zoospore

A motile usually naked spore with one or more flagella. It may be produced either by a zygote or a zoo-sporangium and is dependent on water for dispersal. In some species, e.g. the green alga Ulothrix, two types of zoospore may be developed. In Ulothrix large macrozoospores with four flagella and small microzoospores with two flagella are seen. Zoospores may encyst under adverse conditions. Compare aplanospore.