THE INFECTION OF MOINA-MACROCOPA BY A COLONIAL PERITRICH, EPISTYLIS-DAPHNIAE, AND ITS EFFECTS ON THE HOST

1. The effects of infection by Epistylis daphniae on its host, Moina m acrocopa, were studied in the laboratory at 28-degrees-C by comparing the growth, reproduction and survival between infected and uninfected hosts. 2. Infestation by epizoites had little or no effect on the surv ival of the cladoceran hosts when adequate food was present. 3. The in fected cladocerans had lower growth rates as juveniles, lower net repr oduction rates as adults, and smaller body size at death than uninfect ed hosts. 4. The index of infection at different stages in the life cy cle was related to the durations of intermoult period. Ranked in order of both index of infection and intermoult duration, the development s tages were: old adult > young adult > juvenile.