Fungal longevity: how to measure the age of mycelium

A review proposes measuring fungal age separately for the genetic lineage, the network of fungal filaments, and the filaments themselves

On August 13, a review in Trends in Microbiology proposed dividing the age of a filamentous fungus into three levels: the genetic lineage, the mycelium, which is the network of fungal filaments, and individual hyphae. Each level requires a different type of observation.

In 2018, researchers mapped the boundaries of a single genetically uniform Armillaria gallica organism in a Michigan forest. It covered about 75 hectares. Based on this area and its measured growth rate, the researchers estimated its minimum age at two and a half thousand years.

A mycelium, which is a network of thin fungal filaments called hyphae, grows, loses sections, and forms new ones. Separated parts can retain a common genetic origin. A lineage, a connected network, and individual hyphae therefore have different life histories. One lineage can persist for millennia while the network changes shape and its hyphae appear and disappear.

The review authors propose combining three types of observation. Repeated sampling in the forest and comparisons of genetic markers can show where the same lineage persists. Long-term culture makes it possible to observe how a particular network persists and ages under defined conditions. Microfluidic chips, which are small chambers containing channels for liquids, can be used to track individual hyphae, their connections, their growth, and their death.

The age of 2500 years applies to the genetic lineage. To determine how long a mycelium lives and how it renews itself, biologists need to track the network itself and the fate of its hyphae.