factors and a human density. The results of my data analysis detected that the rates of adaptation showed good variation in relation to spatial scale patterning but no significant correlation patterns between the tested environmental variables and the rates of adaptive evolution were detected. This result did not support my hypothesis that the rates of adaptive change would vary through space with environmental gradients. Many potential factors may have caused this inconclusive result. Further research into this topic would be useful to understand and predict the adaptive evolution of species’ in varying environmental gradients. I propose that studies on this data should aim to utilize more of the available samples within this public dataset such as the aquatic species. Additionally, further research may benefit from narrowing the study size based on location or taxa for significant relationships to be accurately detected.
Open Access
Conservation of genetic diversity using life history predictors of adaptive potential
(2025-04) Goertz, Alyssa; Fraser, Kevin (Biological Sciences); Detwiler, Jillian (Biological Sciences); Garroway, Colin
Biodiversity loss is reducing population sizes globally, leading to a decline in genetic diversity. This is concerning, as genetic diversity is vital for species' survival and adaptation to future environmental change. Conservation frameworks, such as the International Union for Conservation of Nature (IUCN) Red List, assess extinction risk but overlook genetic diversity and adaptive potential. This is primarily because genetic data is not available for most species. My project directly addresses the lack of consideration of genetic diversity conservation framework by examining the relationship between adaptive potential and easy-to-measure life history traits. If easy-to-measure traits reflect adaptive potential, they can be used to guide conservation where direct estimates of adaptive potential are lacking. Adaptive potential reflects the additive genetic variance (VA) underlying fitness. VA reflects genetic diversity and capacity for adaptation and is used in calculating heritability. I hypothesized that life history traits (e.g., body mass, longevity, fecundity, and age of maturity) predict adaptive potential, measured by heritability. The data for heritability were derived from studies by Mittel et al. (2015), Holstad et al. (2024), and life history trait data from Myhrvold et al. (2016). Data inclusion consisted of heritability measured for morphological, life history, behavioural, and physiological traits, for terrestrial vertebrate species and from wild populations. The relationship between heritability and life history traits was measured using generalized linear mixed models. My results revealed significant relationships between heritability and life history traits. Larger body mass and longer lifespan were associated with low heritability, while larger litter/clutch sizes and earlier ages of maturity were associated with high adaptive potential. Morphological heritability estimates exhibited stronger correlations with life history traits compared to other heritability estimates, suggesting they may be a more reliable proxy for predicting adaptive potential. These findings highlight the potential of using life history traits to infer species’ genetic diversity and adaptive potential, offering a valuable tool to improve conservation prioritization.
Open Access
Determining the influence of migratory stopover timing and movement on plant seed dispersal by a short-distance migratory songbird, the American robin, Turdus migratorius
(2024-07-05) Sturch, Tamara; Fraser, Kevin
Animals disperse approximately 50% of seeds worldwide and could assist plants in shifting their distribution in the face of climate change. However, seed dispersal by animals is understudied particularly in temperate areas. American robins (Turdus migratorius) are migratory thrushes which have a frugivorous diet in the fall and may be important seed dispersers. Nineteen American robins were fitted with GPS tracking units at Assiniboine Park, Winnipeg, Manitoba during their fall migration in 2022. The GPS units provided live location data for the birds every 6 hours. This data was used to investigate the seed dispersal potential of American robins during their fall migration by examining the time spent and distance travelled while at stopover, as well as the use of urban versus rural habitats. Fecal samples collected at capture were used to identify the seeds of plant species these robins had consumed and therefore may disperse. I found that individual robins spent 15 to 33 days at fall migratory stopovers (an average of 26.64 days ± 4.95) and travelled extensively at stopovers (29-320 km; average 101.68 km ± 84.95) before continuing migration. Birds made use of both urban and rural habitats while at stopovers. I also found that fecal samples contained both native and non-native seed types, with Malus sp. making up most (62.71%) of the seeds in the samples. Overall, my results show that American robins have the potential to be important dispersers of native and non-native seeds across both rural and urban habitats, due to the large amount of time and distance travelled at fall migratory stopovers. Future studies should evaluate the viability and recruitment of seeds that have been dispersed by robins and examine the movements of American robins during fall stopovers originating from both urban and rural populations.
Open Access
Effects of Infection with Brainworm Parasite (Parelaphostrongylus tenuis) on the Climbing Behaviour in a Host Gastropod Species (Deroceras laeve)
(2025-04) Dalling, Ness; Van Nest, Byron (Biological Sciences); Markham, John (Biological Sciences); Detwiler, Jillian
Brainworm parasite (Parelaphostrongylus tenuis) is a nematode parasite which typically infects white-tailed deer (WTD – Odocoileus virginianus) as a definitive host, where it often causes no severe harm. It develops through larval stages in terrestrial gastropods and is eventually ingested by the WTD to complete its life cycle. Brainworm can infect other ungulates accidentally, most commonly moose (Alces alces), where it causes serious neurological disease and often death. Here, I investigate the potential role of parasite-modified behaviour in influencing the ingestion of the gastropod hosts by the ungulate host. I hypothesize that when infected with P. tenuis larvae, a gastropod host, the meadow slug (Deroceras laeve) will display altered vertical climbing behaviour, predicting an increase in vertical climbing activity. Vertical climbing behaviour was assessed amongst 15 infected and 45 uninfected slug hosts at four different times throughout the day, on two separate days. I found a significant effect of the interaction between the weight of slugs, their infection status, and the time of day on vertical climbing behaviour. This is novel evidence to support the parasite-modified behaviour hypothesis in P. tenuis and suggests that climbing behaviours may play a role in the transmission of brainworm. Further research would be beneficial, as replicates in this study were low, and the presence of coinfection with a secondary parasite in some samples may have provided a confounding effect.
Open Access
Effects of timing of burlap provision on piglet behaviour, welfare, and performance
(2024-07-05) Penner, Amber; Davoren, Gail (Biological Sciences); Yang, Chengbo (Animal Science); King, Meagan; Waterman, Jane
Many factors contribute to high stress at weaning in commercial pigs. Increased stress can lead to increased aggressive behaviours such as tail biting, displacements, and belly nosing. Enrichment, such as burlap, may provide an outlet for stress, providing a positive source of enrichment and allowing piglets to perform natural behaviours. The first objective of this study was to determine if providing burlap as enrichment can reduce the stress of weaning on piglets through reduced aggressive behaviours and fewer lesions. The second is to determine if there is a stage of life (pre- or post-weaning) when it would be most beneficial to introduce burlap to piglets. Piglet behaviour, lesion scores, mortality, and mass data were collected for three weeks pre-weaning and five weeks post-weaning. Four treatments were used to assess the timing of burlap provision: control (no burlap), post-weaning in the nursery room only (N), pre- and post-weaning in farrowing and nursery rooms (FN), and finally to the sow as well as to piglets pre- and post-weaning (SFN). Results of this experiment suggest that burlap enrichment positively impacts piglets through increased socialization and reduced aggressive behaviours. Results showed that burlap may have the greatest positive impact on piglets when provided in both farrowing and nursery rooms through increased piglet interaction with the burlap and fewer displacement behaviours. In summary, burlap is a promising low-cost enrichment option to improve the welfare of commercial piglets.
Open Access
Electrochemical Detection of Platinum-Based Chemoresistance and Correlation with MEK1 Activity in Living Cancer Cells
(2024-07-04) Daou, Roy; Whyhard, Steve (Biological Sciences); Doering, Jennifer (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Kuss, Sabine
Drug resistance is responsible for most chemotherapy failures, making it an urgent issue in modern oncology. In ovarian cancer, resistance to platinum-based chemotherapeutics, such as carboplatin, is common. However, its underlying mechanisms remain poorly understood. A mitogen-activated protein kinase kinase, MEK1, may play a role in the development of this resistance mechanism. This project aims to understand this mechanism by using western blots to measure MEK1 activity in patient-obtained living ovarian cancer cells, comparing between carboplatin-susceptible and carboplatin-resistant cells. Moreover, early detection of chemoresistance can improve treatment outcomes. However, current detection methods are inefficient and time-consuming. To address this, the project also proposes an unconventional approach to identifying chemoresistance. This involves the use of scanning electrochemical microscopy for the rapid and accurate quantification of glutathione, a prominent antioxidant that may serve as a biomarker for platinum-based resistance mechanisms, in both cell lines. The findings suggest a correlation between lower MEK1 activity and increased glutathione levels in the resistant cells. This research may contribute to the development of an efficient and reliable method for detecting chemoresistance, with the potential of significantly improving cancer treatment outcomes.
Open Access
Energy Density of Capelin (Mallotus villosus) and Sand lance (Ammodytes americanus and Ammodytes dubius) during the summer in Coastal Newfoundland
(2024-07-05) Vonderbank, Kate; Stacey, Joy (Biological Sciences); Treberg, Jason (Biological Sciences); Davoren, Gail
Spawning capelin (Mallotus villosus) and non-spawning Atlantic sand lance (Ammodytes americanus, A. dubius) adults and juveniles are important forage fish species in coastal Newfoundland during July and August when high abundances of top predators rely on them as critical energy sources. To determine whether these prey types differ in their energy content, and interannual changes in quality, samples of each prey type were collected during July-August 2020 and 2023. Bomb calorimetry was used to measure whole-body dry energy density (kJ/dry g) and calculate wet energy density (kJ/wet g) and water content. Although sand lance are at the peak of their annual lipid cycle and capelin are at their minimum during the summer, adult female sand lance had lower dry energy density (mean of both years ± SE, 20.7 ± 0.11 kJ/dry g) than all capelin sex and maturity categories, and wet energy densities (4.4 ± 0.09 kJ/g) did not differ from capelin. Within capelin, wet and dry energy densities did not differ among gravid females, spent females and males, which contrasts previous findings from before the capelin population in Newfoundland collapsed. Within sand lance, juvenile dry energy density (20.8 ± 0.14 kJ/g) did not differ from adult females. Juvenile sand lance wet energy density was the only prey type that varied interannually, where energy density in 2020 was higher (5.3 ± 0.15 kJ/g), but this is thought to be because the samples were more dried out before collection. Overall, our findings indicate that although sand lance adults and juveniles are similar in wet energy densities to capelin, their lower wet mass per fish would result in a higher number of sand lance needed to reach a fixed energy content per meal. Other factors, including abundance and distribution of each species, also impact foraging costs and must be paired with energy densities to estimate prey type quality.
Open Access
Evaluating different double-stranded RNA structures for their ability to control pest flea beetles
(2023-04) Verhaeghe, Lauren; Belmonte, Mark (Biological Sciences); Whyard, Steve
Canola is an economically important Canadian crop that suffers significant annual losses by damage from feeding flea beetles (Phyllotreta cruciferae and P. striolata). Increasing incidences of resistance and concerns about off-target effects with current insecticides demands new methods of control. Recently, environmentally safer approaches to pest control have been investigated using RNA interference (RNAi), a sequence-specific gene silencing mechanism triggered by exogenous double-stranded RNA (dsRNA), to selectively induce the mortality of targeted species. This study examined three different dsRNA structures for their ability to kill P. striolata flea beetles and thereby reduce feeding damage on canola leaves. Long linear dsRNAs (212-214 bp), short hairpin RNAs (hpRNAs) (21-24 bp), and short paperclip RNAs (pcRNAs) (21-24 bp) targeting mRNAs of three essential genes, Ras opposite (Rop), Sec23, and Snf7 in P. striolata were investigated. P. striolata adults were fed dsRNA-treated canola leaf disks, and impacts on insect survivorship and leaf material consumption were recorded over an eight-day period. pcRNAs targeting Sec23 and Snf7, and long dsRNAs targeting Sec23 and Rop effectively killed flea beetles, resulting in the reduced consumption of treated canola leaf tissues. Consumption of both the Sec23-specific long dsRNA and pcRNAs caused similar levels of flea beetle mortality (68% and 76%, respectively), whereas only the Rop-specific long dsRNA and the Snf7 pcRNA were effective at killing the beetles (76% and 84%, respectively). hpRNAs proved the least effective across all gene targets, killing at most, between 40-52% of flea beetles, depending on the gene target, and in general, these values were not significantly different relative to the negative controls. While this study examined dsRNAs specific for only three target genes, it provides evidence that RNAi-based pesticides have the potential to control these economically important pests and that short pcRNAs can be as effective as conventional long linear dsRNAs.
Open Access
Evaluating Nitrogen Utilization Strategies in Chlamydomonas reinhardtii
(2025-04) Tibule, Miku; Doering, Jennifer (Biological Sciences); Markham, John (Biological Sciences); Lee, Jae-Hyeok
Nitrogen (N) is a common, yet essential macronutrient required for nucleic acid and amino acid synthesis for cell growth and biomass of photosynthetic eukaryotes which includes algae and plants. Understanding how organisms strategically use N for growth will allow development of economical use of N fertilizer being invested into croplands, which in return mitigates anthropogenic contribution to environmental pollution. This honours thesis explores N-use strategies by examining the N-sensing mechanisms within Chlamydomonas reinhardtii to investigate its necessity for optimal growth under N-limited and N-repleted conditions through comparative growth within individual N source provision of NH4Cl, KNO3, and urea. Using photobioreactor and nitrogen quantification experiments, I obtained biomass productivity data and residual N within the cultures, which allowed for an understanding of algal growth under various N-source concentration conditions. Through a comprehensive data analysis of growth biomass OD and residual N concentrations, my study uncovered that there is a regulatory mechanism of C. reinhardtii that allows for a reduction in N consumption rate under extreme N limitation stress, which in turn allows the algae to shift its metabolic priorities to internal N-use. These insights contribute to the existing literature by highlighting the significance of the N-sensing mechanism within C. reinhardtii, for N-use strategies, discovering a temporal switch in metabolic function, and offering potential further investigations into how the algae prioritize cellular N contents for growth and cellular division. Ultimately, this study provides a deeper understanding of N assimilation and cellular use, paving the way for future research and developments in the field.
Open Access
Exploring the role of ammonia transporters (AMTs) in the branchial tissue of the horseshoe crab, Limulus polyphemus
(2023-05) Whiting, Holly; Campbell, Kevin (Biological Sciences); Treberg, Jason (Biological Sciences); Weihrauch, Dirk
All organisms must manage ammonia as it is highly toxic and a product of many essential biochemical processes. One group of proteins that facilitates the movement of ammonia across cell membranes is the Ammonia Transport Protein family which are generally sorted into three groups—ammonia transporters (AMTs), Rhesus glycoproteins (Rh proteins), and methylamine permeases (MEPs)—expressed in plants, animals, and fungi, respectively. Recently, transcripts of AMTs have also been found in invertebrates, where experimental evidence suggest that they play a role in both ammonia excretion and ammonia sensing. The American horseshoe crab, Limulus polyphemus, expresses at least two AMT and two Rh proteins within the epithelia of their book gills which is the primary surface for ammonia excretion. Each gill lamellae have a ventral ammonia permeable side and a dorsal ammonia impermeable side. mRNA transcripts for both proteins LpAMT-1 and LpAMT-3 were found on the dorsal and ventral surfaces, bringing into question their function in direct ammonia excretion. In oocyte expression trials both AMTs failed to mediate the transport of radiolabeled methylamine, while transport was detected for both a coral and a human Rh protein. Direct evidence of ammonia transport by invertebrate AMTs has not been previously found and further research should be conducted into the function of these proteins in invertebrates.
Open Access
Factors Influencing Testes Size in the Cape Ground Squirrel (Xerus inauris)
(2025) Aston, Gemma; Garroway, Colin (Biological Sciences); Davoren, Gail (Biological Sciences); Waterman, Jane
When males compete through sperm competition, selection favours an increased investment in sperm production to streghten the male’s probability of siring offspring when females multiply mate. This increased investment in sperm quantity results in large testes relative to the species’ size. Thus, testes size can be used as a measure of reproductive fitness in males experiencing intense sperm competition. Despite this relationship, studies investigating testes size have focused on interspecific variation, leaving the factors driving intraspecific variation in testes size an underexplored area of study. I investigated the influence of age, body condition, rainfall, parasite abundance and testosterone concentration on the testes size of Cape ground squirrels, a sciurid known to be under intense sperm competition. Data was collected from males trapped on SA Lombard nature reserve in South Africa between the years 2013-2024 and the influence of each factor on testes mass was assessed using linear regression. Testes mass was found to increase with both age and body condition and body condition also increased with age. While the energetic demands of spermatogenesis appear to shape the relationship between body condition and testes size, declining oxidative stress with age and a terminal investment strategy may drive enhanced testes investment in older individuals. Parasite abundance negatively affected testes size suggesting parasites remove resources from their host that would otherwise be allocated to reproduction. Rainfall and testosterone concentration did not affect testes size. The lack of relationships between rainfall and testes size may have occurred due to the limitations of this study, while testosterone's lack of impact on testes size may be caused by the low testosterone demands of a year-round breeding strategy. These findings aid in our understanding of the factors influencing reproductive success in males experiencing sperm competition and the selective forces shaping intraspecific testes size variation.
Open Access
Herbivory resistance to generalist feeder Trichoplusia ni of faba bean (Vicia faba) exposed to salinity stress
(2025-03) Lavallée-Shrupka, Caleb; John Markham (Biological Sciences); Kevin Fraser (Biological Sciences); Renault, Sylvie; Avila-Sakar, German
Plants are often exposed to multiple stress factors simultaneously. Exposure to one stress can exacerbate or mitigate the response to a subsequent stress. While salinity and herbivory can impair growth and physiological function individually, their combined effects remain poorly understood. To investigate this interaction and determine if salt tolerance influences resistance to herbivory, Vicia faba (cv. Broad Windsor) plants were grown under salinity (0, 50, 75, 100 mM NaCl) and exposed to cabbage looper (Trichoplusia ni) herbivory. Gas exchange parameters (photosynthesis, stomatal conductance, transpiration) were not significantly affected by salinity after 11 days of treatment. After 20 days, salinity did not affect plant height, stem biomass or water content of most tissues but significantly reduced root and lateral leaf biomass. Total phenolic compounds and total soluble proteins in the leaves were also unchanged. Elemental analysis revealed that salinity significantly increased Na and Cl concentrations in all three tissue types (leaves, stems, and roots), with the highest accumulation in roots. Salinity significantly increased the concentrations of macronutrients (N, P, K, Ca, and Mg) and micronutrients (Fe, Mn, Cu, Zn, and Mo) in the leaves, suggesting efficient nutrient retention in photosynthetically active tissues. Constitutive resistance to herbivory was not significantly affected by salinity. However, induced resistance was significantly impaired in salt-treated plants. Together, these findings indicate that V. faba exhibits moderate tolerance to salinity, maintaining gas exchange and nutrient homeostasis under salt stress while minimizing growth impairments. The compromised induced resistance highlights the vulnerability of inducible defenses and suggests that salinity may force a tradeoff between preserving physiological function and sustaining inducible defences against herbivory. These results emphasize the importance of considering stress interactions when evaluating plant defence.

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