September 26, 2008 | David F. Coppedge

Fastest Squirt Gun in the Fungi

A paper on PLoS One described the highest-speed flights in all nature: the spore discharge mechanisms in certain fungi.  A dozen scientists in Ohio worked to capture the action on ultra-high-speed cameras.  It took 250,000 frames per second to reveal how fast the projectiles accelerate.  The answer: from 20,000 to 180,000 g (where g = the acceleration of gravity).  One species launches its projectiles at almost 2 million meters per second squared – winning the title of “fastest recorded flights in nature.”
    In their introduction, they discussed the variety of ways that fungi disperse their spores.  Their language sounds downright military: “Mechanisms include a catapult energized by surface tension that launches mushroom spores, the explosive eversion of a pressurized membrane in the artillery fungus, and the discharge of squirt guns pressurized by osmosis.”  Well, maybe squirt guns are for kid’s playground battles, but army engineers might learn a few things from these lowly fungi.  That’s why the authors said the study of spore-discharge mechanisms has implications for biomimetics (the imitation of nature).  Who else would want to imitate this?
    The four species of fungi studied live on cow manure.  They need to launch their spores out far enough onto the grass so that cows will eat them and spread them around.  Each species has variations on the mechanism, but basically, the spores are ejected in a mass (either in a fluid or solid), within a sporangium, or capsule.  The sporangium usually separates during flight..  This trick, reminiscent of a spacecraft ejecting its cover after achieving orbit, allows the spores to minimize viscous drag on the ascent, then disperse on descent and landing.
    How are such superlative accelerations achieved?  The answer lies not only in the structure of the catapults, but in the viscosity of the specific sugars and ions in the spore capsules.  The liquids allow the build-up of 4.4 atmospheres of turgor pressure.  As the “pressurized squirt gun” undergoes a “controlled and rapid rupture,” almost none of the energy is lost to friction.  The “supremely fast movements” represent a “a series of remarkable feats of natural engineering,” they said.
    Engineers might be curious how these feats were designed.  Their answer was, simply, they “have evolved.”  The authors stated this twice: “A variety of spore discharge processes have evolved among the fungi,” and, “Squirt gun mechanisms are responsible for launching spores at the highest speeds and are most common in the Ascomycota, including lichenized species, but have also evolved among the Zygomycota.”

1.  Yafetto et al, “The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi,” Public Library of Science ONE, 3(9): e3237 doi:10.1371/journal.pone.0003237.

It evolved because it evolved – this is the theory of evolution in a nutshell (see 05/25/2005).  This is sufficient to explain the origin of any feat of natural engineering.  It evolved.  Darwin sure simplified biology, didn’t he?  Scientists used to have to produce explanations the hard way, with logic and evidence.  Now, a simple two-word answer suffices for everything in the world that used to inspire awe, wonder, curiosity and motivation.

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Categories: Amazing Facts, Biomimetics

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