Discussion

We conducted a series of experiments to determine how the age of an individual will influence susceptibility. Our work uses the crustacean Daphnia magna and the bacterial parasite Pasteuria ramosa. Older mothers tended to be more resistant. Offspring born to older mothers were also more resistant. Infection also reduces host longevity, and the expected lifespan-extending effects of dietary restriction are not apparent when individuals are infected. Thus, age structure has considerable potential to alter the rate of disease spread, and infection may in turn alter age structure.