When I encounter puffball fungi, I just can’t help myself. If I locate these fungi fully matured, I find it irresistible to tap them, forcefully puffing out clouds of spores. I’m sorry, but if you find these fruiting bodies and don’t have the slightest urge to do this, the child in you has died. What a fantastic mechanism of spore release! Instead of depending on just wind, raindrops, fallen twigs and sticks as well as animals (including us childlike human adults) that fall on, brush against, or knowingly tap on these fungi forcefully eject spores. These spores launched into the air escape the still boundary layer above the forest floor, entering upwelling currents. This morphology has evolved independently several times over.
Scleroderma citrinum fruiting body that cracked open. Found under white pines in Western NY.
Even though Scleroderma citrinum isn’t that rare, it is still an exciting find. Upon first look, this species looks like many other puffballs, but looking a bit closer, clear distinguishing features present themselves. Unlike most puffballs that develop an opening for spores to be directionally ejected, Scleroderma citrinum eventually just breaks up in an irregular fashion. A cross section of this fungus reveals a dark, purple-black material called gleba. This is where its spores are formed. Other puffball species have much lighter colored gleba. Additionally, its outer skin, also known as the peridium, is thicker than most other puffballs and has asymmetrical, yellowish-brown warts.
Cross section of Scleroderma citrinum. Another cameo of my hiking buddy Stella.
Up close and personal with Scleroderma citrinum. Look at those warts! Found in Western NY.
Reading about Scleroderma citrinum, I was surprised to learn that this species forms mycorrhizal relationships with conifers. Now that I think about it, every time I encounter this species, a stand of pines or Eastern hemlocks hangs over my head. Many other puffballs are saprotrophs, breaking down dead organic matter from the forest floor. Scleroderma citrinum on the other hand explores its soil substrate using filaments of mycelia. Macronutrients required by its host plant are then allocated to the plant’s roots, in return for a sugar reward.
Every time I find this fungus, I hope to also find another species that co-evolved with it. Pseudoboletus parasiticus is an obligate mycoparasite that steals carbohydrates and nutrients from the pigskin puffball. It is actually a pretty rare fungus as well, which is understandable even though Scleroderma citrinum is a wide spread species. Mushroom expert Michael Kuo has contemplated how this parasite survives. The spores could potentially float throughout the year and by chance land on a developing pigskin puffball. The other theory he comes up with is that these parasitic spores may germinate on the forest floor when Scleroderma citrinum mycelium is nearby. These networks could then grow together, and eventually fruit at the same time.
The myco-parasite Pseudoboletus parasiticus growing from the pigskin puffball. Photo by Heather Hallen-Adams.
Scleroderma citrinum and its unique parasite are awesome species that I am looking forward to finding this upcoming season. I really love these mushrooms. They bring out the child in me, reminding me to not take life so seriously. Even while writing this, this fungus speaks to me. It’s telling me to go on a hike. To get my hands dirty. To puff some puffballs. Explore for the sake of exploration. And most importantly, to have fun. These thoughts should run through our heads more often. It’s so easy to get distracted by our jobs in the concreate jungle where most of us reside. The pigskin puffball has brought out the myco-excitement in me. Happy Fungi Friday you fungal fanatics!