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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Bioecologia comparada de duas linhagens de Telenomus remus Nixon (Hymenoptera: Platygastridae) parasitando ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) /

Naranjo Guevara, Natalia. January 2013 (has links)
Orientador: Odair Aparecido Fernandes / Banca: Marta Maria Rossi / Banca: Nelson Wanderley Perioto / Resumo: A criação massal em condições de laboratório afeta a atividade e vigor dos parasitoides e,consequentemente, opotential como agentes de controle biológico. No Brasil, Telenomus remus foi introduzido em1986 e obtiveram-se altos níveis de parasitismo sobre Spodoptera frugiperda em testes de laboratório. Entretanto, estes níveis não foram obtidos em condições de campo.Assim, para ampliar abasegenéticadas linhagens e determinar possíveisdiferenças naatividade e vigor, opresente estudo objetivou: (1) realizara introdução deuma nova linhagem de T. remus no Brasil, a partir da Venezuela; (2) comparar a biologia das duas linhagens (uma coletada em culturas de milho e introduzida e outra,criadapor cerca de 600 gerações em laboratório) por meio da avaliaçãode parâmetros reprodutivos etabela de vida de fecundidade; (3) comparar as respostas funcionais; (4) avaliar a qualidade das linhagens utilizando-se a atividadede voo e a emergência como critérios. A espécie foi confirmada por taxonomista e foi confirmadaa sua especificidade porS. frugiperda. As duas linhagens demostraram similaridade genética em padrõesde restrição para asregiões 16S e ITS1, embora a linhagem importada apresentasse qualidadesuperior. Osparâmetros de fecundidadedemostraram que alinhagem introduzida temum potencial de aumento populacional maior e éintrinsecamente mais agressiva. As duas linhagens apresentaram resposta funcional tipo III, comestabilizaçãodo parasitismo apartirde 200 ovosdohospedeiro. Infere-se que a criaçãoem laboratório de T. remus requer cuidados que limitem a perda do potencial para controle biológico. Avaliaçõessubsequentes de qualidade bem como ametodologia atual de criação precisam ser revistas.O presente estudo resultou numimportante aporte para auxiliar na implementação de programas de controle biológico para a lagarta-do-cartucho. / Abstract: Mass rearing in laboratory conditions affects the activity and vigor of parasitoids and consequentlytheir potentialas biological agents. In Brazil, Telenomus remus was introduced in 1986 and high levels of parasitism on Spodoptera frugiperda were obtained in laboratory tests. However, theselevels were notobtained infield conditions. Thus, tobroaden thegeneticbases of laboratorymaintained strains and to determine possible differencesin activity and vigor, this study aimed to:(1) introduce a new strain ofT. remus from Venezuela in Brazil;(2) compare the biology of two strains of T.remus (one collected in maizefields and introduced, and the other, maintained by over 600generations in laboratory conditions) by evaluatingreproductive parameters and fertilitylife tables, (3)compare the functional responses; (4) evaluate thequality ofthestrains using flightacitivity and emergence as criteria. The introduced species was confirmed by a taxonomist and their specificity for S. frugiperda was confirmed.Both strains demonstrated genetic similarity in restriction patterns for the 16S and ITS1 regions, although the imported strain showed superior quality as biological control agent. The fertility parameters showed thattheintroduced strain has a greater potentialfor population increaseand is inherently more aggressive. The two strains exhibited type IIIfunctional response, with stabilization of parasitism at 200 hosteggs. It is inferred that the laboratory rearingof T. remus requires efforts toprevent lossof biological control potential. Further evaluations of quality must be made and the currentmass rearing methodology should bere-designed. This study resulted in an important contribution that could aid the implementation of biological control programs for fall armyworm. / Mestre
32

Helmintofauna associativa à anfíbios da Ilha Anchieta, litoral norte do estado de São Paulo, Brasil /

Aguiar, Aline. January 2013 (has links)
Orientador: Reinaldo José da Silva / Coorientador: Luciano Alves dos Anjos / Banca: Max Rondon Werneck / Banca: Vanda Lucia Ferreira / Resumo: Os anfíbios ocupam grande variedade de microhabitats refletindo os diversos modos reprodutivos, estilos de vida e parasitas que estes animais apresentam. Os parasitas são indicativos de muitos aspectos biológicos de seus hospedeiros, incluindo a dieta, ocupação do habitat e a filogenia, podendo também ser bons indicadores diretos do estado de qualidade ambiental. A Ilha Anchieta, parque estadual em área de Mata Atlântica, torna-se interessante para estudos biológicos devido a sua dinâmica insular e isolamento geográfico. O objetivo deste estudo foi avaliar a fauna de helmintos de 195 anfíbios da Ilha Anchieta representados por 14 espécies, Flectonotus fissilis (n = 18), Haddadus binotatus (n = 9), Ischnocnema bolbodactyla (n = 4), Ischnocnema parva (n = 20), Rhinella ornata (n = 20), Dendrophryniscus brevipollicatus (n = 3), Hypsiboas albomarginatus (n = 18), Scinax hayii (n = 23), Hylodes asper (n = 2), Hylodes phyllodes (n = 3), Leptodactylus cf. marmoratus (n = 42), Leptodactylus latrans (n = 4), Chiasmocleis carvalhoi (n = 26) e Myersiella microps (n = 3). Foram identificadas pelo menos 14 espécies de helmintos entre as comunidades componentes dos anfíbios: 12 espécies de nematóides (Falcaustra mascula, Oxyascaris oxyascaris, Oswaldocruzia sp., Rhabdias sp., Physaloptera sp., Aplectana crucifer, Aplectana pintoi, Aplectana sp., Cosmocerca brasiliense, Cosmocerca parva, Cosmocerca travassosi e Cosmocerca sp.), uma espécie de cestóide (Cylindrotaenia cf. americana) e uma espécie de Acanthocephala (cistacantos). Este estudo apresenta uma revisão dessas espécies de helmintos com seus anfíbios hospedeiros até hoje relatados; a helmintofauna associada a estas espécies hospedeiras; e uma análise de similaridade das infracomunidades de algumas espécies de anfíbios, mostrando que o habitat pode influenciar na composição e abundância da comunidade parasita / Abstract: The amphibians use a variety of microhabitats, relationship with the various reproductive modes, life style and parasites that these animals presented. The parasites are indicatives about a lot of biological aspects of yours hosts, including feeding, use of habitat and phylogeny. They also may be good indicators about status of environmental quality. The Anchieta Island, state park in Atlantic Rain Forest area, is very interesting for biological studies because insular dynamics and geographical isolation. The aim of this study was to evaluate the helminth fauna of 195 amphibians from Anchieta Island representing 14 species, Flectonotus fissilis (n = 18), Haddadus binotatus (n = 9), Ischnocnema bolbodactyla (n = 4), Ischnocnema parva (n = 20), Rhinella ornata (n = 20), Dendrophryniscus brevipollicatus (n = 3), Hypsiboas albomarginatus (n = 18), Scinax hayii (n = 23), Hylodes asper (n = 2), Hylodes phyllodes (n = 3), Leptodactylus cf. marmoratus (n = 42), Leptodactylus latrans (n = 4), Chiasmocleis carvalhoi (n = 26), and Myersiella microps (n = 3). They were necropsied to examine for helminth parasites. We identified at least 14 helminths species in the component communities of anurans: 12 nematodes species (Falcaustra mascula, Oxyascaris oxyascaris, Oswaldocruzia sp., Rhabdias sp., Physaloptera sp., Aplectana crucifer, Aplectana pintoi, Aplectana sp., Cosmocerca brasiliense, Cosmocerca parva, Cosmocerca travassosi, and Cosmocerca sp.), one cestode species (Cylindrotaenia cf. americana), and one species of Acanthocephala (cystacanths). This study presents a revision about these helminth species with the related hosts to date; the helminth fauna associated to these host species; and the similarity about infracommunities of some amphibian species, showing habitat can influence on composition and abundance of parasite community / Mestre
33

Coevolution between Mutualists and Parasites in Symbiotic Communities May Lead to the Evolution of Lower Virulence

Nelson, Paul G., May, Georgiana 12 1900 (has links)
Most eukaryotes harbor a diverse community of parasitic, mutualistic, and commensal microbial symbionts. Although the diversity of these microbial symbiotic communities has recently drawn considerable attention, theory regarding the evolution of interactions among symbionts and with the host is still in its nascent stages. Here we evaluate the role of interactions among coinfecting symbionts in the evolution of symbiont virulence toward the host. To do so, we place the virulence-transmission trade-off into a community context and model the evolution of symbiont trophic modes along the continuum from parasitism (virulence) to mutualism (negative virulence). We establish a framework for studying multiple infections of a host by the same symbiont species and coinfection by multiple species, using a concept of shared costs, wherein the negative consequences of virulence (or harm) toward the host are shared among symbionts. Our results show that mutualism can be maintained under infection by multiple symbionts when shared costs are sufficiently low, while greater virulence and parasitism toward the host are more likely when shared costs are high. Last, for coinfection by more than one species, we show that if the presence of a mutualist ameliorates some of the costs of pathogen virulence, then the symbiotic community may more often evolve to a more commensal state and maintain mutualisms.
34

Nesting aggregation as a Determinant of Brood Parasitism in Mason Bees (Osmia spp.)

Groulx, Adam January 2016 (has links)
Identifying forces that affect population dynamics can allow us to better understand the distribution and abundance of animals. Both top-down and bottom-up factors can significantly influence animal populations. Mason bees (members of the genus Osmia; Hymenoptera: Megachilidae) are important pollinators for agricultural systems and are vulnerable to exploitation by brood parasites, such as kleptoparasitic wasps. High levels of nesting density have the potential to increase rates of brood parasitism by attracting larger numbers of parasites to areas with aggregations of nests. I conducted a field study in subalpine meadows at the Rocky Mountain Biological Laboratory in Colorado, USA, to assess whether mason bees suffer increased brood parasitism as the size of nesting aggregations increases. Mason bees were allowed to nest in artificial nest boxes and establish natural variations in numbers of nesting individuals within nest boxes. Nest cells constructed by bees were then checked for the presence of kleptoparasite larvae shortly after they were completed. Overall, nest cells constructed in blocks containing multiple active bees were significantly more likely to be oviposited in by brood parasites compared to cells constructed in blocks with fewer active nesting bees. This suggests that gathering in large aggregations for nesting can negatively affect populations of mason bees, given the high levels of brood parasitism observed in areas of high nesting density. In addition, the last nest cell in mason bee nests was significantly more likely to be parasitized than inner cells, suggesting bees may be abandoning nests that are parasitized, representing a potential defensive response of bees to brood parasitism. These results have implications for the management of mason bees as agricultural pollinators, as cultivating them in large groups could reduce their survival.
35

A probability problem arising out of an entomological experiment

Reid, David Buchanan William January 1946 (has links)
The female of Spalangia drosophilae, Ashm, attack the puparia of Drosophila melanogaster, laying eggs between the puparial case and the pupa. The procedure is as follows: the parasite makes a careful examination of the puparia, tapping it with its antennae; then it stings the pupa to immobility and lays an egg. In a series of observations carried at the Imperial Institute of Entomology, Canada, using Spalangia as parasite and Drosophila as host, it was noted that the ovipositing female seemed to avoid superparasitism -- that is, laying eggs in already parasitized puparia. Naturally, if the number of non-parasitized insects still available was relatively small, the restraint exercised by the female tended to break down, and several eggs would be laid in some of the hosts. In order to determine the number of times the female Spalangia could exercise restraint before she was compelled to lay an egg, a series of three hundred and sixty separate experiments were performed. These involved the exposure of groups of five, ten and twenty-five Drosophila puparia to different numbers of parasites for various lengths of time, so that considerable variation in the number of eggs laid occurred. The observational results were expressed in terms of the number of puparia containing zero, one, two, etc., eggs. As the probability theory involved in this type of situation does not seem to be available, it is proposed to develop it in such a manner that experimental results may be analyzed to estimate the number of times the parasite could withhold an egg. The aspect of the experimental data which is of primary interest is the number of cases of superparasitism occurring for any given number of eggs laid and hosts exposed. / Master of Science
36

Influences of Climate, Competition, and Novel Hosts on Parasitoids of Emerald Ash Borer, and their Establishment in Virginia, and North Carolina

Ragozzino, Max Louis 02 July 2020 (has links)
Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a species of wood boring beetle which feeds on the inner bark of ash trees, Fraxinus spp., and white fringe tree, Chionanthus virginicus L. In North America emerald ash borer feeding damages the trees vascular system, killing the tree in 1-6 years after initial infestation. Emerald ash borer's native range is north east China, the Russian Far East, and the Korean peninsula. In the mid-1990s emerald ash borer was accidentally introduced to Michigan from the Hebei and Tianjin city province regions of China. Since then, due to human-aided transport and natural spread, emerald ash borer now infests 35 states and five Canadian provinces. Studies in to Asia discovered several species of parasitic wasps which feed and reproduce on emerald ash borer; four of these species were approved for release in the United States. Three species which attack emerald ash borer larvae Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), Spathius agrili Yang (Hymenoptera: Braconidae), and Spathius galinae Belokobylskij and Strazanac (Hymenoptera: Braconidae), and one species which utilizes emerald ash borer eggs, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae). This research focuses on the control of emerald ash borer using the three larvae-utilizing species of parasitic wasp. The first objective of this research focuses on the synchrony of emerald ash borer larvae with the early spring emergence of S. agrili and S. galinae. The first objective also assessed how two different cold temperature treatments changed the emergence timing, and health of the wasps. The second objective assessed to determine the effects of competition between S. agrili and S. galinae when they were exposed to a single emerald ash borer larvae sequentially, and simultaneously. When exposed sequentially, the first wasp held the competitive advantage, but when exposed simultaneously S. agrili had a small advantage, but did not completely exclude S. galinae. The third objective focused on the potential for two larval parasitoids, S. agrili and S. galinae to parasitize emerald ash borer larvae in the novel host plant white fringe tree. We determined that both parasitoids are capable of finding and parasitizing emerald ash borer larvae within a non-ash host. Finally, we located 13 stands of emerald ash borer infested ash in Virginia and North Carolina in order to determine its life cycle, and overwintering life stage. We determined that emerald ash borer overwinters at different life stages, and has a more complex life cycle than previously reported. Additionally, all three species of larvae-utilizing parasitic wasp were recovered at field sites at least 1 year after release. These results all show promise for the biocontrol program, and indicate that biocontrol of emerald ash borer could be successful in Virginia and North Carolina. / Doctor of Philosophy / Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a wood boring beetle which feeds on the inner bark of ash trees, Fraxinus spp., and white fringe tree, Chionanthus virginicus L. In the mid-1990s emerald ash borer was accidentally introduced to Michigan from the Hebei and Tianjin city province regions of China. Since then, due to human-aided transport and natural spread, emerald ash borer now infests urban and natural forests in 35 states and five Canadian provinces. North American ash trees did not evolve with emerad ash borer, and have little resistance to their attack. A North American ash or white fringe tree attacked by emerald ash borer dies in 1-6 years if left untreated. Systemic insecticide treatments exist, but require annual treatment and are less effective than initially hoped. Additionally, systemic insecticides are impractical to apply to forest ecosystems. Researchers traveled to the Asia, and discovered several species of parasitic wasps which attack emerald ash borer. After years of efficacy and host-exclusivity testing four species were released in the United States. Three species which exclusively utilize emerald ash borer larvae Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), Spathius agrili Yang (Hymenoptera: Braconidae), and Spathius galinae Belokobylskij and Strazanac (Hymenoptera: Braconidae), and one species which utilizes emerald ash borer eggs, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae). My research focuses on the control of emerald ash borer using the three larvae-utilizing species of parasitic wasp. Chapter two focuses on the life cycle of emerald ash borer larvae, S. agrili and S. galinae during the early spring. We determined that both parasitoid species have similarly timed life cycles as EAB, indicating a good climate match in Virginia. Chapter three describes the interactions between S. agrili and S. galinae when competing for EAB larvae. We determined that the first species to attack the larvae has the advantage; and when adult wasps competed to find a larvae neither species completely dominated the other. The third objective focused on the potential for two larval parasitoids, S. agrili and S. galinae to parasitize emerald ash borer larvae in the novel host plant white fringe tree. We determined that both parasitoids are capable of finding and parasitizing emerald ash borer larvae within white fringe tree. Finally, we located 13 stands of emerald ash borer-infested ash in Virginia and North Carolina in order to determine its life cycle, and overwintering life stage. We determined that emerald ash borer overwinters at different life stages, and has a more complex life cycle than previously reported. Additionally, all three species of larvae-utilizing parasitic wasp were recovered at field sites at least 1 year after release. These results all show promise for the biocontrol program, and indicate that biocontrol of emerald ash borer could be successful in Virginia and North Carolina.
37

Life History and Secondary Production of Goniobasis proxima (Prosobranchia: Pleuroceridae) from Four Appalachian Headwater Streams in Western North Carolina

Jeremiah, Nicholas G. 30 November 2007 (has links)
I investigated life history traits and secondary production of populations of Goniobasis proxima in four streams from July 2005 to June 2006. Measurements of canopy cover, conductivity, alkalinity, temperature, and nitrate-nitrogen (NO3-N), as well as snail size, density, and occupied substrate were taken monthly for each stream. Snail growth rates were determined in an aquarium for 10 size classes and secondary production was estimated as the summed product of size class growth rates and field biomass measurements. Size class production estimates tracked biomass with intermediate to larger sized snails dominating production, despite smaller snails growing faster. Production estimates across streams ranged from 1,400 mg m-2 yr-1 to 22,183 mg m-2 yr-1 with noticeable summer highs and winter lows. Annual turnover was slow (0.43-0.49) owing to slow growth and long development time. Snails preferred leaves/wood as a substrate to occupy over rock and sand and showed no appreciable grazing effect on the epilithon community. / Master of Science
38

Traces of Predation/Parasitism Recorded in Eocene Brachiopods from the Castle Hayne Limestone, North Carolina, U.S.A.

Schimmel, Majken K. 20 May 2010 (has links)
The Castle Hayne Limestone (Middle Eocene, North Carolina), noted for its diverse macro-invertebrate fossils, was sampled to assess if early Cenozoic brachiopods from eastern North America record any traces of biotic interactions. Systematic surveys of two North Carolina quarries yielded 494 brachiopods, dominated by one species: Plicatoria wilmingtonensis (Lyell and Sowerby, 1845). Despite subtle variations in taphonomy, taxonomy, and drilling patterns, the two sampled quarries are remarkably similar in terms of quantitative and qualitative paleoecological and taphonomic patterns. Ninety-two brachiopod shells (18.6% specimens) contained a single circular hole. Majority of drillholes were singular, perpendicular to shell surface, and drilled from the outside. In addition, ventral valves were drilled slightly more frequently than dorsal ones and larger brachiopods contained more drillholes than smaller ones. However, the size of drillholes did not correlate with the size of brachiopods. The drillholes record "live-live" biotic interactions, which may represent either predatory attacks or parasitic infestations or combination of those two types of interactions. A notable fraction of specimens bears multiple drillholes, which is consistent with either parasitic nature of interactions or frequent failed predatory events. Drilling frequency was high in both quarries (24.5%); this high frequency reinforces other recent reports (from other continents and Cenozoic epochs) that drilling organisms may be a frequent predator or parasite of brachiopod prey or hosts. The number of case studies reporting high frequencies of drilling in brachiopods is still limited and thus insufficient to draw reliable generalizations regarding the causes and consequences of these occasionally intense ecological interactions. / Master of Science
39

Brood parasitism by shiny cowbirds

Gloag, Rosalyn Suzanne January 2012 (has links)
Brood parasitic birds lay eggs amongst the clutches of other species, which then assume all costs of parental care on their behalf. This thesis addresses several puzzles of avian brood parasitism, using field studies and theoretical modelling of the generalist parasite, the shiny cowbird (Molothrus bonariensis) and select hosts in Argentina. Key findings and conclusions were: • High parasitism intensity in a host population can result in a cost to hosts of removing parasite eggs from their clutches, and so help to maintain host’s acceptance of parasite eggs in evolutionary equilibrium. The cost is to host egg survival: hosts that remove parasite eggs from the clutch increase the risk that their eggs are destroyed by subsequent parasites that visit the nest. • The principal benefit of mobbing as a front-line defence of hosts may be to reduce egg loss due to parasite attack, rather than prevent parasitism itself. • Differences in the acoustic structure of begging calls between parasites and their host’s young can be to the parasite’s advantage. Parents provisioned unparasitized broods more during broadcast at the nest of shiny cowbird calls than calls of their own species’ chicks, in both a common host and a non-host. The long tremulous quality of a cowbird’s call functions analogously to a rapid call rate, thereby exploiting a common provisioning rule of avian parents. • A trade-off for maximum growth in parasite nestlings will variously favour or not favour the evolution of nestmate-killing behaviour, depending on a parasite’s abilities, relative to host young, to solicit and attain provisions from host parents. Generalist parasites can encounter both sides of the trade-off in different hosts. Meanwhile, indirect fitness costs are unlikely to constrain the evolution of nestmate-killing in shiny cowbirds, as they rarely, if ever, share the nest with siblings.
40

The Role of the Dosage Compensation Complex as a Pathway for Spiroplasma to Induce Male Lethality in Drosophila melanogaster

Cheng, Becky 01 January 2017 (has links)
Drosophila melanogaster and many other insects harbor intracellular bacterial symbionts that are transmitted vertically from infected host mothers to their offspring. Many of these bacteria alter host reproductive developmental processes in order to increase their transmission success. For example, Spiroplasma, a spirochete that naturally infects D. melanogaster, selectively kills males during mid-embryogenesis while sparing females. Previous studies suggested that Spiroplasma interacts genetically with the male-specific dosage compensation pathway, which causes ~2-fold up-regulation of most genes located on the male’s single X chromosome so that their expression matches the levels found in females who have two Xs. To further test this idea, I used confocal microscopy to visualize dosage compensation complex (DCC) localization and activity in infected as well as uninfected embryos. In the presence of Spiroplasma, the DCC became abnormally mis-localized across the nucleus. This pattern was accompanied by abnormal acetylation of histone H4K16, a mark induced by DCC activity and needed for proper X chromatin remodeling. My results imply that Spiroplasma directly targets the DCC by misdirecting it to uncompensated regions of the genome, an effect that leads to abnormal gene mis-regulation and consequent lethality (work from other members in our group). To further investigate this interaction, we transgenically expressed low levels of MSL-2 in both Spiroplasma infected and uninfected embryos in order to cause ectopic formation of the DCC in the female sex. I found that when infected, female embryos expressing the DCC showed significantly reduced viability in comparison to uninfected transgenic females. This result supports the notion that Spiroplasma uses the DCC in a dominant gain-of-function manner to kill embryos.

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