Transmission of the microsporidian Glugoides intestinalis in relation to spatial structure of the host Daphnia magna

Abstract

Daphnia magna selects different depths according to its genotype, its size or infection by a parasite. As a result, waterflea populations are often vertically structured. This vertical structure, i. e. different distances between waterfleas, might slow the progress of microparasite epidemics. This would enable avoidance behaviour to evolve. I tested in a set of experiments for both, distance effects and avoidance behaviour. The experiments were performed with the host-parasite system of D. magna and its microsporidian gut-parasite Glugoides intestinalis. Infection depended on spore loads in infected waterfleas. Transmission, however, was not affected by distance to infected animals. Avoidance behaviour was absent. The results suggest that the host's spatial structure does not influence the transmission of G. intestinalis in the populations of Daphnia magna living in shallow water. Rather, successful transmission depends on the dynamics of the water.