Figure 6

Spermatozoa counts in uninfected (left) and infected (right) male hosts. The counting was performed over the period where most of adult infected male Daphnia are expected to have spermatozoa and have survived infection (based on Figure 4). Infected males have fewer spermatozoa than uninfected males (linear regression controlling for variance due to the "Sampling day"; "Infection status", df = 1, F = 25.2, P < 0.001). While spermatozoa counts increased in uninfected males (linear regression with quadratic term, ("Age")^2, df = 1, F = 10.35, P = 0.001 and "Age" df = 1, F = 3.39, P = 0.07, left panel) it did not in infected males (linear regression, "Age", df = 1, F = 0.05, P = 0.82, right panel). Time is given as days after exposure to the parasite. Sample sizes are given in brackets.