The Chytridiomycota is a phylum in the kingdom Fungi, whose members produce unwalled, asexual spores that swim by means of a single, posteriorly directed flagellum. Members are microscopic saprobes or parasites found in fresh and saline water and soils. The phylum contains two classes, the Monoblepharidomycetes with one order and the Chytridiomycetes with seven orders and several undescribed groups. Orders are based on molecular and ultrastructural characters. Many species of chytrids were described without these characters and need to be re‚Äźexamined to place them in the proper orders and genera. Chytrids are important as degraders of cellulose, keratin and chitin and also as algal pathogens, sometimes controlling algal blooms. A few are plant pathogens with Synchytrium endobioticum causing black wart of potatoes. The rhizophydialean chytrid Batrachochytrium dendrobatidis grows in keratinised skin cells of amphibians and is pathogenic to many species, causing amphibian population declines on several continents and extirpation of some species.

Key Concepts:

  • Members of the Chytridiomycota are ubiquitous in aquatic and terrestrial habitats and can be found by microscopically examining baits placed with aquatic debris or with soil plus water.

  • Chytridiomycota reproduce primarily by zoospores, which are mitotically produced, contained by a membrane and motile via a posteriorly directed flagellum.

  • Because of convergent evolution of light microscopic characters, many genera described before the molecular era are polyphyletic and may not be placed in the correct order.

  • Systematics in the Chytridiomycota relies on transmission electron microscopic features of zoospores and on DNA sequence information.

  • Algal parasites are usually species specific and are capable of affecting population levels of planktonic algae.

  • Batrachochytrium dendrobatidis is a chytrid pathogen of amphibians responsible for some amphibian population declines on at least five continents.

Keywords: chytrid; chytridiomycetes; aquatic fungi; fungus; zoosporic fungi

Figure 1.

Major types of development in the Chytridiomycota: (a) endogenous; (b) exogenous, monocentric; (c) exogenous‐endogenous; (d‐f) polycentric; (d) rhizomycelial; (e) mycelial; (f) colonial. ant, antherozoid; o, operculum; oog, oogonium; rs, resting spore; zc, zoospore cyst; zsp, zoosporangium.

Figure 2.

Current phylogenetic theory of Chytridiomycota (orders and clades), Neocallimastigomycota, and Blastocladiomycota, constructed from ribosomal DNA operon sequences (adapted from James et al., ). Authors and year of description or emendment for phyla and orders in parentheses.

Figure 3.

Schematic representation of the kinetosomal areas of the eight orders in the Chytridiomycota: (a) Monoblepharidales; (b) Chytridiales; (c) Cladochytriales; (d) Lobulomycetales; (e) Polychytriales; (f) Rhizophydiales; (g) Rhizophlyctidales; (h) Spizellomycetales. G, Golgi apparatus; K, kinetosome; mb, microbody; mt, microtubule root; MTOC, microtubule organising center; N, nucleus; NFC, nonflagellated centriole; pl, plates; Rh, rhizoplast; SI, striated inclusion.

Figure 4.

Thalli of Batrachochytrium dendrobatidis in skin cells of a northern leopard frog (Lithobates pipiens).



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Longcore, Joyce E, and Simmons, D Rabern(May 2012) Chytridiomycota. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000349.pub3]