Fungal artillery of zombie flies: infectious spore dispersal using a soft water cannon

Jolet de Ruiter, Sif Fink Arnbjerg-Nielsen, Pascal Herren, Freja Høier, Henrik H. De Fine Licht, Kaare Hartvig Jensen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Dead sporulating female fly cadavers infected by the house fly-pathogenic fungus Entomophthora muscae are attractive to healthy male flies, which by their physical inspection may mechanically trigger spore release and by their movement create whirlwind airflows that covers them in infectious conidia. The fungal artillery of E. muscae protrudes outward from the fly cadaver, and consists of a plethora of micrometric stalks that each uses a liquid-based turgor pressure build-up to eject a jet of protoplasm and the initially attached spore. The biophysical processes that regulate the release and range of spores, however, are unknown. To study the physics of ejection, we design a biomimetic 'soft cannon' that consists of a millimetric elastomeric barrel filled with fluid and plugged with a projectile. We precisely control the maximum pressure leading up to the ejection, and study the cannon efficiency as a function of its geometry and wall elasticity. In particular, we predict that ejection velocity decreases with spore size. The calculated flight trajectories under aerodynamic drag predict that the minimum spore size required to traverse a quiescent layer of a few millimetres around the fly cadaver is approximately 10 µm. This corroborates with the natural size of E. muscae conidia (approx. 27 µm) being large enough to traverse the boundary layer but small enough (less than 40 µm) to be lifted by air currents. Based on this understanding, we show how the fungal spores are able to reach a new host.
Original languageEnglish
Article number20190448
JournalJournal of the Royal Society. Interface
Volume16
Issue number159
Number of pages10
ISSN1742-5689
DOIs
Publication statusPublished - 2019

Keywords

  • Fungal spore ejection
  • Entomophthora muscae
  • Biomimetic soft cannon
  • High-speed videography
  • Dispersal range
  • Force-balance model

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