Figure 4.

Optical densitometric measures of 5-HT immunoreactivity within the tritocerebral region of G. pulex infected with P. laevis, P. tereticollis and P. minutus, shown as relative to uninfected controls (dotted line). Only the brains of those individuals showing extreme alteration of normal phototactic behaviour were examined here. Figures show standardized means against site-specific controls, associated 95% CI, sample size and significance as determined by ANOVA. No effect of experimental block was found (p=0.05 for all).