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3.2: Aquatic Fungi (Chytrids)

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    Like many of the earlier fungal lineages, this group has been divided into several distinct lineages. Once all classified as Chytridiomycota, these early, aquatic fungi are now grouped into Blastocladiomycota, Chytridiomycota, and Neocallimastigomycota. Though likely not directly related, these fungi share a few characteristics:

    • Primarily aquatic, though some are parasites of terrestrial plants
    • Swimming spores (zoospores) with a single whiplash flagellum

    Saprotrophic Chytrids

    seeds floating in water, covered by fuzzy white hyphae

    A somewhat elongate sporangium (darker) at the end of a hyphal filament
    Two sporangia (darker) at the end of a hyphal filament. Where the first is produced, the filament takes a turn, goes around it, and ends by producing the second.
    Figure \(\PageIndex{1}\): Chytrids in the genus Allomyces are aquatic decomposers. The top image shows sesame seeds floating in pond water with fungus growing off of them. The second image (bottom left) shows a microcopic image of a zoosporangium produced at the end of a hyphal filament (asexual reproduction). The final image (bottom right) shows two resting sporangia, the result of sexual reproduction. Photos by Tom Bruns, CC-BY-NC.

    Parasitic Chytrids

    Micromyces zygogonii, a chytrid fungus, living inside the cells of Spirogyra
    Figure \(\PageIndex{2}\): This image shows Micromyces zygogonia (Chytridiomycota), a parasite with spiky structures (prosori), inside the cells of the alga Spirogyra. Photo Credit Fahrenheit_66, CC-BY-NC.
    A compilation of 6 pictures, A-F, each with a diatom being parasitized by a chytrid (large, globose structures attached to frustule)
    Figure \(\PageIndex{3}\): In these images, the part of the chytrids you can see is the large, globose struture attached to the outside of the diatom. This is the part of the thallus where spores are made. "Chytrid parasites of marine diatoms. (A) Chytrid sporangia on Pleurosigma sp. The white arrow indicates the operculate discharge pore. (B) Rhizoids (white arrow) extending into diatom host. (C) Chlorophyll aggregates localized to infection sites (white arrows). (D and E) Single hosts bearing multiple zoosporangia at different stages of development. The white arrow in panel E highlights branching rhizoids. (F) Endobiotic chytrid-like sporangia within diatom frustule. Bars = 10 μm. For more details see: Hassett BT, Gradinger R (2016) "Chytrids dominate arctic marine fungal communities". Environ Microbiol, 18(6):2001–2009." Unknown author, CC BY 4.0, via Wikimedia Commons.
    Synchytrium papillatum causing pink pustules on a Geranium
    Figure \(\PageIndex{4}\): A parasite on Geranium, this Synchytrium papillatum (Chytridiomycota) is forming pink growths on the calyx and peduncle of these flowers. Photo Credit: James Bailey, CC BY-NC.
    A frog with lesions on its skin, caused by the chytrid pathogen Batrachochytrium dendrobatidis
    Figure \(\PageIndex{5}\): Likely the most infamous chytrid, Batrachochytrium dendrobatidis (Chytridiomycota) causes a lethal skin infection in many amphibians. This now widespread invasive pathogen is contributing to global amphibian declines and extinctions. Photo by Jonathan (JC) Carpenter, CC BY-NC.

    This page titled 3.2: Aquatic Fungi (Chytrids) is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Maria Morrow (ASCCC Open Educational Resources Initiative) .

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