Chytridiomycetes

(mycology) A class of true fungi.

A monophyletic group of true fungi in the subdivision Mastigomycotina. The zoospore has a single, posteriorly directed, whiplash-type of flagellum; a few species are polyflagellated. The Chytridiomycetes are generally regarded as primitive and are probably representative of the ancestral group for the true fungi, but they have also been classified within the Kingdom Protista and Kingdom Protoctista.

The thallus may be unicellular, colonial, or filamentous and consists of a single reproductive body (monocentric) or many reproductive bodies (polycentric). The asexual reproductive body comprises a zoosporangium that releases zoospores. The five orders are classified primarily on differences in zoospore ultrastructure and include the Chytridiales, Spizellomycetales, Blastocladiales, Monoblepharidales, and Neocallimastigales.

Chytrids are cosmopolitan in distribution and are found in environments from the tundra to the equatorial rainforests, in alkaline or acid soil, in peat bogs, and in fresh or brackish water. Many are saprobes, but some are parasites of microflora and fauna such as algae and rotifers. Some are of interest because they destroy mosquitoes and others are parasites of vascular plants and are of economic concern as vectors of plant viruses. The Neocallimastigales are obligate anaerobes in the rumen and digestive tract of herbivores, where they are important in the breakdown of cellulose and hemicellulose fiber. See also Eumycota; Fungi; Mastigomycotina.