The Wonderful World of Fungi, Part VI
Fascinating Members of the Division Zygomycota
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
In the previous blog on the Zygomycota (part V), I indicated that this group of fungi had some fascinating members regarding their life cycles, spore release, and/or modes of nutrition. In this regard, I wrote a blog on coprophilous (dung loving) fungi in which I detailed some of the fascinating antics of the fungi growing on that nutrient rich and odiferous substratum. One of the most interesting of the coprophilous fungi is the “hat-thrower” or “shotgun fungus” that belongs to the genus Pilobolus. Check that blog for some links to videos showing the amazing spore release of the sporangium from this fungus.
Numerous other members of the Zygomycota deserve to be mentioned regarding unusual features they possess. One group of interest are those fungi placed in the Class Trichomycetes. (The word Trichomycetes means “hair fungi,” and this name is used because of the hair-like or thread-like thallus of the fungus that grows in the gut of the host organism. When growing in dense aggregates the fungal thalli may make the inside of the gut appear hairy.) Nearly all the members of this class live in the guts of living arthropods: insects, millipedes, crustacea, etc. Most members are attached to the gut lining of herbivorous or detritivorous arthropods, not carnivorous species. A given species of trichomycete is not usually limited to a single host species, but also will attach itself to the gut of related species. Most species of trichomycetes appear to be commensals, but at least one species is known to parasitize and kill mosquito larvae. Whether commensal or parasitic the fungi appear to have an obligate association with their hosts. There is much still to be learned about this group of fungi, including a better understanding of their taxonomy and host range.
Other interesting Zygomycetes include those belonging to the Order Entomophthorales. Fungi in this order often attack insects. For example, one species, Entomophthora muscae, infects houseflies and eventually kills them. After infection by the fungus, the flies quickly begin to show symptoms of distress and climb into exposed locations as they near death. At the death of the fly, the fungal thallus bursts through the exoskeleton of the insect and produces masses of sporangiophores that release spores (one mitosporangium per sporangiophore). The mitosporangia are sticky, and once they are shot away from the fly body can adhere to nearby surfaces. Window panes often serve as sites where houseflies who are ultimately killed by the fungus attach themselves, and a white halo of mitosporangia will appear around the fly carcass following their release from the fungal thallus. (see picture in one of the links below) A fly crawling over the discharged mitosporangia can pick up one or more of these reproductive structures. The mitosporangia can germinate and then infect that fly, which permits the continuation of the fungus life cycle.
One other very interesting group of fungi in this fungal division is the Order Zoopagales. There are five families and twenty-one genera in this order and all members are obligate parasites of fungi, nematodes, rotifers, amoebae, etc. The genus Zoopage produces hyphae that are “sticky.” When an amoeba touches a hypha of Zoopage it bonds immediately to it and cannot successfully pull away. The amoeba is held fast by the fungus and the fungal hyphae penetrate the plasma membrane using a lobed or heart-shaped haustorium. The fungus then digests the internal contents of the amoeba until all that remains is an empty shell. The fungi in the Order Zoopagales bring to mind the “poem/nursery rhyme” that is a paraphrase of a poem by Jonathan Swift.
- “Great fleas have little fleas upon their backs to bite ‘em,
And little fleas have lesser fleas, and so ad infinitum.”
Everything has something it seems to feed upon them, no matter how large or how small. Don’t forget to be a “fun-gi” today.
Zoopage feeding on amoebae.