“The spores! The spores!”
When I was in undergrad (which is beginning to seem a depressingly long time ago), all the Biology majors had to take Botany. The pre-meds HATED this class, which not only was not really relevant to medical school, but was also MWF at 8:00am. And had a lab.
It was the lab I remember best. We had a brief section on mycology (the study of fungi), and the TA for the course had us each do a presentation on a different type. She encouraged us to do something interesting: pictures, something clinically relevant (or something people like to eat), or even interpretive dance. Most of the kids in the class did powerpoint presentations, the kind where it’s obvious they are only doing enough to get the desired grade.
I started out bored and did a powerpoint, but about halfway through my prep, I got silly. Could have been the lack of sleep (it was sophmore year and I was also in organic chem). Also the caffeine. Or the sugar. I ended up doing a presentation entitled “Mycology as Performance Art”. I did give the powerpoint, but I also did interpretive dance to a poem I’d written (oh yes, it rhymed) on the reproduction of Ascomycota. The best part was definitely the bit where I burst my arms open, crying “THE SPORES! THE SPORES!” Of course the class rolled their eyes (no art appreciation these days), but the TA fell over laughing (and a good thing, I’d hate to be taken seriously). I think I may have been one of the only As in the lab section. So when in doubt, do the interpretive dance.
Anyway, after that episode the mycotes receeded in my memory. Until today…
Yafetto et al. “The fastest flights in nature: high-speed spore discharge mechanisms among fungi” PLoS ONE, 3(9) 2008.
I didn’t really realize this, but fungi are the artillery of the natural world. And it makes sense. Most of them are pretty close to the ground, so they don’t just want to be shedding their spores downward or they won’t go anywhere. Fungi are also often under fallen leaves and other detritus. How’s a shroom gonna get the word out? Jet propulsion! Cannon fire! EXPLOSIONS!
Some species have catapults that use surface tension of water to launch spores, others explode pressurized membranes, and some use squirt guns! The stalks below the spores (sometimes single spores, sometimes spore-filled sacs called sporangia) fill with fluid by osmosis, and then the pressure of the fluid squirts the spores into the air. The squirt guns produce the fastest launch in the mushroom kingdom (and possibly in nature), and are mostly found among the Ascomycota.
Ascomycota is awfully important to most of us, though I’m sure most people don’t ever think of them or give them the appreciation they deserve. Famous ascomycetes include baker’s yeast, brewer’s yeast, truffles (the most expensive of which are over 4,000 Euros per kilogram!), and morels (which are delicious). So next time you have that pint of glorious pumpkin ale, give a shout out to Ascomycota.
But the kind this paper deals with are the “coprophilous” fungi, which are specialized to grow on the dung of herbivores (cow pats). The reproductive cycle is a bit odd. Basically, the fungus grows on a cow pat. But it needs to spread it’s spores AWAY from the cow pat, so the cow will eat the spores in the grass (most herbivores won’t eat near their own dung), and then poop out grass and spores in a new cow pat, and the cycle starts again. Rather parasitic, except it doesn’t appear to hurt the cow (or deer, or whatever).
In order to get the spores well and away from the dung, the fungi really have to knock them out of the park, and they do so with the squirt gun approach. It was obvious that this required some really high velocity stuff, but no one really knew how fast the spores were going. People had tried to measure velocity with spores landing on discs that were spinning at a known speed, by having spores interrupt beams of light, or just by looking at the distance and doing math. The problems arose when people tried to come up with a good model. No one seemed to be able to really define what kind of drag the spores were dealing with (the spores don’t come out dry, they’re surrounded by fluid), let alone the pressures they were undergoing prior to launch, and so the real velocity could never be found.
This group managed to get ultra high speed cameras, set them up to watch some fungi, and waited. What they got were incredibly precise measurements of how the spores were fired, what kind of drag they were undergoing, and even what else was coming out with them. And they got some killer video! They also managed to clarify some problems with the previous models used to estimate spore velocity. And they found that the major propelling force was turgor pressure, which makes a lot of sense, because the fungi were not required to evolve a new mechanism to get their spores in the world, as turgor pressure (the pressure of cell contents against a cell wall) was already in use.
And of course this could have implications for us humans as well. Many of the mechanisms that fungi use for spore deployment are also used by humans for things like ballistics (though we came up with them before we knew how the shrooms did it). It’s possible that the models they have come up with, as well as their ways to detect and measure viscous drag, could help researchers in other areas develop the next generation of underwater missiles. Or maybe the next big squirt gun. Move over, Super Soaker! Here comes the Ascomycota 4000!
Make sure to check out the video! It shows the kind of power these little guys can achieve. And be prepared for Verdi.
Levi Yafetto, Loran Carroll, Yunluan Cui, Diana J. Davis, Mark W. F. Fischer, Andrew C. Henterly, Jordan D. Kessler, Hayley A. Kilroy, Jacob B. Shidler, Jessica L. Stolze-Rybczynski, Zachary Sugawara, Nicholas P. Money, Amy S. Gladfelter (2008). The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi PLoS ONE, 3 (9) DOI: 10.1371/journal.pone.0003237
Filed under: Natural Sciences |