Tesi: "Ecology parasite"

1

Prior, Kimberley Faith. "The evolutionary ecology of circadian rhythms in malaria parasites." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29562.

Testo completo

Abstract (sommario):

Biological rhythms are thought to have evolved to enable organisms to organise their activities according to the Earth’s predictable cycles, but quantifying the fitness advantages of rhythms is challenging and data revealing their costs and benefits are scarce. More difficult still is explaining why parasites that exclusively live within the bodies of other organisms have biological rhythms. Rhythms exist in the development and traits of parasites, in host immune responses, and in disease susceptibility. This raises the possibility that timing matters for how hosts and parasites interact and, consequently, for the severity and transmission of diseases. Despite their obvious importance in other fields, circadian rhythms are a neglected aspect of ecology and evolutionary biology. The ambitions of this thesis are to integrate chronobiology, parasitology and evolutionary theory with mathematical models to obtain a greater understanding about how and suggest why malaria parasites have rhythms as well as the effect of infection on host rhythms. First, I identify how malaria parasites lose their developmental rhythms in culture, when they lack any potential time cues from the host. Next, I characterise parasite rhythms inside the mammalian host in terms of synchrony and timing and demonstrate there is genotype by environment interactions for characteristics of parasite rhythms. Then, I investigate the effect that parasite infection has on host rhythms and show there is variation between parasite genotypes in their effect on host locomotor activity and body temperature rhythms during infections. Finally, I explore which host rhythms may be driving parasite synchrony and timing and demonstrate the importance of peripheral host rhythms for the timing of malaria parasite developmental rhythms. The data presented here provides novel and important information on the role of rhythms during disease and opens up a new arena for studying host-parasite coevolution.

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Tompkins, Daniel Michael. "Evolutionary ecology of bird-parasite associations." Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:a5f5ea19-b799-490b-b738-99ff52df25c1.

Testo completo

Abstract (sommario):

This thesis investigates the ecological determinants of chewing louse (Insecta: Phthiraptera) host-specificity on four species of Malaysian swiftlets (Aves: Apodidae). Influences of host coloniality on louse ecology were also demonstrated, illustrating the dependence which these permanent ectoparasites have on their hosts. Louse collections were made to look for incidences of host-specific lice occurring on the "wrong" host ("straggling"). Straggling was observed, implying that lice disperse among host species. Thus, opportunity for louse dispersal (or lack thereof) does not govern the host-specificity of chewing lice on swiftlets. Experimental transfers of lice between hosts were conducted. Louse survival was reduced on foreign host species. This implies adaptation to specific host characters, suggesting that specialisation governs chewing louse host-specificity on swiftlets. There was no evidence for reciprocal adaptation of swiftlets to their normal louse species. Lice had no impact on the fitness of either swiftlets or the related common swift. Furthermore, neither swiftlet nor swift lice were transmitting pathogenic endoparasites. This implies that chewing lice and Malaysian swiftlets have not "coevolved". Survival of transferred lice was determined by the relatedness of donor and recipient hosts. Closer related swiftlet species are more similar in body size and feather dimensions. When the feather dimensions of the microhabitat distributions of the same louse species on different hosts were compared the results suggested that lice keep the dimensions of barb and barbule diameter, at which they occur, "constant" through microhabitat shifts. This suggests that feather dimensions are the host characters which determine the survival (and host-specificity) of chewing lice on birds. The ability of chewing lice to survive on hosts with similar feather morphology implies that "host-switching", between distantly related hosts with similar morphological characters (due to parallel or convergent host evolution), may have been an important factor in the evolution of bird-louse associations.

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Gregory, Richard D. "Host-parasite interactions : population and community ecology." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276582.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

O'Brien, Chris. "Appreciating the Importance of Parasites: Analyzing and Understanding the Ecology of Parasite-Host Interactions." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194212.

Testo completo

Abstract (sommario):

There is a growing interest in the nature of parasite-host interactions, the role these relationships play in ecological communities, and how human activities alter these associations. Furthermore, because inference about these interactions is usually gained by methods of statistical hypothesis testing, additional importance should be placed on the analysis and interpretation of parasite-host interactions. In this dissertation I address these ideas in three separate but interrelated studies with the three following questions: 1) How do two parasites with complex life-cycles alter the behavior of a novel amphipod host, and how do host and non-host predators respond to infected amphipod prey? In contrast to other studies, I found that two parasites of an endemic amphipod at Montezuma Well had little affect on their amphipod host, and that these associations had little affect on predation rates by both host and non-host predators. Results from this study underscore the importance of further investigating novel parasite-host interactions and placing them in their phylogenetic and evolutionary context. 2) Does human recreation affect spatial patterns of infection in an otherwise natural ecosystem? This study demonstrates that human visitors to Montezuma Castle National Monument alter patterns of waterfowl space use that in turn affect spatial patterns of disease in invertebrate hosts. This is the first study to document such an effect, and I discuss the important implications of this finding. 3) How is hypothesis testing applied in studies of wildlife disease, what conclusions can we make about the relative usefulness of these methodologies, and how can the analysis and interpretation of wildlife disease studies be improved? In this final study I conducted a literature review, computed statistical power for methodologies used in the literature, and re-analyzed published data to provide an example of the advantages of my suggested approach. I conclude that many studies report findings using methods that could be more informative and some studies may lack statistical power, demonstrating the importance of using prospective power analysis in the design of future studies. Furthermore, using statistical techniques that estimate the observed effect size can aid in increasing information transfer in studies of wildlife disease.

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Mahmud, Muayad Ahmed. "Evolutionary ecology of virulence in a fish parasite." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32945/.

Testo completo

Abstract (sommario):

Virulence (parasite- induced host fitness reduction) is thought to correlate positively with pathogen reproduction rates, but its relationship with pathogen transmission is likely to be determined by a trade- off between the costs and benefits of harming hosts. This project aims to investigate factors which affect host-parasite interactions and particularly those which may play a role in virulence evolution. In doing so, it describes experiments carried out using a monogenean ectoparasitic flatworm (Gyrodactylus arcuatus) and its three-spined stickleback (Gasterosteus aculeatus) host. Populations of this fish species experience a range of both environmental and ecological conditions. Such environmental heterogeneity has been found to drive changes in fish phenotypic traits such as morphology, behaviour, life history and physiology which may consequently affect parasite fitness. I demonstrate that under these conditions, parasite strains from different host populations evolve variation in virulence levels. I also reveal that coevolution in this host parasite system is likely to lead to local adaptation of G. arcuatus at the host population level. I show that competition between parasite species sharing a single host leads to increased parasite reproduction rates, but it shortens the infection time which may be due to earlier stimulation of host immune responses. I show that virulence is neither influenced by the population density, immunity (epidermal mucus), social behaviour of fish hosts nor the natural parasite life expectancy. Lastly, I find that virulence in this system is negatively influenced by the density of stickleback predators and positively associated with loch water pH. Taken together, these results suggest that in this host parasite system, both ecological and environmental factors which drive phenotypic changes in fish hosts may evolutionarily feedback to affect parasite virulence.

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Lynsdale, Carly L. "Evolutionary ecology of parasite infection in Asian elephants." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19058/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Jackson, M. H. "The epidemiology and ecology of toxoplasmosis." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381379.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Keeling, Matthew James. "The ecology and evolution of spatial host-parasite systems." Thesis, University of Warwick, 1995. http://wrap.warwick.ac.uk/30/.

Testo completo

Abstract (sommario):

All ecological and epidemiological systems are embedded in space and composed of individuals; these facts often have a profound effect on the dynamics and means many tools and definitions require reformulation. Modelling has always been about taking highly complex dynamical systems, such as the natural environment, and attempting to simplify them to a leve that can be conceptualised, in the process losing all the features that are not understood or not anticipated. The individual based spatial models which form the basis of this work start from the simple rules for individuals and build up to a complex system, allowing new, unexpected phenomenon to arise naturally. The local interactions in spatial models lead to short scale correlations and self-induced spatial heterogeneity as the small fluctuations of environmental noise are amplified into macro-scale patterns. These spatial patterns can lead to ephemeral refuges for hosts from where they can disperse stabilising the dynamics. After discussing the importance and variety of host-parasite interactions several techniques to be used in this work are developed and explained on simple examples. Chapters III and IV introduce a caricature host-pathogen model and how how this deviates from the standard mean field theory approximations. Attention is then turned to host-parasitoid systems and the spatially extended Nicholson-Bailey equations; probems with this coupled map lattice are highlighted and an alternative artificial ecology is formulated. Remaining with the Nicholson-Bailey equations these are forced to be integer based by utilising stochastic events, this greatly stabilises the dynamics hence the method was applied to the persistence of measles epidemics in small populations (=500000). Chapter VII demonstrates how the inclusion of space enhances the effects of parasitism in increasing the evolutionary advantage of sexual hosts over asexual ones. Finally general techniques are developed to implicitly model the effects of spatial correlations and stochastic individual based interactions.

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Fedna, Jimmy. "Prévalence du parasite Angiostrongylus cantonensis en Haïti chez les rats et gastéropodes." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCD017.

Testo completo

Abstract (sommario):

Ma recherche examine la prévalence et la répartition du parasite Angiostrongylus cantonensis en Haïti, également connu sous le nom de ver pulmonaire du rat, et qui est la première cause de méningite à éosinophiles chez l’homme dans le monde. Ce parasite a un cycle de vie complexe impliquant à la fois des hôtes définitifs (rats) et des hôtes intermédiaires (escargots et les limaces). J’ai documenté l'écologie du parasite et sa persistance deux décennies après sa découverte initiale dans le pays. Trois objectifs ont été fixés : synthétiser les connaissances sur les dimensions spatiales et écologiques d’A. cantonensis, déterminer sa présence et sa répartition en Haïti parmi les populations de rats et de gastéropodes à l'aide d'analyses moléculaires et morphologiques, et identifier les similitudes génétiques entre les souches haïtiennes et celles provenant d’autres régions du monde. Nous avons ciblé deux contextes écologiques contrastés : la vallée de l'Artibonite (milieu rural) et la zone urbaine de Port-au-Prince. L'échantillonnage a eu lieu pendant la saison des pluies et à la fin de la saison des pluies en raison de l'influence potentielle de la saisonnalité hydrologique sur la prévalence du parasite.Une revue systématique utilisant la méthode PRISMA a synthétisé les connaissances existantes sur la niche écologique du parasite, en mettant l'accent sur les facteurs abiotiques et biotiques affectant sa dynamique. Soixante-dix rats ont été capturés :23 Rattus norvegicus et 47 Rattus rattus. Sous la loupe binoculaire, nous avons récupéré des vers adultes chez seulement cinq rats (7%, 5/70) mais la détection moléculaire a révélé une prévalence d'A. cantonensis dans les poumons de rat de 31,4 %, (22/70), le parasite étant détecté dans quatre des huit sites, dont Port-au-Prince. La prévalence du parasite n’était pas reliée de manière significative aux variables prédictives telles que l'âge, la saison, le sexe et l'espèce de rat. Un seul haplotype COX1, le génotype II-G, a été identifié en Haïti, ce qui suggère une large répartition similaire à celle d'autres régions. La technique qPCR AcanR3990 a permis d'identifier deux échantillons positifs d'espèces de gastéropodes : Subulina octona à Port-au-Prince et une limace de la famille des Veronicellidae dans l’Artibonite, concordant avec la présence du parasite retrouvé chez les rats à ces endroits.C'est la première étude sur A. cantonensis en Haïti portant à la fois sur les hôtes définitifs et intermédiaires. Les diagnostics moléculaires par PCR révèlent une prévalence plus élevée que l'identification morphologique, ce qui est prometteur pour l'étude systématique de la contamination potentielle des espèces hôtes. Les résultats indiquent une endémicité du parasite potentiellement principalement liée à deux espèces de gastéropodes : l'escargot terrestre S. octona et les limaces Veronicellidae, ainsi que les rats R. rattus et R. norvegicus, soulignant les risques importants pour la santé des populations locales My research examines the prevalence and distribution of the parasite Angiostrongylus cantonensis, also known as the rat lungworm, in Haiti. It is the leading cause of eosinophilic meningitis in humans worldwide. This parasite has a complex life cycle involving definitive hosts (rats) and intermediate hosts (snails and slugs). I documented the parasite's ecology and persistence two decades after its initial discovery in the country. Three objectives were set: synthesizing knowledge on the spatial and ecological dimensions of A. cantonensis’ niche, determining its presence and distribution in Haiti among rat and gastropod populations using molecular and morphological analyses, and identifying genetic similarities between Haitian strains and those from other regions of the world. We targeted two contrasting ecological contexts: the Artibonite Valley (rural environment) and the urban area of Port-au-Prince. Sampling occurred during and at the end of the rainy season due to the potential influence of hydrological seasonality on parasite prevalence. A systematic review using the PRISMA method synthesized existing knowledge on the parasite's ecological niche, focusing on abiotic and biotic factors affecting its dynamics. Seventy rats were captured:23 Rattus norvegicus and 47 Rattus rattus. Under a binocular loupe, we recovered adult worms from only five rats (7%, 5/70), but molecular detection revealed a prevalence of A. cantonensis in rat lungs of 31.4% (22/70), with the parasite detected in four of the eight sites, including Port-au-Prince. Parasite prevalence was not significantly related to predictive variables such as age, season, sex, and rat species. Only one COX1 haplotype, genotype II-G, was identified in Haiti, suggesting a widespread distribution similar to other regions. The qPCR technique AcanR3990 identified two positive samples of gastropod species: Subulina octona in Port-au-Prince and a Veronicellidae slug in the Artibonite, indicating the presence of the parasite found in rats at these locations. This is the first study on A. cantonensis in Haiti addressing both definitive and intermediate hosts. Molecular diagnostics by PCR reveal a higher prevalence than morphological identification, promising for the systematic study of potential host species contamination. Results indicate that endemicity of the parasite may primarily be linked to two gastropod species: the land snail S. octona and Veronicellidae slugs, as well as R. rattus and R. norvegicus rats, highlighting significant health risks for local populations

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Aguirre, Macedo Maria Leopoldina. "Study on helminth and other parasite communities of oysters." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337758.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Carter, Lucy Mary. "Evolutionary ecology of reproductive strategies in malaria parasites." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9910.

Testo completo

Abstract (sommario):

For vector-borne parasites such as malaria, how within- and between-host processes interact to shape transmission is poorly understood. In the host, malaria parasites replicate asexually but for transmission via mosquitoes to occur, specialized sexual stages (gametocytes) must be produced. Once inside the mosquito vector, gametocytes immediately differentiate into male and female gametes, and motile male gametes must swim through the hostile environment of the bloodmeal to find and fertilise female gametes. Despite the central role that gametocytes play in disease transmission, explanations of why parasites adjust gametocyte production in response to in-host factors remain controversial. Furthermore, surprisingly little is known about the mating behaviour of malaria parasites once inside the mosquito. Developing drugs and/or vaccines that prevent transmission by disrupting sexual stages are major goals of biomedicine, but understanding variation in gametocyte investment and male gamete behaviour is key to the success of any intervention. First, I propose that the evolutionary theory developed to explain variation in reproductive effort in multicellular organisms provides a framework to understand gametocyte investment strategies in malaria parasites. I then demonstrate that parasites appear to change their reproductive strategies in response to environmental cues and in a manner consistent with our predictions. Next, I show how digital holographic microscopy can be used to characterise the morphology and motility of male gametes. I then provide evidence for non-random movement of male gametes and that gamete interactions with red blood cells appear to hinder mating success in a bloodmeal. Finally, I discuss the variation in gametocyte differentiation and fertilisation success when exposed to a number of factors implicated in gametocyte activation. The data presented here provides important information on the basic biology of malaria parasite reproductive stages and demonstrates considerable variation in parasite traits and behaviours in response environmental changes; both in the host and in the mosquito vector.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Pereira, Felipe Bisaggio. "Estrutura da comunidade de helmintos associados ao lagarto Tropidurus torquatus (Squamata: Tropiduridae) em uma área de afloramento rochoso no distrito de Toledos, Juiz de Fora, MG." Universidade Federal de Juiz de Fora (UFJF), 2010. https://repositorio.ufjf.br/jspui/handle/ufjf/3017.

Testo completo

Abstract (sommario):

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-12-16T12:33:44Z No. of bitstreams: 1 felipebisaggiopereira.pdf: 1115383 bytes, checksum: c4128dd85e239865ce346d0569b37b98 (MD5) Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-12-19T12:34:46Z (GMT) No. of bitstreams: 1 felipebisaggiopereira.pdf: 1115383 bytes, checksum: c4128dd85e239865ce346d0569b37b98 (MD5) Made available in DSpace on 2016-12-19T12:34:46Z (GMT). No. of bitstreams: 1 felipebisaggiopereira.pdf: 1115383 bytes, checksum: c4128dd85e239865ce346d0569b37b98 (MD5) Previous issue date: 2010-02-24 CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico A comunidade parasitária do lagarto Tropidurus torquatus em uma área de campo rupestre localizada no estado de Minas Gerais, sudeste do Brasil, foi estudada. Dos 110 hospedeiros analisados, 92 (83,6%) estavam infectados. Foram encontradas cinco espécies de helmintos, três de nematóide: Physaloptera lutzi, Parapharyngodon sp. e Oswaldofilaria sp., uma espécie de cestóide e um cistacanto não identificados. Apenas as espécies de nematóides apresentaram dados suficientes para analises ecológicas, sendo P. lutzi a espécie mais prevalente (67,3%) e com maior intensidade parasitária (4,86±4,85). Somente para Oswaldofilaria sp. foram encontradas diferenças significativas na prevalência e intensidade parasitária entre hospedeiros fêmeas e machos, esses últimos apresentando os maiores valores. A intensidade parasitária total e de P. lutzi também diferiram entre os sexos de hospedeiros com machos apresentando os maiores valores. O tamanho corporal do hospedeiro correlacionou-se de forma positiva com a intensidade de infecção de todas as espécies de nematóides. A sazonalidade local não influenciou de forma significativa a estrutura da comunidade componente de parasitos estudada. Aspectos do hospedeiro como dieta, dimorfismo sexual e comportamento (territorialiasmo e forrageamento) representaram importantes fatores na determinação da estrutura dessa comunidade de helmintos. De maneira geral, a comunidade parasitária apresentou baixa riqueza de espécies e um caráter não interativo, características comuns em comunidades parasitárias de répteis como hospedeiros. The helminth community of the lizard Tropidurus torquatus from a rocky outcrop located in Minas Gerais state, southeast Brazil, was studied. Ninety two of the one hundred ten individuals examined (83,6%) harbored helminths. A total of five helminth species were found, tree nematodes: Physaloptera lutzi, Parapharyngodon sp. and Oswaldofilaria sp., one cestode species and one acanthocaphalan cystacanth not identified. Only nematode species had sufficient data to perform ecological analysis with Physaloptera lutzi showing the highest prevalence (67,3%) and mean intensity (4,86±4,85). Prevalence and intensity of infection between males and females hosts differed only for Oswaldofilaria sp., with males showing the highest values. Total and P. lutzi intensity of infection were different among males and females hosts, with males showing the highest values. The host body size was positively related to intensity of infection for all nematode species. Local seasonality had no influence in the helminth community structure. Host diet, sexual dimorphism and behavior (territorialism, forage strategy) represented important factors in the structuring of this parasite community. In general lines, the helminth community was species poor and non interactive, representing a typical community structure found in herps hosts.

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Lello, Joanne. "The community ecology of rabbit (Oryctolagus cuniculus) parasites." Thesis, University of Stirling, 2003. http://hdl.handle.net/1893/25418.

Testo completo

Abstract (sommario):

This thesis investigates aspects of the community ecology of rabbit parasites with particular emphasis upon the gut helminths, utilising a 23 (later extended to 26) year time series of rabbits and their parasites. A clearer understanding of parasite communities can lead to more effective biological control strategies. Rabbits are regarded as a serious pest species throughout Europe and the Antipodes and the use of the myxomatosis virus, as a biological control agent, has already been tried and failed. However, a clearer picture of the parasite community may offer future possibilities for control. Additionally, the rabbit is a good model for other grazing species, as it carries a similar gut helminth community. Drug resistance is an increasing problem in a wide range of parasites. A clearer appreciation of parasite communities could also aid in the search for effective and environmentally sound pathogen control strategies (e.g. via cross immunity or competition with benign species). Theoretical models have revealed the importance of aggregation to the stability of the host parasite relationship, to parasite evolution and to interspecific parasite interactions. A number of models have considered the effect of varying aggregation upon these dynamics with differing outcomes to those where aggregation was a fixed parameter. Here the stability of the distribution for each of the rabbit helminths was examined using Taylor's power law. The analyses revealed that aggregation was not a stable parameter but varied with month, year, host sex, host age, and host myxomatosis status. Evidence for the existence of interspecific parasite interactions in natural systems has been equivocal. Factors influencing parasite intensity were evaluated for the gut helminth. A network of potential interactions between the parasites was revealed. Only month was shown to be of greater influence on the community. Following, from the above analyses, a community model was constructed which incorporated both seasonal forcing and interspecific parasite interactions, with interaction mediated via host immunity. One unexpected emergent property was an interaction between the seasonality and the immune decay rate with slower immune decay resulting in a shift of the immune response out of phase with the species against which it was produced. The model was also used to assess the potential effects of two control strategies, an anticestodal and a single species vaccine. The vaccine had greater effects on the whole community than the anticestodal because of the immune- mediated interactions. The host is also an integral part of the community as the parasite dynamics are linked with that of their host. Therefore an assessment of the parasites' impact upon host condition and fecundity was also undertaken. This revealed a variety of positive and negative associations between the parasites and their host, with potential implications for future host control strategies. This study has shown that ignoring parasite-parasite or parasite-host interactions and interactions of both the host and the parasite with the external environment, could result in a poor description of the community dynamics. Such complexities need to be considered and incorporated into theory if future control strategies for either host or parasites are to be effective.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

STRONA, GIOVANNI. "Investingating the relationships between fish parasites and their hosts: an ecological approach." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/10932.

Testo completo

Abstract (sommario):

Fish parasite assemblages from different areas and environments were examined in search for significant patterns related to parasite host specificity. Ecological niche models were used to test the relevance of ecological factors in the qualitative determination of the parasite species assemblages on host species. The host/parasite cospeciation paradigm was discussed, with the proposal of a theoretical framework aimed to integrate the role of coevolutionary and ecological factors in the determination of parasite host range. Host specificity was investigated through different statistical techniques. A new protocol to assess relative nestedness within a species assemblage was developed. Relative nestedness of parasite taxa was then proposed as a measure of their intrinsic host specificity. Trophic ecology of fish hosts resulted to be a key factor in determining the qualitative composition of parasite assemblages. The fundamental ecological and evolutionary role played by contactability (the reciprocal potentiality of a host and a parasite to come in contact) provided new insights on the traditional theoretical paradigm stating that host range of a parasite species results from the intersection between the set of compatibile host species and that of encountered ones.

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Berry, Katharine M. "The role of parasites in the invasion ecology of Harmonia axyridis." Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/27336.

Testo completo

Abstract (sommario):

The success of an invasive alien species is often attributed to the ecological advantage gained from natural enemy release. Numerous factors have been suggested as contributing to the success of Harmonia axyridis as an invasive alien species, including enemy release. This thesis studied the interactions of several parasites with H. axyridis, investigating parasite transmission, growth and virulence as well as host immune responses, thereby shedding light on the potential role of enemy release in the invasion biology of this ladybird. Benefits gained by invasive alien species from enemy release diminish if parasites of native species shift hosts to exploit the novel invader. The fungal ectoparasite Hesperomyces virescens began infecting H. axyridis shortly after it invaded the UK, probably as a result of a host shift from Adalia bipunctata. This study found a rapid increase in H. virescens prevalence over three years in London H. axyridis populations. Laboratory study showed H. virescens transmission and growth to be more efficient on A. bipunctata than the novel host. In addition, reciprocal interspecific transfers of H. virescens strains isolated from A. bipunctata and H. axyridis revealed that the infection characteristics of the fungi from these two hosts differed, suggesting strains may have diverged after the initial shift from A. bipunctata to better exploit the host from which they were derived. Laboulbenialian fungi were previously thought to have negligible impacts on host fitness. A detailed examination of H. virescens infecting H. axyridis found distinct virulence, with infections resulting in a 50% reduction in host lifespan. In addition, chronic H. virescens infection in males caused acceleration in the age-associated decline in body condition while for females, infection triggered fecundity senescence and a faster age-related decline in fertility. While their role in accelerating ageing is debated, the results presented here provide evidence that infectious diseases can drive the ageing process in this insect species. In nature, multiple parasites affecting a single host are common. The effect of co-infection on the virulence caused by two fungal infections was characterised using H. axyridis and A. bipunctata hosts. The ability of two ladybird species to defend against an acute fungal parasite, while infected with the relatively avirulent H. virescens was found to be sex-specific. While for females, the presence of co-infection did not alter the virulence seen in singly infected females, a higher mortality rate existed for co-infected males compared with those infected singly. Previously, H. virescens has been considered to be avirulent, however, this study provides evidence that this chronic fungal parasite may be important when considering the mortality associated with co-infections in the field. The invasive success of H. axyridis has, in part, been attributed to a more vigorous immune ability compared with other competitor species. Previously, field studies have shown that the prevalence of the parasitoid wasp Dinocampus coccinellae in H. axyridis is considerably lower than in the UK primary host of this wasp, Coccinella septempunctata. The extent to which the prevalence asymmetry in the field is driven by differences in host encapsulation response was tested by first comparing the encapsulation ability of C. septempunctata and H. axyridis directed against an artificial implant. Following this, the encapsulation response of D. coccinellae parasitized individuals was assessed and compared between the two host species. While encapsulation ability did not differ between the host species, and D. coccinellae did not affect the immune response of H. axyridis, wasp parasitism did alter the encapsulation ability of C. septempunctata, although it was inconsistent across sexes and populations. Overall, this thesis furthers our understanding of the fungal parasite H. virescens and its association with the notorious invader H. axyridis. The research presented here also demonstrates the use of H. axyridis as a model system in areas other than invasion ecology and furthermore, contributes to understanding the role of infectious disease in the rate of ageing. Finally, sex-specific effects were found across the chapters of this thesis, demonstrating the use of H. axyridis in the study of sex-specific effects of infections.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Tseng, Michelle. "Virulence ecology and evolution in a mosquito and its protozoan parasite." [Bloomington, Ind.] : Indiana University, 2005. http://wwwlib.umi.com/dissertations/fullcit/3204298.

Testo completo

Abstract (sommario):

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2005. Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0059. Adviser: Curtis Lively. "Title from dissertation home page (viewed Feb. 21, 2007)."

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Hutchence, Katherine Jane. "The evolutionary ecology of host-parasite interactions between drosophila and spiroplasma." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548770.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Brickle, Paul. "The parasite ecology of the Patagonian toothfish (Dissostichus eleginoides Smitt, 1898)." Thesis, University of Aberdeen, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425070.

Testo completo

Abstract (sommario):

In this study the parasites of the Patagonian toothfish were examined from the Patagonian Shelf and the Southern Ocean. The study presents a catalogue and reviews the parasites recovered. Only 21.6% of the parasite fauna is specific to D. eleginoides and it is infected with many generalist species which infect some of the fish on which it preys upon and are likely to be directly transferred from predator to prey, this feature appears to be characteristic of predatory fish species. On the Patagonian Shelf a total of 27 parasite taxa were recorded and this diverse fauna was comparable to other predatory fish within the area. In this area a number of parasites exhibited significant correlations with host size and showed significant changes in prevalence with depth and season. In the Antarctic a total of 32 parasite taxa were recovered. It became clear that the parasite fauna became less diverse the further east you moved from the Falkland Islands around the Antarctic. The potential for using parasites as tools for examining the stock structure of D. eleginoides around Patagonian Shelf and the Antarctic was examined. The study employed the multivariate cluster and linear discriminant function analyses on the parasite communities of D. eleginoides from the different study areas examined. It is concluded that the analyses of the parasites fauna in the Southern Ocean could provide fisheries management with a powerful tool to study the discreteness of stocks and to follow host movements.

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Ferreira, Susana Carolina Martins. "Parasite ecology in spotted hyena in Serengeti National Park in Tanzania." Master's thesis, Universidade de Lisboa. Faculdade de Medicina Veterinária, 2015. http://hdl.handle.net/10400.5/10191.

Testo completo

Abstract (sommario):

Dissertação de Mestrado Integrado em Medicina Veterinária Allostatic load is the energetic cost required to maintain homeostasis. A significant increase in allostatic load which cannot be fulfilled by increased food intake would be expected to result in resource allocation trade-offs, i.e., reduced allocation of resources to one life-process so that allocation of resources to another, more critical process can be maintained. In young animals, maintenance of growth is essential, and when food intake is insufficient, other life processes such as components of the immune system may be down regulated, leading to increased susceptibility to infections. This study aimed to investigate the impact of allostatic load, indicated by faecal glucocorticoid metabolite concentrations (fGCM), on the susceptibility to parasite infections as a result of resource allocation trade-offs, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. Therefore, I measured the allostatic load using a cortisol-3-CMO enzyme immunoassay verified for this species (Benhaiem et al., 2012) and assessed the parasite burden using faecal egg counts (FEC) of the three most abundant parasite species (Ancylostoma, Spirometra and Cystoisospora) with the expectation that FECs would increase with allostatic load. In general, the results indicated that juvenile spotted hyenas have an overall high prevalence of gastrointestinal parasites (98%, n = 104), with a mean of 3.1± 1.6 parasite genera per juvenile. The genus Ancylostoma, Cystoisospora, Spirometra, Trichuris, Dipylidium and parasites from the family Taeniidae and Spirurida were found. The fGCM concentration ranged between 4.9 and 503.2 ng/g with a mean of 55.8 ± 72.4 ng/g. I demonstrated that fGCM concentrations were significantly correlated to FECs of Ancylostoma spp., Spirometra sp. and Cystoisospora spp. in relation to fGCM (Spearman’s rank correlation test, ρ=0.371, p<0.001, ρ=0.272, p<0.05, ρ=0.287, p<0.01 respectively). In addition, I investigated the factors modulating infection intensity of Ancylostoma spp. and revealed that age and co-infecting interactions are key factors of infection intensity. Furthermore, a preliminary phylogenetic analysis of the coccidian parasites from several carnivores living in the Serengeti National Park is provided, indicating that several coccidian are present in the carnivores living in the Serengeti ecosystem. This study provides important information on the mechanisms shaping parasite infections in a free-ranging carnivore. RESUMO - Ecologia dos parasitas da hiena malhada do Parque Nacional do Serengeti na Tanzânia - A carga alostática refere-se ao desgaste associado aos mecanismos que mantêm a homeostase. Quando há um aumento significantivo da carga alostática que não seja compensado por um aumento de recursos disponíveis, é espectável que haja alocação de recursos de um sistema fisiológico para outro, para que processos críticos possam ser mantidos. Em juvenis, o crescimento é essêncial e quando há uma diminuição de recursos disponíveis, outros processos, como componentes do sistema imunitário, podem diminuir a sua atividade para que o crescimento seja mantido, consequentemente aumentando a suscetibilidade a infeções. Este estudo tem como objectivo avaliar o impacto da carga alostática, por intermédio da mensuração de metabolitos de glucocorticóides fecais (fGCM) na susceptibilidade a infeções parasitárias como resultado de “trade-offs” na alocação de recursos, em juvenis de hienas malhadas (Crocuta crocuta) do Parque Nacional do Serengeti, Tanzânia. Para a medição da carga alostática foi aplicado um teste imunoenzimático, cortisol-3-CMO, verificado para esta espécie (Benhaiem et al., 2012). A carga parasitária de hienas malhadas juvenis (<24 meses) é acedida através de contagens fecais de formas parasitárias (FEC) das espécies mais abundantes (Ancylostoma, Spirometra and Cystoisospora) com a expectativa que FEC aumente com a carca alostática. Os resultados indicam uma prevalência elevada de parasitas gastrointestinais (98%, n = 104), com uma média de 3.1± 1.6 géneros de parasitas por juvenil. Foram encontrados os géneros Cystoisospora, Spirometra, Trichuris, Dipylidium e as famílias Taeniidae e Spirurida. A concentração de fGCM varia entre 4.9 e 503.2 ng/g com uma média de 55.8 ± 72.4 ng/g. Foi demonstrada uma correlação significativa entre FEC de Ancylostoma spp., Spirometra sp. e Cystoisospora spp. com fGCM (teste de correlação de Spearman, ρ=0.371, p<0.001, ρ=0.272, p<0.05, ρ=0.287, p<0.01 respetivamente). Adicionalmente foram analisados possíveis fatores que influenciam a intensidade de infeção com Ancylostoma spp. e foi demonstrado que a idade e interações entre parasitas presentes são fatores chave na intensidade de infeção. Ademais foi feita uma análise filogenética preliminar dos coccidias presentes em vários carnívoros que co-habitam no Parque Nacional do Serengeti, revelando vários coccidias presentes no ecosistema. Este estudo providência informações relevantes dos mecanismos que modulam infeções num carnívoro de vida livre. Financial support was provided by the Leibniz Institute for Zoo and Wildlife Research

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Blunt, Sarah Jane. "The ecology of Polymyxa betae, a fungal root parasite of Beta vulgaris." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316297.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Nie, Pin. "Ecology of the Helminth parasites of the eel Anguilla anguilla in Devon." Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253542.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Smar, Matt. "The ecology of Protocalliphora (Diptera:Calliphoridae) parasitism of two cavity nesting passerine birds in southwestern Québec." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22806.

Testo completo

Abstract (sommario):

The ecology of Protocalliphora parasitism was studied for a two-year period in two species of cavity nesting passerine birds breeding in southwestern Quebec, the eastern bluebird (Sialia sialis Linnaeus) and the tree swallow (Tachycineta bicolor Vieillot). Both species occupied next boxes in open field habitats. Nests were parasitized primarily by Protocalliphora sialia Shannon and Dobroscky. The relationship between the number of Protocalliphora larvae per nest and selected nesting variables was examine for the two species. The variables included hatching date of the host young, nest material volume, number of fledglings, and percent canopy cover above the nest box. In bluebirds, the number of larvae per nest was significantly correlated with nest material volume in 1989 and number of fledglings in 1990. In tree swallows, the number of larvae per nest was significantly correlated with hatching date and number of fledglings in 1989. Information on reproduction in Protocalliphora was obtained. Gravid flies were captured in active nests up to the last end of the second week of the nestling period. P. sialia was determined to be at last bivoltine through mark, release, and recapture studies. It was determine that nulliparous P. sialia can complete egg development within 9 or 10 days after eclosion. The practicality of a new Protocalliphora trapping technique and a mark, release, and recapture technique was demonstrated. (Abstract shortened by UMI.)

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Barker, Elizabeth Rachel. "Growth and carbon relations of the tomato-Orobanche aegyptiaca host-parasite association." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265912.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Vogwill, Tom. "The ecology and evolution of host-parasite interactions in spatially structured populations." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533910.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Ferguson, Heather M. "The ecology and evolutionary implications of malaria parasite virulence in mosquito vectors." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/14838.

Testo completo

Abstract (sommario):

A laboratory study with the rodent malaria parasite P. chabaudi and A. stephensi vector indicated that mosquito morality varied with parasite genotype, infection diversity and nutrient availability. In standard conditions, mixed clone infections were the most lethal, but when glucose water was limited, mortality was highest in mosquitoes infected with CR. A second experiment showed that under standard conditions, mixed infections also had the greatest impact on vector fecundity. The virulence of mixed infections could not be explained by parasite load, nor their rate of resource uptake by parasites within the mosquitoes. During the parasite development period, infected mosquitoes had the same amount of three key physiological resources (lipids, glycogen, proteins), as those that were uninfected. Furthermore, mosquitoes infected with the most virulent parasite genotypes had an increased abundance of glucose relative to the controls. This is consistent with Plasmodium manipulating mosquito sugar-feeding behaviour in order to increase its own transmission. Several laboratory studies of malaria parasites and some field observations suggest that Plasmodium virulence in vertebrates is positively correlated with transmission to mosquitoes. A final experiment was undertaken to test whether the transmission advantage of infections that are virulent to vertebrates could be offset by an increased probability of causing death to their vectors. Mice were infected with one of seven distinct genetic clones of P. chabaudi that are known to vary in virulence. Infection virulence in mice (weight loss and anaemia) was positively correlated with mosquito infection rate but not with mosquito survival. Vector survival was influenced only by parasite clone and oocyst burden (negative association). These results suggest that vector fitness should not place an upper limit on malaria virulence. Overall, this research demonstrates that Plasmodium can be virulent to its vector, and that the magnitude of virulence is dependent on parasite genotype, infection diversity and environmental conditions. Although P. chabaudi virulence in vectors was not correlated with virulence in vertebrates, parasite genetic differences do impact vector fitness. Thus differential vector mortality could play an important role in determining the genetic composition of Plasmodium populations.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Dunlop, Judy. "The ecology and host parasite dynamics of a fauna translocation in Australia." Thesis, Dunlop, Judy (2015) The ecology and host parasite dynamics of a fauna translocation in Australia. PhD thesis, Murdoch University, 2015. https://researchrepository.murdoch.edu.au/id/eprint/29146/.

Testo completo

Abstract (sommario):

Despite the frequency of fauna translocations as a technique to improve the conservation status of threatened species, new populations frequently fail to establish. Translocations often lack experimental manipulation to determine ‘best practice’ methods to improve success. One poorly understood element of translocation science is the impact of parasites and disease-‐causing pathogens on the animals moved and the ecosystem they are moved into. Of 58 published Australian translocations in the last 40 years, only 20 (35%) employed any level of parasite management, despite potential contribution of disease to initial fauna declines. I closely investigated a translocation of boodies (Bettongia lesueur) from Barrow Island and Dryandra to Lorna Glen, and ‘island dwarf’ golden bandicoots (Isoodon auratus) from Barrow Island to Lorna Glen and Hermite Island. Bandicoots born into the new populations showed an increased skeletal size and body mass (males) and reproductive output in the number and average size of young (females). These changes occurred within 18 months of release, suggesting that responses were due to phenotypic plasticity, rather than selective pressure occurring over many generations. I conclude that the small size of bandicoots on Barrow Island is a response to resource limitation, rather than true island dwarfism. I determined the impact on parasite load and survivorship of translocated animals by treating half the population with a topical antiparasitic. Despite frequent trapping (six-‐ weekly) and very high recapture rate (64–99%), repeated dosage did not significantly impact ectoparasite or haemoparasite infection, or survival of the marsupials. I observed transmission of parasites between animals of different origin and to offspring, and a decline in species diversity present in the translocated population due to the failure of some species to persist. This thesis identified knowledge gaps in the translocation literature and addressed some key concepts of species ecology, population dynamics and parasitology via post-translocation monitoring.

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Seibert, Sara Rose. "Host-parasite interactions: comparative analyses of population genomics, disease-associated genomic regions, and host use." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1590585260282244.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Coon, Courtney A. c. "Host-Parasite Interactions in an Invasive Songbird." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5004.

Testo completo

Abstract (sommario):

Introduced species are the greatest threat to biodiversity after habitat loss. Understanding the processes that permit organisms to become successful invaders may provide opportunities to prevent or limit their dispersal and establishment and thereby alleviate some of their harmful effects. The goal of my dissertation research has been to investigate whether invasive species have distinctive interactions with parasites, and some of the mechanisms that may underlie that variation. I used one of the world's most successful vertebrate invaders as a case study: the house sparrow (Passer domesticus; Introduction). Previous research in the house sparrow suggested that loss of parasite diversity may contribute to invasion success. However, my work demonstrates that infection with common avian malaria parasites is primarily a function of environmental heterogeneity and is not a predictor of time since introduction for house sparrows that are currently expanding their range in Kenya (Chapter 1). Interestingly, in spite of a large proportion of the population being infected with avian malaria, a state that should reduce competitive ability of house sparrow populations, this species is still able to establish themselves among native competitors. Though there are a number of potential mechanisms that could explain this pattern, one of the most convincing explanations is that house sparrows, and perhaps other introduced species, have adaptive differences in immunity. As such, the findings of Chapter 1 inspired two studies in which my collaborators and I showed that house sparrows from two non-native populations seem capable of maintaining normal health, performance and behavior during immune challenge, a response often referred to as parasite tolerance. Specifically, in Chapter 2, we found that when Floridian house sparrows, established since ~1870, were challenged with synthetic pathogens that mimicked infection with a fungi, an RNA virus or Gram-negative bacteria, only individuals challenged by the synthetic bacteria showed measurable sickness behaviors and secretion of an inflammatory protein. In Chapter 3, we compared parasite tolerance in Kenyan house sparrows (introduced in ~2000) and a native congener, the grey-headed sparrow (P. griseus) to a common intestinal parasite of songbirds. We found that both species were tolerant in that they were able to maintain fat reserves, protein reserves and vertical flight ability during infection. However, house sparrows maintained burdens that were, on average, more than 10x those of grey-headed sparrows. Moreover, when examining nutrient allocation in the two species, house sparrows appeared to assimilate nutrients more efficiently than grey-headed sparrows and did not change how nutrients were allocated among immune and reproductive organs during experimental infection. Grey-headed sparrows, however, did shift nutrient allocation among immune and reproductive organs during experimental infection. Together, the larger nutrient pool and maintenance of nutrient allocation patterns in challenged house sparrows suggests that no physiological trade-offs occurred and that house sparrows experienced a lower cost of parasite exposure. In the fourth Chapter, I explored why house sparrows had such high coccidia burdens in comparison to their congeners. We suspected burden was a function of the frequency of exposure to coccidia. Consequently, we explored heterogeneity in foraging preferences and other behaviors in Floridian house sparrows and their role in coccidia burden. As expected, we found that house sparrows did not avoid contaminated food. In fact, they ate contaminated and uncontaminated foods indiscriminately. What was surprising was a lack of correlation between burden and consumption of contaminated foods and all of the behaviors we monitored (i.e., aggression, activity, feeding rates and defecation frequency). Overall, these data suggest that house sparrows do not benefit from typical parasite-avoidance behaviors. In sum, this dissertation research implies that house sparrows respond to parasite infection differently than many other known vertebrates, most likely in an effort to maximize efficient use of resources and, in so doing, augment competitive ability and invasion success.

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Chandler, Mark. "The evolutionary ecology of parasitism in relation to recombination in a neotropical community of anurans." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39826.

Testo completo

Abstract (sommario):

The rate of recombination and parasite load of species of anuran from Peruvian Amazonia were examined to test the idea that recombination functions to diversify progeny in order to resist the continual counter-adaptation of parasites. The anurans were found to be hosts to over 32 species of macroparasite, as well as a wide variety of protistan and moneran parasites. It was found that a combination of three variables (diet, habitat, abundance), together with host body size accounted for a substantial proportion of the variation in mean parasite richness and parasite species distribution among host species. The relationship between parasites and ecology was found to be independent of host phylogeny. The demonstration of substantial environmental heterogeneity in parasitization predicates that a positive relationship between parasite richness and recombination should be found in this case. This prediction was supported by the data: highly parasitized species of anuran had higher rates of recombination. This is the first study to demonstrate a direct positive relationship between recombination (rather than sex) and parasites.

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Leung, Tommy Ling Fong, and n/a. "Interspecific and intraspecific interactions of trematodes parasitising the New Zealand cockle Austrovenus stutchburyi." University of Otago. Department of Zoology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20090105.160127.

Testo completo

Abstract (sommario):

Most organisms are rarely infected with just a single species of parasite and are usually simultaneously infected with a range of species. Thus, the parasite fauna of a host represents an entire community composed of multiple individuals from many different species. In nature, it is within the host that parasites can encounter conspecifics and individuals from other species. As in any ecosystem, while such interactions between parasites can be antagonistic due to competition or conflicting interests, association between different species can also be beneficial. In this thesis, I investigated patterns of associations between parasites in the New Zealand cockle Austrovenus stutchburyi through a combination of descriptive and experimental studies employing both standard ecological field techniques and molecular biology methods. It was found that the presence and infection intensity of various parasites species are not independent of each other. Among cockles, an association was found between two trematode taxa, i.e. between the infection intensity by foot-encysting echinostomes and the metacercariae of Gymnophallus sp. It was also found that the presence of the parasitic copepod Pseudomyicola spinosus was associated with greater infection intensity by the echinostomes but not Gymnophallus sp. While it was postulated that the positive association between the echinostomes and Gymnophallus sp. was due to the latter�s preference to infect cockles that are stranded on the sediment surface as a result of heavy echinostome metacercariae burden in their foot, a field experiment found that Gymnophallus cercariae did not preferentially infect cockles that have been forced to remain above the sediment surface as opposed to those that were forced to remain buried. Meanwhile, the two species of echinostomes known to encyst in the cockle�s foot, Acanthoparyphium sp. and Curtuteria australis, were found to represent cryptic species complexes. The presence of such cryptic species means that it is possible that some potential interspecific interactions are overlooked. A study of the population structure of Gymnophallus sp. found that each cockle contains multiple genetically distinct individuals and that clonal individuals rarely co-occur in the same cockle. This adds to the growing body of evidence suggesting that in addition to acting as a means of reaching the definitive host, the second intermediate host also acts to promote genetic diversity by accumulating cercariae shed by multiple first intermediate hosts in the environment. An experimental infection study conducted with Curtuteria australis cercariae deriving from singly-infected first intermediate hosts revealed that different clonal lineages varied with respect to their contribution to host manipulation. It was found that while certain lineages have a preference for host manipulation, others tend to adopt a "hitch-hiker"-type life history strategy. However, this genetic predisposition was also found to be a phenotypically plastic trait, as the presence of a higher number of manipulators seems to encourage newly-arrived cercariae to become manipulators, regardless of clonal lineage. This thesis provides evidence that patterns of interactions can affect various aspects of parasite life history. Apart from host condition, parasites can also be affected by other parasites. Studying the dynamics of mixed infections can provide informative insights for evolutionary and ecological research.

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Magee, Catherine Anne. "Host-parasite interactions : the ecology and neurobiology of helminth infections in Apodemus sylvaticus (L.)." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359113.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Northover, Amy Susan. "The ecology of parasite transmission during fauna translocations: Observations from the woylie (Bettongia penicillata)." Thesis, Northover, Amy Susan (2019) The ecology of parasite transmission during fauna translocations: Observations from the woylie (Bettongia penicillata). PhD thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/45922/.

Testo completo

Abstract (sommario):

Fauna translocations play a pivotal role in the management of threatened wildlife, though we are limited by our understanding of how the host-parasite community changes during translocation and in response to antiparasitic drug treatment. This project aimed to quantify changes in parasite community structure and host health in woylies following translocation, and in response to ivermectin treatment. This is the first study to evaluate changes to the broader parasite community in translocated and resident animals following translocation. During two fauna translocations to three different locations within south-western Australia, woylies were sampled for blood-borne, ecto- and gastrointestinal parasites, and morphometrics were measured. Prior to translocation, half of the translocated woylies were treated with ivermectin. Post-translocation monitoring was undertaken for up to 12 months following translocation. Destination site and time since translocation had the strongest effect on parasite dynamics and host health following translocation. Significant changes to the parasite community occurred within the first few months after translocation, and the parasite communities of translocated and resident woylies generally converged to become more similar over time, with failure of some parasite taxa to persist and new host-parasite associations emerging. Trypanosoma spp. richness and the prevalence of haemoparasite coinfection increased after translocation. Ivermectin treatment did not significantly reduce the prevalence/abundance of target parasites, or improve body condition in treated hosts. In translocated woylies, the presence of coccidia during the first three months following translocation, and increasing Strongyloides-like egg counts were associated with lower body condition. Results from this study highlight the importance of long-term parasite monitoring to better understand the biological implications (for individuals, populations and ecosystems) of wildlife translocations on host-parasite ecology. Insights gained from this study are broadly applicable to the management of threatened fauna and their parasite taxa, and enhance our fundamental understanding of the potential ecosystem impacts of wildlife translocations.

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Koskella, Britt L. "An examination of host-parasite coevolution and negative frequency-dependent selection in a snail-trematode system." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3331252.

Testo completo

Abstract (sommario):

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2008. Title from PDF t.p. (viewed on Jul 27, 2009). Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6617. Adviser: Curt M. Lively.

Gli stili APA, Harvard, Vancouver, ISO e altri

34

McLeish, Jenny. "Non-native bullhead in Scotland : molecular and morphological identification and parasite links with native fauna." Thesis, Edinburgh Napier University, 2018. http://researchrepository.napier.ac.uk/Output/1253308.

Testo completo

Abstract (sommario):

The arrival of a non-native species to has the potential to shape native communities by influencing ecological interactions such as predation, foraging, competition and disease transfer. A designation of invasive is applied to an introduced non-native species that has the potential to threaten the continued wellbeing of a native species, pose a risk to human health or negatively impact the economy. The European bullhead (Cottus perifretum) is a freshwater benthic-dwelling fish that is native to England but considered invasive in Scotland. The species was first reported in Scotland in the 1950's and thriving populations are now established in the waters of the Clyde, Forth and Tweed catchments. Bullhead presence is thought to negatively impact native stone loach (Barbatula barbatula) and brown trout (Salmo trutta) parr, due to shared preferences for habitat and prey resources. They are also thought to prey upon the eggs of native Atlantic salmon (Salmo salar) and brown trout, two species that are of high commercial value in Scotland. In other areas of introduction, bullheads have been found to increase parasite infection rates in native fishes. The species therefore has the capacity to incite competition and alter parasite/host interactions in areas of introduction, to the potential detriment of native fauna and the Scottish economy. The European bullhead has been the subject of considerable taxonomic scrutiny in recent years, resulting in its reclassification as a species complex. What was once considered a single species with a distribution encompassing Europe, Russia, Asia and Scandinavia, has been shown to consist of at least 15 distinct species. Genetic examination of bullheads from England confirmed the presence of Cottus perifretum, not Cottus gobio as traditionally listed in all UK literature and legislation. Native English bullhead is currently protected under Annex II of the European Commission Habitats Directive 92/43/EEC, based on the historic assumption that the species present is C. gobio. Analysis of the taxonomic identity of Scottish bullheads has remained outstanding. In this study the invasive status of bullhead was explored by examining feeding and parasitological interactions between bullheads and native freshwater communities in south-east Scotland. An assessment of the feeding preferences of native brown trout and stone loach in the presence and absence of bullheads tested competition for prey resources. Parasitological interactions were investigated by examining the shared parasite fauna of bullheads and native fish and invertebrate species. Bullheads from the Clyde and Forth catchments were analysed to provide a molecular and morphological description of this introduced species. Phylogenetic analysis of COX1 sequences obtained from Scottish bullheads, and a pair-wise distance calculation based on a Kimura 2-parameter model, showed that samples clustered in a distinct clade with English C. perifretum. Significant intraspecific variation was reported in all morphological features examined, but pooled data also revealed a resemblance to the published description provided for C. perifretum. Scottish bullhead is therefore confirmed to be an introduced pocket of the native English species, which is considered under threat in some areas due to habitat modifications and population decline. Comparisons between the dietary compositions of bullheads, brown trout and stone loach showed that the prey selection of brown trout and stone loach varied in the sample locations that contained co-occuring bullheads, when compared to locations where bullheads were absent. However, no direct evidence of trophic competition between bullheads and either brown trout or stone loach was reported. An examination of parasitological interactions recovered eight parasite species from four distinct taxonomic groups in total, of which four species (Echinorhynchus truttae, Apatemon gracilis, Diplostomum volvens and Raphidascaris acus) were shared between bullheads and one or more native fishes. Echinorhynchus truttae was also shared with gammarid crustaceans. Bullhead presence was found to coincide with D. volvens infections in European minnow (Phoxinus phoxinus) and a reduced prevalence of E. truttae in brown trout. Diplostomum volvens was only reported from minnow found in sites with bullheads, strongly suggesting bullheads were responsible for introducing this parasite to native minnows. Bullheads functioned as an alternative host for E. truttae, diluting brown trout parasite loads and reducing overall infection rates in sites where bullhead and brown trout co-exist. The findings reported for both feeding preference and parasite burdens in the presence and absence of bullheads suggest that bullheads do have some effect on the ecology of native species, but these are considered minimal and unlikely to impact the long-term survival of native species. Eradication of Scottish bullhead may contradict the conservation effort that is currently in place. Given the current lack of evidence to validate bullhead's invasive qualities and the recent confirmation of its genetic lineage, revisiting the designation of the bullhead as invasive is warranted. Active eradication should be treated with caution until a significant negative impact can be proven.

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Muzaffar, Sabir Bin. "Ectoparasites of auks (Alcidae) at the Gannet Islands, Labrador, diversity, ecology and host-parasite interactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0015/MQ55531.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Shaw, Jennifer Lyn. "Epidemiology of the caecal threadworm Trichostrongylus tenuis in red grouse (Lagopus lagopus scoticus Lath.)." Thesis, University of Aberdeen, 1988. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU010263.

Testo completo

Abstract (sommario):

The prevalence of Trichostrongylus tenuis in red grouse was high and the distribution of parasites in their hosts highly aggregated. The prevalence and intensity of threadworms were greater in old birds than in young ones. There was no relationship between the body condition of individual grouse and their burden of adult worms. On the moor, T. tenuis eggs did not develop to third-stage infective larvae during the winter. In the summer, when development did occur, yields of third-stage larvae were dependent on temperature. Third-stage larvae moved laterally through the heather but were relatively short-lived and very few survived over winter. The proportion of larvae, ingested by captive grouse, which developed to adult worms varied with season and between individuals. Red grouse acquired little or no effective immunity to reinfection after challenge with infective larvae. Consequently, caecal threadworms produced a chronic infection in grouse: mature worms survived for over two years with very little mortality. Parasite fecundity decreased as the worms aged but not with intensity of infection. Third-stage larvae ingested by wild red grouse in the autumn were found to go into arrested development over the winter, resuming their development in the spring. Captive grouse with parasite burdens were later in starting to lay in spring and laid fewer eggs at a slower rate than uninfected hens. However developing larvae had greater effects than adult worms on egg production. Effects of developing larvae included inappetence and a reduced gain in body weight prior to laying. Consequently, overwintering larvae developing simultaneously in spring may reduce the breeding success of wild red grouse. This observation may also explain why outbreaks of trichostrongylosis are usually found in spring and summer. The transmission of T. tenuis is presumably influenced mainly by the density of infective larvae, which in turn was affected by weather, particularly temperature. A major regulatory constraint on this parasite is host mortality. Mortality, however, is unlikely to be linearly related to parasite intensity because developing larvae were more pathogenic than adult worms. Furthermore, there seemed to be no important intensity-dependent processes acting to regulate T. tenuis in red grouse populations. On the moor, T. tenuis eggs did not develop to third-stage infective larvae during the winter. In the summer, when development did occur, yields of third-stage larvae were dependent on temperature. Third-stage larvae moved laterally through the heather but were relatively short-lived and very few survived over winter. The proportion of larvae, ingested by captive grouse, which developed to adult worms varied with season and between individuals. Red grouse acquired little or no effective immunity to reinfection after challenge with infective larvae. Consequently, caecal threadworms produced a chronic infection in grouse: mature worms survived for over two years with very little mortality. Parasite fecundity decreased as the worms aged but not with intensity of infection. Third-stage larvae ingested by wild red grouse in the autumn were found to go into arrested development over the winter, resuming their development in the spring. Captive grouse with parasite burdens were later in starting to lay in spring and laid fewer eggs at a slower rate than uninfected hens. However developing larvae had greater effects than adult worms on egg production. Effects of developing larvae included inappetence and a reduced gain in body weight prior to laying. Consequently, overwintering larvae developing simultaneously in spring may reduce the breeding success of wild red grouse. This observation may also explain why outbreaks of trichostrongylosis are usually found in spring and summer. The transmission of T. tenuis is presumably influenced mainly by the density of infective larvae, which in turn was affected.

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Bouillon, Daniel Richard. "Ecology of the Arctic charr (Salvelinus alpinus) in northern Labrador with reference to their parasite faunas." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63309.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Allen, Geoffrey Rowland. "Behaviour and ecology of the primary parasitoids Cotesia urabae and Dolichogenidia eucalypti (Hymenoptera: Braconidae) and their host Uraba lugens (Lepidoptera: Noctuidae)." Title page, contents and preface only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09pha425.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Kosciuch, Karl L. "Host-parasite interactions on an experimental landscape." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/186.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Garnier, Romain. "Ecologie évolutive de la transmission maternelle d'anticorps." Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0045/document.

Testo completo

Abstract (sommario):

Chez les vertébrés, la réponse immunitaire acquise représente un mécanisme sophistiqué de réponse face aux parasites dont l‟une des particularités est la possibilité qu‟il offre aux mères de transférer certains de ses effecteurs à leurs nouveau-nés. Pourtant, malgré un intérêt croissant pour les effets maternels, les déterminants écologiques et évolutifs du transfert d‟anticorps maternels n‟ont pas encore été beaucoup étudiés. L‟analyse d‟un cadre théorique spécialement développé pour inclure le transfert transgénérationnel d‟immunité montre que l‟évolution de la capacité à transférer une immunité temporaire aux jeunes dépend des caractéristiques de l‟hôte et du parasite. En particulier, l‟augmentation de l‟espérance de vie de l‟hôte favorise l‟évolution de réponses immunitaires acquises, et la protection conférée par ces réponses est aussi supposée durer plus longtemps chez les hôtes longévifs. En accord avec cette prédiction, une étude de vaccination transgénérationnelle chez une espèce d‟oiseau de mer longévive a permis de mettre en évidence une demi-vie des anticorps maternels particulièrement longue. Les conditions sociales sont aussi un élément clé, et chez une espèce de mammifère, j‟ai pu montrer qu‟elles permettent un élargissement du répertoire d‟anticorps maternels. Le transfert d‟anticorps maternels est aussi à même de modifier les dynamiques épidémiologiques et pourrait présenter un atout non négligeable si la vaccination était utilisée en conservation. Enfin, ce mécanisme pourrait être mis à profit pour estimer l‟exposition des mères, et ainsi inférer la dispersion entre différentes zones d‟habitat In vertebrate species, acquired immune response represents a sophisticated protection mechanism against parasites that has the particularity of enabling mothers to transmit part of its effectors to their newborns. Yet, despite an increasing interest in maternal effects, ecological and evolutionary determinants of the transfer of maternal antibodies remain poorly studied. The analysis of a theoretical framework specially developed to include a transgenerational transfer of immunity show that the evolution of an ability to temporarily protect offspring depends on the characteristics of both the host and the parasite. In particular, increasing the life span of the host favors the evolution of acquired immune responses and increases the duration of the protection offered by these mechanisms. Accordingly, a transgenerational vaccination study in a long-lived seabird revealed a particularly long half-life of maternal antibodies. Social conditions also proved important in a mammal species as they can allow for the broadening of the repertoire covered by maternal antibodies. The transfer of maternal antibodies could also modify epidemiological dynamics and could bbe an interesting asset if vaccination was used as a conservation tool. Finally, this mechanism could be used to estimate the exposure of mother and thus infer the dispersal rate between different habitat patches

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Cecile, Anna Sarabian. "Exploring the origins of disgust: Evolution of parasite avoidance behaviors in primates." Kyoto University, 2019. http://hdl.handle.net/2433/242653.

Testo completo

Abstract (sommario):

付記する学位プログラム名: 霊長類学・ワイルドライフサイエンス・リーディング大学院 Kyoto University (京都大学) 0048 新制・課程博士 博士(理学) 甲第21615号 理博第4522号 新制||理||1649(附属図書館) 京都大学大学院理学研究科生物科学専攻 (主査)准教授 Andrew MacIntosh, 教授古市剛史, 教授髙井正成 学位規則第4条第1項該当

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Schneider, Lea Dominique. "Conservation ecology of the thick-shelled river mussel Unio crassus : The importance of parasite-host interactions." Doctoral thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-47636.

Testo completo

Abstract (sommario):

Unionoid mussels are globally threatened and their conservation requires species-specific knowledge on their ecology and parasite-host interaction. Unio crassus is one of Europe’s most threatened unionoid species and has a temporary obligate parasitic life stage (glochidia) on fish. A lack of suitable hosts is probably a major limitation for mussel recruitment, but host species composition, suitability and availability in time and space have yet to be fully explored. This thesis examines different aspects of the host fish species, including their composition, suitability and ecological importance, in relation to U. crassus, using both field and laboratory studies. The effects of mussel and host density on mussel reproductive potential were considered, as were aspects of evolutionary adaptations between mussels and fish and how climate change may affect their interaction. The results show that U. crassus is a host generalist, parasitizing a variety of fish species. Host suitability and density, which varied among fish species and rivers, affected the level of glochidia encapsulation, hence mussel reproductive potential, more so than the density of mussels taking part in reproduction. Ecologically important hosts included both highly suitable primary hosts, and less suitable hosts that were highly abundant. Whether or not U. crassus has specific adaptations to its hosts to enhance juvenile transformation remains unclear. No distinct pattern of local adaptation was found, nor was there an effect of host fish presence on the timing of glochidia release by adult mussels. Instead, temperature played a major role, with results suggesting that changes in spring water temperature regimes can cause temporal and spatial mismatches in the mussel-host interaction. This thesis indicates that investigations of local mussel-host interactions help in identifying mechanisms important for unionoid conservation management and prioritization. Många sötvattenmusslor har en komplex livscykel där larverna (glochidier) under sin utveckling till frilevande musslor parasiterar på gälarna hos lämpliga värdfiskar. Flera av våra musslor, såsom den tjockskaliga målarmusslan (Unio crassus), är globalt hotade och för att kunna bevara och förvalta dessa arter på bästa sätt behöver vi lära oss mer om deras ekologi och samspelet mellan musslan och dess värdfiskar. Avsaknaden av värdfiskar innebär förmodligen en stor begränsning för rekryteringen av juvenila musslor, men det finns trots detta en begränsad kunskap om hur artsammansättningen i fisksamhället och dess tillgänglighet påverkar musselpopulationer. Min avhandling undersöker olika aspekter av interaktioner mellan U. crassus och dess värdfiskar, som hur värdfisksamhällen och fiskarters värdlämplighet påverkar musslans reproduktionspotential. Jag har även studerat hur tätheter av olika fiskarter och vuxna musslor påverkar rekryteringen, eventuella evolutionära anpassningar samt om en förhöjd temperatur skulle kunna påverka interaktionen mellan U. crassus och dess värdfiskar. Resultaten visar att U. crassus är en generalist som parasiterar på en mängd olika fiskarter. Jag fann dock en stor variation i dominerande fiskarter och lämpliga värdar mellan olika åar, vilket påverkade reproduktionspotentialen hos musslorna mer än vad tätheten vuxna musslor som deltog i reproduktionen gjorde. Som ekologiskt viktiga värdar fanns således både särskilt lämpliga, primära värdarter, men också mindre lämpliga arter som förekom i höga tätheter. Ingen tydlig lokal anpassning kunde observeras, och fiskens närvaro påverkade inte tidpunkten för när de vuxna musslorna släppte sina glochidielarver. Däremot fann jag att temperaturen spelade en viktig roll för musslans reproduktion, där ökad temperatur föreslås ha negativa effekter på interaktionen mellan musslan och dess värdfiskar. Avhandlingen visar på vikten av att studera interaktioner mellan den tjockskaliga målarmusslan och dess värdar på lokal skala för att bättre kunna identifiera och prioritera viktiga naturvårdsåtgärder. UnioCrassusforLIFE (European LIFE+ project: LIFE10 NAT/SE/000046)

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Watson, Harold. "The ecology and pathology of Trichostrongylus tenuis (Nematoda), a parasite of red grouse (Lagopus lagopus scoticus)." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/9171/.

Testo completo

Abstract (sommario):

Trichostrongylus tenuis is a nematode that lives in the caeca of wild red grouse. It causes disease in red grouse and can cause fluctuations in grouse pop ulations. The aim of the work described in this thesis was to study aspects of the ecology of the infective-stage larvae of T.tenuis, and also certain aspects of the pathology and immunology of red grouse and chickens infected with this nematode. The survival of the infective-stage larvae of T.tenuis was found to decrease as temperature increased, at temperatures between 0-30 C? and larvae were susceptible to freezing and desiccation. The lipid reserves of the infective-stage larvae declined as temperature increased and this decline was correlated to a decline in infectivity in the domestic chicken. The occurrence of infective-stage larvae on heather tips at caecal dropping sites was monitored on a moor; most larvae were found during the summer months but very few larvae were recovered in the winter. The number of larvae recovered from the heather showed a good correlation with the actual worm burdens recorded in young grouse when related to food intake. Examination of the heather leaflets by scanning electron microscopy showed that each leaflet consists of a leaf roll and the infective-stage larvae of T.tenuis migrate into the humid microenvironment' provided by these leaf rolls. Scanning electron microscopy showed that the adult nematodes burrowed into the mucosa as well as lying on its surface and that the caecal mucosa of heavily infected grouse became disrupted in areas of nematode activity. The caecal mucosa of lightly infected grouse exhibited little damage and the caecal mucosa of grouse treated with an anthelmintic and shot 5-6 months later was similar to that of lightly infected birds. Some of the nematodes from these treated birds were covered in rosette-shaped cells which have been tentatively identified as adherent lymphocytes. The cuticle of adult T.tenuis was superficially annulated but did not possess cuticular ridges, as described in some other trichostrongyle nematodes. Primary and challenge infections with T.tenuis were established in the domestic chicken and these reached patency but nematodes were expelled in blood-stained balls of mucus and all adult nematodes had been expelled from the birds 30 days after dosing with infective-stage. Following trickle doses of larvae, there was a rise and then a fall in nematode egg output but larvae administered later in the trickle infection appeared to fail to establish. Light and scanning electron microscopy showed haemorrhagic lesions and blood spots on the caecal mucosa of infected chickens and nematodes were found to burrow beneath mucus secreted on the mucosal surface. There were significant increases in the proportions of circulating leucocytes in infected chickens, but only on certain days of infection. No antibodies to T.tenuis were detected in the blood of infected chickens. There was a decrease in the length of the caeca of infected chickens during the period when the Ill nematodes were being expelled from the caeca. Nematode egg output continued to rise during an infection in young red grouse and there was no expulsion of nematodes from these infected birds. Infective-stage larvae that had been attenuated by cobalt 60 irradiation stimulated some degree of resistance to challenge infection in the domestic chicken but not in the red grouse. It was concluded that immunization with irradiated larvae would be of little use in the control of T.tenuis in red grouse.

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Rasch, Jennifer A. "Reproductive Ecology and Sexual Biology of the Seagrass Shrimp Ambidexter symmetricus (Caridea| Processidae) and its Isopod Parasite Urobopyrus processae (Bopyroidea| Bopyridae)." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002449.

Testo completo

Abstract (sommario):

The purpose of the current study was to analyze the reproductive ecology and sexual system in Ambidexter symmetricus, a nxocturnal seagrass shrimp and its parasite Urobopyrus processae. (Abstract shortened by UMI.)

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Simpson, Lunden A. "Carcinonemertes conanobrieni| A Nemertean Parasite Infecting the Caribbean Spiny Lobster, Panulirus argus| Species Description, Host-Use, and Effect on Host Reproductive Health." Thesis, Clemson University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10816034.

Testo completo

Abstract (sommario):

Marine ecosystems are one of the world’s most heavily used and valuable natural systems. However, over the past decades, they have seen changes in the oceans’ pH, temperature, salinity, and other abiotic factors - all of which appear to have impacted the health of these systems, and there seems to be a global trend indicating that diseases in marine environments are emerging at an increased rate. Infection by a disease can result in a variety of negative effects on the health of a host, all of which are especially relevant in instances where commercially important hosts are infected. Disease can lead to changes in growth, longevity, reproduction, embryo survival, and marketability of a host. One ecologically and commercially important species that appears to have been impacted by this trend of increased disease emergence is the Caribbean spiny lobster, Panulirus argus. Panulirus argus plays host to a number of previously described and newly emergent pathogens. However, here, a new species of nemertean worm belonging to the genus Carcinonemertes is described from egg masses of P. argus from the Florida Keys, Florida, USA. Though P. argus ranges throughout the Caribbean, this worm has thus far only been observed infecting gravid female lobsters in the Florida Keys. This is the first species of Carcinonemertes reported to infect P. argus or any other lobster species in the greater Caribbean and western Atlantic Ocean. To determine the host use, infection prevalence, and infection intensity of this new parasite on P. argus , male, non-gravid female, and gravid female lobsters were captured along the Florida Key reef tract from and examined for infection. Furthermore, infected gravid females were also used in estimating the impact that infection by this nemertean had on three levels of reproductive performance (reproductive output, fecundity, and brood mortality).

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Vieira, Vivian Suane de Freitas. "Metazo?rios parasitos de Pimelodus spp. e estrutura da comunidade parasit?ria de Pimelodus maculatus (Siluriformes: Pimelodidae) coletados em duas bacias hidrogr?ficas do Brasil." Universidade Federal Rural do Rio de Janeiro, 2016. https://tede.ufrrj.br/jspui/handle/jspui/1199.

Testo completo

Abstract (sommario):

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-09-14T11:46:46Z No. of bitstreams: 1 2011 - Vivian Suane de Freitas Vieira.pdf: 2001045 bytes, checksum: 2cce4947186746927e3f6cc35826b411 (MD5) Made available in DSpace on 2016-09-14T11:46:46Z (GMT). No. of bitstreams: 1 2011 - Vivian Suane de Freitas Vieira.pdf: 2001045 bytes, checksum: 2cce4947186746927e3f6cc35826b411 (MD5) Previous issue date: 2016-01-20 Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES A list of metazoan species associated to Pimelodus Lac?p?de, 1803 genus has been prepared in this work. The total of 516 records in 10 host species of genus was compiled. Were included in the list of new geographic records monogeneans parasites of Pimelodus maculatus Lac?p?de, 1803 collected from Midwest, Southeast and South of Brazil. New morphological data of Cucullanus pinnai pinnai Travassos, Artigas & Pereira, 1928, parasite of P. maculatus collected in the Guandu river, in the State of Rio de Janeiro have been reported. This work noted that the position of the excretory pore and deirids of the specimens are at the level or posterior to the oesophagus- intestine junction in the most specimens and gubernaculums size is greater than in other previously studied of C. pinnai pinnai. Nematodes were studied using light and scanning electron microscopy (SEM) and differential interference contrast (DIC) and analyzes confirmed morphological details of the cephalic region and the caudal papillae that species. Comparative study of parasitic communities of P. maculatus was also performed. 50 specimens of the P. maculatus were collected from Guandu river, in the State of Rio de Janeiro and others 50 from Mogi-Gua?? river, State of S?o Paulo. In the samples from Guandu river were identified the following species: Ameloblastella paranaensis Fran?a, Isaac, Pavanelli & Takemoto, 2003 (P= 8%; MI= 1,0?0,0); A. satoi Monteiro, Kritsky, Brasil-Sato, 2010 (P= 8%; MI= 1,0?0,0); Demidospermus bidiverticulatum Suriano & Incorvaia, 1995 (P= 8%; MI= 1,0?0,0); D. paravalenciennesi Guti?rrez & Suriano, 1992 (P=90%; MI=14,77?5,04), D. uncusvalidus Guti?rrez & Suriano, 1992 (P=90%; MI=12,37?4,86), D. valenciennesi Guti?rrez & Suriano, 1992 (P=56%; MI=6,06?3,95) e Cucullanus pinnai pinnai Travassos, Artigas & Pereira, 1928 (P=64%; MI=3,28?4,87). In the rio Mogi-Gua?? the parasites identified were: Ameloblastella paranaensis (P= 8%; MI= 1,0?0,0), Ameloblastella satoi (P= 8%; MI= 1,0?0,0), Demidospermus paravalenciennesi (P=86%; MI=18,58?10,79), D. uncusvalidus (P=84%; MI=16,73?7,74), D. valenciennesi (P=52%; IM=6,84?4,55) e Cucullanus pinnai pinnai (P= 44%; MI= 3,88?4,87). The females of P. maculatus had higher weight and length of males in both samples. The sex and o length of the hosts did not influence the level of parasitism. Positive correlation was observed between weight of host and abundance of D. uncusvalidus only in the sample of the Guandu river. Aggregate distribution was observed in all the prevalent species of metazoan parasites of P. maculatus in the two localities. D. paravalenciennesi showed a higher frequency of dominance and relative dominance in the samples of Guandu river and D. uncusvalidus in the samples of Mogi-Gua?? river. The results of the qualitative similarity index Jaccard (CJ) and quantitative Sorensen (CS) within the collected samples were homogenea. The Jaccard index indicated heterogeneity while Sorensen index indicated homogeneity between samples. The results demonstrated that the relationship between parasites and their hosts are constant even in different river basins. Uma lista de esp?cies de metazo?rios associados ao g?nero Pimelodus Lac?p?de, 1803 foi elaborada neste trabalho. O total de 516 registros em 10 esp?cies de hospedeiros do g?nero foi compilado. Foram inclu?dos na lista novos registros de geogr?ficos de parasitos monogen?ticos de Pimelodus maculatus Lac?p?de, 1803 coletados nas regi?es Centro-oeste, Sudeste e Sul do Brasil. Novos dados morfol?gicos de Cucullanus pinnai pinnai Travassos, Artigas & Pereira, 1928, parasito de P. maculatus coletado no rio Guandu, no Estado do Rio de Janeiro foram relatados. Foi observado que a posi??o do poro excretor e deir?deos nos esp?cimes estudados s?o posteriores ao final do es?fago na maioria dos esp?cimes e o tamanho do gubern?culo ? maior do que em outros de C. pinnai pinnai estudados anteriormente. Os nematoides foram estudados utilizando microscopia eletr?nica de varredura (MEV) e contraste interferencial de fase (DIC) e as an?lises confirmaram detalhes morfol?gicos da regi?o cef?lica e as papilas caudais dessa esp?cie. Estudo comparativo das comunidades parasit?rias de P. maculatus tamb?m foi realizado. Foram coletados 50 esp?cimes de P. maculatus no rio Guandu, no Estado do Rio de Janeiro e outros 50 exemplares no rio Mogi-Gua??, no Estado de S?o Paulo, foram examinados para o estudo de sua parasitofauna, no per?odo de maio ? dezembro de 2012. No rio Guandu foram coletadas as seguintes esp?cies: Ameloblastella paranaensis Fran?a, Isaac, Pavanelli & Takemoto, 2003 (P= 8%; IM= 1,0?0,0); A. satoi Monteiro, Kritsky, Brasil-Sato, 2010 (P= 8%; IM= 1,0?0,0); Demidospermus bidiverticulatum Suriano & Incorvaia, 1995 (P= 8%; IM= 1,0?0,0); D. paravalenciennesi Guti?rrez & Suriano, 1992 (P=90%; IM=14,77?5,04), D. uncusvalidus Guti?rrez & Suriano, 1992 (P=90%; IM=12,37?4,86), D. valenciennesi Guti?rrez & Suriano, 1992 (P=56%; IM=6,06?3,95) e Cucullanus pinnai pinnai Travassos, Artigas & Pereira, 1928 (P=64%; IM=3,28?4,87). No rio Mogi-Gua?? os parasitos identificados foram: Ameloblastella paranaensis (P= 8%; IM= 1,0?0,0), Ameloblastella satoi (P= 8%; IM= 1,0?0,0), Demidospermus paravalenciennesi (P=86%; IM=18,58?10,79), D. uncusvalidus (P=84%; IM=16,73?7,74), D. valenciennesi (P=52%; IM=6,84?4,55) e Cucullanus pinnai pinnai (P= 44; IM= 3,88?4,87). As f?meas de P. maculatus apresentaram peso e comprimento maiores que dos machos nas duas amostras. O sexo e o comprimento dos hospedeiros n?o influenciaram o n?vel de parasitismo. Correla??o positiva foi observada entre o peso e a abund?ncia de D. uncusvalidus somente na amostra do rio Guandu. Foi observada distribui??o agregada de todas as esp?cies mais prevalentes de metazo?rios parasitos de P. maculatus nas duas bacias de coleta. D. paravalenciennesi apresentou maior freq??ncia de domin?ncia e domin?ncia relativa no rio Guandu e D. uncusvalidus no rio Mogi-Gua??. Os resultados dos ?ndices de similaridade qualitativa de Jaccard (CJ) e quantitativa de Sorensen (CS) dentro das amostras coletadas demonstraram homogeneidade. O ?ndice Jaccard indicou heterogeneidade e o ?ndice de Sorensen indicou homogeneidade entre as amostras. Os resultados demonstram que o relacionamento entre parasitos e seus hospedeiros s?o constantes, mesmo em diferentes bacias hidrogr?ficas.

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Zemmer, Sally A. "Trematode Communities of the Appalachian Stream Snail, Elimia proxima: the Importance of Scale in Parasite Ecology Research." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82832.

Testo completo

Abstract (sommario):

Understanding the ecological processes that impact parasite abundance and distribution is critically important for epidemiology and predicting how infectious disease dynamics may respond to future disturbance. Digenean trematodes (Platyhelminthes: Trematoda) are parasitic flatworms with complex, multi-host life cycles that include snail first-intermediate hosts and vertebrate definitive hosts. Trematodes cause numerous diseases of humans (e.g. schistosomiasis) and livestock (e.g. fascioliasis), and impact the ecology of wildlife systems. Identifying the ecological mechanisms that regulate these complex, multi-host interactions will advance both our understanding of parasitism and the dynamics of infectious disease. By examining patterns of infection in Elimia (= Oxytrema = Goniobasis) proxima snails, my dissertation research investigated the environmental factors and ecological processes that structure trematode communities in streams. First, I examined temporal variation in trematode infection of snails in five headwater streams. Over a three year period, I found no consistent seasonal patterns of trematode infection. There was consistency across sites in trematode prevalence, as sites with high prevalence at the beginning of the study tended to remain sites of high infection, relative to lower prevalence sites. Second, I examined landscape level variation in trematode infection by characterizing the regional distribution, abundance and diversity of E. proxima infections in 20 headwater streams. I found a broad scale spatial pattern in trematode communities due to regional turnover in dominant species. This pattern was correlated with elevation, but there were no significant relationships with other environmental variables. Additionally, molecular characterization of trematodes indicated the presence of cryptic (morphologically indistinguishable) species complexes within this system, and variation in genetic diversity among trematode types may reflect differences in host dispersal abilities. Third, I examined trematode infection within a single stream network across multiple headwaters and the mainstem. I found a decreasing downstream gradient of trematode prevalence related to several environmental variables including elevation, snail density, conductivity, and stream depth. Additionally, headwater communities were nested subsets of the communities found in the mainstem. By combining approaches at different temporal and spatial scales, my dissertation research increases our understanding of the processes that impact the abundance and distribution of parasites. Ph. D.

Gli stili APA, Harvard, Vancouver, ISO e altri

48

Skelton, James. "Towards an understanding of symbiont natural history through studies of crayfish and their annelid associates." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51663.

Testo completo

Abstract (sommario):

Crayfish throughout North America, Europe, and Asia host assemblages of obligate ectosymbiotic annelid worms called branchiobdellidans. The work presented here is a detailed experimental and observational study of the ecological interactions between crayfish and their worms. In a comprehensive literature review, I show that branchiobdellidans have complex and context-dependent effects on their hosts, serving as both beneficial cleaners and tissue-consuming parasites. Using a field survey and laboratory experiments, I provide novel evidence for age-specific resistance as an adaptation to maximize life-long benefits of a mutualism. Specifically, I show that Cambarus crayfish display a consistent ontogenetic shift in resistance to the colonization of branchiobdellidans and this shift likely reflects underlying changes in the costs and benefits of symbiosis. I then show that this change in host resistance creates predictable patterns of symbiont diversity and composition throughout host ontogeny. Host resistance limits within-host symbiont communities to a few weakly interacting species, whereas relaxed resistance leads to more diverse symbiont communities that have strong interactions among symbiont taxa. Thus, host resistance has direct effects on within-host symbiont community structure by selectively filtering colonizing species, and indirect effects by moderating the strength of interactions among symbionts. Lastly, in a detailed study of the worm Cambarincola ingens, I depict a symbiont dispersal strategy that yields highly predictable transmission dynamics during pairwise host-host encounters and shows that variation in transmission dynamics can be explained by the fitness outcomes for dispersing symbionts. Field observations revealed that worm reproduction is contingent on host size and intraspecific competition for preferred microhabitats. Using a predictive model that assumes transmission of symbionts only when current conditions yield fitness below a minimum threshold, I was able to predict individual transmission events much more accurately than a comparable null model that assumed a fixed probability of transmission. My work provides empirical support for the emerging trend among researchers that advocates the adaptation of general ecological frameworks to understand symbiont population structure and diversity, but my work also emphasizes the value of detailed natural history studies to uncover system-specific ecological and co-evolutionary processes such as partner control mechanisms, symbiont microhabitat selections, and symbiont dispersal strategies. Ph. D.

Gli stili APA, Harvard, Vancouver, ISO e altri

49

August, Thomas Adam. "The social structure, ecology and pathogens of bats in the UK." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/4341.

Testo completo

Abstract (sommario):

This thesis examines the ecology, parasites and pathogens of three insectivorous bat species in Wytham Woods, Oxfordshire; Myotis nattereri (Natterer’s bat), M. daubentonii (Daubenton’s bat) and Plecotus auritus (Brown long-eared bat). The population structure was assessed by monitoring associations between ringed individuals, utilising recent advances in social network analysis. Populations of both M. daubentonii and M. nattereri were found to subdivide into tight-knit social groups roosting within small areas of a continuous woodland (average minimum roost home range of 0.23km2 and 0.17km2 respectively). If this population structure is a general attribute of these species it may make them more sensitive to small scale habitat change than previously thought and has implications for how diseases may spread through the population. M. daubentonii had a strong preference for roosts close to water, away from woodland edge and in areas with an easterly aspect. The factors driving roost choice in M. nattereri and P. auritus remain elusive. The segregation of M. daubentonii into bachelor and nursery colonies was not a result of the exclusion of males from roosts close to water by females, or variation in microclimate preferences between the sexes, as was predicted. Body condition (weight/forearm length) was correlated with host characteristics including age and reproductive status, and weather variables. Astroviruses and Coronaviruses, which have characteristics typical of zoonotic viruses, were identified in UK bat species for the first time. Coronaviruses identified formed species-specific clades while Astroviruses were highly diverse. Though not closely related to human viruses these are potential zoonotic diseases of the future. Models of Coronavirus and ectoparasite distribution suggest individual attributes (e.g. sex and age) and population structure (e.g. the formation of nursery and bachelor colonies) are important predictors of parasite and pathogen prevalence. This study characterises a system that offers many opportunities for future research including studies of sociality, disease modelling and conservation management.

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Ortega, Nicole. "Flames and Frogs – The Impact of Environmental Disturbances on Host-Parasite Dynamics." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7640.

Testo completo

Abstract (sommario):

The successful completion of this work is dedicated first to my grandparents for having always shown their unwavering love and encouragement in my journeys (most of which they kindly and politely only pretended to understand) and for having also served as life-long role models who upheld an unparalleled work ethic. To many whom I consider to be my chosen family, especially Ann Williams and Brittany Sears, who kept me laughing, but more importantly, kept my crazy train from derailing during these tumultuous years. To Wayne Price and Tom Jackman, who fostered the success of my career and are the epitome of patience and kindness. To DeAngelis, for the many hours of laughter, conversations, and adventuresome treks that further kindled my knowledge, love, and respect for Florida’s ecology. To family in Alabama who have either helped shape my brazen character or made this education possible. To Taego, the one to whom I am bound through so many of the stories that begin with, “Remember when…?” and who is often so kind and thoughtful though he still holds tightly to the stereotype of the selfish youngest sibling. Finally, to Fen for being my smiling, bright blue-eyed, spunky kid who has been on this journey with me from the get-go; for keeping me from getting too big for my britches; for your intrinsic fire that burns for equality, fairness, and friendship; and for inspiring me to be the best example of a mother that I can possibly be.

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Ecology parasite"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili