REPEATED ZOOSPORE EMERGENCE IN SAPROLEGNIA-PARASITICA

A method of determining the number of phases of repeated zoospore emergence in vitro in the water mould Saprolegnia parasitica was developed. Using vortexing to encyst zoospores it was possible, in a synchronous manner, to achieve up to six consecutive generations of cysts and laterally biflagellated zoospores. It was found that the length of time the zoospores were allowed to swim influenced the number of zoospore generations which could be produced. After zoospore encystment the spores can be triggered to either germinate or release a new zoospore depending upon the addition of external nutrients. Germination of cysts could 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: either repeated zoospore emergence or germ tube formation.