DISPERSAL AND COLONIZATION OF THE EPIBIONT ALGA KORSHIKOVIELLA GRACILIPES (CHLOROPHYCEAE) ON DAPHNIA PULICARIA (CLADOCERA)

The dispersal and colonization of Korshikoviella gracilipes (Lambert) Silva on Daphnia pulicaria Forbes collected from a small high mountain lake in southern Spain were investigated in a series of laboratory experiments. Results of these laboratory experiments were related to previous field data. Massive release and detachment of zoospores, which is the dispersal stage of the epibiont, occurred just before molting. A lower number of zoospores was dispersed from the discarded molts and a scant number dispersed during the intermolt period. Release of cysts, which is the overwintering stage of the epibiont, mainly occurred immediately after the molt was discarded. The production of dispersal forms (zoospores and cysts) shows precise temporal synchronization with the molting process in Daphnia. The colonization of uninfected individuals from infected molts and from infected individuals was rapid. Our results suggest that colonization of field animals in this lake is efficient and is facilitated by the coincident aggregates of substrate and epibiont.