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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.
11

Aedes aegypti population dynamics : the effects of food availability and experimentally induced mortality of late instar larvae

Cermark, Paul M. January 1998 (has links)
The effects of food availability and selective control of late instar larvae of Aedes aegypti on preimago population structure, mortality, adult abundance, sex ratios, and size of females were examined. Food availability i an important factor in determining preimago population structure and mortality. At optimal food availability more adults emerged, females were larger and in higher proportions than at suboptimal food availability. The effects of selective control on preimago population structure and post treatment larval mortality differed with food availability. At suboptimal food availability the type of control applied had a significant effect. Simulated pathogen-induced mortality resulted in a shift of the population to late instars and temporarily reduced density dependent mortality. The findings suggest that although both pathogens and predators reduce intraspecific competition by directly killing competitors, pathogens also provide an influx of food. Compensatory mortality may result from a reduction of intraspecific competition caused by biocontrol agents.
12

Nutrition, competition and mortality : the impact of Plagiorchis elegans on the development of Aedes aegypti

Nguyen, Duyen. January 1998 (has links)
No description available.
13

Aedes aegypti population dynamics : the effects of food availability and experimentally induced mortality of late instar larvae

Cermark, Paul M. January 1998 (has links)
No description available.
14

The effects of nutrition deficiency as a causal agent of population cycling and the impact of various densities of Plagiorchis elegans on the population structure of Aedes aegypti pre-imagos /

Hartley, Bruce J. January 1996 (has links)
No description available.
15

Presença de Ascogregarina spp. em populações de Aedes (Stegomyia) spp. no estado de Santa Catarina e aspectos da interação parasito-hospedeiro em Aedes aegypti / Presence of Ascogregarina spp. IN Aedes (Stegomyia) spp. populations in Santa Catarina state and aspects of parasite- host interaction in Aedes aegypti

Pereira, Thiago Nunes January 2016 (has links)
Ascogregarina taiwanensis e Ascogregarina culicis são protozoários que parasitam Aedes albopictus e Aedes aegypti, respectivamente, e são conhecidos por interferir fisiologicamente em seus hospedeiros. Alguns estudos têm relatado a distribuição destes protozoários em diferentes regiões do globo, entretanto, no Brasil, relatos destes protozoários são raros. O objetivo deste trabalho foi verificar a presença de Ascogregarina spp. em Ae. albopictus e Ae. aegypti no estado de Santa Catarina e a possível influência de seu parasitismo aliado aos inseticidas temephos e ao óleo de neem Azadirachta indica. Os resultados revelaram a presença de A. taiwanensis em larvas de Ae. albopictus nas cidades de Capivari de Baixo, Laguna e Gravatal. Somente em Tubarão foram encontradas as duas espécies de mosquitos albergando este protozoário. Com relação aos bioensaios químicos onde se testou insetos parasitados (+) e não parasitados (-) por A. taiwanensis, as CL50 foram 0.025 mg/L (+) e 0.063 mg/L (-) para temephos e 0,815 mg/L (+) e 1.812 mg/L (-) para óleo de A. indica. Os resultados demonstram que houve diferença significativa entre os valores de mortalidade em relação ao grupo controle com P<0.001. Divergindo dos relatos na literatura cientifica, observou-se infecção por A. taiwanensis em Ae. aegypti, porém, a transmissão vertical em laboratório foi observada somente em Ae. albopictus.Este é o primeiro registro de A. taiwanensis para Santa Catarina e o terceiro para o Brasil. A utilização dessa espécie de gregarina associada a inseticidas poderia ser um método interessante para futuros estudos de controle de Ae. aegypti. / Ascogregarina taiwanensis and Ascogregarina culicis are protozoa parasites of Aedes albopictus and Aedes aegypti, respectively and these parasites are able to interfere physiologically in their hosts. Some studies have reported the distribution of these protozoa in different parts of the world, however in Brazil, reports about these protozoa are rare. The aim of this study was to verify the presence of Ascogregarina spp. in Ae. albopictus and Ae. aegypti in Santa Catarina and the possible influence of its parasitism with insecticide temephos and the Azadirachta indica oil. The results demonstrated the presence of A. taiwanensis in Ae. albopictus larvae in the cities of Capivari de Baixo, Gravatal and Laguna. Only in the city of Tubarao the two species of mosquitoes have been found harbouring Ascogregarina taiwanensis. Regarding to bioassays evaluating parasite (+) and non-parasited (-) mosquitoes by A. taiwanensis, the LC50 0.063 mgL (+) and 0.025 mgL (-) for temephos and 0.815 mgL(+) and 1,812 mgL (-) for A. indica oil. The results show that there was significant difference between the mortality values comparing to the control group with P<0.001. Diverging from scientific literature reports, infection of this gregarine was observed, both in field and laboratory reared Ae. aegypti populations. However, the vertical transmission of A. taiwanensis could be observed only in Ae. albopictus. This is the first record of A. taiwanensis in Santa Catarina and the third in Brazil. The use of this species of gregarine in association with insecticides this could be an interesting method for future studies about control of Ae. aegypti.
16

Behavioural responses of fourth instar Aedes aegypti (Diptera:Culcidae) larvae to Plagiorchis elegans cercariae

Kioulos, Ilias P. January 2003 (has links)
Exposure of fourth instar Aedes aegypti larvae to graded concentrations of the entomopathogenic cercariae of the digenean Plagiorchis elegans, induced fundamental changes in the partitioning of time among a number of major behavioural activities. In the absence of the parasite, swimming, breathing and feeding remained stable over time. Grooming was rarely observed. In the presence of cercariae, larvae increased grooming 26-fold. Concomitantly, feeding was reduced to 33% of control values. Times spent swimming and breathing remained unchanged. The increase in grooming activity was attributable to the attachment of cercariae to the surface of the mosquito larvae, but was independent of infection. Grooming reduced cercarial penetration. Seventy-five percent of cercariae were lost to predation by larvae, but their caloric value was insignificant and failed to compensate for the loss of feeding time due to grooming. The findings are discussed in the context of their impact on larval growth, development and survival.
17

The impact of selective oviposition, egg hatchability, food availability and infection with Plagiorchis elegans on the pre-imago population dynamics of Aedes aegypti (Diptera:Culicidae) /

Schwab, Anne Elisabeth. January 2000 (has links)
Cercariae of the digenean Plagiorchis elegans cause high levels of morbidity and mortality among larvae of Aedes aegypti . The impact of this parasite on the larval population dynamics of the experimental host as mediated through intraspecific competition, egg hatchability and ovipositional preference was assessed by calculating the probability of pre-imagos to develop from one stage to the next, or to die within consecutive 24 h intervals. Attractiveness of the water to ovipositing females in a dynamic larval population was not affected by exposure to the parasite, but varied significantly over time, regardless of food abundance. In optimally fed populations, these changes were positively correlated with pupal production, but were not affected by early instar development. Most of the entomopathogenic effects of the parasite were expressed in the pupal stage. Thus, exposure to the parasite significantly reduced adult emergence, but did not greatly impair pre-imago development. Nonetheless, exposure to various levels of the parasite significantly increased mortality of all larval stages. Suboptimally fed larval populations displayed severely impaired development and produced few adults. Exposure to P. elegans increased adult production slightly, suggesting depensatory mortality. In nutritionally stressed populations, no correlation was found between biomass and ovipositional preference, but attractiveness of the water was significantly increased by the removal of individuals by pupation or mortality. Egg hatchability was not significantly affected by population structure, but varied with the nutrient content of the water. This study provides new insight into the use of parasites as agents in the biological control of mosquitoes.
18

The influence of experimental Plagiorchis nobeli (Trematoda: Plagiorchiidae) infections on the survival and development of Aedes aegypti /

Dempster, Shiona Jane January 1988 (has links)
No description available.
19

The effects of Plagiorchis noblei, Park, 1936 on the reproductive success and behaviour of adult Aedes aegypti /

Kimoro, Charles Omuoyo January 1990 (has links)
Aedes aegypti pupae were exposed to cercariae of the digenean Plagiorchis noblei in order to assess the effects of infection on the spontaneous flying activity and reproductive success of surviving adults. Infections established primarily in the thorax and abdomen of the insects (mixed infections) or in the abdomen alone. In mixed infections, as few as one or two metacercariae in the thorax reduced the spontaneous flying time of females by almost half. Such infections also reduced total egg production, the number of ovarian cycles, fecundity per cycle, as well as fertility and life span of female hosts. The fertility and life span of males was similarly affected. Purely abdominal infections reduced the life span of males and females as well as the fertility of males, but only at high intensities. Such effects on adult behaviour, reproductive success and life span may augment the known lethal effects of the parasite.
20

Aedes aegypti (Diptera:Culicidae) oviposition attractionrepellency

Zahiri, Nayerolsadat. January 1997 (has links)
Waters from normal larvae of Aedes aegypti (L.) are highly attractive to ovipositing conspecific females, whereas waters from larvae infected with the entomopathogenic digenean parasite, Plagiorechis elegans Rudolphi, are rendered strongly repellent. The production of the repellent appears to be mediated by the degree of environmentally induced stress experienced by the larvae. Whereas waters from fully fed larvae were highly attractive as an oviposition site, these were rendered progressively less attractive, and eventually strongly repellent as the larvae were deprived of food over a period of 7 days. Crowding of the larvae elicited similar repellent effects as did close contact between larvae and the walls of the container in which they were reared. The site of infection in the tissues of the mosquito larvae also influenced the intensity of repellency. Thus, infections of the head and thorax induced the highest degree of repellency, and infections of the abdomen the lowest. The repellent effect overrode attraction and remained stable for more than one week at 27°C, and even longer at lower temperatures. Stressors which induced repellency all precipitated similar physical and physiological changes in mosquito larvae. They reduced wet and dry weights and the concentration of serum carbohydrates, amino acids, proteins and lipids. Both infection and crowding rendered larvae anorexic. As well, infected larvae appeared to be unable to convert trehalose to glucose, thereby exacerbating the energy deficit. Incubating infected larvae in a dilute glucose solution significantly reduced the repellent effect of their waters. Addition of glucose to already repellent waters had little effect. Larvae of another species, Aedes atropalpus Coquillett, were equally capable of producing repellent effects when infected with P. elegans, and gravid females of Ae. aegypti were equally sensitive to these as to conspecific waters. This sensitivity, however, was not reciprocal. Aedes

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