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1
Kruitbos, Laura Marina. "Influence of habitat on the behaviour of entomopathogenic nematodes." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25963.
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2
Valadas, Vera Mónica Piegas. "Genetic diversity of entomopathogenic nematodes (Nematoda: Steinernematidae and Heterorhabditidae) and the nematode Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) from continental Portugal." Doctoral thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/15718.
Full textAbstract:
“Diversidade genética dos nemátodes entomopatogénicos
(Nematoda: Steinernematidae e Heterorhabditidae) e do
nemátode Bursaphelenchus xylophilus (Nematoda:
Aphelenchoididade) em Portugal continental”
Os nematodes entomopatogénicos são utilizados como agentes de controlo
biológico. Para compreender a sua diversidade, foi realizada uma prospecção
em Portugal. Cinco espécies, nomeadamente Steinernema feltiae, S.
intermedium, S. kraussei, Steinernema sp. e Heterorhabditis bacteriophora
foram identificadas. As sequências de ITS, região D2D3 do 28S rRNA, COXI e
cytb foram utilizadas para estudar a diversidade genética das duas espécies
mais abundantes, S. feltiae and H. bacteriophora, não tendo sido encontradas
diferenças significativas entre isolados.
O nemátode da madeira do pinheiro, Bursaphelenchus xylophilus, provoca
doença nos pinheiros tendo sido detectada pela primeira vez na Europa e em
Portugal em 1999. Para avaliar a diversidade genética dos isolados
Portugueses e identificar o padrão de propagação da doença, foram utilizadas
a sequência da região IGS do 5.8S rRNA, e os genes cytb e cellulase,
combinados com os padrões ISSR. Os padrões de ISSR mostraram elevada
diversidade genética entre os recentes isolados Portugueses, sugerindo a
possibilidade de uma nova introdução. As árvores filogenéticas dos genes da
celulase e cytb sugeriram uma origem Asiática para os isolados Portugueses; ABSTRACT: Entomopathogenic nematodes are used as biocontrol agents. To understand
their diversity, a survey was undertaken in Portugal. Five species, namely
Steinernema feltiae, S. intermedium, S. kraussei, Steinernema sp. and
Heterorhabditis bacteriophora were identified. The ITS, 28S rRNA D2D3 region,
COXI and cytb sequences, used to study the genetic diversity of the two most
abundant species, S. feltiae and H. bacteriophora, showed no significant
differences among the isolates.
Bursaphelenchus xylophilus causes severe disease in pine trees and was
detected for the first time in Europe and in Portugal in 1999. To evaluate the
genetic diversity of Portuguese isolates and identify disease spread pathways,
the sequence of 5.8S rRNA IGS region, cytb and cellulase genes, combined
with ISSR fingerprints were used. ISSR fingerprints show a high genetic
variability among recent Portuguese isolates, suggesting the possibility of a new
introduction. Phylogenetic trees based on cellulase and cytb genes suggests an
Asian origin for Portuguese isolates.
3
Briar, Shabeg Singh. "Nematodes as bioindicators of soil food web health in agroecosystems a critical analysis /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173284523.
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4
Zervos, S. "Population regulation of thelastomatid nematodes (Nematoda: Thelastomatidae) of cockroaches." Thesis, University of Canterbury. Zoology, 1986. http://hdl.handle.net/10092/4791.
Full textAbstract:
Populations of thelastomatid nematodes in cockroach hosts were
investigated.
The population biology, life history, habits. distribution, and
gross morphology of cockroaches involved are discussed.
New species of thelastomatid nematodes from cockroaches are
described and keys to species of Protrellus and Blatticola are given.
Evidence for population regulation in six species of
thelastomatids in eight species of cockroaches collected from the field
is presented. No host contained two adult males, infrapopulations with
two juvenile males were very rare, the number of adult females per host
was small. and monogamy was common. Juvenile males were rare while
juvenile females were relatively common, indicating that, compared to
females, males develop and are eliminated rapidly from hosts (leaving
one), or that males are less common to start with. Infection prevalence
varied markedly between the cockroach species.
Reproductive competition due to crowding, and cyclical egg
production were found in two species.
these phenomena are discussed.
Mechanisms which may control
The effects of density-independent climatic factors on seasonal
variation in incidence and infrapopulation structure of one thelastomatid
population were transient.
Evidence for population self-regulation in Protrellus dixoni
was obtained from laboratory studies. Infrapopulations were regulated
by a density-dependent and sex-dependent reduction in infection intensity
with infrapopulation age. This reduction was not equal in initial speed
or intensity between the sexes (reduction in number of males was faster)
and led to infrapopulations with never more than a single adult male. and
few adult females. In structure. these laboratory-produced infrapopulations
resembled those in field collected hosts.
Unmated females produced male progeny only (probably by
arrhenotokous parthenogenesis). Female offspring probably result
from amphimixis.
Possible methods of thelastomatid infrapopulation regulation are
discussed. It is concluded that regulation is parasite-mediated and due
to chemical interference competition. Regulation benefits the surviving
nematodes because per capita fecundity is greater in uncrowded infrapopulations.
Self-regulation may be common among thelastomatids and
other parasites.
5
Cho, Hyun-Bae. "Molecular characterization and phylogenetics of entomopathogenic nematodes (nematoda: stienernematidae) from Asia." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192304.
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6
Paiva, Sílvia Rodrigues de. "O efeito da remoção da palha de cana-de-açúcar na população de nematoides do solo e raiz em duas situações edafoclimáticas distintas." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-09032017-094823/.
Full textAbstract:
Os nematoides causadores de doenças em cana-de-açúcar ocasionam graves problemas no rendimento desta cultura. Os gêneros mais agressivos são Meloidogyne e Pratylenchus que formam galhas e necroses nas raízes, respectivamente. A retirada da palha de cana-de-açúcar do campo para produção de etanol de segunda geração pode resultar em mudanças no comportamento das comunidades de nematoides. Assim o objetivo deste trabalho foi quantificar a abundância de nematoides em diferentes quantidades de palha presentes na superfície do solo. O experimento foi conduzido em Capivari - SP na unidade Bom Retiro (BR) e em Valparaíso - SP na unidade Univalem (UV). O tipo de solo de cada área experimental era, respectivamente, Latossolo Vermelho distrófico típico (textura média na camada superficial) e Argissolo Vermelho-Amarelo distrófico típico (textura arenosa na camada superficial). O delineamento foi o de blocos ao acaso com seis tratamentos e quatro repetições, compostos por quantidades de palha em Mg ha-1 de massa de matéria seca, sendo em BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), e em UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). As amostragens de solo e raiz coletadas na profundidade de 0-20 cm na linha e entrelinha da cultura foram realizadas em BR em maio e em UV em junho, ambas em 2015. Pratylenchus zeae teve maior dominância nas áreas, seguido de nematoides de vida livre, e Helicotylenchus sp. e Meloidogyne javanica apenas foi observada na área de solo arenoso e em médias densidades. O manejo de remoção da palha de cana-de-açúcar não promoveu mudanças significativas nas abundâncias das comunidades contidas no solo, tanto de textura média quanto arenosa. Por outro lado, houve interferência das quantidades de palha na infecção pelos nematoides nas raízes, no solo de textura média 4,2 Mg ha-1 de palha diminuiu a comunidade de nematoides e no solo de textura arenosa a maior comunidade de nematoides foi em 13,2 Mg ha-1 de palha. Todavia, múltiplos fatores podem ter afetado esses resultados, não apenas o manejo de remoção da palha. São necessários mais estudos em longo prazo para se afirmar o real efeito da retirada de palha do campoThe nematodes that cause diseases in sugarcane represent serious yield problems. The most aggressive genera are Meloidogyne and Pratylenchus that form gall and necrosis in the roots, respectively. Sugarcane straw removal from the field for second generation ethanol production may change the behavior of nematode communities. Thus the objective of this study was to quantify nematode abundance in different quantities of sugarcane straw left on soil surface. The experiment was conducted in Capivari - SP at Bom Retiro (BR) mill and Valparaíso - SP at Univalem (UV) mill. The soil type of each experimental area was, respectively, Oxisol (medium texture in the surface layer) and Alfisol (sandy texture in the surface layer). The experimental design was a randomized block with six treatments and four replicates, composed of quantities of straw in Mg ha-1 of dry matter mass, where in BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), and in UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). Soil and root samples were collected at 0-20 cm depths in the row and inter-row position of the sugarcane crop in BR in May and UV in June, both in 2015. Pratylenchus zeae had greater dominance in both evaluated areas, followed by free-living nematodes, and Helicotylenchus sp., Meloidogyne javanica was only observed in the sandy soil area and in medium densities. Due to the high densities it would be necessary to control nematodes in the areas. In terms of communities abundance in the soil there was no difference in relation to the treatments in the two areas. However, there was interference of the straw in the nematodes infection in the roots, and this result cannot be inferred by the straw deposition. Additional long-term studies are needed to understanding the effect of straw removal from the field on nematode community
7
Shrestha, Roshi. "A physiological and genetic mapping study of tolerance to root-knot nematode in rice." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=24807.
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8
McVeigh, P. "Neuropeptide signalling in nematodes." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411747.
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9
Storey, N. "Immunity to filarial nematodes." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356035.
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10
Sutherland, Ian Alexander. "Anthelmintic resistance in nematodes." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329191.
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11
Banton, Matthew Camille. "Dehydration stress in nematodes." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608461.
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12
Farr, C. R. "Treatment of Rootknot Nematodes." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/204511.
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13
Nunn, Gary B. "Nematode molecular evolution : an investigation of evolutionary patterns among nematodes based upon DNA sequences." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334855.
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14
Pelinganga, Osvaldo Manuel. "Developing phytonematicides using indigenous cucumis africanus and cucumis myriocarpus fruits for tomatoproduction systems." Thesis, University of Limpopo, 2013. http://hdl.handle.net/10386/1354.
Full textAbstract:
Thesis (Ph. D. Agriculture (Plant Protection)) -- University of Limpopo, 2013Global withdrawal of synthetic fumigant and non-fumigant nematicides due to their ecounfriendly impacts and high toxicity to non-target organisms, respectively, increased the research and development of alternatives for managing population densities of plantparasitic nematodes, particularly the root-knot (Meloidogyne species) nematodes. Although Meloidogyne species had been managed using genotypes that are resistant to plant-parasitic nematodes in various crops, various challenges negate the available or introgressed nematode resistance. In tomato (Solanum lycopersicum) production, nematode races and instability of nematode resistant genotypes under certain conditions necessitated the continued research and development of alternatives since most of the existing commercial tomato cultivars are highly susceptible to various biological races of Meloidogyne species. The aim of the study was to research and develop appropriate dosages of two phyto- nematicides which could be applied through drip irrigation system in open field tomato production systems, while the specific objectives were to: (1) determine whether a computer-based model could provide nonphytotoxic concentrations to tomato plants using fresh fruits of wild watermelon (Cucumis africanus) and wild cucumber (C. myriocarpus) under greenhouse conditions, (2) determine whether computer-based concentrations from the two plant species when using dried fruits would be less phytotoxic and more suppressive to nematodes, (3) investigate application time intervals for the two products, (4) determine responses of plant growth in tomato and nematode suppression in respect to the derived dosages, and and (5) validate dosages of fermented crude extracts from the two plant species with respect to plant growth of tomato and suppression of nematode numbers. xxxiii Greenhouse, microplot and field studies were set to test the hypotheses intended to achieve the stated objectives, with reliability of measured variables being ensured by using statistical levels of significance (P ≤ 0.05) and coefficients of determination (R2), while validity was ensured by conducting experiments at the same location over two seasons and/or by setting up factorial treatments. Firstly, fermented plant extracts of fresh fruits from C. africanus and C. myriocarpus consistently reduced population densities of Meloidogyne species by 80-92% and 50-90%, respectively. Tomato plants were highly sensitive to the two products as shown by the total degree of sensitivities (Σk) and biological index of 0 and 3, respectively. Also, the mean concentration stimulation range (MCSR) of 11% and 7% concentrations, respectively, attested to this phytotoxicity. Secondly, fermented crude extracts of dried fruits from C. africanus and C. myriocarpus also reduced population densities of Meloidogyne species by 78-97% and 87-97%, respectively. Tomato plants were highly tolerant to the two products in dried form as shown by the total degree of sensitivities (Σk) and biological index of 4 and 3, respectively. The MCSR values for C. africanus and C. myriocarpus dried fruits on tomato were 2.64% and 2.99%, respectively, which for the purpose of this study were individually adjusted to 3%, which translated to 36 L undiluted material/ha of 4 000 tomato plants. In subsequent studies, 3% concentration was used as the standard, along with double strength concentration, namely, 6% concentration. Thirdly, the MCSR values derived in Objective 4, namely 3% and 6% concentration for both Cucumis species using the CARD model were used in the optimisation of application time interval using the innovative concept of weeks (0, 1, 2, 3 and 4) in a 30-day month period. Application time interval for 3% and 6% concentrations of C. africanus fruits was xxxiv optimised at 2.40 and 2.61 weeks in a 30-day month period, respectively, which translated to 18 days [(2.4 weeks/4 weeks) × 30 days] and 20 days [(2.6 weeks/4 weeks) × 30 days], respectively. In contrast, for both concentrations from fermented crude extracts of C. myriocarpus fruits, application time interval was optimised at 16 days for 2.2 and 2.1 weeks, respectively. During optimisation of application frequencies, fermented crude extracts from C. africanus and C. myriocarpus reduced final population densities of M. incognita race 2 by 70-97% and 76-96%, respectively. Fourthly, optimum application intervals (time), allowed computation of dosage, which is a product of concentration and application frequency (dosage = concentration × application frequency). Fifthly, validation of the dosages under open field conditions suggested that 6% × 16-day dosage under crude extracts from C. myriocarpus fruit significantly (P ≤ 0.05) improved growth of tomato plants when compared with those of either 0% (untreated control) or 3% at 16 days. In contrast, dosages of C. africanus fruit at two application frequency had no effect on growth of tomato plants – suggesting that either of the dosages was suitable for use in tomato production since both reduced nematode numbers. During validation, the materials reduced nematode numbers by margins similar to those observed previously under other environments. In conclusion, crude extracts of the two Cucumis species have stimulatory concentrations which have potential similar reductive effects on population densities of Meloidogyne species and could serve as botanical nematicides. However, since plant responses to the two products differed in terms of their respective dosages and active ingredients, it implied that for further improvement of the two, the overriding focus should be on their interaction with the protected plants and nematode numbers. Ideally, future research xxxv should include environmental impact studies, especially on the influence of the products fruit quality of tomato, earthworms, fish and bees.
15
Ross, Jenna Louise. "Diversity and mass production of slug-parasitic nematodes." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until Jan. 8, 2015, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=61013.
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16
Hourston, Mathew. "The ecology of free-living nematodes in nearshore marine and estuarine sediments of the microtidal lower west coast of Australia." Thesis, Hourston, Mathew (2009) The ecology of free-living nematodes in nearshore marine and estuarine sediments of the microtidal lower west coast of Australia. PhD thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/1672/.
Full textAbstract:
The overarching aim of this thesis was to describe the ecology of the assemblages of free-living nematodes in the sediments of nearshore marine and estuarine waters on the microtidal lower west coast of Australia. The thesis also provides descriptions of ten previously undescribed species as well as develops and tests a habitat classification scheme for the Swan River Estuary using these biotic assemblages.
The first section of my thesis has determined the ways in which the characteristics of the nematode assemblages in nearshore marine waters along the microtidal lower west coast of Australia are related to habitat type, time of year and shore-perpendicular zones. Three habitat types, which had previously been identified on the basis of a suite of enduring environmental characteristics, could be broadly described as highly sheltered from wave activity and containing dense seagrass (habitat type 1), moderately sheltered from wave activity and with sparse seagrass (habitat type 2) and relatively exposed to wave activity and with no seagrass (habitat type 6). Sampling in five consecutive seasons yielded > 15 000 nematodes, representing 75 species. The number of species and densities in habitat type 1, and particularly those in its subtidal zone, were far greater than those in the other two habitat types. Both of these biotic variables underwent marked seasonal changes, declining to low levels during winter. The compositions of the assemblages differed significantly among the three habitat types, with the differences between habitat types 1 and 6 being particularly marked. Paracomesoma sipho, Dichromadora sp., Marylynnia annae and Pomponema sp., which, on the basis of their buccal cavity morphology, are assumed to feed primarily on benthic diatoms, were particularly abundant at the most sheltered habitat type, whereas Gonionchus australis, Theristus sp. and Bathylaimus australis, which are assumed to be deposit feeders, were relatively abundant at the most highly exposed habitat type. The compositions of the assemblages differed among seasons and were most discrete in spring, due to marked increases in the densities of certain species. However, differences in the compositions in the different zones of each habitat type were relatively small, presumably reflecting the influence of the small tidal regime of this region.
The second component of this thesis has determined the ways in which the density, number of species, species composition and trophic structure of free-living nematode assemblages in the subtidal waters of a large microtidal estuary change spatially and temporally, and has explored whether those four biotic characteristics are related to certain environmental factors. Based on data derived from samples collected seasonally at 12 sites throughout the estuary, the densities and number of species of nematodes decreased progressively with distance from estuary mouth, to reach a minimum at sites where salinities were most variable, and then increased slightly in the uppermost part of the estuary where salinities were least. Densities were also generally greatest in spring, due largely to increases in the abundance of epistrate-grazing species at the time when the amount of primary food (microphytobenthos) peaked. The spatial distribution of the composition of the nematode assemblages was closely correlated with salinity and, to a lesser extent, grain-size composition and amount of particulate organic material in the sediment (%POM). Although species composition changed sequentially along the estuary, the change was particularly pronounced between sites above and below the area where salinities started to decline markedly and become more variable and %POM increased markedly. This reflected, in particular, far greater abundances of Spirinia parasitifera at the six downstream sites, and of Theristus sp. 1 at the six sites further upstream. Species composition underwent pronounced seasonal cyclical changes at all sites, presumably reflecting interspecific differences in the timing of peak reproduction and thus of recruitment. The trophic structure of the nematode assemblages changed both spatially and temporally in relation to the relative abundance of different food sources. Thus, for example, non-selective deposit feeders, such as Theristus sp. 1, dominated samples in the upper estuary, where %POM was by far the greatest, and was rare or absent at downstream sites. Conversely, epistrate grazers, such as species of the Chromadoridae, were most abundant at downstream sites in spring, when the density of the microphytobenthos reached its maximum.
The data for the nematode assemblages in nearshore subtidal marine sediments of the lower west coast of Australia were compared with those in nearshore subtidal sediments in the upper and lower regions of the Swan River Estuary. The densities and average species richness in cores from the marine environment were much lower than in cores from both estuarine regions. However, the total number of species found in the marine environment was much greater than in the estuary. The compositions of the nematode assemblages were more variable in marine than estuarine sediments. The assemblages from the two estuarine regions were far more similar to each other than to those from the marine region at a species level, and also, but to a lesser extent, at the generic and family levels.
While the trophic compositions of the nematode assemblages in the upper estuarine region was dominated by non-selective deposit feeding species and those of the lower estuarine region were dominated by epistrate grazing species during spring and non-selective deposit feeding species in other seasons, the dominant functional feeding groups varied among the sites representing the marine region. That variability presumably reflects differences in the relative contributions of the different potential food sources. Surprisingly, the trophic composition in the upper estuarine region, i.e. comprising predominantly non-selective deposit feeders, was similar to that at the very different environment of the most exposed marine site. The dominance of this feeding group at the marine site is assumed to be attributable to the fact that the only food source of any note is POM and, even then, it occurs in only small amounts. Taxonomic descriptions have been produced for ten new species of nematodes found during the ecological studies of the free-living aquatic nematofaunas of south-western Australia. These species were chosen because they were members of families for which the other species had been described and, in a number of cases, were important for distinguishing between the compositions of a priori groups. They comprised four species of Axonolaimidae, representing the genera Ascolaimus, Parascolaimus, Odontophora and Parodontophora, and six species of Desmodoridae, representing single species of Bolbonema, Eubostrichus, Catanema and Leptonemella and two species of Onyx.
As a complement to the nematological study of the Swan River Estuary, a novel habitat classification system was developed and then applied in this environment. This system was based on enduring environmental characteristics and employed the relatively new multivariate statistical routines SIMPROF and LINKTREE. The applicability of habitat types produced by this classification system to biotic assemblages was tested using the data for the estuarine nematode assemblages described above. The results demonstrate that the compositions of the assemblages differed significantly among each of the habitat types defined by the classification system. While there were also significant differences between the compositions of the nematofaunas at sites belonging to the same habitat type, the extent of these differences were generally less than those between habitat types. A significant and strong correlation was also found between the spatial pattern exhibited by the environmental characteristics used to define habitat types, and that of the nematofauna.
17
Hourston, Mathew. "The ecology of free-living nematodes in nearshore marine and estuarine sediments of the microtidal lower west coast of Australia." Hourston, Mathew (2009) The ecology of free-living nematodes in nearshore marine and estuarine sediments of the microtidal lower west coast of Australia. PhD thesis, Murdoch University, 2009. http://researchrepository.murdoch.edu.au/1672/.
Full textAbstract:
The overarching aim of this thesis was to describe the ecology of the assemblages of free-living nematodes in the sediments of nearshore marine and estuarine waters on the microtidal lower west coast of Australia. The thesis also provides descriptions of ten previously undescribed species as well as develops and tests a habitat classification scheme for the Swan River Estuary using these biotic assemblages.
The first section of my thesis has determined the ways in which the characteristics of the nematode assemblages in nearshore marine waters along the microtidal lower west coast of Australia are related to habitat type, time of year and shore-perpendicular zones. Three habitat types, which had previously been identified on the basis of a suite of enduring environmental characteristics, could be broadly described as highly sheltered from wave activity and containing dense seagrass (habitat type 1), moderately sheltered from wave activity and with sparse seagrass (habitat type 2) and relatively exposed to wave activity and with no seagrass (habitat type 6). Sampling in five consecutive seasons yielded > 15 000 nematodes, representing 75 species. The number of species and densities in habitat type 1, and particularly those in its subtidal zone, were far greater than those in the other two habitat types. Both of these biotic variables underwent marked seasonal changes, declining to low levels during winter. The compositions of the assemblages differed significantly among the three habitat types, with the differences between habitat types 1 and 6 being particularly marked. Paracomesoma sipho, Dichromadora sp., Marylynnia annae and Pomponema sp., which, on the basis of their buccal cavity morphology, are assumed to feed primarily on benthic diatoms, were particularly abundant at the most sheltered habitat type, whereas Gonionchus australis, Theristus sp. and Bathylaimus australis, which are assumed to be deposit feeders, were relatively abundant at the most highly exposed habitat type. The compositions of the assemblages differed among seasons and were most discrete in spring, due to marked increases in the densities of certain species. However, differences in the compositions in the different zones of each habitat type were relatively small, presumably reflecting the influence of the small tidal regime of this region.
The second component of this thesis has determined the ways in which the density, number of species, species composition and trophic structure of free-living nematode assemblages in the subtidal waters of a large microtidal estuary change spatially and temporally, and has explored whether those four biotic characteristics are related to certain environmental factors. Based on data derived from samples collected seasonally at 12 sites throughout the estuary, the densities and number of species of nematodes decreased progressively with distance from estuary mouth, to reach a minimum at sites where salinities were most variable, and then increased slightly in the uppermost part of the estuary where salinities were least. Densities were also generally greatest in spring, due largely to increases in the abundance of epistrate-grazing species at the time when the amount of primary food (microphytobenthos) peaked. The spatial distribution of the composition of the nematode assemblages was closely correlated with salinity and, to a lesser extent, grain-size composition and amount of particulate organic material in the sediment (%POM). Although species composition changed sequentially along the estuary, the change was particularly pronounced between sites above and below the area where salinities started to decline markedly and become more variable and %POM increased markedly. This reflected, in particular, far greater abundances of Spirinia parasitifera at the six downstream sites, and of Theristus sp. 1 at the six sites further upstream. Species composition underwent pronounced seasonal cyclical changes at all sites, presumably reflecting interspecific differences in the timing of peak reproduction and thus of recruitment. The trophic structure of the nematode assemblages changed both spatially and temporally in relation to the relative abundance of different food sources. Thus, for example, non-selective deposit feeders, such as Theristus sp. 1, dominated samples in the upper estuary, where %POM was by far the greatest, and was rare or absent at downstream sites. Conversely, epistrate grazers, such as species of the Chromadoridae, were most abundant at downstream sites in spring, when the density of the microphytobenthos reached its maximum.
The data for the nematode assemblages in nearshore subtidal marine sediments of the lower west coast of Australia were compared with those in nearshore subtidal sediments in the upper and lower regions of the Swan River Estuary. The densities and average species richness in cores from the marine environment were much lower than in cores from both estuarine regions. However, the total number of species found in the marine environment was much greater than in the estuary. The compositions of the nematode assemblages were more variable in marine than estuarine sediments. The assemblages from the two estuarine regions were far more similar to each other than to those from the marine region at a species level, and also, but to a lesser extent, at the generic and family levels.
While the trophic compositions of the nematode assemblages in the upper estuarine region was dominated by non-selective deposit feeding species and those of the lower estuarine region were dominated by epistrate grazing species during spring and non-selective deposit feeding species in other seasons, the dominant functional feeding groups varied among the sites representing the marine region. That variability presumably reflects differences in the relative contributions of the different potential food sources. Surprisingly, the trophic composition in the upper estuarine region, i.e. comprising predominantly non-selective deposit feeders, was similar to that at the very different environment of the most exposed marine site. The dominance of this feeding group at the marine site is assumed to be attributable to the fact that the only food source of any note is POM and, even then, it occurs in only small amounts. Taxonomic descriptions have been produced for ten new species of nematodes found during the ecological studies of the free-living aquatic nematofaunas of south-western Australia. These species were chosen because they were members of families for which the other species had been described and, in a number of cases, were important for distinguishing between the compositions of a priori groups. They comprised four species of Axonolaimidae, representing the genera Ascolaimus, Parascolaimus, Odontophora and Parodontophora, and six species of Desmodoridae, representing single species of Bolbonema, Eubostrichus, Catanema and Leptonemella and two species of Onyx.
As a complement to the nematological study of the Swan River Estuary, a novel habitat classification system was developed and then applied in this environment. This system was based on enduring environmental characteristics and employed the relatively new multivariate statistical routines SIMPROF and LINKTREE. The applicability of habitat types produced by this classification system to biotic assemblages was tested using the data for the estuarine nematode assemblages described above. The results demonstrate that the compositions of the assemblages differed significantly among each of the habitat types defined by the classification system. While there were also significant differences between the compositions of the nematofaunas at sites belonging to the same habitat type, the extent of these differences were generally less than those between habitat types. A significant and strong correlation was also found between the spatial pattern exhibited by the environmental characteristics used to define habitat types, and that of the nematofauna.
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Yu, Hao. "Parasitism of Subterranean Termites (Isoptera: Rhinotermitidae: Termitidae) by Entomopathogenic Nematodes (Nematoda: Steinernematidae: Heterorhabditidae)." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195263.
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The biological control of subterranean termites (Isoptera: Rhinotermitidae; Termitidae) using entomopathogenic nematodes (Nematoda: Steinernematidae; Heterorhabditidae) (EPN) was investigated. The desert subterranean termite Heterotermes aureus Snyder was found to be very susceptible to Steinernema riobrave Cabanillas, Poinar and Raulston. In laboratory bioassays S. riobrave (355, TP, 3-8b and 7-12 strains), S. carpocapsae Weiser (Mexican 33 strain), S. feltiae Filipjev (UK76 strain), and Heterorhabditis bacteriophora Poinar (HP88 strain) were all capable of infecting and killing H. aureus, Reticulitermes flavipes Kollar, R. virginicus Banks, Coptotermes formosanus Shiraki and Gnathamitermes perplexus Banks. In sand assays, S. riobrave caused > 90% H. aureus mortality in 3 days and 100% mortality by day 5 at 22 °C. TP strain of S. riobrave caused 75% R. flavipes mortality and 90.91% C. formosanus mortality in 7 days. EPNs utilizing termites as hosts produced smaller sized offspring, with the exception of S. feltiae. Stunted females of S. feltiae were frequently found in termite cadavers, but no progeny. Small IJs of S. carpocapsae, S. riobrave and H. bacteriophora infect, reproduce and form normal size IJs after subsequent infection in Galleria mellonella L. The progeny of small IJs were as effective as the normal size IJs, with regard to subsequent induced mortality, under the conditions tested. In laboratory two-container choice experiments, H. aureus were repelled by EPN treated areas for up to 10 days at 10,000 IJs per device. The repellency threshold was found to vary among nematodes species. We hypothesis that it is the physical movement of the nematodes that repels the termites. Temperature is a key factor affecting nematode pathogenicity. Temperature tolerance of the nematodes varied between species. After a gradual heat adaptation process, S. riobrave and H. bacteriophora caused significantly higher H. aureus mortality at 32 °C compared with original laboratory cultured strains. Further work may result in the contribution of commercially available strains with enhanced heat tolerance. Preliminary field studies confirmed EPN protection of a structure, however, termites began to reinfest 4 weeks after the application. Additional tests are necessary to provide more evidence before we can conclude nematodes as useful in the field.
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Jordan, Katerina Serlemitsos. "The ecology of plant-parasitic nematodes and their antagonists on golf course greens turf in southern New England /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3188061.
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Grainger, John Robert. "Immune modulation by parasitic nematodes." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3809.
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Almost 2 billion people world-wide are infected with parasitic helminths. These complex multicellular eukaryotic organisms are capable of establishing long-term infections even in the face of an intact immune response. Typically, in these settings regulatory components of the immune response, such as Foxp3+ T regulatory cells (Tregs), become dominant, limiting protective effector responses towards the parasite. Helminths are thought to have evolved mechanisms, including release of immunomodulatory molecules termed excretory-secretory products (ES), to sway the balance between the regulatory and effector arms of the immune response to favour their persistence. In this thesis both the development of a protective immune response toward, and the potential manipulation of the immune response by, the rodent gastrointestinal nematode Heligmosomoides polygyrus have been studied. Firstly, the effects of H. polygyrus ES (HES) on bone-marrow derived dendritic cells (DCs) were analysed. Although HES did not alter the phenotype of the DC it was found to be able to suppress the ability of the DC to respond to inflammatory stimuli. This activity was lost when HES was heat-inactivated (hiHES). After adoptive transfer, HES-pulsed DCs were able to induce a HESspecific T helper (Th)2-type response even if co-treated with an inflammatory stimulus. Th2-type responses are protective against H. polygyrus infection. Surprisingly, the ability of HES to generate a Th2-response in a co-treatment situation was not related to its anti-inflammatory properties; DCs co-treated with hiHES and an inflammatory stimulus were able to drive an equivalent Th2-response to HES in this situation. Next, making use of mouse strains with different susceptibility phenotypes to primary H. polygyrus infection, potential mechanisms of resistance were characterised. Development of granulomas in the gut wall were found to be associated with reduced worm burdens. Furthermore, in highly susceptible C57BL/6 mice, production of IL-23 was shown to be counter-regulatory to this process, as mice on the same background but deficient in this cytokine have increased numbers of granulomas and dramatically enhanced resistance. Susceptibility to H. polygyrus was also considered at the level of epigenetic regulation. A protein that binds specifically to methylated DNA, methyl-CpG binding domain protein (MBD)2, was found to affect the proportion of Foxp3+ Tregs within the CD4+ T cell population in vivo. Additionally, in vitro induction of Foxp3 in response to TGF-β was enhanced in MBD2-/- CD4+ T cells. MBD2-/- mice had a trend towards increased worm burdens when infected with H. polygyrus, suggesting that the difference in proportion of Tregs may limit generation of an effector response. Finally, the ability of HES to directly affect the regulatory arm of the immune response was focussed upon. It was found that HES was able to induce Foxp3 expression in naïve peripheral T cells, and that this was mediated by stimulation of the TGF-β pathway. The TGF-β mimic was of parasite origin as a pan-vertebrate TGF-β antibody was unable to block its effects but sera from H. polygyrus infected animals was competent to do this. Activity of this type was not limited to HES as ES from the ovine helminth Haemonchus contortus was found to have the same property. These data imply that some helminth parasites have evolved mechanisms to support generation of Foxp3+ Tregs, thus favouring the regulatory arm of the immune response and hence their own persistence.
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Almond, N. M. "Humoral responses to parasitic nematodes." Thesis, Open University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482683.
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Nowell, Mari Ann. "Immunological stress responses in nematodes." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267622.
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Cleator, M. "Developmental hormones in parasitic nematodes." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356250.
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O'Hanlon, Graham Michael. "Developmental hormones in ascarid nematodes." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293137.
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Losson, B. J. "Immunological unresponsiveness to gastrointestinal nematodes." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372886.
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Tornoe, Calilla. "Nicotinic acetylcholine receptors in nematodes." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363452.
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Sutov, Grigorij. "Glycomic studies of parasitic nematodes." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/56060.
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Haemonchus contortus and Dictyocaulus viviparus are parasitic nematodes which infect small ruminants and cattle, respectively worldwide causing huge economic losses. The current major control method is the usage of anthelmintic drugs. However, increasingly this strategy is failing due to an increase in parasite drug resistance. New control methods are therefore urgently needed and an attractive potential choice would be vaccination. However, all the attempts to create recombinant vaccines to date have failed therefore a potentially novel approach would be the development of carbohydrate-based vaccines. One of the major bottlenecks in this approach is the lack of structurally characterized parasitic nematode glycans. In this thesis mass-spectrometry-based structural glycomic characterization of protein linked N- and O-glycans from Haemonchus contortus and Dictyocaulus viviparus adult and L3 stage parasites has been performed. The adult Haemonchus contortus glycomic analysis revealed previously unseen Gal-Fuc structures present in both N- and O-glycans. None of these structures were detected in L3 stage N- and O-glycan analysis. In comparison phosphorylated Galβ1-3(Galβ1-6)-GalNAc Core O-glycans were observed. The O-glycan analysis of L3 stage Dictyocaulus viviparus revealed the presence of Galβ1-3(Galβ1-6)-GalNAc Core glycans which can be further modified with fucose and α/β-galactoses. In contrast to L3 stage, the adult O-glycan analysis reveals mainly Core-2 based structures with the highest molecular weight structure forming the Lewisx antenna which is also abundantly observed in adult N-glycans.
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Laetsch, Dominik Robert. "On the evolution of effector gene families in potato cyst nematodes." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31244.
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Potato cyst nematodes (PCN) are economically relevant plant parasites that infect potato crops. The genomes of three PCN species are available and genome data have been generated for several populations of PCN, to address questions related to the molecular basis of plant parasitism. In this thesis, I employ approaches of comparative genomics to highlight differences and similarities between PCNs and other nematode species. I present two new software solutions to address challenges associated with the field of comparative genomics: BlobTools, a taxonomic interrogation toolkit for quality control of genome assemblies, and KinFin, a solution for the analysis of protein orthology data. I apply both software solutions to genomic datasets of nematodes, platyhelminths, and tardigrades. Based on KinFin analysis of plant parasitic nematodes, I identify protein families in PCNs likely to be involved in host-parasitic interaction, termed effectors, and discuss their functions. I highlight examples of horizontal gene transfer from bacteria to plant parasitic nematodes. Through genomic data of European and South American populations of PCNs, I address variation in populations, infer phylogenetic relationships, and try to estimate the effect of selection on effector genes identified through KinFin. Furthermore, I estimate the rate of variation across the reference genomes of two PCNs.
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Ratnasinghe, Gamini. "Biological control of diamondback moth, Plutella xylostella (Lepidoptera: yponomeutidae) with entomopathogenic nematodes (Nematoda: rhabditida)." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308035.
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Nobbs, J. M. "The distribution and abundance of nematodes (especially the plant parasites) in the arid region of South Australia /." Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phn744.pdf.
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LASSERRE, FRANCOISE. "Lutte integree contre heterodera avenae (nematoda) : consequences sur une communaute de nematodes en ecosysteme cerealier." Rennes 1, 1994. http://www.theses.fr/1994REN10053.
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L'objet de cette etude etait de proposer un modele de gestion integree des populations de nematodes en agroecosysteme cerealier. Six itineraires de lutte bases sur une rotation de type mais-ble-ble, differant par le degre de couverture chimique par un nematicide et par l'introduction ou non d'une variete resistante en premier ble, ont ete compares selon des criteres economiques et ecologiques. La variete resistante a permis un gain de 10% sur le deuxieme ble; par contre, la protection chimique du mais s'est averee d'efficacite tres dependante des conditions climatiques. Par ailleurs, l'etude a considere les effets a long terme de la culture repetee de l'avoine panema resistante a h. Avenae. La chute subsequente de ce nematode entraine une multiplication des effectifs de pratylenchus neglectus, nematode des lesions necrotiques, a des effectifs nuisibles sur ble d'hiver; elle cause egalement une chute durable de l'inoculum du champignon endoparasite verticillium chlamydosporium dont l'absence favorise les remontees foudroyantes des populations d'h. Avenae des que des cultures hotes succedent a la variete resistante. L'application repetee du meme gene de resistance a egalement selectionne un pathotype virulent sur l'avoine panema. Les structures genetiques de ce dernier (polymorphisme enzymatique) se sont averees significativement differentes de celles de la population d'origine. Il est important de tenir compte de tels risques dans une strategie d'utilisation optimale de la resistance, elle-meme faisant partie d'un programme de gestion integree des populations de nematodes
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Morris, John R. (John Robert) 1949. "Biological Control of the Red Imported Fire Ant by the Entomopathogenic Nematode, Steinernema Carpocapsae (Weiser)." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc500266/.
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Field trials were conducted in 1988 to evaluate the effectiveness of Steinernema (=Neoaplectana) carpocapsae (Weiser) in controlling the fire ant. Infective juveniles (IJ) of the nematode were applied as drench on 235 and 422 mounds, respectively for 2-month summer and 6-week fall evaluation periods. In comparative trials, amidinohydrazone (Amdro) was applied to 249 (summer) and 65 (fall) active mounds, with 245 (summer) and 78 (fall) untreated active as controls. Nematode treatments resulted in an average of 47% control (Abbott's formula) in summer trials and 19-88% control in the fall trials, compared with 39% and 47% control, respectively with amidinohydrazone. Active mounds treated with nematodes or amidinohydrazone had significantly fewer individuals than control mounds in summer trials.
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Lendner, Matthias. "Functional analysis of tropomyosin of parasitic nematodes." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16137.
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Parasitische Würmer gehören mit über 3,5 Milliarden Betroffenen zu den weltweit verbreitetesten Infektionskrankheiten. Der Erfolg dieser Parasiten beruht auf ihren ausgefeilten Mechanismen mit denen sie das Immunsystem ihrer Wirte manipulieren. Interessanter Weise gehen Wurminfektionen mit einer geringeren Wahrscheinlichkeit an Allergien zu erkranken einher. Wie genau die Parasiten das Immunsystem manipulieren ist weitgehend unbekannt. Um diese Mechanismen besser studieren zu können, wurde im Rahmen dieser Arbeit versucht RNA interference (RNAi), anhand des Modellmoleküls Tropomyosin zu etablieren. Wie sich am Beispiel des Strongyliden Heligmosomoides polygyrus bakeri zeigte, ist RNAi als Manipulationsmethode für Nematoden nicht oder nur in geringem Maße geeignet. Dies lässt sich auf das Fehlen von Aufnahme- und Verbreitungsmechanismen für Doppelstrang-RNA zurückführen. Desweiteren wurden die Auswirkungen von rekombinantem Tropomyosin der Filarie Acanthocheilonema viteae (rAv-TMY) auf die Entstehung allergischer Atemwegserkrankungen im Mausmodell untersucht. Eine viermalige Behandlung mit rAv-TMY in einem Zeitraum von vier Wochen führte zu verringerten entzündlichen Reaktionen in den Atemwegen. Die Analyse immunologischer Parameter ergab, dass rAv-TMY signifikant den Einstrom von Entzündungszellen in die Atemwege reduziert, allem voran den Einstrom von Eosinophilen. Dies lässt sich durch die verringerte Ausschüttung an IL-5, Eotaxin und MCP-5 zurückführen. Zudem wurde die Bildung von antigenspezifischen IgE verringert während sich die Produktion blockierender IgG1 Antikörper erhöhte. Diese Arbeit belegt somit die anti-allergischen Eigenschaften von rAv-TMY. Damit stellt rAv-TMY ein interessantes Kandidatenmolekül zur Behandlung allergischer Reaktionen dar. Desweiteren kann der Vergleich von allergenem, nicht allergenem und modulatorischem Tropomyosin wichtige Informationen über die allgemeinen Eigenschaften von Allergenen und ihrer molekularen Struktur geben.Parasitic worms are among the world''s most prevalent infectious diseases with more than 3.5 billion. The success of these parasites is based on their sophisticated ways to manipulate the immune system of their hosts. Interestingly, worm infections abate the risk to develop allergic disorders. How exactly parasitic worms modulate the immune system is so far largely unknown. In order to be able to investigate parasite induced modulation, this work aimed to establish RNA interference (RNAi), a method of genetic manipulation, using tropomyosin as target gene. As shown for the example of Heligmosomoides polygyrus RNAi is not or only to a small extent useful as method to genetically manipulate nematodes. This can be explained with the lack of uptake and spreading mechanisms for double stranded RNA. Furthermore, this work examined the impact of the recombinant muscle protein tropomyosin of Acanthocheilonema viteae (rAv-TMY) on the course of a rodent model of allergic airway inflammation. A four-time treatment with rAv-TMY over a period of four weeks resulted in decreased inflammatory responses in the airways. The analysis of immunological parameters showed that rAv-TMY significantly reduces the influx of inflammatory cells into the airways, especially eosinophils. The reduced eosinophil influx can be attributed to the decreased expression of IL-5, eotaxin and MCP-5 in the airways. In addition, the formation of antigen-specific IgE was impaired whereas the production of the blocking antibody IgG1 was increased. These results demonstrate the anti-allergic properties of rAv-TMY. For this reason rAv-TMY becomes an interesting model molecule for the treatment of allergic diseases. Furthermore, the comparison of allergenic, non-allergenic and modulatory tropomyosin might put some light on the nature of allergens and their molecular patterns.
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Jagdale, Ganpati Baburao. "Adaptation to temperature in entomopathogenic nematodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25772.pdf.
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Johnson, Maureen Jane. "Coproantigen capture ELISA for GI nematodes." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240993.
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Young, Catriona Jean. "Modulated enzyme expression in gastrointestinal nematodes." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318123.
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Roder, Alexandra Catherine, and Alexandra Catherine Roder. "Influence of Xenorhabdus Symbionts on Gonad Development and Pheromone Production of First-Generation Adult Steinernema Nematodes (Nematoda: Steinernematidae)." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/626344.
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Entomopathogenic Steinernema nematodes (Nematoda: Steinernematidae) have a mutualistic relationship with Xenorhabdus bacteria (Gamma-Proteobacteria Enterobacteriaceae). The two partners form an insecticidal alliance that is successful in killing a wide range of insects. A few studies have shown that Steinernema IJs have an enhanced virulence and reproductive fitness when they associate with their cognate symbionts. However, there are unanswered questions regarding the physiological interactions that govern and perpetuate the interactions between different nematode developmental stages and their bacterial partners. In this study, we evaluated gonad development and maturation time of first-generation adults of S. carpocapsae and S. feltiae adults when reared under four bacterial scenarios: a) cognate symbiotic, b) non-cognate symbiotic bacterial strain, c) non-cognate symbiotic bacterial species and d) non-symbiotic bacteria (Serratia proteamaculans). For comparative purposes, we also considered adult nematodes reared in vivo in Galleria mellonella larvae to assess nematode development under natural conditions. Furthermore, in this study we also measured production of nematode pheromones (ascarosides), which play a key role in mating and reproduction. For this purpose, we considered in vitro rearing methods (with cognate and non-cognate Xenorhabdus symbionts) to qualitatively and quantitatively characterize ascarosides produced by first-generation adults. Our data showed that for both Steinernema spp. tested, time to adult maturation and gonad development was tightly dependent on the bacterial conditions under which juveniles were reared. However, contrasting results were observed when assessing total body length and gonad size. S. feltiae males and females size (body length and width) and respective gonad length were smaller when reared with a non-cognate symbiotic species. Additionally, non-symbiotic bacteria did not sustain S. feltiae maturation to adult stages. Contrarily, S. carpocapsae juveniles developed to adults when reared with any of the bacterial conditions tested, including with non-symbiotic Serratia proteamaculans. Additionally, S. carpocapsae adults, unlike S. feltiae, did not exhibit enhanced body and gonad size when reared with their cognate symbiont. In fact, S. carpocapsae males and females had larger gonad lengths when reared with a non-cognate symbiotic strain, XnAna (X. nematophila associated with S. anatoliense). S. carpocapsae males and females had significantly underdeveloped gonads when reared with non-symbiotic bacteria. In both Steinernema spp., sex ratio was not impacted by the bacterial condition. However, sex ratio (female:male) S. carpocapsae, decreased from 2:1 to 1:1 when reared with non-symbiotic bacteria. The body and gonad sizes of Steinernema spp. reared in vitro with their cognate symbiont were significantly smaller than those grown in vivo. Ascaroside production in either Steinernema spp. was not significantly impacted by the rearing conditions. In S. carpocapsae, a significant increase in glucoside-1 was observed when the nematodes were reared with cognate or non-cognate bacteria. No detectable quantities of asc-C11 were produced by S. feltiae nematodes when reared with a non-cognate symbiotic bacterial species. We conclude that bacterial symbionts influenced maturation and development of first-generation adults’ in both Steinernema spp. tested in this study. However, response to the bacterial symbionts was species specific. Additionally, this study showed that Xenorhabdus as a food source plays an important role in the type and amount of ascarosides produced by Steinernema spp.
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KC, Ashmit. "Plant-Parasitic Nematodes on Sugarbeet in North Dakota and Minnesota." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/29884.
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Field surveys were conducted in the Red River Valley (RRV) of North Dakota and Minnesota during 2016 and 2017 to determine the incidence, abundance, and distribution of plant-parasitic nematodes (PPNs) on sugarbeet. Seventy-two and 65 % of the fields surveyed were positive for PPNs in 2016 and 2017, respectively. The major genera of PPNs identified from sugarbeet production fields were Heterodera, Helicotylenchus, Tylenchorhynchus, Paratylenchus, Pratylenchus, Paratrichodorus, Hoplolaimus, and Xiphinema. Eight of PPNs were identified at the species level using species-specific PCR assays, and sequencing of the ribosomal rDNA gene. Stubby-root nematode, Paratrichodorus allius, is one of the important nematode pests for sugarbeet production worldwide. An experiment was conducted to determine the host status of sugarbeet and their rotational crops for P. allius under greenhouse conditions. The results from two experiments indicated sugarbeet and most rotational crops support the reproduction of P. allius.Sugarbeet Research and Education Board (Minn.)
Sugarbeet Research and Education Board (N.D.)
American Crystal Sugar Company
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Engelbrecht, Emil Ettiene. "Nematode (Phylum Nematoda) community assemblages : a tool to implement environmentally–sound management strategies for root–knot nematodes (Meloidogyne spp.) in potato–based cropping systems / Emil Ettiene Engelbrecht." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8095.
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those special or additional educational needs and goals that would enable students to fulfil their future roles in their communities and beyond. It is also argued that the mini–education systems of non–governmental institutions could make a major contribution to solve these problems. In particular, the analysis and discussion of the mini–education system of the Foundation for Cross–Cultural Education, has demonstrated that the mini–education system of a private educational initiative can make a substantial contribution towards the educational upliftment of a community in a particular rural area.
The study provides an instrument to plan and facilitate the mini–education systems of private education initiatives working in developing communities to effect the required transformational development. To confer advice to these private educational initiatives in SSA and to address the current global concern regarding the quality of formal education, the study adapted Steyn et al.’s (2002) framework for strategic education system planning. The adapted framework guidelines can be used to increase the efficiency of all the components and elements of the particular mini–education systems functioning in developing communities. The particular strategic framework was also applied to identify and describe the needs and determinants influencing quality education in developing communities in Sub–Saharan Africa in general.
It was also found that the specific framework for strategic planning was applicable to position the mini–education system, of a particular education private initiative, in such a way that it can effectively provide in the real education needs of a particular developing community. The framework also provides valuable guidelines to educational investors, as private initiatives, and national governments that wish to integrate their education provisioning in order to improve the quality of formal education provision in SSA.Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.
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Silva, Lidiane Aparecida Firmino da. "Helmintos parasitas de Ameivula pyrrhogularis (Squamata Teiidae) na caatinga, Brasil /." Botucatu, 2018. http://hdl.handle.net/11449/153498.
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Orientador: Robson Waldemar ÁvilaResumo: A Caatinga é um ecossistema a ser investigado, pois apresenta distintos ambientes e uma fauna endêmica de lagartos. Ameivula pyrrhogularis é um teídeo encontrado no Nordeste, na zona de transição entre Caatinga, Cerrado e floresta estacional decidual e, até o presente momento, nenhum estudo parasitológico foi conduzido para esta espécie. A presente pesquisa teve como objetivo registrar o parasitismo em A. pyrrhogularis procedentes de quatro áreas do Ceará. É apresentado um inventário das espécies de helmintos, o qual foi constituído de nove taxa: Oochoristica travassosi (Cestoda), cistacantos (Acanthocephala), larvas de nematoide não identificadas, Cruzia sp., Oswaldofilaria sp., Physaloptera sp. e espécimes adultos de Parapharyngodon sp., Pharyngodon cesarpintoi e Physalopteroides venancioi (Nematoda). Para estes parasitas, foram verificados os parâmetros de infecção, trazendo a informação dos hospedeiros em que estas espécies já foram registradas. Foi observado que fatores biológicos (ontogenia, tamanho e sexo) do hospedeiro não influenciaram a abundância parasitária, mas significativas diferenças foram constadas de acordo com as estações e localidade analisadas, sendo que as maiores abundâncias de parasitas foram registradas em período de estiagem e em área conservada, indicando que os helmintos podem ser favorecidos em seus ciclos biológicos pela condição ambiental. Foi caracterizada a dieta de A. pyrrhogularis e demonstrado que a mesma sofre influencia espacial, o que re... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Caatinga is a Brazilian ecosystem still to be investigated due to its different environments and an endemic fauna of lizards. Ameivula pyrrhogularis belongs to the Teiidae and is found in the Northeast of Brazil, in the transition area between Caatinga, Cerrado, and temporary deciduous forest. To date, any parasitological study has been performed for this species. This research aimed to record the parasitism in A. pyrrhogularis from four areas of Ceará State, Brazil. An inventory of the helminth species is presented, which was composed by nine taxa: Oochoristica travassosi (Cestoda), cystacanths (Acanthocephala), larvae of unidentified nematode, Cruzia sp., Oswaldofilaria sp., Physaloptera sp., and adult specimens of Parapharyngodon sp., Pharyngodon cesarpintoi, and Physalopteroides venancioi (Nematoda). Infection parameters were verified for these parasites, bringing information on the hosts in which these species have already been registered. It was observed that biological factors (ontogeny, size, and sex) of the hosts did not influence the parasite abundance, but significant differences were recorded according to stations and locations, with the greatest parasite abundance reported in the dry season, indicating that the helminths can be favored in their biological cycles by environmental conditions. The diet of A. pyrrhogularis was characterized and showed that it is spatially influenced, which reflects the availability of prey. Moreover, it is suggested that food ite... (Complete abstract click electronic access below)
Doutor
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Fairbairn, Jonathan Paul. "Spatial and temporal dynamics of entomopathogenic nematodes." Thesis, University of Stirling, 2001. http://hdl.handle.net/1893/26685.
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The life-history and infection parameters of the entomopathogenic nematodes Steinernema feltiae (Filipjev)(Nematoda:Rhabditida) and Heterorhahditis megidis (Poinar, Jackson & Klein)(Nematoda:Rhabditida) were examined to provide specific details for the construction of mathematical SI models for biological control of soil insect pests. Laboratory experiments using the Greater Waxmoth, Galleria mellonella as the model host were undertaken to specifically examine the transmission behaviour of infective juvenile nematodes. The proportion of infective juveniles of S. feltiae which infected hosts was dependent on time. Previous studies declared that the proportion of infective juveniles which can infect is static, however, over a period of 5 days most of the infective juveniles infected hosts, demonstrating that the proportion infecting is dynamic. Infection of hosts by both species of nematode was compared using two mathematical representations of the transmission rate. Whereas the most parsimonious form of transmission for H. megidis was the linear Mass Action function, it was evident that, when measured at the individual nematode scale, S. feltiae transmission was non-linear. I postulated that this functional difference is due to the biology of the two species of nematodes. The subsequent effect of including the non-linear response on model predictions were investigated and it was demonstrated that the dynamics of the host nematode interaction became less stable. Spatial models of S. feltiae infection were parameterised from laboratory experiments, and control prediction of these models examined. The horizontal rate of dispersal through sand columns was determined in the presence and absence of hosts. Infective juveniles were found to disperse preferentially towards hosts. The predicted dynamics of pest control using the spatial moqel were highly dependent on the degree of nematode dispersal, host dispersal and the attraction of nematode infective juveniles towards hosts. The overall findings of this thesis have been placed in the context of epidemiological models created elsewhere, and predict that entomopathogenic nematodes may be targeted to specific pest systems with a high degree of success. An understanding of the infection biology of these nematode species is crucial in determining how and when pests may be controlled, and equally importantly, which systems successful control is not predicted.
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Wasmuth, James D. "Computational analysis of proteomes from parasitic nematodes." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/14636.
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The focus of this thesis is the comparison of nematode proteomes. I describe my work to identify sequences and sequence features that have patterns of interest to nematode biology. Such patterns include proteins that are unique to a parasitic feeding strategy, and protein domains that have been lost in certain nematode lineages. This involved not only global comparisons of the proteomes, but also delineating the protein domain complement of each species. One vital step in the analysis is identifying credible coding regions within the error-prone EST sequences. Robust identification of the coding regions presents an opportunity to perform comparative analysis previously confined to those working with complete genomes. To achieve this, I built the translation pipeline prot4EST, a hierarchical collection of freely-available algorithms. The benchmarking showed that prot4EST produced coding region predictions that were better than its constituent algorithms. Exploring the effect of sequence composition of both the studied species and the program’s training sets improved the accuracy of prediction. A database of high quality protein translations for all nematodes studies was generated, called NemPep. This was accompanied by a collection of predicted domains (NemDom). The decoration of protein sequences with domain annotation is not trivial, especially given the incomplete nature of ESTs. It was necessary to explore domain model assignment to ensure the most accurate results. The rigorous analysis of these resources has revealed: (1) proteins specific to certain nematode lineages; (2) the level and potential effects of contamination in the original cDNA libraries; (3) the extent of protein loss and domain modification in the caenorhabditid lineage.