Year

2012

Degree Name

Doctor of Philosophy

Department

School of Biological Sciences

Abstract

There are two commonly used environmental manipulations that have been shown to extend longevity across a range of animal species: temperature (in ectotherms) and dietary restriction (in endotherms and ectotherms). Using these two manipulations in model organisms, a number of correlations between levels of oxidative damage and longevity have been found, which are largely consistent with the „oxidative stress hypothesis of ageing‟. However, before mechanisms identified in a few model organisms can be accepted as being general features of the ageing process, it is essential that these manipulations are shown to extend lifespan in a broader group of animals.

Ageing is measured through both demographic measures of mortality and by determination of changes in physiological functionality at cellular and molecular levels. Rodent models are typically used, due to their physiological similarity to humans and because their body size enables thorough biochemical analysis. The lifespans of rodents, however, require experiments lasting several years to obtain demographic measurements. By contrast, invertebrate models have the demographic advantage of short lifespans and relative ease of husbandry and experimental manipulation, but their small size often limits biochemical measures, which are based on pooled samples from many individuals. The ageing process is not however, constant across tissue-types, therefore, pooling individuals can lead to both underestimating individual variation in the ageing process and missing age-related tissue specific effects.

This thesis examines longevity and membrane fatty acid composition in a new model organism, the blowfly, Calliphora stygia. This species has the advantage of a short lifespan but a relatively large body size among flies, that allows for individualbased measurements. This is advantageous not only for biochemical measures, but also for implementation of treatments such as dietary restriction, where food consumption of populations can be measured over the entire lifespan. I examined the effects of temperature and diet energy content on longevity and demographic and cellular senescence. Temperature effects were examined both after exposure to constant temperatures, and after transfer to lower or higher temperatures. Diet energy content was varied by either altering the sugar content of the diet, or by varying the yeast content of the diet, to examine potential differences between diet composition and energy consumption.

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