Many higher fungi have converged on using gills or pores to utilize wind to transport potential offspring to other suitable habitats. Though, for millennia, evolution has driven some pretty bizarre adaptations for fungal spore dispersal. This diverse kingdom is clearly not limited to just using wind currents. For example, truffle forming fungi utilize mammal dispersers. The zoospores of lower aquatic fungi actually swim towards potential hosts. Puffball and birds nest fruiting bodies exploit the kinetic energy of rain to eject their spores. The stinkhorns, similar to flowering plants, attract carrion insects to carry spores throughout the forest floor. Few fungi create their own osmotic pressure to forcibly eject fungal spores, but I already had the chance to talk about one of these fungal types; the dung loving Pilobolus fungi. Once I learned about Sphaerobolus fungi, I knew I had another species worthy of headlining a Fungi Friday. Everybody, I’d like you to meet Sphaerobolus stellatus. Sphaerobolus stellatus, everybody.
Fungi in the genus Sphaerobolus are also known as the cannonball fungus. To live up to its fitting common name, S. stellatus creates six layers of tissue in which five of the layers eventually develop into an inner and outer cup. One of the layers dissolves and creates a sticky layer surrounding the spore mass. The spore mass, which is also called the peridiole, contains many sexual and asexual spores that can remain dormant until proper conditions induce germination.
In Greek this genus translates to sphere thrower, as sphaer, means "sphere", and obolus, means "to throw" while stellatus refers to the star shape that occurs as the fungus peels open, once the peridiole becomes exposed. Once the spore mass is revealed, the fungus releases enzymes that convert a stored carbohydrate-glycogen, into the simple sugar glucose. This enzymatic conversion rapidly increases the osmotic pressure in the inner cup until it forcibly springs up, launching the peridiole up to 18 feet. For a fungus that is one eighth of an inch, this is quite the feat!
This beautiful, wood loving, star shaped fungus is an evolutionary spectacle that you should appreciate if you find in your mulch bed. Some see it as a nuisance, since it readily sticks to vinyl siding and porches. Though, S. stellatus represents the diversity of the forest floor, and reminds us of the wide array of adaptations that aptly carry out the spore dispersing role.