Pilobolus umbonatus NRRL 6349 v1.0
Figure 1) Hat-shaped sporangium of P. umbonatus, which sits atop a turgor-filled phototropic subsporangial vesicle. Figure 2) Discharged sporangia adhere to the surface they land on via sticky material on the sporangium undersurface (red arrow). Images by Kerry O'Donnell.
Figure 1) Hat-shaped sporangium of P. umbonatus, which sits atop a turgor-filled phototropic subsporangial vesicle. Figure 2) Discharged sporangia adhere to the surface they land on via sticky material on the sporangium undersurface (red arrow). Images by Kerry O'Donnell.

Pilobolus umbonatus NRRL 6349 (= ATCC 42663) [family Pilobolaceae, order Mucorales, phylum Mucoromycota; Spatafora et al. 2016] was isolated originally from herbivore dung in Michigan and deposited in the ARS Culture Collection (NRRL) in 1977.  Commonly known as the “hat throwers,” members of this iconic genus explosively discharge a hat-shaped sporangium, which sits atop a turgor-filled phototropic subsporangial vesicle (Fig. 1).  Sporangia are shot towards light at a distance of up to eight feet (Yafetto et al. 2008).  Discharged sporangia adhere to the surface they land on via sticky material on the sporangium undersurface (Fig. 2, see arrowhead).  To complete the asexual phase of its coprophilous life-cycle, sporangia need to land on vegetation such as grass and then the sporangiospores must pass through the gastrointestinal track of a herbivore ungerminated.  Once the spores are excreted, the spores germinate and colonize the dung where it produces another round of phototrophic sporangiophores.  For ultra-high speed videos of the ballistic sporangia (Yafetto et al. 2008), which are ejected in fluid accelerated at 20,000 g, see https://www.youtube.com/watch?v=TrKJAojmB1Y.  Unlike many isolates of Pilobolus that require special supplements or dung extract for cultivation in the lab (Page 1962), P. umbonatus NRRL 6349 grows and sporulates abundantly on the following medium (17 g corn meal agar, 17 g dextrose, 2 g dextrose, 3 g sucrose, 1 g yeast extract per L distilled water).  A monophyletic Pilobolaceae as presently circumscribed includes Pilobolus and Utharomyces, which differ in that sporangia are passively dispersed in the latter (O’Donnell et al. 2000; Walther et al. 2013).  The whole-genome sequence of P. umbonatus provides a representative of the Pilobolaceae for the 1000 Fungal Genome Project (http://1000.fungalgenomes.org/home/), which is focused on elucidating evolution of the early diverging fungi.

References:

O’Donnell K, Lutzoni F, Ward TJ, Benny GL. 2000. Evolutionary relationships among mucoralean fungi (Zygomycota): Evidence for family polyphyly on a large scale. Mycologia 93:286─296.

Page RM. 1962. Light and the asexual reproduction of Pilobolus. Science 138:1238─1245.

Spatafora JW, Chang Y, Benny GL, Lazarus K, Smith ME, Berbee ML, Bonito G, Corradi N, Grigoriev I, Gryganskyi A, James TY, O’Donnell K, Roberson RW, Taylor TN, Uehling J, Vilgalys R, White MM, Stajich JE. 2016. A phylum-level phylogenetic classification of zygomycete fungi based on genome-scale data. Mycologia 108:1028─1046.

Walther G, Pawłowska J, Alastruey-Izquierdo A, Wrzosek M, Rodriguez-Tudela JL, et al. 2013. DNA barcoding in Mucorales: an inventory of biodiversity. Persoonia 30:11–47.

Yafetto L, Carroll L, Cui Y, Davis DJ, Fischer MWF, Henterly AC, Kessler JD, Kilroy HA, Shidler JB, Stolze-Rybczynski JL, Sugawara Z, Money NP. 2008. The fastest flights in nature: High-speed spore discharge mechanisms among Fungi. PLoS ONE 3(9): e3237. doi:10.1371/journal.pone.0003237