water moldalso spelled water mouldany of about 150 species of
fungi belonging to the order Saprolegniales within the class
Oomycetes(phylum Oomycota, kingdom Chromista). Many of them live
in fresh or brackish water or wet soils. Most species are
saprobic (i.e., they live on dead or decaying organic matter),
although some cause diseases in certain fishes, higher plants,
algae, protozoans, and marine invertebrates. The mycelium
(filaments composing the body of the fungus) is conspicuous
around bits of decaying organic matter. Reproduction is by
motile, asexual spores (zoospores), which may be of two types:
pear-shaped with two apical whiplike structures (flagella) or
kidney-shaped with two flagella on the concave side. Zoospores
are used to classify different species of water molds. In sexual
reproduction, fusion of gametes (sex cells) from differentiated
sex organs takes place in an oogonium.