Members of phycomycetes produce motile naked uninucleated zoospores. The zoospores are formed endogenously within the zoosporangium. They are found mostly in aquatic fungi. The members possess the uninucleated or the multinucleated flagella. 1-2 flagella are borne anteriorly posteriorly or laterally. The examples of the fungus are Albugo, Synchytrium, Phytophthora, and Achyla. These fungus are classified into two that is based on number of flagella i.e. a. uniflagellate zoospores and b. the biflagellate zoospores.
a. The uniflagellate zoospore is again divided into two that is based on the type and position of flagella. They are:
1. Zoospores with posterior whiplash flagella.
2. Zoospores with anterior tinsel type flagella.
Zoospores with posterior whiplash flagella:
The zoospore is tadpole like with a pear shaped head and a single trailing flagellum. The crescent shaped nuclear cap surrounds the transparent nucleus and the flagellum originates from the basal body or the kinetosome. The movement of zoospore occurs by the rhythmic lashing of flagellum it is also capable of amoeboid changes of shape.
Zoospores with anterior tinsel type flagella:
This type of zoospore is found in hypochitridiomycetes group. The zoospore swims in a spiral path by the undulation of its anterior flagellum. The nucleus is in the anterior flagellum which arises from a kinetosome, which is nearer to the nuclear membrane. The membrane bound nuclear cap is absent; there are numerous ribosomes, lipid bodies, vacuoles, microtubules a dictyosome and the endoplasmic reticulum.
b. Biflagellate zoospore: The biflagellate zoospore is the characteristic of Oomycetes. This zoospore is heterokont i.e. it has two types of flagella one of the tinsel types and the other one whiplash type flagella. The flagellum is inserted apically or laterally arising from the groove. The tinsel type flagellum is directed forward and whiplash type flagella is directed backwards. The zoospore is ovoid with blunt anterior end with a longitudinal groove or furrow. The posterior flagella are longer than the anterior.