The Wonderful World of Fungi
Part XVII – Division Basidiomycota – Fascinating Members Stinkhorns and Bird’s Nest Fungi
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
AAAC Collection Station—Birmingham, Alabama
It has been awhile since I wrote about the group of fungi called basidiomycetes and some of the incredibly fascinating members of this division or phylum. I first want to give a brief description of the taxonomy of this phylum and some of the groups of fungi included there before discussing in more detail the fungi known as stinkhorns and bird’s nest fungi.
The phylum basidiomycota (referred to in my blogs as basidiomycetes) has three subdivisions: Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina. The Agaricomycotina include the fungi most people are familiar with which includes the mushrooms, puffballs, bracket fungi and other polypore fungi, earth stars, boletes, chanterelles, stinkhorns, and jelly fungi. The largest percentage of these fungi are placed in the class Agaricomycetes, while a very small percentage are placed in the classes Tremellomycetes and Dacrymycetes, the jelly fungi. Jelly fungi have gelatinous fruiting bodies that are most conspicuous following rain showers. The fungi absorb moisture and swell, developing the gelatinous texture which gives them the name jelly fungi.
Members of the subdivision Agaricomycotina produce sexual spores called basidiospores on club-shaped structures called basidia, structures that vary in shape and which may or may not possess septa. Most of the fungi in this subdivision were traditionally referred to as hymenomycetes. Fungi formerly placed in this traditional taxon form their basidia on the outer surface(s) of the fruiting bodies, but the term hymenomycetes is no longer taxonomically relevant. Other members of the Agaricomycotina subdivision were traditionally referred to as gasteroid fungi (obsolete class Gasteromycetes) because they produced spores inside their basidiocarps instead of on the outer surface. A great way of seeing the traditional way that the Basidiomycota division was divided into taxa is to access, https://www.thefreedictionary.com/Basidiomycota.
Two very interesting members of the Agaricomycotina subdivision are stinkhorns and bird’s nest fungi. These fungi were traditionally placed in the gasteroid group because the spores produced are formed inside the basidiocarp.
The stinkhorns are placed in the family Phallaceae in the order Phallales. Stinkhorns are best known for their sticky spore masses that attract flies, beetles, and other insects because of the carrion or dung-like odor. One often smells these fungi before seeing them. The insects attracted to the foul-smelling gleba (the spore mass) serve to disperse the spores to new habitats. The gleba is initially gelatinous in texture but liquifies upon absorption of moisture which assists in the spores sticking to the feet and bodies of insects frequenting the mushroom.
In general, stinkhorns are most prevalent in tropical environments. However, this group has members that are found throughout the world. There is great diversity in the shape of the fruiting bodies among the genera in this family, but all species begin their life similarly as oval or round structures referred to as “eggs”. The spore mass is often located on the end of a fleshy stalk that may be cylindrical (e.g., Phallus, Mutinus), star-shaped (e.g., Aseroe), or latticed, the term clathrate is used to describe this shape (e.g., Clathrus). It is difficult not to notice why the type genus is given the name, Phallus. Many members of this group of fungi are brightly colored and readily stand out from their surroundings. It is of interest that at least one species of this group is eaten, the Chinese “bamboo fungus”, P. indusiatus. The cap, the area containing the evil-smelling spore mass, is removed before the fungus is consumed. (Pictures of selected stinkhorns are shown at the end of this blog.)
Bird’s nest fungi are placed in the family Nidulariaceae in the order Agaricales. There are five genera in the family that are separated from one another based on morphology and peridiole (the eggs) structure. The peridioles vary in color from brown to yellow to red-brown to black. They are commonly called bird’s nest fungi because the basidiocarps resemble tiny bird nests containing eggs. These eggs are typically dispersed by rain which ejects the peridioles when raindrops fall into the “nest”. If the raindrop hits at the proper angle, the eggs are expelled to as much as one meter away. Some species have a thread, a funicular cord, attached to the peridiole that will attach to a twig or grass blade it encounters in flight by swinging around and wrapping itself around the twig or grass blade. The peridioles are thought to be ingested by herbivores, pass through their digestive system, and then deposited in the herbivore dung where they can germinate and continue the life cycle of the fungus. The nests are small; size between 5-15 mm wide and 4-8 mm high. They may be urn- or vase-shaped.
Most bird’s nest fungi are saprobes; the mycelium feeds on decaying vegetative materials such as decaying wood, plant debris, or mulch. The fungal mycelium feeds on the organic substrate and produces the interesting fruiting bodies most commonly in moist, cool locations during the fall. An interesting note is that members of the Nidulariaceae are edible, though it would take quite a few basidiocarps to make it worthwhile eating them. (Pictures of several types of bird’s nest fungi are shown below.)