Parasite Development
A total of 192 out of the 300 jars had at least one D. magna that
showed signs of visible infection by the end of the experiment. In the
experiment with live D. magna , we observed a general increase in
the proportion of jars with infected hosts with increasing temperature,
with between 90-100 % being infected from 15 oC
upwards for both resistotypes. At 10 and 12.5 oC the
more-resistant clones had much lower prevalence than the
more-susceptible ones (15 vs 55 % at 10 oC, 20 vs. 55
% at 12.5 oC), resulting in a significant interaction
between resistotype and temperature (estimate= -0.61 ± 0.25, p=0.017)
(Figure 2c). For animals that became infected, main effects of
temperature and resistotype on time to visible infection were detected,
with time to infection decreasing with increased temperature (estimate=
-4.12 ± 0.19; p<0.0001), and more-susceptible resistotypes
becoming visibly infected faster than more-resistant ones (estimate=
-4.17 ± 1.5; p=0.005) within each temperature (Figure 2e).
In the ephippia treatment, prevalence by the end of the experiment was
also positively associated with temperature (estimate 1.38 ± 0.4;
p=0.0005) (Figure 2d). However, in contrast to the live D. magnatreatment, below 15 oC no infections were observed and
the overall proportion of jars with infected animals at higher
temperature were lower than for live D. magna treatments (30 %
at 15 oC, 65% at 17.5 and 20 oC).
Among ephippia hatchlings that became infected, time to infection
shortened with increasing temperature (estimate= -1.87 ± 0.36;
p<0.0001) (Figure 2f). The time to visible infections for
these animals was comparable to those born from asexual reproduction at
these temperatures.