TY - JOUR

T1 - Fungal artillery of zombie flies

T2 - Infectious spore dispersal using a soft water cannon

AU - De Ruiter, Jolet

AU - Arnbjerg-Nielsen, Sif Fink

AU - Herren, Pascal

AU - Høier, Freja

AU - De Fine Licht, Henrik H.

AU - Jensen, Kaare H.

PY - 2019/10/2

Y1 - 2019/10/2

N2 - 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.

AB - 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.

KW - Biomimetic soft cannon

KW - Dispersal range

KW - Entomophthora muscae

KW - Force-balance model

KW - Fungal spore ejection

KW - High-speed videography

U2 - 10.1098/rsif.2019.0448

DO - 10.1098/rsif.2019.0448

M3 - Journal article

C2 - 31662074

AN - SCOPUS:85074261424

VL - 16

SP - 1

EP - 10

JO - Journal of the Royal Society. Interface

JF - Journal of the Royal Society. Interface

SN - 1742-5689

IS - 159

M1 - 20190448

ER -