By: Lotus Lofgren
For most species, it’s not good enough simply to make babies. In order for a species to spread their genes, those offspring need to travel. Nature has evolved some remarkable mechanisms for distributing the next generation to new locations. Most animals can simply transport themselves to a new home. Bacteria can hitch rides on hosts, in soil, or along waterways. Plants spread themselves around using seeds which can fly in the breeze, float downriver, or seduce a multitude of creatures (including us) to do the heavy lifting for them- carrying their fruits to every corner of the globe. It’s just as important to get around if you happen to be a fungus, and like plants, fungi employ some amazing ways to ensure their offspring get to see the world.
Turn over a mushroom cap and you might find any number of beautiful textures- knife like true gills such as those found in Agaricus bisporus (the common grocery store mushroom), false gills (like those found on Chanterelles, which look like true gills that have melted in the heat), pores (found on many bracket fungi) or teeth (such as those found on hedgehog mushrooms). These structures may look different, but they all serve the same purpose- to house and distribute tiny fungal spores. Spores are the fungal equivalent of seeds, and these varied structures are indicative of the many strategies that fungi employ to get around. We call all these different structures ‘spore bearing surfaces’ and this week at the market, we set out to investigate why mushrooms make them.
When you slice off a mushroom’s gill section and look at it under a microscope, you will see 4 tiny spores suspended on a structure known as a ‘basidium’ (plural: basidia). The gills support these basidia and hold them at a very specific spacing. The little spores are ejected from the basidia with tremendous velocity, but are halted almost immediately when their small size slams against the viscous air. Then they drop, straight down, in a flight path that clears the adjacent basidia while maximizing the number of spores that can fit in a given area of the gill. After the spores have fallen clear of the cap, they are perfectly positioned to hitch a ride on tiny air currents, which insure they land at the greatest distance possible from the parent mushroom.
At the market this week, we explored mushroom biology by making gill stamp critters. After taking a look at some diverse examples of fungal spore bearing surfaces under a dissecting microscope, our kid-scientists carefully peeled back the mushroom cap margin to expose the gills and used the gill surface as a stamp. The stamps preserved the important gill spacing of the mushrooms and provided a print to create mushroom critters! Our scientists then glued on googley-eyes, plant materials, fungi and lichens. Like the little mushroom spores traveling far from where they were born, our kid-made art dried in the sun and made its way back to the artists’ homes- with a story to tell about why mushrooms have gills and how some fungal spores travel the world.