Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
5 results
Search Results
Item Assessing vertebrate biodiversity across the Chesapeake Bay using environmental DNA metabarcoding(2023) Rodriguez, Lauren Kelly; Bailey, Helen; Woodland, Ryan J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Through the collection and sequencing of trace genomic evidence from environmental samples (e.g., water, air, and soil), environmental DNA (eDNA) metabarcoding can detect a range of vertebrates. Despite the dynamic characteristics of estuarine environments, which often hinder the persistence of genomic material, this project successfully employed metabarcoding to assess the distribution of vertebrates in the Chesapeake Bay. Primarily, the study evaluated the effects of using various eDNA sampling, laboratory, and post-hoc analysis techniques when investigating species presence and biodiversity of an area. This study also identified spatially-explicit fish communities along salinity gradients as described by a Generalized Additive Mixed Model (GAMM) and a Permutational Multivariate Analysis of Variance (PERMANOVA). Community compositions were similar to previous findings by traditional trawling and seining methods. This research supports the usefulness of eDNA metabarcoding to assess species presence across spatiotemporal extents, making it a promising tool for future biomonitoring efforts in the Chesapeake Bay.Item SOCIAL AND ECOLOGICAL FACTORS INFLUENCING COLLECTIVE BEHAVIOR IN GIANT DANIO(2016) Chicoli, Amanda; Paley, Derek A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A fundamental problem in biology is understanding how and why things group together. Collective behavior is observed on all organismic levels - from cells and slime molds, to swarms of insects, flocks of birds, and schooling fish, and in mammals, including humans. The long-term goal of this research is to understand the functions and mechanisms underlying collective behavior in groups. This dissertation focuses on shoaling (aggregating) fish. Shoaling behaviors in fish confer foraging and anti-predator benefits through social cues from other individuals in the group. However, it is not fully understood what information individuals receive from one another or how this information is propagated throughout a group. It is also not fully understood how the environmental conditions and perturbations affect group behaviors. The specific research objective of this dissertation is to gain a better understanding of how certain social and environmental factors affect group behaviors in fish. I focus on two ecologically relevant decision-making behaviors: (i) rheotaxis, or orientation with respect to a flow, and (ii) startle response, a rapid response to a perceived threat. By integrating behavioral and engineering paradigms, I detail specifics of behavior in giant danio Devario aequipinnatus (McClelland 1893), and numerically analyze mathematical models that may be extended to group behavior for fish in general, and potentially other groups of animals as well. These models that predict behavior data, as well as generate additional, testable hypotheses. One of the primary goals of neuroethology is to study an organism's behavior in the context of evolution and ecology. Here, I focus on studying ecologically relevant behaviors in giant danio in order to better understand collective behavior in fish. The experiments in this dissertation provide contributions to fish ecology, collective behavior, and biologically-inspired robotics.Item Ecological Risk To Cetaceans From Anthropogenic Ocean Sound; Characterization Analysis Using A Professional Judgment Approach To Uncertainty(2007-11-26) Truett, Amanda Ann; Mihursky, Joseph; Fogarty, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The recommendations of anthropogenic ocean sound impact criteria by an expert community of scientists have been monitored over the 10-year period from 1996 - 2006. This dissertation approaches this topic in three ways; 1: by content analyzing 94 peer-reviewed publications specific to this topic (representing 20 countries and 27 species of cetaceans, and virtually all oceans), from which up to fifteen variables were coded for exploratory analysis, 2: by an anonymous Internet survey questionnaire administered to 91 of the 119 authors of these 94 publications, one that was designed to identify common patterns and points of departure in how these expert scientists currently independently and anonymously characterize their data on the species they study, and 3: Logistic regression analysis to help determine the functional relationship, or measure of association (risk) between anthropogenic ocean sound and impacts to cetaceans and fish. Results indicate an increasing risk of disturbance behaviors in response to increasing anthropogenic sound levels, and that observed free-ranging populations (n >1486 animals) have lower behavioral thresholds to anthropogenic sound than observed captive individuals (n = 25 animals). Empirical estimates indicate a .945 probability that the sound threshold for free-ranging animals lies below the 180dB rms NMFS status quo criterion. Survey data suggests a significant increase in the concern over global ocean sound over the 10-year period - with 51% of criteria recommendations dropping from the 180dB rms status quo to 140dB p-p and below, representing more than a 50% shift toward the 100dB rms average ambient assumed in this study. It is concluded that these empiricists demonstrated a cooperative strategy which is in the early stages of adaptive management favoring integrating solutions to sustainability problems by way of collective management, and advocate precautionary behavior. Communications strategies are identified and discussed and recommendations include open data base collaborations. This project thus demonstrates the utility of a transparent international data base instrument and suggests a broader strategy for greater scientific leadership in guiding policy toward achieving sustainable management of living marine resources.Item Development of Standardized Antimicrobial Susceptibility Testing Methods and Aeromonas salmonicida Epidemiologic Cutoff Values for Antimicrobial Agents Used in Aquaculture(2007-07-27) Miller, Ron Ashley; Kane, Andrew S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pharmacokinetics describes the time course of drug absorption, distribution, metabolism and excretion. Pharmacodynamics is the relationship between unbound drug concentration over time and the resulting antimicrobial effect. Pharmacokinetic/ pharmacodynamic (PK/PD) indices quantify the relationship between pharmacokinetic parameters (i.e., area under the concentration-time curve, AUC) and microbiological parameters (i.e., minimal inhibitory concentrations, MICs), and are used to establish interpretive criteria or clinical breakpoints. The three primary PK/PD indices used are the AUC over 24 h at steady-state/MIC (AUCss/MIC), the peak concentration/MIC (Cmax/MIC), and the percentage of time over 24 hours that the drug concentration exceeds the MIC at steady-state pharmacokinetic conditions (T>MIC). These indices can be used to determine both appropriate dosage regimens and index magnitudes required for efficacy and reduced antimicrobial resistance emergence. The goal of this work was to determine the relevant PK/PD index target (AUCss/MIC) for oxytetracycline (OTC) against Aeromonas salmonicida, causative agent of furunculosis in salmonids. To achieve this goal we first established a standardized MIC testing method for aquatic bacterial pathogens, then used this method to determine the in vitro susceptibility cutoff concentration (epidemiologic cutoff value) for OTC (and three other antimicrobial agents) against 217 A. salmonicida isolates. We conducted additional in vivo studies using rainbow trout to monitor achievable serum OTC concentrations in both healthy and A. salmonicida-challenged fish. We confirmed OTC to be highly efficacious against a susceptible A. salmonicida strain in vivo, and through pharmacokinetics studies, calculated the OTC AUCss in healthy and challenged fish to be 27.2 and 20.1 μg∙h/mL, respectively. The PK/PD index target reported in a neutropenic mouse model as the most applicable to the tetracyclines is an AUCss/MIC of ≥5. Either of the AUCss values divided by the current epidemiologic cutoff value for A. salmonicida isolates (1 μg/mL) yields a product greater than this AUCss/MIC target of ≥5. This work demonstrates PK/PD indices commonly used in studies in mammals to predict therapeutic efficacy can be applied in studies in fish.Item Unconventional Myosins in Fish Ears(2005-04-21) Coffin, Allison; Popper, Arthur N; Kelley, Matthew W; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Unconventional myosins are critical motor proteins in the vertebrate inner ear. Mutations in both myosins VI and VIIa cause multiple forms of human hereditary deafness but the precise function of these proteins is unknown. This dissertation uses a comparative approach to better understand the role of myosins VI and VIIa in vertebrate ears. Gene expression and protein distribution for these two myosins is examined in the ears of evolutionarily diverse fishes. RT-PCR data shows that myo7a is expressed in the ears of all taxonomically diverse fish species examined here, and immunofluorescence reveals that myo7a protein is distributed throughout the sensory hair bundles of all inner ear regions. Myosin VI expression and distribution is more complex. Studies in other laboratories show that zebrafish (Danio rerio) have two myo6 paralogs with differing gene expression patterns. This dissertation extends previous findings by showing that all teleost fishes have two myo6 genes while non-teleost fishes and tetrapods have one, suggesting that myo6 duplication occurred in an ancestral teleost, probably during a genome-wide duplication. RT-PCR experiments suggest that both myo6 paralogs are expressed in teleost ears. mRNA localization with in situ hybridization shows, however, that myo6a is not expressed in sensory epithelia. Immunocytochemical data shows that myo6 protein is distributed throughout hair bundles in all inner ear end organs of the sea lamprey (Petromyzon marinus) and the zebrafish but is not found in utricular hair bundles in other fishes. While protein expression studies find that the myo6 antibody used in this dissertation binds to both myo6 proteins in the zebrafish, the gene expression studies suggest that only myo6b is expressed in hair cells, and therefore that this is differential distribution of a single protein. This dissertation adds depth to current studies of myo6-associated hereditary deafness and suggests that comparative studies between zebrafish and other fishes such as shad (Alosa sapidissima) that differ in myo6 protein distribution will help elucidate the function of this critical hair cell protein. Comparisons between the two myo6 paralogs will further aid in functional studies and shed light on evolutionary processes during the teleost radiation.