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Title: Evolutionary trade-offs with innate immune resistance : implications for ageing, oxidative stress resistance and motor function
Author: Williamson, Kirstin
ISNI:       0000 0004 5349 2440
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2014
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Resistance to infection is essential to ensure survival and thus maximise offspring potential. However, resistance is not ubiquitous across the animal kingdom, or even within a population from the same species. It is thought that this is due, in part, to the costs involved in producing and maintaining a competent immune system and a corresponding decrease in other fitness-related characteristics. The focus of this research was to determine how immune resistance can impact upon mechanisms relating to ageing, resistance to oxidative stress and motor function. In order to do this a Drosophila melanogaster model system was implemented, selected for resistance to larval parasitism by the parasitoid wasp, Asobara tabida. Firstly, it was necessary to gain a greater understanding of the immune mechanisms within the Drosophila model. This included how aspects of the immune system changed over time, in order to determine how these might act upon other processes at different stages of the ageing system. Resistance to larval parasitism corresponded to an increased number of circulating immune cells during the larval phase. This difference was no longer apparent in the adult Drosophila. Young resistant adult females revealed increased levels of overall cell metabolism, measured by the production of intracellular reactive oxygen species (ROS), a finding not seen in males or in the developing larvae. Lifespan was reduced in the resistant female, but not male, Drosophila. It was hypothesised that this reduction may in part be due to the augmented production of intracellular ROS in the young adult female, which at high concentrations can cause oxidative stress with known cytotoxic effects. However, differences in resistance did not translate to altered survival under acute oxidative stress, induced by the consumption of the toxin paraquat. Other factors may regulate these changes in longevity in the resistant females, such as genetic or resource-based trade-offs. Functional assays were performed to assess motor function in the larvae and adult Drosophila. Resistant larvae showed less turning behaviour on a non-food background than their control counterparts, a trait generally linked to more proficient motor function. Differences in motor function continued into the adult females, where increased climbing velocities were found irrespective of age. This implies that changes in motor function may be determined during development, thus variations in resistance during this phase can cause life-long impacts on the individual, presumably by altering the development of other physiological systems.
Supervisor: Mudher, Amritpal ; Kraaijeveld, Alex Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH301 Biology ; QR180 Immunology