The Fastest Flights in Na­ture

by Elio

If you were a fun­gus grow­ing on dung and if, for prop­a­ga­tion, you de­pended on hav­ing your spores in­gested by an an­i­mal, you'd have a prob­lem. Few an­i­mals graze near their poop. The so­lution would be to evolve a pow­er­ful dis­charge mech­a­nism that en­sured that your spores trav­eled far afield. In the words of a pi­o­neer in this area, Nik Money: "Evo­lu­tion has over­come this ob­sta­cle by pro­duc­ing an ar­ray of mech­a­nisms of spore dis­charge whose el­e­gance trans­forms a cow pie into a cir­cus of mi­cro­scopic cat­a­pults, tram­po­lines, and squirt guns."

Spo­ran­gio­phore dis­charge in Pi­lobo­lus kleinii cap­tured with high speed video. This il­lus­tra­tion is a mon­tage of 6 im­ages from a video ob­tained at a frame rate of 50,000 frames per sec­ond. The se­lec­tion shows every 10th frame, rep­re­sent­ing 200 mi­crosec­ond in­ter­vals. The launch is com­pleted in <0.25 mil­lisec­onds or <1/400 of an eye blink. (In­ci­den­tally, 'Pi­lobo­lus' is also the name adopted by a famed Amer­i­can dance com­pany.)

A pa­per from Money's lab at Mi­ami Uni­ver­sity in Ox­ford, Ohio, and col­leagues at the Col­lege of Mount St. Joseph in Cincin­nati, Ohio, re­veals how fun­gal squirt guns fire spores over dis­tances of more than 2 me­ters. The re­search­ers used high speed cam­eras run­ning at up to 250,000 frames per sec­ond to cap­ture these blis­ter­ingly fast move­ments.

Click here to view a mon­tage of high-speed video clips show­ing spo­ran­gio­phore dis­charge in Pi­lobo­lus kleinii. The videos were made at cam­era frame rates of up to 250,000 fps. Each dis­charge is com­pleted in Anvil Cho­rus from Verdi's Trova­tore.

Spores are launched at max­i­mum speeds of 25 me­ters per sec­ond – re­mark­able for a mi­cro­scopic cell. This cor­re­sponds to ac­cel­er­a­tions of 180,000 g_n, no less! In terms of ac­cel­er­a­tion, these are the fastest flights in na­ture. The fungi stud­ied were two as­comycetes (As­cobolus im­mer­sus and Po­dospora anse­rina) and two zy­gomycetes (Pi­lobo­lus kleinii, and Ba­sid­iobo­lus rana­rum).

How do these fungi do it? Fun­gal cells make use of os­mo­tic pres­sure, but just how is the pres­sure gen­er­ated? The au­thors iden­ti­fied sev­eral sug­ars and other os­molytes re­spon­si­ble for the wa­ter in­flux into the guns. The long flights of spores do not re­sult from un­usu­ally high pres­sure but from the ex­plo­sive way the pres­sure drop is har­nessed for spore propul­sion. There ap­pear to be some sim­i­lar­i­ties to the ex­pul­sion of ink droplets through noz­zles on inkjet print­ers.

As the au­thors state in a press re­lease:"This in­for­ma­tion is very im­por­tant for fu­ture bio­phys­i­cal stud­ies on spore and pollen move­ment, which have im­pli­ca­tions for the fields of plant dis­ease con­trol, ter­res­trial ecol­ogy, in­door air qual­ity, at­mos­pheric sci­ences, vet­eri­nary med­i­cine, and bio­mimet­ics."

We thank Nik for pro­vid­ing us the movie. We had fea­tured his work on the dis­charge of spores in ba­sid­iomycetes (which in­clude mush­rooms) pre­vi­ously. An in­ter­view with Nik broad­cast on CBC ra­dio is also avail­able. (Scroll down to the third pro­gram seg­ment.)