Thesis (Ph. D.)--New York University, 1945. / "Literature cited": p. 136-138.

Thesis (M.A.)--Florida State University, 2004. / Advisor: Dr. Peter Ruppert, Florida State University, College of Arts and Sciences, Dept. of Modern Languages and Linguistics. Title and description from dissertation home page (viewed Aug. 27, 2004). Includes bibliographical references.

Thesis (M.S.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains vi, 113 p. Includes bibliographical references p. 42-47.

No description available.

The Amazon rainforest along the Andean foothills contains exceptionally high diversity, much of it recent. The complex geology of the Andes and paleoclimate fluctuations preclude complex dispersal scenarios. This, in turn, has contributed to idiosyncratic speciation modes among shallowly-diverged Amazonian taxa. The poison frog genus Ameerega recently radiated throughout the Andes and Amazon (MRCA ~8.7 mya), with some taxa diverging as recently as the late Pliocene and early Pleistocene. Some species-level relationships remain poorly resolved, especially among recently diverged taxa. Here, I define ancestral populations and address the phylogenetic relationships among three recently diverged Peruvian Ameerega species (A. cainarachi, A. petersi, and A. smaragdina), using multiple species tree methods, including one that accounts for reticulate evolution. I complement species tree inference with assessments of behavioral divergence and niche overlap to better resolve species boundaries. I further explore the phylogeographic history of these species of Ameerega with demographic inference, considering evidence for population expansions. These analyses provide the basis to address speciation hypotheses in the Andean lowlands, including the refugial hypothesis and dispersal-vicariance hypothesis. I find support to synonymize A. smaragdina with A. petersi, and that divergent and convergent reticulation processes and historical range expansion impacted the A. petersi group’s speciation history. In addition, I use species distribution modeling (SDM) to infer the A. petersi group’s range dynamics since the mid-Pleistocene (785 kya). SDMs reveal periods of range expansion, contraction, and shifts, tracking climate fluctuations during the Pleistocene. In order to explicitly consider the relative roles of climate and geography in structuring genetic diversity at different time periods, I use a landscape genetics approach and consider 21 isolation-by-resistance hypotheses. These hypotheses include climatic resistance layers from five time periods in the Pleistocene, a stability layer, two geographic layers that reflect the two species’ natural history (distance-from-river and mid-elevation resistance), and composite layers that pair geographic and environmental layers. I find that climate stability and river proximity best explain gene flow. I find that phylogeographic, niche modeling, and landscape genetic evidence supports a dispersal-vicariance model of speciation in the A. petersi group.

The ontogeny of the enzyme LDH has been studied in two species of amphibians (Amblystoma gracile and Rana aurora) as it provides a sensitive gauge of the state of differentiation of the organism, since the number and proportions of LDH isozymes present exhibit temporal and species specificity, thereby reflecting the degree of activity of the controlling genes. The presence of LDH in all stages of both species examined was established by assaying embryo homogenates for LDH activity, and the LDH was resolved into isozymic patterns by the methods of starch gel and disc electrophoresis. Specific enzyme activity for each developmental stage was correlated with the morphological events then occurring and the isozyme patterns obtained were discussed in terms of showing an increase in complexity during ontogeny and in terms of the current LDH isozyme hypothesis. A modified hypothesis was advanced to account for some of the experimental findings. / Science, Faculty of / Zoology, Department of / Graduate

Temporal features in the vocalizations of animals and insects play an important role in a diverse range of species-specific activities such as mate selection, territoriality, and hunting. The neural mechanisms underlying the response to such stimuli remain largely unknown. Two species of anuran amphibian provide a starting point for the investigation of the neurological response to species-specific advertisement calls. Neurons in the anuran midbrain of Rana pipiens and Hyla regilla exhibit an atypical response when presented with a fixed number of advertisement calls. The general response to these calls is mostly inhibitory; only when the correct number of calls is presented at the correct repetition rate will this inhibition be overcome and the neurons reach a spiking threshold. In addition to rate-dependent call-counting, these neurons are sensitive to missed calls: a pause of sufficient duration—the equivalent of two missed calls—effectively resets a neuron to its initial condition. These neurons thus provide a model system for investigating the neural mechanisms underlying call-counting and interval specificity in audition. We present a minimal computational model in which competition between finely-tuned excitatory and inhibitory synaptic currents, combined with a small propagation delay between the two, broadly explains the three key features observed: rate dependence, call counting, and resetting. While limitations in the available data prevent the determination of a single set of parameters, a detailed analysis indicates that these parameters should fall within a certain range of values. Furthermore, while network effects are counter-indicated by the data, the model suggests that recruitment of neurons plays a necessary role in facilitating the excitatory response of counting neurons—although this hypothesis remains untested. Despite these limitations, the model sheds light on the mechanisms underlying the biophysics of counting, and thus provides insight into the neuroethology of amphibians in general.

Two types of ventilation cycle were recorded in unanaesthetised but restrained frogs (Rana pipiens); one concerned with ventilation of the buccal cavity alone (buccal cycle) and the other with lung ventilation (lung cycle). During the former the nares were open and the glottis closed so that only small pressures were generated by the movement of the buccal floor. The onset of a lung ventilation was signalled by activity in the laryngeal dilator muscle and when the glottis opened lung pressure and volume fell while buccal cavity pressure and volume increased. After narial closure the buccal floor was rapidly raised and gas was forced into the lungs from the buccal cavity. At peak pressure in the lungs and buccal cavity the glottis closed and nares opened, the recovery stroke of the pump being passive. Air flow recordings made at the external nares showed two phases of flow during each buccal cycle, while four phases accompanied each lung ventilation cycle. By plotting pressure/volume loops from the buccal pump an analysis was made of the mechanical work performed in one lung ventilation cycle, and the proportion of this work available for lung inflation after various losses against viscous and flow resistive forces in the pump itself; while measurement of the areas of typical sequences of such loops together with respiratory frequency enabled the mechanical work output of the pump to be determined for frogs ranging in size from 24 to 86 grams. Using Hill's classical equation for muscle efficiency, it was possible to estimate mechanical efficiency for single respiratory cycles by calculating the heat of maintenance and heat of shortening of the buccal floor muscles, while simultaneously measuring mechanical work output. Calculated efficiencies of lung ventilation cycles rose as mechanical work performed increased from 7.4% at 0.65 gram.cm/cycle to 19.3% at 2.73 gram.cm/cycle. Diving apnoea in Rana pipiens was induced by the presence of water at the level of the external nares, at which point the nares closed, no water entering the buccal cavity during the dive. Occasional ventilation cycles occurred during the dive in which gas entered the buccal cavity from the lungs, an equal volume then being pumped back into the lungs, but there was no ventilatory exchange with the external medium. Bilateral section of the trigeminal nerves resulted in an abnormal response to submergence, in that water entered the buccal cavity, and in some cases the lungs, while surfacing often did not result in resumption of ventilation. Skin mechanoreceptors in the region of the external narial openings serving the ophthalmic branch of the trigeminal were found to be capable of responding to the minimum stimulus encountered on submersion, movement of a water meniscus across the narial region, while a tonic response to hydrostatic pressure occurred in some preparations. In control experiments cutaneous mechanoreceptors innervated by the spinal nerves were shown to have no response to a water meniscus passing across their receptive fields, suggesting that they possess higher thresholds than the narial receptors. Periods of apnoea could be induced in air in Rana pipiens by bilateral or unilateral stimulation of the cut peripheral ends of the ophthalmic branch of the trigeminal nerve at threshold voltages as low as 30 mv, at a frequency of 200 Hz. Increase in stimulating voltage resulted in longer periods of apnoea before ventilation "broke through", and in these periods the external nares were closed and buccal pressure was held independent of atmospheric pressure. Reduction of the stimulation frequency by a factor of ten after the initiation of apnoea, simulating adaptation of the sensory nerves, proved as effective in maintaining apnoea as continued stimulation at the original frequency. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Algumas doenças associadas à piscicultura de tilápias trazem enormes prejuízos aos criadores, resultando em expressivos coeficientes de morbidade e mortalidade entre animais de todas as idades. Nesse sentido, exigências para o aprimoramento do diagnóstico laboratorial de doenças de natureza infecto-contagiosa tornaram-se constantes, face às perdas vinculadas. Os Ranavirus são vírus que infectam vertebrados ectotérmicos causando necrose generalizada, hemorragias focais e apoptose celular nos animais infectados. O presente estudo objetivou a realização de infecções experimentais em larvas e alevinos de tilápia do Nilo (Oreochromis niloticus), através de 3 diferentes modelos de infecção, utilizando estirpe de Ranavirus Frog vírus 3-like; recentemente detectada e isolada no Brasil, para avaliação das patologias associadas, incluindo o sequenciamento e análise do genoma da cepa viral. Vários sinais clínicos macroscópicos e microscópicos foram observados, hemólise, hemácias com anisocitose e policromasia, alterações relacionadas a média dos volumes das hemácias e hemoglobina, índices hepato-somáticos e espleno-somáticos com interações estatisticamente significantes, linfócitos reativos, alterações nos níveis das enzimas alanina aminotransferase e corpúsculos de inclusão basofílicos em diferentes tecidos dos animais experimentados com Ranavirus FV3-like foram observados dentro do período de 60 dias pós-infecção. Além disso, animais experimentalmente infectados foram positivos ao Ranavirus através de qPCR. O genoma de cepa brasileira de Ranavirus FV3-like apresentou 105 kilobases, contendo 54,98% de guanina + citosina, sendo 94 potenciais ORFs anotadas. A reconstrução filogenética, baseada em sequencias nucleotídicas, agrupou a amostra brasileira de Ranavirus no clado dos Frog vírus 3-like e as maiores identidades do genoma se deram com cepas norte-americanas de FV3-like. Doze potenciais eventos de recombinação, estatisticamente significantes (p < 0,05), foram identificados entre a cepa brasileira e amostras de referência de Ranavirus FV3-like. Nesse sentido, o presente trabalho contribui para o melhor entendimento da infecção causada por estirpe brasileira de Ranavirus FV3-like em tilápias do Nilo (Oreochromis niloticus). Além disso, adiciona e reforça a potencial recombinação entre diferentes estirpes de Ranavirus, colaborando para uma melhor compreensão das características de agentes virais associados a graves surtos em vertebrados ectotérmicos no país. / Some diseases associated with tilapia fish farming cause enormous losses to breeders, resulting in significant morbidity and mortality rates among animals of all ages. In this sense, requirements for the improvement of the laboratory diagnosis of diseases of infectious-contagious nature, became constant, in view of the related losses. Ranaviruses are viruses that infect ectothermal vertebrates causing widespread necrosis, focal haemorrhages and cell apoptosis in infected animals. The present study aimed to perform experimental infections in Nile tilapia (Oreochromis niloticus) fry and larvae through 3 different infection models, using Ranavirus Frog virus 3-like strain recently detected and isolated in Brazil, to evaluate the associated pathologies, including sequencing and genome analysis of the viral strain. Several macroscopic and microscopic clinical signs were observed, hemolysis, red blood cells presenting anisocytosis and polychromasia, alterations related to the mean red blood cell volumes and hemoglobin present in the red blood cells, hepato-somatic and spleno-somatic indexes showing statistically significant interactions, reactive lymphocytes, alterations in the levels of the enzymes alanine aminotransferase and basophilic inclusion corpuscles in different tissues of animals tested with Ranavirus FV3-like were observed within the 60-day post-infection period. In addition, experimentally infected animals were positive to Ranavirus through qPCR. The genome of the Ranavirus FV3-like Brazilian strain presented 105 kilobases, containing 54.98% of guanine + cytosine, with 94 potential ORFs annotated. The phylogenetic reconstruction, based on nucleotide sequences, grouped the Brazilian sample of Ranavirus in the clade of Frog virus 3-like, the greater identities of the genome were with North American strains of FV3-like. Twelve potential recombination events, statistically significant (p <0.05), were identified between the Brazilian strain and reference samples of Ranavirus FV3-like. The present work contributes to a better understanding of the infection caused by the Brazilian strain of Ranavirus FV3-like in Nile tilapia (Oreochromis niloticus). In addition, it adds and reinforces the potential recombination between different strains of Ranavirus, contributing to a better understanding of the characteristics of viral agents associated with severe outbreaks in ectothermic vertebrates.