Experiment 2: Intraspecific selectivity
(a) Succession of infection stages among diatoms grown under light conditions. In
Cgranii cultures infected by P.diadema, the diatoms were not equally infected by
flagellates, but there was a succession of stages of infection among diatoms. Infection
started to spread ~2 days after inoculation, and on Day 3 the first empty frustules
of infected cells were found (Figure 2). Although on Day 4 the number of
infective flagellates was several orders of magnitude higher than that of diatoms,
so that all cells could have been multiply infected, - 1 % of the C.granii still
remained uninfected. These cells were not resistant, however, but were also
infected the following day. This succession of infection stages indicated that
C.granii grown under light conditions were individually different in their attractiveness
for infection by the parasitoids.