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Pilobolus -- Fungal Shotgun



spore trajectory

A cow stays close to its calf to make sure it will get everything it needs to grow. In the grass around their hooves, the fungus Pilobolus does exactly the opposite. To help its spores, Pilobolus uses a "shotgun" to blast them as far away as possible.

Pilobolus lives in cow dung. This life habit may seem terrible to us, but fungi like Pilobolus are very important in nature. These fungi, called "decomposers" break down non-living organic matter by feeding on it. Some bacteria and animals are also decomposers. Without them, we would be surrounded everywhere by piles of dead plants, animals and dung.

To live in cow dung, the Pilobolus fungus must first get into the cow's dung. The cow has to eat the spores of Pilobolus while grazing. Spores are very tough. The cow cannot digest them. They pass through the animal's digestive system and are excreted in the dung, where they will grow.

Pilobolus has evolved a way to shoot its spores on to the grass. Its "shotgun" is a stalk swollen with cell sap, bearing a black mass of spores on the top. Below the swollen tip is a light-sensitive area. The light sensing region affects the growth of Pilobolus by causing it to face toward the sun. As the fungus matures, water pressure builds in the stalk until the tip explodes, shooting the spores into the daylight.

The spores fly away at 35 feet per second (10.8 m per second), at a height of six feet (2 m), and land as far away as 8 feet (2.5 m). Pilobolus, without knowing it, can shoot over a cow.

Shooting the spores into the daylight gives them a better chance of landing in a sunny place where grass or other plants are growing. The cows that made the dung for the previous batch of Pilobolus will probably eat these spore covered plants and start the process all over again.


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Last update: 5 Sep 96. © 1996, Robert Fogel, Ivins, UT 84738. Edited by Patricia Rogers. Photograph courtesy of M.J. Wynne