The evidence suggests that the flagellate was a cause, rather than a consequence, of the poor condition of the cladocerans. In support of its role as a pathogenic parasite is the following: (i) strong association between bodonid infection and mortality of M. macrocopa, (ii) strong association between sea salt treatment and reduced mortality, and (iii) no association between otherwise stressed Moina populations (population density, starvation, age) and flagellate infection.