REPEATED ZOOSPORE EMERGENCE IN SAPROLEGNIA-PARASITICA

A method of determining the number of phases of repeated zoospore emer gence in vitro in the water mould Saprolegnia parasitica was developed . Using vortexing to encyst zoospores it was possible, in a synchronou s manner, to achieve up to six consecutive generations of cysts and la terally biflagellated zoospores. It was found that the length of time the zoospores were allowed to swim influenced the number of zoospore g enerations which could be produced. After zoospore encystment the spor es can be triggered to either germinate or release a new zoospore depe nding upon the addition of external nutrients. Germination of cysts co uld only be triggered within 45 min of mechanically induced encystment . Thus, it is now possible in this species to study in detail the two alternative developmental pathways which follow after encystment: eith er repeated zoospore emergence or germ tube formation.