Having excluded differences in engulfment by macrophages, spleen closure and spleen blood flow as reasonable explanations for the significantly higher numbers of 17X than 17XL parasites observed in the red pulp of the spleen, we aimed to characterize the dynamic behaviour of these parasites and to quantify their mobility within the spleen.
Many parasites have been assessed for their impact on fish behaviour (reviewed in [9]) but only a limited number of studies have considered the reverse situation, i.e. the direct impact of shoaling behaviour on parasite transmission [12], [13], [14].
This result may be due primarily to changes in the light conditions caused by the attack behaviour of the parasite.
In summary, we have shown the impact of sex-specific differences in shoaling behaviour on parasite transmission within a group-living host species.
We hope in future to more clearly separate the influence of sex and host behaviour on the spread of parasites within a host group, and explicitly test the relationship between shoaling and parasite transmission.
Recent work has also clarified the economic behaviour of investments in parasite eradication [3], [6], [7].
In measles, an external forcing (alternation of holidays and school terms) stimulates an intrinsic oscillatory behaviour of the host-parasite system caused by its short duration of infection and long-lasting host immunity [e.g. [ 16, 17]].
The assay determines the median effective time (ET50), i.e., the time required until impaired swimming and/or attachment behaviour becomes apparent in 50% of parasites, by conducting repeated examinations of test animals starting at the time point where exposure to a set drug concentration commences.
In the same way as bumblebees have adapted their foraging behaviour to reduce the uptake of parasites (Fouks & Lattorff, 2011), bumblebees may be adapted to modify their diet with curative nectars once infected.
Parasites may differentially impact host lineages due to lineage differences in immunocompetence and genetic diversity associated with parasite resistance, differences in physiology or behaviour and environmental differences affecting the prevalence of parasites or their intermediate hosts [19].
