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- Creator:
- Melendez, Christopher
- Description:
- Environmental temperature is a crucial environmental factor that influences many physiological functions in fishes. Rainbow trout (Oncorhynchus mykiss) are a native anadromous species that inhabit a variety of freshwater rivers and lakes and are widely distributed throughout the western portion of the United States. Resident rainbow trout populations occupy interior freshwater environments for the entirety of life. Interior bodies of water are most susceptible to changes in environmental temperatures. Therefore, resident rainbow trout are likely to be impacted by variable and rising temperatures, particularly during embryonic development. Understanding temperature effects during development is likely to provide insight into the overall thermal biology of a species and its persistence in a changing climate. To assess the effect of temperature on development of rainbow trout, we examined phenotypes of hatchery embryos reared in various incubation temperatures (5°C, 10°C, 15°C and 17.5°C). To identify the presence of embryonic developmental plasticity within developmental time points, embryos incubated in 5°C were exposed to either 10°C, 15°C or 17.5°C during gastrulation, organogenesis, system integration or growth windows and a 3-dimensional critical window model was applied. An increase in constant incubation temperature increased oxygen consumption rate (V̇O2), and decreased hatchling survival, mass, yolk size, body length and time to 50% hatch. Thermally shifting embryos into increased temperature during distinct windows of development also reduced survival at hatch, and this was most evident following exposure during organogenesis, which may signify the presence of a critical window for this trait. Likewise, thermally shifting embryos into increased temperature resulted in smaller hatchlings. Although there was an initial increase in V̇ O2 in response to temperature, experiencing thermal shifts during development had no persistent effect on V̇ O2 when measured at hatch at 5°C compared to 5°C constant embryos. Collectively, these results suggest that survival and morphological traits of rainbow trout embryos are most sensitive to increased temperature during organogenesis and system integration, but increased temperature does not appear to have a long-term effect on energy use. Environmental temperature plays a fundamental role in developing aquatic vertebrates. Thus, critical window studies such this performed across species will eventually allow for the identification of commonalities in plasticity between different species in response to variables such as temperature.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Akimi, Desiree
- Description:
- To better understand the neural mechanisms for human physiology, an invertebrate’s control on its cardiovascular system should be investigated. The leech’s heartbeat is controlled by segmental ganglia and has a phase delay in its peristaltic heartbeat pattern. This thesis hypothesized a neuromodulator, dopamine, can disrupt the phase delay by affecting inhibitory post synaptic potentials (IPSP). We dissected the leech, isolated a chain of ganglia onto a petri dish, and placed it onto a rig to record synaptic potentials. We recorded and analyzed the ganglia when submersed in saline, dopamine, and saline rinse. We looked at HN4/HN7 phase delay on HE8/HE12 of segmental ganglia. Our results showed dopamine had no effect on any HN/HE pair, except HN 7 and HE 8, HN 4 and HE 8, and HN 7 and HE 12. For HN 7 and HE 8, there was a significant difference in spike-triggered average, area under the IPSP curve, and resting potential between control and rinse. Moreover, there was a significant difference in area under the IPSP curve between control and saline rinse. HN4/HE8 and HN7/HE12 had a significant difference in IPSP size before dopamine and during saline rinse. Overall, the weak synapse between HN 7 and HE 8 might not be due to dopamine because the dopamine effect was not seen in the stronger synapses before and during dopamine (HN4/HE8 and HN7/HE12). We cannot fully conclude dopamine has a significant effect on the synaptic strength between HNs and HEs without more research done.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Cruz, Michelle S.
- Description:
- Chronic non-healing wounds are a growing clinical burden, impacting 6.5 million patients in the United States alone (Sen et al., 2009). A variety of cells take part in the complex process of wound healing, which includes stages such as inflammation, re-epithelialization and maturation. T cells help mediate this process by secreting cytokines, growth factors and activating other cells to infiltrate the region. Two major subtypes of T cells reside in the skin: those expressing an αβ T cell receptor (TCR) chain and those expressing a γδ TCR chain on their cell surface. αβ and γδ T cell receptors recognize unique ligands and thus cells that express these receptors are likely to have different roles in immunity and homeostasis, yet those specific functions are not well known especially in humans. The goal of this study is to develop a method of cellular isolation and characterization for future studies to analyze T cell populations present in the skin. This will allow better understanding of the common and distinct roles played by αβ and γδ T cells in skin immunity and tissue repair. Currently there is intense research in elucidating the specific function of αβ and γδ T cells in human skin (Cruz, Diamond, Russell, & Jameson, 2018). Developing methods of isolation and characterization will allow new avenues for research and will further elucidate the specific roles of αβ and γδ T cells in human skin surveillance and wound repair.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Sheldon, Sarah
- Description:
- San Clemente Loggerhead Shrikes (Lanius ludovicianus mearnsi) have been bred in captivity since 1991 following their listing as an endangered subspecies in 1977. For 25 years, breeding of this captive population has been managed to avoid inbreeding using protocols based on behavior, demographics, genetics, and ecology. Yet despite the broad application of these comprehensive protocols, inbreeding within this subspecies has never been quantified outside this framework. To evaluate the effects of the population bottleneck and captive management techniques on the population, analysis of overall levels of inbreeding, founder representation, and the division of inbreeding into partial coefficients attributable to founder lines was conducted using the pedigree of the population. Inbreeding depression was then measured by comparing inbreeding levels to measures of survival (egg fate and overwintering survival) and to measures of reproductive success (the numbers of offspring produced). Gene diversity was 93%, and the largest average contribution from a single founder to the inbreeding level was 18% in 2015 (founder SB 235). Moderate inbreeding depression (2B=5.38 and 3.06) was identified in juvenile survival and egg fate, but later life history traits that affect fecundity were not affected by inbreeding. This study supports the continuation of releases and parent-rearing as part of the population’s management. It also provides specific recommendations for breeding that avoid descendants of SB 235, while seeking out descendants of SB 230, who has made negligible contribution to the measured levels of inbreeding. These findings should help this longstanding project maintain a viable and sustainable population of Loggerhead Shrikes on San Clemente Island.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Maziarz, Jacob
- Description:
- Wetland ecosystems are among the most biologically productive ecosystems on Earth, yet they are being lost and degraded at an alarming rate. A growing trend to offset this loss is to construct artificial wetlands to replace the destroyed natural wetlands, yet our understanding of how to construct artificial wetlands, and make them functional, is vastly underdeveloped. This study sampled stocks of nitrogen (N) and carbon (C) in an artificial wetland on the California State University San Marcos (CSUSM) campus and compared them to stocks from local wetlands. Samples were taken from both plant biomass and soil to assess the stocks of C and N throughout the wetlands. Plant cover was also measured at each site via a line-intercept method. We hypothesized that C and N stocks would be significantly lower in the artificial wetland than the natural wetlands due to the young age of the artificial wetland while plant cover and biodiversity (species richness) would be similar across all wetlands. The study revealed a large degree of variation among the three wetlands and that soil and vegetation C and N stocks of the CSUSM wetland appeared to plateau after 11 years. However, the CSUSM wetland C and N stocks and plant cover were higher than, or comparable to, the two local wetlands. Plant species composition was unique for each wetland, with only five species shared among two or more sites. The local wetlands showed a great deal of variation between themselves. Batiquitos showed very low soil and plant C and N stocks, while the site at Cannon Road had much higher stocks, especially in its plant biomass. While this study demonstrated that CSUSM was functioning at least on par with local wetlands, it also raises a number of implications regarding the functional status of wetlands in California. The two local wetlands have a history of anthropogenic disturbance and alteration. California wetlands, both those sampled in this study and those from other studies, showed high variability amongst themselves. In some comparisons, artificial wetlands seem to sequester nutrients even better than a natural wetland, but in other comparisons, failed to match nutrient stocks. This high variability can originate from differences in wetland hydrology, plant abundance and species composition, differences in surrounding terrain, and anthropogenic alterations. California wetlands had much lower nutrient stocks compared to wetlands in other parts of the U.S., which is presumably caused by regional differences in hydrology.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Naumann, Kenneth
- Description:
- DNA storage in the nuclei of cells is important for both compaction and the regulation of gene expression. DNA packaging is altered by chemical modifications to the tails of the histone octamer around which the DNA is wrapped, specifically histones H3 and H4. Collectively these various histone marks make up a pattern which has been termed the “histone code”. The multiple interactions between histone modifications and gene expression is not well known in diseased cells. The objective of this study is to better understand the histone modification differences between normal and cancerous cells, and the potential for manipulating this code, due to the reversible state of modifications. By comparing malignant and non-malignant cells before and after treatment with inhibitors targeting histone modification pathways, we are able to observe changes in histone post-translational modification (PTM) levels. These changes indicate it is possible to change the histone pathways to effect gene expression.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Zinda, Joel
- Description:
- The ability to understand the neurophysiological mechanisms that influence any behavior to occur in an organism is the ultimate goal of neurobiology. Neuroscience researchers want to create a neuronal model of the human brain to know how we can produce physiological functions such as walking, throwing, and jumping. Vertebrates have neural structures that are too complex to map neuronal models, so we must start at the invertebrate level. Leeches are simple invertebrates who possess the necessary characteristics to study neuronal regulation. Easily identifiable neurons in the leech allow researchers to record action potential burst activity and evaluate the mechanisms behind physiological functions. Central pattern generators (CPGs) are the “brain” of the leech and are known to control the rhythmic action potential bursting activity that cause certain behaviors to occur. The focus of this investigation was the CPGs that regulate the heart contractions in leeches. Inhibitory heart interneurons 4 (HN(4)) and 7 (HN(7)) within this system of CPGs influence burst activity on heart motor neurons. These heart motor neurons regulate contractions of the heart vessels. Dopamine is a known neuromodulator that either excite or inhibit the bursting of action potentials to produce a variety of behaviors in organisms. The overall goal in this experiment was to assess the effects of dopamine on HN(4) and HN(7) to further establish a model for neuronal regulation in leeches. Response variables of timing and strength of the action potential bursts were calculated before and after different concentrations of dopamine treatment were applied on HN(4) and HN(7). The treatment of dopamine significantly increased the number of spikes in an action potential burst in HN(4) and HN(7), and altered the rhythmic pattern timing of bursting in HN(7). Future experiments will enable researchers to distinguish if these specific inhibitory interneurons regulate the heart contraction by themselves or if the heart motor neurons play the dominate role with a concentration of 1x10-6M dopamine.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Ainslie, Nicholas
- Description:
- Paralemanea is a freshwater red alga genus in the family Lemaneaceae, of which Paralemanea catenata is a member. The cues by which it regulates its triphasic sexual life history are not well known, either in terms of environmental stimuli or mechanisms. The P. catenata genome has not been sequenced, and RNA sequencing was used to perform the initial investigation. Comparing morphological and ecological measurements (total length, internodal length, spermatangial ring height, number of nodes, and node width; temperature, pH, total dissolved solids, photoperiod, salinity, and conductivity) taken over its growing season, in concert with the RNA sequencing data, suggests photoperiod is the environmental stimulus by which P. catenata regulates its life cycle. Involved in this regulation are phototropins and cryptochromes, which are light-sensitive proteins that allow the alga to continuously monitor light levels and respond to this stimulus.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Fleming, Timothy
- Description:
- In 2011 Mars et. al. proposed a novel approach to identifying three different subspecies within European waters of Ulva flexuosa, (subsp. pilifera, paradoxa, and flexuosa). Their use of morphological and molecular techniques to separate each subspecies was used as a guide for this study to determine if these techniques would work for U. flexuosa within California waters. Eleven freshwater, five brackish water, and two saltwater samples of Ulva were collected and were assessed using classic morphological methods and molecular techniques. The molecular methods examined the DNA region ITS1-5.8S-ITS2 (ITS) and the chloroplast RUBISCO LSU (rbcL) genes. The morphological methods followed Mares et al. guide to differentiate between subspecies. All the samples collected, except one, were determined, morphologically to be the within the species criteria for Ulva flexuosa, however, this guide was not able to separate any specimen down to the subspecies level. The molecular analysis suggested that all of the freshwater samples were indeed U. flexuosa and only half of those could be aligned with the subspecies paradoxa. The other freshwater samples did not align themselves with any subspecies and none were aligned with the subspecies pilifera. The samples that were collected in the brackish or saltwater were not shown to be U. flexuosa by molecular analysis but instead two different species either Ulva torta or Ulva linza. The finding of this study suggest that Mares et al. (2011) is not an acceptableguide to assess the identity of U. flexuosa down to the subspecies level with in Southern California, especially in water with higher salinity. The morphological plasticity within the genus Ulva demonstrates the need for more molecular techniques in the identification of U. flexuosa and its subspecies.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Flanders, Elayna
- Description:
- Often the first step in petitioning for a species to be listed under the Endangered Species Act (ESA), or for evaluating management alternatives, is to conduct a population viability analysis (PVA). A PVA is a case-by-case risk analysis used to assess the probability of extinction in the future (Schaffer 1990). PVAs use data on demographic rates, and assumptions about population processes, as well as assumptions about threat conditions and their effects on demography (Doak, et al., 2015). A PVA can indicate the urgency of instituting recovery efforts, identify which demographic rates are particularly important for persistence, and provide information needed to determine eligibility for listing of a species under the ESA. This project assesses whether information needed to run a PVA for species of conservation concern can be found in the Birds of North America (BNA), which is a comprehensive set of species accounts written by recognized experts, for all breeding birds in North America. The BNA was used to document whether data on demographic characteristics, ecological characteristics, and anthropogenic threats were available for each 721 bird species. Because consistent patterns of missing information can help direct research efforts, possible explanations for knowledge gaps of information needed to run a PVA were researched; body mass, ecoregion occupancy, conservation status listing, and taxonomic order were explored as the potential drivers of knowledge gaps. Species mass did not prove to be a significant driving factor; however, limited data were available for analysis. Conservation status listing was not a significant driving factor, data indicated no consistent tendency for listed species to have more or less information known about them. Overall results show that the ecoregions a species occupies (p=0.005) and the taxonomic Order it belongs to (p=0.005) are the best predictors of knowledge gaps for species of breeding birds of North America. Taxonomic Order indicated that anthropogenic threats are either all well known together or all unknown together for bird Orders observed. Additional research is needed to identify why these patterns exist and how to fill the gaps in knowledge. Surprisingly, across all species there was no information about the anthropogenic threats evaluated 42% of the time. Anthropogenic threat studies will become increasingly important as bird populations fluctuate and human impacts on the environment continue to increase.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science