Author: Jan Scholten
Name: Chytrids, the Greek chytridium meaning little pot, describing the structure containing unreleased zoospores.
Clades: Chytridiomycetes, Chytridiomycota, Fungi.
Mycology: Chytrids are saprobic, degrading refractory materials such as chitin and keratin, and sometimes act as parasites.
Chytridiomycota are zoosporic organisms in the kingdom Fungi. Chytrids are one of the early diverging fungal lineages, and their membership in kingdom Fungi is demonstrated with chitin cell walls, a posterior whiplash flagellum, absorptive nutrition, use of glycogen as an energy storage compound, and synthesis of lysine by the α-amino adipic acid (AAA) pathway.
Species of Chytridiomycota have traditionally been delineated and classified based on development, morphology, substrate, and method of zoospore discharge. However, single spore isolates (or isogenic lines) display a great amount of variation in many of these features; thus, these features cannot be used to reliably classify or identify a species. Currently, taxonomy in Chytridiomycota is based on molecular data, zoospore ultrastructure and some aspects of thallus morphology and development.
The chytrids have also been included among the Protoctista, but are now regularly classed as fungi.
In older classifications, chytrids, except the recently established order Spizellomycetales, were placed in the class Phycomycetes under the subphylum Myxomycophyta of the kingdom Fungi. Previously, they were placed in the Mastigomycotina as the class Chytridiomycetes. The other classes of the Mastigomycotina, the Hyphochytriomycetes and Oomycetes, were removed from the fungi to be classified as heterokont pseudofungi.
The class Chytridiomycetes has over 750 chytrid species distributed among ten orders. Additional classes include the Monoblepharidomycetes, with two orders, and the Hyaloraphidiomycetes with a single order.
Molecular phylogenetics, and other techniques such as ultrastructure analysis, has greatly increased the understanding of chytrid phylogeny, and led to the formation of several new zoosporic fungal phyla.
1. Vegetative body is coenocytic and thalloid, either globose or ovoid structure, either an elongated simple hypha, or well, developed mycelium.
2. Cell wall is mainly made up of chitin and glucan.
3. Nuclear division is intranuclear and centric type.
4. Members of this group produce motile cells at some stage of their life cycle.
5. Motile cells (zoospores and gametes) possess single posteriorly placed, whiplash type of flagellum except a few polyflagellate cells.
6. Sexual reproduction takes place by planogametes developed in gametangia. The fused gametes form zygote. Zygote on germination develops either into a resting spore or resting sporangium except’ a few those develop diploid thallus.
Synchytrium, Monoblepharis, Rhizophidium
Asterophlyctaceae: 2 genera
Chytridiaceae: 33 genera and 238 species
Chytriomycetaceae: 12 genera.
Familia: Nephridiophagaceae: 4 genera
Septochytriaceae: Allochytridium, Septochytrium.
Rhizophydiales: 16 families.
Polychytriaceae: 5 genera
Powellomycetaceae: 4 genera
Spizellomycetaceae: 4 genera
Lobulomycetaceae: 5 genera
Synchytriaceae: 4 genera
Polyphagaceae: 2 genera
Gonapodyaceae: 2 genera
Sanchytriaceae: Amoeboradix, Sanchytrium