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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Reproductive ecology and life history trade-offs in a dimorphic polygynous mammal, the New Zealand fur seal

Negro, Sandra Silvia January 2008 (has links)
Polygyny is the most common mating system in mammalian species (95%), yet our understanding of polygynous systems and microevolutionary processes is still limited. Pinniped mating systems range from extreme polygyny (e.g. elephant seals) to sequential female defence by males and hence have often been used as models for mating system studies. Parentage analysis has enabled the examination of mating success, the identification of pedigrees, and the elucidation of social organisation, greatly enhancing our understanding of mating systems (Chapter 1). However, such analyses are not without pitfalls, with erroneous assignments common in open systems (i.e. when parental and offspring samplings are incomplete). We investigated the effects of the user-defined parameters on the accuracy of parental assignment using two commonly used parental allocation programme, CERVUS and PASOS (Chapter 2). We showed that inaccurate user-defined parameters in CERVUS and PASOS can lead to highly biased output e.g. the assignment rate at 95% CL of offspring with a sampled known mother to sampled males decreased from 58% to 32% when the proportion of candidate males sampled in the parameter options decreasing 4-fold. We found that the use of both CERVUS and PASOS for parentage assignment can increase the likelihood of correctly allocating offspring to sampled parents to 97% in our study system. Incorrect parental assignment can bias estimates of various biological parameters, such as lifetime reproductive success and mate choice preference, and hence bias ecological and evolutionary interpretations. Here, we propose solutions to increase the power of parentage assignment and hence decrease the bias in biological parameter estimates. In addition, we analysed the effects of the intrinsic bias in likelihood assignment approaches towards assigning higher probability of parentage on individuals with rare alleles and those with heightened offspring-parent matches, which increase with the number of homozygous loci (Chapter 3). We showed that, as a consequence of the algorithms employed in the programmes CERVUS and PASOS, heterozygote males with rare genotypes are assigned higher rates of parentage than males with common alleles. Consequently, where two males could both be biological fathers of a given offspring, parentage assignment will more often go to the male with the rarer alleles (most often in heterozygous loci). Thus, the commonly used parentage assignment methods may systematically bias the results of parentage analyses towards supporting the notion that females prefer more genetically unusual, most often heterozygous, males. Such a bias may sway investigators towards incorrectly supporting the concept that females choose genetically more unusual males for heterozygosity fitness benefits that underpin the good genes hypothesis, when in fact no such relationship may exist. In polygynous mammals, successful males mate with multiple females by competing with and limiting the access of other males to females. When the status of many males (age, size, health, genetic etc.) prevents them from achieving the primary mating tactic, theory predicts selection for a diversification of male mating tactics. Recent studies in pinnipeds have shown that observed male mating success was correlated to male paternity success in some species (elephant-seals), but not in others (grey seals). The existence of alternative mating strategies can explain those discrepancies. Chapter 4 implemented the guidelines provided in Chapter 2 and 3 and focused on the polygynous New Zealand fur seal Arctocephalus forsteri, predicting that 1) competition for females is likely to cause a diversification of male mating tactics; and 2) that alternative tactics can yield reproductive success. Our results indicated three male behavioural profiles; one corresponded to large territorial males and two illustrated a continuum of alternative tactics employed by non-territorial subordinate males. Our study highlights that holding a territory is not a necessary condition for reproductive success in a population of otariids. The degree of sexual size dimorphism in polygynous species is expected to increase with the degree of intra-sexual competition and in turn with the degree of polygyny. The life history of an individual is the pattern of resource allocations to growth, maintenance, and reproduction throughout its lifetime. Both females and males incur viability costs of mating and reproduction. However, male viability costs due to increase growth and male-male competition can be greater than female viability costs of mate choice and reproduction. Although an abundant literature on sexual dimorphism in morphology, physiology, and parasite infections is available, little is known on the intra-sexual differences in physiology and parasite infections associated to the reproductive success of different mating strategies in mammalian species. Chapter 5 examined the reproductive costs between territorial and subordinate males New Zealand fur seal related to their relative reproductive success using a multidisciplinary approach (behaviour, genetics, endocrinology, parasitology). We found that dominant New Zealand fur seal males endure higher reproductive costs due to the direct and indirect effects of high testosterone levels and parasite burdens. Our study highlights that holding a territory confers a higher reproductive success, but induces higher costs of reproduction that may impair survival. Understanding microevolutionary processes associated to polygynous systems is fundamental in light of the ongoing anthropogenic alteration of the environment through climatic variations and habitat reduction which ultimately affect opportunity for sexual selection and shape the life history trade-offs.
102

L'adaptation d'escherichia coli à la carence en phosphate / Adaptation of Escherichia coli to phosphate starvation

Guillemet, Mélanie 17 December 2010 (has links)
E. coli K-12 peut survivre lors d'une incubation prolongée en carence en Pi, en condition aérobie, grâce à l'induction par RpoS de poxB et gadB. Les mutants rpoS survivent en utilisant une nouvelle stratégie. Le métabolisme des mutants rpoS nécessite l'activité du répresseur Fur pour diminuer la synthèse du petit ARN RyhB, qui inhibe la synthèse de protéines riches en fer (Sdh et FumA). L'activité Fur et l’absence de RpoS permettent ensemble qu’une activité substantielle du cycle TCA se poursuive en phase stationnaire, ce qui diminue la production d'acide acétique et, finalement, permet la croissance sur l'acide acétique et le Pi excrété dans le milieu. Lors d'une évolution expérimentale dans un milieu minimum limitant en Pi, les bactéries de type sauvage donnent rapidement naissance à des mutants qui détoxiquent l'acide acétique du milieu et survivent lors d'une incubation prolongée. Une souche évoluée ajoutée en minorité dans une culture mixte peut croître entre les jours 1 et 3 d’incubation grâce à l’acquisition de deux mutations : une délétion de 1 pb qui inactive RpoS et une délétion de 8 bp qui active PhnE, un transporteur de produits phosphorylés qui est normalement cryptique. Les mutants phnE+ rpoS- peuvent croître dans des cultures contenant une majorité de bactéries de type sauvage (phnE- rpoS+) grâce à 1°) l'activité PhnE, qui pourrait récupérer des produits phosphorylés excrétés par les bactéries de type sauvage carencées en Pi, et 2°) le manque d'activité RpoS qui, d’une part favorise l'induction du régulon PHO et donc de phnE, et d’autre part maintient l’entrée du flux métabolique dans le cycle TCA. / E. coli K-12 can survive prolonged incubation under aerobic, Pi starvation conditions as a result of the induction by RpoS of poxB and gadB. However, rpoS mutants survived Pi starvation by using a new strategy. Metabolism in rpoS mutants required the activity of Fur in order to decrease the synthesis of the small RNA RyhB that might otherwise inhibit the synthesis of iron-rich proteins such as SDH and FumA. Fur activity and the lack of RpoS activity allow a substantial activity of the TCA cycle to continue in stationary phase in rpoS mutants, which decreases the production of acetic acid and, eventually, allows growth on acetic acid and Pi excreted into the medium. During experimental evolution experiments conducted in Pi-limiting medium containing no glutamate, wt cells rapidly evolved mutants that detoxified acetic acid from the medium and survived during prolonged incubation. One evolved strain, added as a minority in mixed culture, could grow between days 1 and 3 of incubation provided that the PHO regulon was induced. One mutation that inactivated RpoS activity and one that activated the PhnE phosphorylated products-transport activity (normally cryptic) were necessary and sufficient to provide such phenotype. phnE+ rpoS- double mutants can grow in cultures containing a majority of wt cells (phnE- rpoS+) probably because PhnE activity scavenges low levels of phosphorylated products excreted by wt cells, when the lack of RpoS activity helps to maintain induction of the PHO regulon and a substantial activity of the TCA cycle in slow growing cells.
103

hommage

SÖDERLUND, DAVID January 2010 (has links)
hommagethis work is built upon and intended as an homage to the writingstyle of the author Jean Genet. this through post modernreference collage and pastiches of selected works from thequeer cultural heritage.Genets style could be described asa strikingly beautiful, yet morbid, corporeal world ofmasculinities. the dualism of disgustand the embrace of the decay of morality. / Program: Modedesignutbildningen
104

Claiming the Best of Both Worlds: Mixed Heritage Children of the Pacific Northwest Fur Trade and the Formation of Identity

Beason, Alanna Cameron 01 May 2015 (has links)
Intimacy and family have been pillars of the North American fur trade since its conception. This is especially true for fur trading companies centered in Canada, specifically the Hudson’s Bay Company and the Northwest Company. Kinship ties formed through intimate relations between European fur traders and indigenous women allowed the fur trade to flourish and created an environment for stable, mixed heritage family units to emerge. As mixed heritage children grew into adulthood, they learned to identify with both sides of their parental cultures. However, the connections they formed with each other proved the most valuable and a separate, distinct culture emerged. In Canada this group of people are known as the Métis, a French word meaning mixed. The fur trade continued its move west and eventually reached the Pacific Ocean. This region known as the Pacific Northwest was the farthest removed from fur trade headquarters in Montreal and was home to many different Indigenous Nations. These nations, in combination with fur traders many of whom where Métis, also created families and a new culture once again came into being. It shared aspects of Métis, European, and indigenous cultures, but was something distinctly new. Through the examination of education, kinship ties, language and borders, this groups understanding of self and community came into focus.
105

Biology and conservation of the Cape (South African) fur seal arctocephalus pusillus pusillus (Pinnipedia: Otariidae)from the Eastern Cape Coast of South Africa

Stewardson, Carolyn, Louise. Unknown Date (has links)
No description available.
106

Contrôle de l'homéostasie de fer au cours du cycle infectieux d'Erwinia chrysanthemi 3937

Boughammoura, Aida 23 April 2007 (has links) (PDF)
Erwinia chrysanthemi 3937 est une bactérie phytopathogène responsable de maladies de type pourriture molle sur une large gamme de plantes. Durant l'infection, les bactéries se disséminent de manière extracellulaire, au niveau de l'apoplasme des tissus aériens du végétal où elles doivent s'adapter à des conditions de stress oxydant et une faible disponibilité en fer. Comme cet élément est essentiel et paradoxalement génère des radicaux hydroxyles hautement toxiques via la réaction de Fenton, une régulation fine des quantités intracellulaires en fer est primordiale pour la bactérie. L'homéostasie du fer implique une classe de protéines dénommées ferritines qui séquestrent le fer sous forme non réactive et biodisponible notamment lorsque le métal devient limitant dans l'environnement. Le génome d'E. chrysanthemi 3937 comporte une centaine de gènes dédiés au métabolisme du fer dont 4 sont supposés être impliqués dans le stockage intracellulaire du fer : le gène ftnA codant une ferritine de type eucaryote, le gène bfr codant une bacterioferritine contenant des groupements hème et les gènes dps1 et dps2 codant deux protéines Dps (DNA-binding proteins from starved cells). L'inactivation de ces gènes a montré que la ferritine FtnA contribue principalement au stockage intracellulaire du fer. Le rôle des ferritines ne se limite pas à servir de réserves de fer intracellulaire : ainsi la protéine FtnA participe à la résistance au stress oxydant et la protéine Dps1 pourrait jouer un rôle dans la détoxication du peroxyde d'hydrogène. Conformément à leur rôle dans le stockage intracellulaire du fer, les gènes ftnA, bfr et dps1 sont exprimés en réponse à la biodisponibilité en fer par la protéine Fur (Ferric uptake repressor), mais de manière temporellement différentielle au cours de la croissance bactérienne et selon des mécanismes distincts. Seule l'induction du gène ftnA par le fer et Fur est dépendante de l'ARN anti-sens RyhB. Par ailleurs, les gènes bfr et dps1 sont induits en phase stationnaire de croissance par le facteur σS. Les travaux réalisés au cours cette thèse ont permis de caractériser les intervenants de l'homéostasie du fer chez E. chrysanthemi 3937, d'acquérir une vue globale du trafic intracellulaire du fer et d'en apprécier leur contribution respective dans la pathogénie.
107

Re-conceptualizing the traditional economy: indigenous peoples' participation in the nineteenth century fur trade in Canada and whaling industry in New Zealand

Parker, Leanna 06 1900 (has links)
Contemporary resource use on Indigenous lands is not often well understood by the general public. In particular, there is a perception that traditional and commercial resource use are mutually exclusive, and therefore there is often an assumption that Indigenous communities are abandoning their traditional economy when they participate in the commercial sector of the larger regional economy. This perceived tension between traditional and commercial resource use is caused in part by a limited understanding of the participation of Indigenous peoples in commercial industries historically and the subsequent process of the commercialization of some aspects of Indigenous peoples pre-contact economies. This dissertation examines the seasonal cycle of activities and the patterns of consumption and production of the Indigenous peoples who participated in the fur trade at Ile a la Crosse in northwestern Saskatchewan and the whaling industry at the Otakou shore station in southern New Zealand. A systematic analysis of the daily journals and accounting records kept by company employees in these two regions demonstrate that participation in these industries allowed the Indigenous economies to be transformed from pre-contact times. While this participation did not completely subsume the Indigenous economies, the changes that were made created a need for the Indigenous people to continue accessing the European-style goods that had been incorporated into their livelihoods, a need that was exacerbated as local resources declined as a result of over-use. Thus, there is a need to re-conceptualize what is generally thought of as the traditional economy. The traditional economy in contemporary Indigenous communities is often perceived as an Indigenous approach to resource use that has changed little, except perhaps in the technology used, from pre-contact times. This dissertation, however, clearly demonstrates that participation in commercial industries historically encouraged the adaptation of Indigenous economies in response to changing opportunities and circumstances. It becomes clear then that the so-called traditional economy of today, is an Indigenous economy that has already been shaped and influenced by participation in historical commercial economies. Understanding the adaptability of Indigenous economies has important implications for economic development initiatives in Indigenous communities today. / Comparative Indigenous Economic History
108

Olfactory discrimination ability of South African fur seals (Arctocephalus pusillus) for enantiomers

Kim, Sunghee January 2012 (has links)
The sense of smell in marine mammals is traditionally thought to be poor. However, increasing evidence suggests that pinnipeds may use their sense of smell in a variety of behavioral contexts including communication, foraging, food selection, and reproduction. Using a food-rewarded two-choice instrumental conditioning paradigm, I assessed the ability of South African fur seals, Arctocephalus pusillus, to discriminate between 12 enantiomeric odor pairs, that is, between odorants that are identical in structure except for chirality. The fur seals significantly discriminated between eight out of the twelve odor pairs (according to p < 0.05, with carvone, dihydrocarvone, dihydrocarveol, limonene oxide, menthol, beta-citronellol, fenchone, and alpha-pinene), and failed with only four odor pairs (isopulegol, rose oxide, limonene, and camphor). No significant differences in performance were found between the animals (p > 0.05). Cross-species comparisons between the olfactory performance of the fur seals and that of other species previously tested on the same set of odor pairs lend further support to the notion that the relative size of the olfactory bulbs is not a reliable predictor of olfactory discrimination abilities. The results of the present study suggest that sense of smell may play an important and hitherto underestimated role in regulating the behavior of fur seals.
109

Northern Fur Seals (Callorhinus ursinus) of the Commander Islands: Summer Feeding Trips, Winter Migrations and Interactions with Killer Whales (Orcinus orca)

Belonovich, Olga Andreevna 2011 August 1900 (has links)
The northern fur seal (NFS) population on the Pribilof Islands (PI) is currently declining while the population on the Commander Islands (CI which includes Bering and Medny Islands) is stable. The reasons for the different population trajectories remain unknown. Comparing differences in behavioral ecology and predation pressure between these two populations could provide an explanation. This study examined lactating NFS female behavior to determine: 1) summer foraging patterns (trip duration, trip direction, dive depth) of animals from two nearby rookeries on Bering Island, 2) winter migration from Medny and Bering Islands relative to patterns of ocean productivity, and 3) the potential impact of killer whale predation on population dynamics. Data were collected from 2003 to 2010 using visual observations and telemetry. Twenty-one satellite transmitters, 29 time-depth recorders and 17 geolocation recorders were deployed. Shore-based observations of killer whale predation and photo-identification were conducted near the CI rookeries in 19992010. During lactation, both mean foraging trip duration and mean maximum diving depth (3.4 plus/minus 1.3 days and 17.7 plus/minus 6.8 m, respectively) for NFS adult females (n = 28) did not significantly change among years. Although foraging areas of NFS from the two rookeries on Bering Island overlapped, the mean direction of travel from Severo-Zapadnoe rookery was significantly (p<0.01) different compared with Severnoe rookery. The foraging patterns suggested that these females had a reliable food source that did not change despite potential environmental changes or the effects of fisheries. During their winter migration, NFS females from the CI traveled to the Transition Zone Chlorophyll Front (32° N-42° N) in the North Pacific Ocean. Their winter migration routes and the location of overwinter foraging areas were positively correlated with high ocean productivity (near surface chlorophyll a concentration). Over 82 percent (n=17) of these females spent 38 months near the eastern coast of Hokkaido, Japan and followed the coastal high productivity areas on their way back to the CI. Transient killer whales in groups of 2-12 individuals were repeatedly observed preying mostly on NFS males during the summer. The simulation model showed little impact on population dynamics as long as male fur seals were the primary prey. However, if the number of killer whales increased or they changed their diet to include females and pups, then the NFS population on the CI could decline. The winter migration of NFS from CI and PI are similar. Lactating NFS from the PI exhibit greater summer foraging effort (longer average trip duration and bout duration; greater number of deep dives) compared with females from the CI.
110

Early Migratory Behavior of Northern Fur Seal (Callorhinus ursinus) Pups from Bering Island, Russia

Lee, Olivia Astillero 2011 May 1900 (has links)
I examined the population trends of northern fur seals (Callorhinus ursinus) using an age-specific metapopulation model that allowed migration between rookeries. Mortality and birth rates were modified to simulate future population trends. I also examined the early migratory behavior and habitat associations of pups from Bering Island (BI), Russia. I instrumented 35 pups with Mk10-AL satellite tags and stomach temperature telemeters which provided diving, foraging and location data. I hypothesized that some aspects of pup behavior from the stable BI population differed from the behavior of pups from the unstable Pribilof Islands (PI). The population model revealed that emigration did not contribute significantly to the current PI population decline. However, large source populations contributed significantly to population growth in newly colonized rookeries. A stabilization of the PI population was predicted with a 10 to 20 percent reduction in both juvenile and adult female mortality rates. The diving behavior of pups showed a general progression towards longer and deeper dives as pups aged, particularly between 1600 – 0400 (local time), that was similar to PI pup behavior. However, unlike pups from the PI, I found three main diving strategies among BI pups: 1) shallow daytime divers (mean depth = 3.56 m), 2) deep daytime divers (mean depth = 6.36 m) and 3) mixed divers (mean depth = 4.81 m). The foraging behavior of pups showed that most successful ingestion events occurred between 1600 – 0400, with successful ingestion events lasting 25.36 plus/minus 27.37 min. There was no significant difference among the three strategies in the depth of successful foraging dives. I also examined the foraging search strategies in adult females and pups. Both pups and adults conducted Levy walks, although pups foraged in smaller patches (1 km scales). Using a logistic model to determine habitat associations, I found that pup locations were positively correlated with increasing chlorophyll a concentrations, distances from shore, and sea surface temperatures, and were negatively correlated with depth. There was no significant relationship between all pup locations and the regions (peripheries or centers) or types (cyclonic or anti-cyclonic) of eddies, but ingestion event locations were related to mesoscale eddy peripheries.

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