Honors Theses (Biology)
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Item Open Access EFFECTS OF FLOW VELOCITY AND SETTLEMENT LOCATION ON GROWTH RATES OF EARLY JUVENILES OF THE PEDUNCULATE BARNACLE, POLLICIPES POLYMERUS, SOWERBY 1833(University of Oregon, 2021-11-10) Everson, Hannah N.The intertidal lepadomorph barnacle, Pollicipes polymerus, is known for its propensity to aggregate in rosette-shaped or irregular clusters. The gregarious lifestyle is ensured by the species’ settlement preference. Cyprids of P. polymerus settle almost exclusively on the peduncle of adult conspecifics, while settlement in cracks and crevices and on acorn barnacles is rare. For gregarious settlement behavior to evolve and persist, individuals should gain some benefit that would otherwise not be achieved with a solitary lifestyle - such as defense against predators (Riipi et al. 2001) or to facilitate cross-fertilization (Wu 1981) Due to increasing demand for P. polymerus in culinary markets, the gregarious settlement behavior makes them particularly susceptible to overharvesting. This study examines whether gregarious settlement results in higher growth rates of juveniles compared to growth of solitary individuals. I asked if and how P. polymerus gains in overall fitness from gregarious settlement. I address two questions: 1) Is the growth rate of early juveniles dependent on the velocity of water in which they feed? and 2) Does settlement on conspecifics benefit early juveniles by increasing growth rate? Two treatment groups (solitary and gregarious) were studied, with individuals ranging in size from 1mm - 3mm rostro-carinal length. An apparatus, utilizing a rotating disc, was constructed to create a range of experimental velocities. For two trials carried out in a marina environment (trial 1 and 2), growth rates ranged from 0.1mm - 1.2mm/wk at any given velocity. For two trials in a tank environment (trials 3 and 4) individual growth never exceeded 0.6mm/wk. Overall results indicate that neither current velocity nor settlement location had consistent effects on early juvenile growth rates. In the tank environment, where food concentrations were lower, velocity had a significant negative effect on the growth rate of gregarious but not solitary juveniles. In only 1 of 4 trials, settlement on a conspecific had a significant positive effect on average juvenile growth. The absence of consistent trends within and across trials together with few significant results indicate that velocity and settlement location for early juveniles may not be primary factors in gregarious settlement of this barnacle. Other factors or these factors at different life stages may account for settlement behavior. My findings also suggest that aquaculture of these barnacles does not require specific flow speeds or adult substrata to cultivate newly settled barnacles.Item Open Access The Distribution of Two Marine Cladocerans During Upwelling and Relaxation Events Off the Oregon Coast(2010-11) Thomas, KateOffshore surface currents that appear during upwelling events have the potential to carry nearshore coastal zooplankton offshore. I tested the hypothesis that the marine cladocerans Podon leuckarti and Evadne nordmanni are pushed offshore during summer upwelling. Additionally, stratified horizontal currents during upwelling, with surface regions moving offshore and deeper layers moving onshore, could differentially distribute reproductive stages or sizes that have different vertical distributions. I tested the hypothesis that reproductive stages and sizes of cladocerans would be distributed differentially from one another during upwelling and relaxation events. The fecundity of marine cladocerans off Oregon was also investigated. A vertically stratified transect of 7 stations located from 0.5 to 28 km offshore near Coos Bay, Oregon was sampled for zooplankton on four days in the summer of 2007. Two of the sample dates (27 June and 14 August) were characterized by upwelling conditions, and two (3 and 18 July) were characterized by relaxation or weak downwelling conditions. Preserved cladocerans were counted, measured, and assigned a reproductive stage. In females the number of embryos was counted. Neither cladoceran species showed evidence of offshore surface transport during upwelling, and both showed densest concentrations nearshore, although a deeper offshore concentration of E. nordmanni may have been affected by deep onshore upwelling currents. Parthenogenic P. leuckarti with early embryos were distributed similarly to those with advanced embryos, and males tended to stay near the bottom or surface nearshore. All stages of E. nordmanni stayed primarily near the bottom or surface nearshore. Smaller cladocerans and parthenogenic females with early embryos were found in larger proportions closer to shore, while larger cladocerans and parthenogenic females with advanced embryos were found farther offshore. Cladoceran fecundity in Oregon was high, with a mean and 95% confidence interval of 5.42±0.37 embryos per parthenogenic P. leuckarti and 10.21±0.247 embryos per parthenogenic E. nordmanni. Complex interactions between physical oceanography and cladoceran behavior may account for observed cladoceran distributions off the Oregon coast.Item Open Access The subtidal Bryozoan fauna off Cape Arago, Oregon(2013-05) Cottrell, DylanThe subtidal marine biodiversity off the Oregon coast is poorly studied and not well understood. The few subtidal studies in Oregon have focused on vertebrates with little regard to invertebrate assemblages. Oregon’s subtidal Bryozoa play key roles in these assemblages by providing habitat, food, and, potentially, pollution sequestration. Using dredge samples collected over two years, we assembled a comprehensive list of Bryozoa found between 30-60 m depth off Cape Arago, Oregon. A total of 41 species were collected, including one new species in the genus Fenestruloides. Although 25 families were represented in our samples, 17 (68%) families were only represented by one species and only two families (8%) were represented by more than three species. This data provides the first comprehensive survey of Oregon’s subtidal bryozoan biodiversity and is an important first step in understanding the region’s biodiversity.Item Open Access The role of uxs1 in chondrocyte organization, morphogenesis, and signaling pathways during skeletogenesis(2007-07-13T02:14:01Z) Smith, GabrielThe role proteoglycans play in molecular-genetic mechanisms of skeletogenesis is not completely understood. UDP-glucuronic acid decarboxylase 1 (Uxs1) converts UDP-glucuronic acid to UDP-xylose which is used by xylosyltransferase 1 to initiate assembly of a common tetrasaccharide linker critical to the biosynthesis of chondroitin sulfate, dermatan sulfate, and heparan sulfate proteoglycans, all of which are found in abundance within the extracellular matrix of cartilage. In this paper, we present two alleles, hi3357 and mow, that have mutations in uxs1. Zebrafish embryos with uxs1 mutations presented an absence of Alcian staining from cells in the pharyngeal cartilages. Fluorescent confocal microscopy revealed improper chondrocyte organization and morphogenesis in cartilage elements of the neurocranium and pharyngeal skeleton. Additionally, we observed reductions in Alizarin red staining at endochondral and intramembranous ossification centers indicating improper bone development. Whole-mount in situ hybridization experiments revealed uxs1 expression to be ubiquitous in developing embryos until 2 dpf and thereafter localized to the pharyngeal skeleton, suggesting a critical role for uxs1 expression during skeletogenesis. These results suggest that chondrocyte organization and morphogenesis, endochondral ossification, and intramembranous ossification are all dependent upon uxs1 function. In mutants homozygous for uxs1hi3357 and uxs1mow, wheat germ agglutinin staining revealed a reduction in proteoglycans in the extracellular matrix. Moreover, antibodies against heparan sulfate revealed deletion of heparan sulfate proteoglycans in the pharyngeal cartilage elements. The deletion of heparan sulfate proteoglycans in uxs1 mutants suggests that Wnt, Fibroblast growth factor, or Hedgehog signaling cascades may be disrupted as previously shown to occur in the fruit fly Drosophila. These findings reveal an absence of UDP-xylose dependent proteoglycans from the extracellular matrix due to mutations in uxs1. Experiments also showed a deletion of type II collagen from the extracellular matrix of chondrocytes, suggesting a role for Uxs1 or proteoglycans in the secretory or localizing mechanisms. Additionally, expression of col10a1 was absent from endochondral ossification centers and reduced at intramembranous sites, suggesting that uxs1 is necessary for proper reciprocal signaling pathways between perichondrial cells and chondrocytes critical for bone formation. Thus, we conclude that UDP-xylose dependent proteoglycans are absent in uxs1 mutants which is altering the composition of the extracellular matrix and disrupting reciprocal signaling between cells. This study provides new insight into the role proteoglycans play in skeletogenesis and the evolutionarily conserved role of uxs1 across life on earth.Item Open Access Traumatic Brain Injury & Acidosis(Robert D. Clark Honors College, 2006-11) Force, LisaTraumatic Brain Injury (TBI) is a significant cause of death in the United States, and is the leading cause of disability in children and young adults. Acidosis is one of the most frequent secondary brain injuries and is associated with longer Intensive Care and hospital length of stay. This thesis investigated the interaction between a primary mechanical injury and a secondary acidosis injury using an innovative experimental TBI model consisting of organotypic cultured rat hippocampus. Propidium Iodide imaging was used to assess percent cell death, with results tentatively suggesting an additive rather than a sensitizing interaction between TBI and acidosis. However, analysis of the dentate gyrus indicated that there may be both regional specificity of vulnerability and regional interaction between TBI and acidosis. Amiloride and psalmotoxin were investigated as possible neuroprotective agents, with psalmotoxin but not amiloride producing promising results for reducing cell death by acidosis. Immunocytochemistry and Western blot techniques were utilized to confirm presence of ASIC channels in the organotypic rat hippocampus cultures, with results demonstrating presence of ASIC1a and ASIC2a in control cultures, and a decrease in ASIC1a concentration following TBI. Dendritic spine imaging was used to explore synaptic structural changes resulting from TBI and acidosis. The data obtained from these imaging studies suggests that following an injury dendritic spine density decreases while varicosity density increases, implying that the mechanisms of cell death for TBI and acidosis are likely not spine mediated. Taken together, these results further our understanding of the interactions between TBI and acidosis and are important for considering the clinical treatment of TBI. Future research should investigate further the regional specificity of injury, psalmotoxin as a possible neuroprotective agent, and the role of dendritic spine remodeling following TBI and/or acidosis.Item Open Access A Novel Method for Investigation of Postembryonic Neural Reorganization in the Tobacco Hornworm, Manduca sexta(2006-06) Patterson, Kelly McNamaraThe tobacco hornworm, Manduca sexta, provides a model system for examining the reorganization of neural circuits during metamorphosis. The larval tobacco hornworm exhibits a pre-ecdysis behavior which serves to loosen the old cuticle at the culmination of each molt before the old cuticle is shed at ecdysis. These insects undergo behavioral changes during metamorphosis involving reorganization of the neural circuits that produce the pre-ecdysis behavior, decreasing the strength of the pre-ecdysis behavior during the molt from the larval to pupal life stages. The methodology used in the past for experiments investigating this important model system was extremely complex, relying on precise staging of the insects as well as lengthy dissections and methods for nervous system preparation. This study examined the effectiveness of exposure of isolated abdominal nerve cords to synthetic Pre-Ecdysis Triggering Hormone in initiating the motor pattern that produces the pre-ecdysis behavior.Item Open Access IDENTIFYING CORE CONSCIOUSNESS IN ANIMALS(2006-06) Stevens, Nicholas StamerProving whether animals are either capable or incapable of feeling (i.e. core consciousness) is a problem that is difficult to address because mental states cannot be directly observed. Many animals exhibit behavior similar to our own, and consequently it is easy to attribute to them corresponding mental states. The assumptions underlying these attributions, however, are subject to error; there is no absolute rule by which mental states correlate with behavior, and we have no means of verification through verbal reports. A different approach must therefore be taken. Revealing the presence in animals of the neural structures responsible for producing core consciousness in humans would essentially prove that such animals too are capable of feeling. Unfortunately, at present little is known about the biology responsible for producing core consciousness in humans. At best general regions containing the necessary structures are slowly being located. Based upon similarity of structures, evidence suggests that at least mammals are core conscious and perhaps all other vertebrates as well.Item Open Access Chromatophore Organization and Development in the Cuttlefish Sepia officinalis(2006-06) Gosling, Allyson A.The cuttlefish species Sepia officinalis possesses a unique and complex behavior referred to in this paper as body patterning behavior. This behavior allows these animals to modulate their external dermal pattern in response to environmental changes. The resulting patterns are used for both camouflage and communication purposes. This behavior is achieved by the mass coordination of millions of tiny pigment-containing organs, termed chromatophores, which are structures located in the skin. The control of these organs is unique in that they are directly innervated by motor neurons which project from the animal’s central nervous system. Using a regenerative model, the organization and post-embryonic maturation of individual chromatophores was examined in this study. Over a 30 day period the regeneration of a small excised section of tissue, taken from the anterior region of the fin, was digitally recorded. The analyses of the resulting images, which include data from the regenerating region as well as the undamaged surround, support the following conclusions: 1) Established chromatophores do not change positions. 2) The spacing between chromatophores in the undamaged control region did not significantly change throughout the 30 day experimental period. 3) As the regeneration progressed, the spacing of chromatophores in the regenerating region became increasing similar to that of chromatophores in the control region, significantly so in the last stages of regeneration.Item Open Access Analysis of Current Migraine Treatments: Intersections of Pharmacologic and Non-pharmacologic, Acute and Preventative Methods of Care(University of Oregon, 2006-04) Bryn, TanaMigraine affects 23.6 million people in the United States alone. Treatment options can be sub-typed as abortive and preventative, as well as pharmacologic and nonpharmacologic. Due to the debilitating nature of migraine, patients and physicians often rely heavily on abortive treatments. A review of the literature, along with a series of personal interviews suggests that preventative measures, used alone or with abortive treatment, increase the patient's control over the migraines . Additionally, nonpharmacologic interventions such as relaxation training, biofeedback, and dietary modification may offer migraine relief while improving the patient's quality of life. The integration of several treatment avenues represents a growing change in western culture toward prospective medicine, and will aid in maximizing treatment efficacy for migraine.Item Open Access Peripheral Visuospatial Attention: An fMRI Study(2005-09-30T16:05:57Z) Dugan, James PatrickWe used functional magnetic resonance imaging (fMRI) to demonstrate the effects of directing sustained attention to near and far peripheral locations ( <12 and >20 degree eccentricities, respectively) on blood oxygen level dependent (BOLD) response. Using a Hillyard paradigm we presented 8 Hz flashing light stimuli at 8, 12, 22, and 33 degree eccentricities in the upper left and right quadrants of the visual field. The 8 and 12 degree locations were presented randomly using a projection system. In a separate session the 22 and 33 degree locations were presented with the same timing, but using fiber optics to direct stimuli near the eye. During the presentation of the stimuli the subjects alternated their attention between a single left and right location while maintaining central gaze. BOLD response to the stimuli at the attended and unattended locations was evaluated. All subjects showed a response in visual areas V1, V2/VP, and MT+, in both attended and unattended conditions. A number of parietal locations also responded well to the visual stimuli. At all of these locations subjects showed a significant modulation of activation with sustained attention. The magnitude of the modulation was similar for the near and far periphery, but varied by visual region; MT+ showed the greatest modulation.Item Open Access A TALE OF TWO TRNAS: TRANSLATING THE SAME CODON DOES NOT IMPLY REDUNDANCY(University of Oregon, 2004-08) Murrill, ElizabethA transfer RNA (tRNA) can form codon-anticodon interactions either by standard Watson-Crick base pairing or by forming a wobble base pair between the first position of the anticodon and the third position of the codon. This means that within the same isoaccepting tRNA group, one codon may be read by two individual tRNAs each interacting in one of the two ways. This leads to the question: Why would such redundancy occur? Through the inactivation of the gene that encodes for the threonine isoaccepting tRNA with the anticodon CGU (tRNA-CGU), it was found that the tRNA-CGU, which interacts with its cognate codon through Watson-Crick base pairing, is not essential for life in Escherichia coli. Yet, the tRNA-CGU is present in a majority of bacteria, leading one to expect that it must have a meaningful role in the process of translation that has caused it to either be a retained or a gained molecule for such bacteria. Evidence showed that the tRNA-CGU has specific properties that allow the tRNA to contribute more at increased temperatures to the translation of its codon, while the properties of the tRNAs that “wobble” to read the codon contribute less at increased temperatures. One possible, contributing property of the tRNA-CGU is the more stable codon-anticodon interaction formed by the standard Watson-Crick base pair. Since bacteria have to live in different environments and at various temperatures, such chemical stability may be key to the survival of these bacteria and why so many bacterial genomes have a tRNA that is seemingly redundant.