The social insects provide a unique system for the study of aging and senescence. The striking differences in longevity that exist between queens and workers can be used to examine how different life histories can lead to very different aging patterns despite shared genetic heritage. In the ant Lasius niger, for example, workers live up to two years while queens have been known to live as long as 29 years.
For this reason, insect societies have been used to test models such as the free radical theory of aging. This model predicts that longer lifespan can be achieved by investing more resources into the removal from the organism of damaging oxidising agents such as Reactive Oxygen Species (ROS). These agents are predicted to damage not only lipids and proteins, but also DNA by generating mutations. The accumulation of such mutations in the soma (non germ-line tissues) over time are assumed to play a part in the degeneration associated with senescence.
Intrigingly, studies on social insect systems have consistently found results opposite to expectations: shorter-lived workers show greater expression of ROS removal genes than longer-lived queens. It is necessary now to take a step back and ask whether the different levels of damage of the type predicted by the free radical theory, such as DNA mutations, do indeed exist. Furthermore, enquiries are needed into whether the counter-intuitive pattern shown by ROS-removal genes are consistent across other maintenance processes such as DNA repair. Using quantitative PCR and single-molecule PCR, and using L. niger as a study species, I aim to find out:
a. Whether queens and workers show an increase in somatic DNA mutations with age.
b. Whether this increase occurs more rapidly in workers than queens.
c. Whether queens invest more than workers in expression of DNA repair genes.
This study will further our understanding of the causes of senescence and of the evolution of life history strategies that can prolong lifespan.
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