Summoning the wind: Hydrodynamic cooperation of forcibly ejected fungal spores

TL;DR

This study demonstrates how forcibly ejected fungal spores coordinate their release to generate airflow that enhances spore dispersal over long distances, combining experimental, numerical, and analytical approaches.

Contribution

It reveals the cooperative mechanism of spore ejection in fungi, showing how synchronized release creates airflow to improve dispersal, a novel insight into fungal spore dynamics.

Findings

Spores eject simultaneously to form a sheet-like jet that aids dispersal.

Synchronization is self-organized but can be delayed to reduce sacrifice.

Flow simulations show spores sculpt a cooperative wind for dispersal.

Abstract

The forcibly launched spores of the crop pathogen \emph{Sclerotinia sclerotiorum} must eject through many centimeters of nearly still air to reach the flowers of the plants that the fungus infects. Because of their microscopic size, individually ejected spores are quickly brought to rest by drag. In the accompanying fluid dynamics video we show experimental and numerical simulations that demonstrate how, by coordinating the nearly simultaneous ejection of hundreds of thousands of spores,\emph{Sclerotinia} and other species of apothecial fungus are able to sculpt a flow of air that carries spores across the boundary layer and around intervening obstacles. Many spores are sacrificed to create this flow of air. Although high speed imaging of spore launch in a wild isolate of the dung fungus \emph{Ascobolus} shows that the synchronization of spore ejections is self-organized, which could lead to spores delaying their ejection to avoid being sacrificed, simulations and asymptotic analysis show that, close the fruit body, ejected spores form a sheet-like jet that advances across the fruit body as more spores are ejected. By ejecting on the arrival of the sheet spores maximize \emph{both} their range and their contribution to the cooperative wind.