9 Ecological and Economical Importance of Parasitic Zoosporic True Fungi

Abstract

Species of zoosporic true fungi have been observed by light microscopy in terrestrial, freshwater, and marine habitats. Most of the described species are saprotrophs or mutualists, but some species are parasites of higher plants, animals, and phytoplankton. Some species play significant ecological roles or cause economically important diseases. A few may cause emerging infectious diseases. Many other species are known only from rDNA sequences obtained from environmental surveys. Unfortunately, in general zoosporic true fungi have been poorly sampled and poorly studied. We predict that many more species will be discovered in the future. Ten examples from three taxonomic groups (Chytridiomycota, Blastocladiomycota, and the Olpidium clade) are discussed in this chapter. The pathosystem model provides an excellent basis for understanding host–parasite relationships and the effect of environmental parameters on these microorganisms. The important ecological roles of zoosporic parasites in food-web dynamics are highlighted. These fungi are particularly well-adapted to their environments because of motile zoospores and resistant sporangia.