"What on Earth?"
Article by Ray Barbehenn. Photos by Photos by David Cox
Mushrooms are often likened to the fruit of fungi and called "fruiting bodies." They are reproductive structures whose purpose is to release billions of spores into the air. Aside from this function, it is difficult to generalize about them. Some last for only a few days; some last for years. Some are edible; some are poisonous. Some have gills; some have pores; some even have "teeth"! The first photo above shows a side view of a species that is covered with little tooth-like structures: the Lion's Mane mushroom. It was found by David Cox growing at the base of a dead branch on a live Beech tree in SNP on August 25, 2024. These fist-sized mushrooms are delicacies, and can occasionally be found in grocery stores. In the wild, they are seldom found, and are prized by mushroom hunters. This one has attracted a party of 2-mm-long beetles. They, in addition to fly maggots, are a major reason why most kinds of mushrooms do not usually last long in the woods.
The second photo is a top view of a Ganoderma shelf mushroom (probably
Ganoderma sessile). They grow directly out of the sides of trees without being attached by stalks. This specimen was about 8-9 inches wide, and was found growing on a live Sycamore tree by David Cox in SNP on August 25, 2024. Their top surfaces develop a shiny, varnished look, while their white undersurfaces are covered by a layer of tiny pores. They grow in concentric rings, all in the same season. You won't find this species in the grocery store, but you might see one on a hike. Unlike the great majority of mushrooms, they can grow and release spores for several months.
How does the Ganoderma shelf mushroom last so long?
A. It is poisonous.
B. It is tough or woody.
C. Both.
The answer is at the bottom of the page!
Fun Facts and Musings
Fungi may seem more like plants than animals, but really, they are somewhere between these other two kingdoms. Fungi are best known as decomposers of plants and animals. No sunlight is needed for them to grow, but sunlight powers the growth of most of the food that they devour. In that way, they are more like us animals!
If you want to understand how shelf mushrooms last for so long, then you need to know about the different types of hyphae ("high-fee") that form them! What are hyphae? These are their long, fluid-filled cells – microscopic rootlets. The hyphae of fungi that decompose things release digestive enzymes onto their food and then absorb the nutrients. In time, they grow into a large web-like structure, typically hidden from view inside a tree or in the leaf litter.
Different species of mushrooms are made with either one, two, or three types of hyphae, which appear to correspond to short-, intermediate-, or long-lasting mushrooms. Most gilled mushrooms, such as our store-bought button mushrooms, are composed of only one type of hypha. These short-lived mushrooms are brittle and easily broken. Mushrooms that are composed of two of the three types of hyphae often feel rubbery when flexed. These species, such as the Lion's Mane, can remain active for a period of weeks. Shelf mushrooms, such as Ganoderma, become tough or woody because of an additional, third type of hypha – the "binding" hypha. As this name suggests, this third type of hypha binds together the other two types of hyphae. With binding hyphae, a mushroom can become a long-lasting, rigid structure.
Is there a benefit for some species of mushrooms to be woody – to be made with three kinds of hyphae? This is probably a strategy to maximize their spore output. Thus, if a tree-feeding fungus succeeds in getting into a living tree, it might benefit the fungus to maintain its "fruiting bodies" for a long time. Indeed, some species of Ganoderma
shelf mushrooms can continue to grow larger and shed billions of spores for years! By comparison, the species of fungi made with one type of hypha often produce their mushrooms quickly in response to wet weather. They can be numerous across the forest floor, but are often gone in a week.
The reproductive strategies of plants and animals show this same kind of pattern – species that live a long time and produce few offspring, in contrast to species that have short lives and produce large numbers of offspring. The plant kingdom has its trees and its weeds, the animal kingdom its whales and its insects. Both are good strategies in their own ways.
For those readers who want to know one more interesting fact about hyphae, it is their production of chitin ("KIE-tin"). Besides fungi, there are few types of organisms on Earth that can produce this tough, plastic-like substance. Insects, crabs, and other invertebrates use chitin to rigidify their shells. However, the great majority of other animals are unable to make chitin. And, no plant makes chitin. Chitin fibers act like strands of fiberglass, helping fungi strengthen their cell walls.
In the photo of the Ganoderma mushroom above, you can see a white outer ring where the mushroom was growing and still soft. Presumably, this ring is toughened after it is fully expanded by the binding hyphae. This sequence of mature rings and a growing ring also seems like a good way to keep the mushroom from sagging under its own weight on a tree trunk. The function of the waxy "varnish" on top of the mature rings is not known. These mushrooms are not poisonous, but neither are they considered edible. They are eaten by some people who use them as an herbal medicine.
Lion's Mane mushrooms can be found growing on either living or dead hardwood trees. They prefer older trees and non-living parts, such as the heartwood. Once they get inside a tree through a wound or a dead branch, Lion's Mane hyphae can eventually rot the heartwood, creating a hollow tree. The Ganoderma fungus can also grow on living or dead trees, but it is best known as a pathogen of living trees. It is especially adept at getting into wounds in the lower trunk and roots, where it kills portions of a tree. Fortunately for the trees, these mushrooms are relatively uncommon.
Should you try to help trees by breaking off shelf mushrooms that are on them? Don't bother. Remember that these are just the reproductive structures of the fungi, and masses of hyphae remain feeding inside the trees. In addition, even if Ganoderma mushrooms are on a tree, it is not a death knell for the tree; infected trees can last for many years as they slowly lose portions of themselves to the fungi.
Finally, about those tiny beetles having a party on the Lion's Mane – they are probably Shining Fungus Beetles. And, there is probably no other place where you will ever notice these little creatures. As is the case with many animals, they gather together to breed at a particularly attractive spot. This gathering is where the beetles all feed, where the males compete for the attention of females, and where the females lay their eggs. They have to hurry because once the fungus-feeding flies and other insects arrive, the party will soon run out of food.
Answer: B!
Send your photos and ideas for topics to Ray at rvb@umich.edu.
