Theses (M.S.)--University of New Hampshire (Dept. of Zoology), 2008. / Includes bibliographical references. Also available online.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 157-165). Also available via the World Wide Web.

We examined aspects of hearing in the red bat (Lasiurus borealis) related to its use of biosonar. Evoked potential audiograms, obtained from volume-conducted auditory brainstem responses, were obtained in two bats, and the sound pressure transformation of the pinna was measured in three specimens. Field-recorded echolocation signals were analysed for comparison. The fundamental sonar search calls sweep from 45 to 30 kHz (peak energy at 35 kHz), approach-phase calls sweep from 65 to 35 kHz (peak 40 kHz) and terminal calls sweep from 70 to 30 kHz (peak 45 kHz). The most sensitive region of the audiogram extended from 10 kHz to 45-55 kHz, with maximum sensitivity as low as 20 dB SPL occurring between 25 and 30 kHz. A relative threshold minimum occurred between 40 and 50 kHz. With increasing frequency, the acoustic axis of the pinna moves upwards and medially. The sound pressure transformation was noteworthy near 40-45 kHz; the acoustic axis was closest to the midline, the -3 dB acceptance angles showed local minima, and the pinna gain and interaural intensity difference were maximal. These results are related to the known echolocation and foraging behavior of this species and match the spectral components of approach- and final-phase calls. We conclude that coevolution with hearing prey has put a higher selective pressure on optimizing localization and tracking of prey than on improving detection performance.

Most vertebrates have separate sexes, and sex-specific traits that are regulated by genes with sex-biased expression patterns. In many species with genetic sex determination system, genetic recombination is suppressed in genomic regions linked to the master regulator of sex determination – the gene or set of linked loci that orchestrate sexual differentiation. Natural selection may favour alleles with sex-specific effects - including those with sexually antagonistic (SA) fitness effects (e.g., beneficial to females but harmful to males) – to become fixed in or be translocated to these non-recombining regions of sex chromosomes, because sex-specific or sex-biased modes of inheritance can resolve genomic conflict associated with SA. Sexually antagonism may also be resolve by sex-biased gene expression, and in theory these two mechanism (sex-linkage and sex-biased gene expression) could operate synergistically. However, there are relatively few empirical studies that test whether genes with sex biased expression patterns are indeed more abundant on sex chromosomes – and especially on newly evolved sex chromosomes. We explored this question with an African frog species Xenopus borealis, whose sex chromosome evolved within the last 25 million years (my) and have a large (~50Mbp) region of suppressed recombination, making it a young sex chromosome system compared to many other intensively studied systems, such as the sex chromosomes of mammals. We tested the possibility that a higher proportion of genes with sex-biased expression would be located on the sex-linked region of the sex chromosome of this species. By examining gene expression in adult liver and gonad and also tadpole gonad/mesenephros at two developmental stages, we found that the sex-linked region of these sex chromosome do have a higher proportion of sex biased genes compared to the non-sex-linked region of the same sex chromosomes, compared to (i) a homeologous genomic region in the tetraploid genome of X. borealis, and also (ii) the autosomes of this species. We did not observe the same pattern in a closely related frog species, Xenopus laevis, which has sex chromosome that are not homologous to those of X. borealis and, unlike X. borealis, lacks a large region of suppressed recombination on its sex chromosome. Using Brownian Motion model, we found as well that expression divergence evolution of genes in the sex-linked region of X. borealis is faster compared to its non-sex-linked homeologs (within X. borealis), and also compared to orthologous regions that are also non-sex-linked. One possible explanation for these observations is that natural selection favoured an expansion of recombination suppression (via unknown mechanisms) on chromosome such that polymorphic regulatory regions became linked (or unlinked) to the sex determining locus in such a way to resolve SA. Alternatively, it is possible that these sex-biased expression pattern evolved rapidly after recombination suppression. / Thesis / Master of Science (MSc) / Sexual selection favours the evolution of distinctive traits in each sex in order to optimize the reproductive success of each one. However, because most of the genome is shared between the sexes, sexual selection may result in genomic conflict when mutations are beneficial to one sex but harmful to the other; this conflict is known as sexual antagonism. Genomic conflict associated with alleles with sexually antagonistic (SA) fitness effects can be resolved via the origin of sex-biased expression patterns and this may be catalyzed by genetic linkage to a sex-determining locus on a sex chromosome. Consequently, one might predict there to be an enrichment of genes with sex-biased expression patterns on the sex chromosome as compared to the autosomes. We tested this expectation in an African frog species Xenopus borealis, which has a relatively young sex chromosomes and a large region of recombination suppression on the female-specific W-chromosome. We found enrichment of sex-biased genes on the nonrecombining region of the sex chromosomes of this species in adult liver and gonad tissue and also tadpole mesenephros/gonads at two developmental stages. Additionally, we found that expression divergence of genes in the non-recombining region have a faster rate of evolution as compared to the rate of expression divergence of genes in other genomic regions. One possible explanation for these observations is that natural selection favours an expansion of recombination suppression (via unknown mechanisms) on sex chromosome such that polymorphic regulatory region become linked (or unlinked) to the sex determining locus in such a way as to resolve SA.

The measurement of stress hormone levels in wild free-living animals is becoming an increasingly effective method for examining proximate mechanisms of animal behavior and the physiological impacts of human activities on wildlife. In these studies I measured plasma levels of the stress hormone corticosterone in the endangered red-cockaded woodpecker (Picoides borealis) to determine their role in the reproductive behavior of individuals in this species, and whether they are affected by human disturbance. In chapter one, I provide an introduction to the vertebrate stress response and I describe the natural history of the red-cockaded woodpecker. In chapter two, I compare corticosterone and reproductive hormone levels between breeding males and helper males to examine hormonal mechanisms of reproductive suppression in helper males. No hormonal differences existed between breeding and helper males. However, baseline corticosterone levels were lower in all males living in groups with two or more helper males, suggesting that male helpers reduce the workload of all other group members. In chapter three, I compare corticosterone levels between birds living in clusters subject to two different training restriction regimes on a military installation. Males living in clusters without training restrictions had lower baseline corticosterone than those living in clusters with training restrictions, suggesting that males habituate to chronic disturbance by downregulating baseline corticosterone levels. / Master of Science

Thesis (M.M.S.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 83-90.

LAMBDA was an exploration of science and art in two components: a performance-lecture and an art installation. This project asserted that performance and art are effective methods of delivering scientific information to a general audience. The first component was a solo performance-lecture that used lights, projection, costumes, props, and sound in a hybrid classroom space. The performance-lecture covered the topics of light, the Aurora Borealis, gravitational lensing, and the cosmic microwave background. The art installation used light emitting objects to visually represent the gravitational disturbances that exist within a section of space-time. / text

An ice nucleating protein (INP) with 66% amino acid sequence identity to the better-known INP of Pseudomonas syringae has been described in an environmental isolate of P. borealis and designated InaPb. Despite the fact that INPs are classified as ice-binding proteins, InaPb showed little affinity for pre-formed ice and showed incorporation rates similar to Ina- strains. Additionally, it appeared to lack in the ability to shape ice or limit its growth. However, it was an effective ice nucleator. Using the coding sequence for InaPb and a green fluorescent protein tag (GFP), an InaPb-GFP fusion protein construct was inserted into a broad host expression vector in order to visualize the expression and localization of the protein in E. coli and an Ina- strain of P.syringae. The InaPb-GFP protein appears to localize at the poles of E. coli, but the nucleation temperature for these cells was only marginally above -9°C, which indicated poor nucleation activity. When expressed in Ina- P. syringae, the proteins showed clustering throughout the cell and an increased ability to nucleate ice following cold conditioning. The ability to nucleate ice was further increased by the removal of the GFP tag resulting in an average nucleation temperature more consistent with that seen in the native host P. borealis. Since inaPb transcript levels did not appear to change after cold conditioning, the clustering seen using fluorescence microscopy was likely the result of increased aggregation of protein in the membrane. Most INP- producing bacteria are associated with plant disease, but experiments with P. borealis suggested that the Ina+ phenotype was not indicative of pathogenicity in this strain. It is hoped that my contribution to the functional characterization of this INP will lead to a better understanding of these special proteins and their importance to the handful of bacteria that exhibit this activity. / Thesis (Master, Biology) -- Queen's University, 2012-05-15 09:55:52.506

Mémoire (M.P.Aquat.)-- Université du Québec à Chicoutimi, 1991. / Bibliogr. : f. 75-83. Document électronique également accessible en format PDF. CaQCU

The present study adopted an integrative approach to conduct a population comparison of vulnerability to environmental stress in a commercially important species of ectotherm. Specifically, I investigated how differing environmental conditions in native habitats may drive intra-species divergence and alter performance when conditions shift. This study used northern prawn (Pandalus borealis Krøyer 1838) populations with known morphological differences from two spatially proximate fjord sites differing in oxygen regime as a model system. The genetic population structure was analysed and whole organism, physiological, and metabolomic performance under hypoxia and thermal stress were assessed. Genetic analyses displayed no significant dissimilarities between P. borealis from the normoxic and the seasonally hypoxic site. It was hypothesised that phenotypic plasticity may act as mechanism by which P. borealis may persist in the seasonally hypoxic fjord. Subsequently, a common garden experiment, in which individuals from the two fjords were exposed to hypoxia and the additional stress of elevated temperature, was carried out. The populations did not show significantly different physiological performance as determined by metabolic rates and stamina. However, the experiment did confirm the negative impacts of hypoxia on this species. Finally, P. borealis were exposed to hypoxia in the field in a translocation experiment. As the laboratory methods used would not have been possible to replicate, performance was assessed by survivorship and metabolite regulation. P. borealis from the two fjords showed significantly different levels of survivorship and the metabolomic profiles demonstrated that both populations possess different levels or forms of phenotypic plasticity, as they responded differently to translocation. This thesis presents the first use of the mtDNA control region of this species being used to determine its genetic variation and emphasises the need for multidisciplinary, holistic and multi-population approaches to assessing species vulnerability.