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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.
1

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

Nguyen, Duyen. January 1998 (has links)
The effects of food availability and the presence of the parasite, Plagiorchis elegans, on the probability of Aedes aegypti preimagos to transform from one immature stage to the next over consecutive 24- or 48-hour periods of time were determined. Under conditions of low food availability, 24- and 48-hr transition probabilities of all larval instars, to the next were reduced. Increases in food availability reversed this process, causing significant decreases in same-stage transition probabilities. However, as transition to successive stages increased among first, second, third and fourth instars, there was concomitant significant increase in first and fourth preimago mortality. Addition of Plagiorchis elegans cercariae caused significant decreases in the 24 and 48-hour same-state probabilities for all pre-imago stages. Successive stage transitions for first, second and third instars were significantly increased while those of fourth instars and pupae were significantly decreased following exposure to the parasites. The mortality of all preimago stages significantly increased with exposure to parasite, but was highest among fourth instars and pupae. There were strong food-by-parasite interaction effects among first, second and third instars. Differences in transition probabilities increased with increasing food levels between controlled and parasite-exposed groups. The opposite was true for fourth instars and pupae. While there was no significant interactive effect between food and the presence of the parasite on pupae regardless of food concentration, this was not true for mortality probabilities among fourth instars. Significantly more fourth instars died in response to parasite exposure and there were significant interactive effects of food and parasites on the probability of fourth instars transformation to pupae over 48 hrs.
2

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.
3

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

Nguyen, Duyen. January 1998 (has links)
No description available.
4

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.

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